3.3: Ecosystem Diversity - Biology

3.3: Ecosystem Diversity - Biology

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3.3: Ecosystem Diversity

3.3: Ecosystem Diversity - Biology

Figure 1. Each of the world’s eight major biomes is distinguished by characteristic temperatures and amount of precipitation. Polar ice caps and mountains are also shown.

There are eight major terrestrial biomes: tropical rainforests, savannas, subtropical deserts, chaparral, temperate grasslands, temperate forests, boreal forests, and Arctic tundra. Biomes are large-scale environments that are distinguished by characteristic temperature ranges and amounts of precipitation. These variables affect the types of vegetation and animal life that can exist in those areas. Because a biome is defined by climate, the same biome can occur in geographically distinct areas with similar climates (Figure 1 above).

Tropical rainforests are found in equatorial regions (Figure 1) are the most biodiverse terrestrial biome. This biodiversity is under extraordinary threat primarily through logging and deforestation for agriculture. Tropical rainforests have also been described as nature’s pharmacy because of the potential for new drugs that is largely hidden in the chemicals produced by the huge diversity of plants, animals, and other organisms. The vegetation is characterized by plants with spreading roots and broad leaves that fall off throughout the year, unlike the trees of deciduous forests that lose their leaves in one season.

The temperature and sunlight profiles of tropical rainforests are stable in comparison to other terrestrial biomes, with average temperatures ranging from 20 o C to 34 o C (68 o F to 93 o F). Month-to-month temperatures are relatively constant in tropical rainforests, in contrast to forests farther from the equator. This lack of temperature seasonality leads to year-round plant growth rather than just seasonal growth. In contrast to other ecosystems, a consistent daily amount of sunlight (11–12 hours per day year-round) provides more solar radiation and therefore more opportunity for primary productivity.

The annual rainfall in tropical rainforests ranges from 125 to 660 cm (50–200 in) with considerable seasonal variation. Tropical rainforests have wet months in which there can be more than 30 cm (11–12 in) of precipitation, as well as dry months in which there are fewer than 10 cm (3.5 in) of rainfall. However, the driest month of a tropical rainforest can still exceed the annual rainfall of some other biomes, such as deserts.Tropical rainforests have high net primary productivity because the annual temperatures and precipitation values support rapid plant growth. However, the high amounts of rainfall leaches nutrients from the soils of these forests.

Tropical rainforests are characterized by vertical layering of vegetation and the formation of distinct habitats for animals within each layer. On the forest floor is a sparse layer of plants and decaying plant matter. Above that is an understory of short, shrubby foliage. A layer of trees rises above this understory and is topped by a closed upper canopy—the uppermost overhead layer of branches and leaves. Some additional trees emerge through this closed upper canopy. These layers provide diverse and complex habitats for the variety of plants, animals, and other organisms. Many species of animals use the variety of plants and the complex structure of the tropical wet forests for food and shelter. Some organisms live several meters above ground, rarely descending to the forest floor.

Figure 2. Species diversity is very high in tropical wet forests, such as these forests of Madre de Dios, Peru, near the Amazon River. (credit: Roosevelt Garcia)

Figure 3. A MinuteEarth video about how trees create rainfall, and vice versa.

Savannas are grasslands with scattered trees and are found in Africa, South America, and northern Australia (Figure 4 below). Savannas are hot, tropical areas with temperatures averaging from 24 o C –29 o C (75 o F –84 o F) and an annual rainfall of 51–127 cm (20–50 in). Savannas have an extensive dry season and consequent fires. As a result, there are relatively few trees scattered in the grasses and forbs (herbaceous flowering plants) that dominate the savanna. Because fire is an important source of disturbance in this biome, plants have evolved well-developed root systems that allow them to quickly re-sprout after a fire.

Figure 4. Although savannas are dominated by grasses, small woodlands, such as this one in Mount Archer National Park in Queensland, Australia, may dot the landscape. (credit: “Ethel Aardvark”/Wikimedia Commons)

Subtropical deserts exist between 15 o and 30 o north and south latitude and are centered on the Tropic of Cancer and the Tropic of Capricorn (Figure 6 below). Deserts are frequently located on the downwind or lee side of mountain ranges, which create a rain shadow after prevailing winds drop their water content on the mountains. This is typical of the North American deserts, such as the Mohave and Sonoran deserts. Deserts in other regions, such as the Sahara Desert in northern Africa or the Namib Desert in southwestern Africa are dry because of the high-pressure, dry air descending at those latitudes. Subtropical deserts are very dry evaporation typically exceeds precipitation. Subtropical hot deserts can have daytime soil surface temperatures above 60 o C (140 o F) and nighttime temperatures approaching 0 o C (32 o F). Subtropical deserts are characterized by low annual precipitation of fewer than 30 cm (12 in) with little monthly variation and lack of predictability in rainfall. Some years may receive tiny amounts of rainfall, while others receive more. In some cases, the annual rainfall can be as low as 2 cm (0.8 in) in subtropical deserts located in central Australia (“the Outback”) and northern Africa.

Figure 5. A MinuteEarth video about the global climate patterns which lead to subtropical deserts.

The low species diversity of this biome is closely related to its low and unpredictable precipitation. Despite the relatively low diversity, desert species exhibit fascinating adaptations to the harshness of their environment. Very dry deserts lack perennial vegetation that lives from one year to the next instead, many plants are annuals that grow quickly and reproduce when rainfall does occur, then they die. Perennial plants in deserts are characterized by adaptations that conserve water: deep roots, reduced foliage, and water-storing stems (Figure 6 below). Seed plants in the desert produce seeds that can lie dormant for extended periods between rains. Most animal life in subtropical deserts has adapted to a nocturnal life, spending the hot daytime hours beneath the ground. The Namib Desert is the oldest on the planet, and has probably been dry for more than 55 million years. It supports a number of endemic species (species found only there) because of this great age. For example, the unusual gymnosperm Welwitschia mirabilis is the only extant species of an entire order of plants. There are also five species of reptiles considered endemic to the Namib.

In addition to subtropical deserts there are cold deserts that experience freezing temperatures during the winter and any precipitation is in the form of snowfall. The largest of these deserts are the Gobi Desert in northern China and southern Mongolia, the Taklimakan Desert in western China, the Turkestan Desert, and the Great Basin Desert of the United States.

Figure 6. Many desert plants have tiny leaves or no leaves at all to reduce water loss. The leaves of ocotillo, shown here in the Chihuahuan Desert in Big Bend National Park, Texas, appear only after rainfall and then are shed. (credit “bare ocotillo”: “Leaflet”/Wikimedia Commons)

The chaparral is also called scrub forest and is found in California, along the Mediterranean Sea, and along the southern coast of Australia (Figure 7 below). The annual rainfall in this biome ranges from 65 cm to 75 cm (25.6–29.5 in) and the majority of the rain falls in the winter. Summers are very dry and many chaparral plants are dormant during the summertime. The chaparral vegetation is dominated by shrubs and is adapted to periodic fires, with some plants producing seeds that germinate only after a hot fire. The ashes left behind after a fire are rich in nutrients like nitrogen and fertilize the soil, promoting plant regrowth. Fire is a natural part of the maintenance of this biome.

Figure 7. The chaparral is dominated by shrubs. (credit: Miguel Vieira)

Temperate grasslands are found throughout central North America, where they are also known as prairies, and in Eurasia, where they are known as steppes (Figure 8 below). Temperate grasslands have pronounced annual fluctuations in temperature with hot summers and cold winters. The annual temperature variation produces specific growing seasons for plants. Plant growth is possible when temperatures are warm enough to sustain plant growth, which occurs in the spring, summer, and fall.

Annual precipitation ranges from 25.4 cm to 88.9 cm (10–35 in). Temperate grasslands have few trees except for those found growing along rivers or streams. The dominant vegetation tends to consist of grasses. The treeless condition is maintained by low precipitation, frequent fires, and grazing. The vegetation is very dense and the soils are fertile because the subsurface of the soil is packed with the roots and rhizomes (underground stems) of these grasses. The roots and rhizomes act to anchor plants into the ground and replenish the organic material (humus) in the soil when they die and decay.

Figure 8. The American bison (Bison bison), more commonly called the buffalo, is a grazing mammal that once populated American prairies in huge numbers. (credit: Jack Dykinga, USDA ARS)

Fires, which are a natural disturbance in temperate grasslands, can be ignited by lightning strikes. It also appears that the lightning-caused fire regime in North American grasslands was enhanced by intentional burning by humans. When fire is suppressed in temperate grasslands, the vegetation eventually converts to scrub and dense forests. Often, the restoration or management of temperate grasslands requires the use of controlled burns to suppress the growth of trees and maintain the grasses.

Temperate forests are the most common biome in eastern North America, Western Europe, Eastern Asia, Chile, and New Zealand (Figure 9 below). This biome is found throughout mid-latitude regions. Temperatures range between –30 o C and 30 o C (–22 o F to 86 o F) and drop to below freezing on an annual basis. These temperatures mean that temperate forests have defined growing seasons during the spring, summer, and early fall. Precipitation is relatively constant throughout the year and ranges between 75 cm and 150 cm (29.5–59 in).

Deciduous trees are the dominant plant in this biome with fewer evergreen conifers. Deciduous trees lose their leaves each fall and remain leafless in the winter. Thus, little photosynthesis occurs during the dormant winter period. Each spring, new leaves appear as temperature increases. Because of the dormant period, the net primary productivity of temperate forests is less than that of tropical rainforests. In addition, temperate forests show far less diversity of tree species than tropical rainforest biomes.

The trees of the temperate forests leaf out and shade much of the ground. However, more sunlight reaches the ground in this biome than in tropical rainforests because trees in temperate forests do not grow as tall as the trees in tropical rainforests. The soils of the temperate forests are rich in inorganic and organic nutrients compared to tropical rainforests. This is because of the thick layer of leaf litter on forest floors and reduced leaching of nutrients by rainfall. As this leaf litter decays, nutrients are returned to the soil. The leaf litter also protects soil from erosion, insulates the ground, and provides habitats for invertebrates and their predators.

Figure 9. Deciduous trees are the dominant plant in the temperate forest. (credit: Oliver Herold)

The boreal forest, also known as taiga or coniferous forest, is found roughly between 50 o and 60 o north latitude across most of Canada, Alaska, Russia, and northern Europe (Figure 10 below). Boreal forests are also found above a certain elevation (and below high elevations where trees cannot grow) in mountain ranges throughout the Northern Hemisphere. This biome has cold, dry winters and short, cool, wet summers. The annual precipitation is from 40 cm to 100 cm (15.7–39 in) and usually takes the form of snow relatively little evaporation occurs because of the cool temperatures.

The long and cold winters in the boreal forest have led to the predominance of cold-tolerant cone-bearing plants. These are evergreen coniferous trees like pines, spruce, and fir, which retain their needle-shaped leaves year-round. Evergreen trees can photosynthesize earlier in the spring than deciduous trees because less energy from the Sun is required to warm a needle-like leaf than a broad leaf. Evergreen trees grow faster than deciduous trees in the boreal forest. In addition, soils in boreal forest regions tend to be acidic with little available nitrogen. Leaves are a nitrogen-rich structure and deciduous trees must produce a new set of these nitrogen-rich structures each year. Therefore, coniferous trees that retain nitrogen-rich needles in a nitrogen limiting environment may have had a competitive advantage over the broad-leafed deciduous trees.

The net primary productivity of boreal forests is lower than that of temperate forests and tropical wet forests. The aboveground biomass of boreal forests is high because these slow-growing tree species are long-lived and accumulate standing biomass over time. Species diversity is less than that seen in temperate forests and tropical rainforests. Boreal forests lack the layered forest structure seen in tropical rainforests or, to a lesser degree, temperate forests. The structure of a boreal forest is often only a tree layer and a ground layer. When conifer needles are dropped, they decompose more slowly than broad leaves therefore, fewer nutrients are returned to the soil to fuel plant growth.

Figure 10. The boreal forest (taiga) has low lying plants and conifer trees. (credit: L.B. Brubaker, NOAA)

The Arctic tundra lies north of the subarctic boreal forests and is located throughout the Arctic regions of the Northern Hemisphere. Tundra also exists at elevations above the tree line on mountains. The average winter temperature is –34°C (–29.2°F) and the average summer temperature is 3°C–12°C (37°F –52°F). Plants in the Arctic tundra have a short growing season of approximately 50–60 days. However, during this time, there are almost 24 hours of daylight and plant growth is rapid. The annual precipitation of the Arctic tundra is low (15–25 cm or 6–10 in) with little annual variation in precipitation. And, as in the boreal forests, there is little evaporation because of the cold temperatures.

Plants in the Arctic tundra are generally low to the ground and include low shrubs, grasses, lichens, and small flowering plants (Figure 11 below). There is little species diversity, low net primary productivity, and low above-ground biomass. The soils of the Arctic tundra may remain in a perennially frozen state referred to as permafrost. The permafrost makes it impossible for roots to penetrate far into the soil and slows the decay of organic matter, which inhibits the release of nutrients from organic matter. The melting of the permafrost in the brief summer provides water for a burst of productivity while temperatures and long days permit it. During the growing season, the ground of the Arctic tundra can be completely covered with plants or lichens.

Figure 11. Low-growing plants such lichen and grasses are common in tundra. Credit: Nunavut tundra by Flickr: My Nunavut is licensed under CC BY 2.0

Watch this Assignment Discovery: Biomes video for an overview of biomes. To explore further, select one of the biomes on the extended playlist: desert, savanna, temperate forest, temperate grassland, tropic, tundra.

What Is Biodiversity?

Biodiversity refers to the variety of life and its processes, including the variety of living organisms, the genetic differences among them, and the communities and ecosystems in which they occur. Scientists have identified about 1.9 million species alive today. They are divided into the six kingdoms of life shown in Figure 2. Scientists are still discovering new species. Thus, they do not know for sure how many species really exist today. Most estimates range from 5 to 30 million species.

Figure 2. Click for a larger image. Known life on earth

Ecosystem Examples

Ecosystem examples are limitless. An ecosystem does not have to cover a large region. They exist in small ponds, inside human homes, and even in the human gut. Alternatively, ecosystems can cover huge areas of the planet.

A small, shaded pond in a temperate region represents an aquatic ecosystem. Water-logged soil and excess shade affect plant life biodiversity, where only species suited to this environment will proliferate. The availability of producers affects which organisms thrive in and around the pond. Primary consumers (herbivores) must provide enough energy for secondary consumers, and so on. Should pesticides be added to the pond, or should the pond freeze over or become choked with thick layers of weed, the ecosystem of this pond must adjust.

On a much larger scale, but an artificial one, the Eden biome – a smaller representation of the global ecosystem – contains multiple ecosystems for research purposes, where separate domes have varying climates and light levels, and support different producers, consumers and decomposers. In an artificial biome many variables are tightly controlled. One does not usually place a herd of elephants in an artificial biome.


  • 1916 – The term biological diversity was used first by J. Arthur Harris in "The Variable Desert," Scientific American: "The bare statement that the region contains a flora rich in genera and species and of diverse geographic origin or affinity is entirely inadequate as a description of its real biological diversity." [48]
  • 1974 – The term natural diversity was introduced by John Terborgh ("The Preservation of Natural Diversity: The Problem of Extinction Prone Species," BioScience 24 (12): 715–722. [49]
  • 1980 – Thomas Lovejoy introduced the term biological diversity to the scientific community in a book. [50] It rapidly became commonly used. [51]
  • 1985 – According to Edward O. Wilson, the contracted form biodiversity was coined by W. G. Rosen: "The National Forum on BioDiversity . was conceived by Walter G.Rosen . Dr. Rosen represented the NRC/NAS throughout the planning stages of the project. Furthermore, he introduced the term biodiversity". [52]
  • 1985 - The term "biodiversity" appears in the article, "A New Plan to Conserve the Earth's Biota" by Laura Tangley. [53]
  • 1988 - The term biodiversity first appeared in a publication. [54][55]
  • The present - the term has achieved widespread use.

Prior term Edit

"Biodiversity" is most commonly used to replace the more clearly defined and long established terms, species diversity and species richness. [56]

Alternate terms Edit

Biologists most often define biodiversity as the "totality of genes, species and ecosystems of a region". [57] [58] An advantage of this definition is that it seems to describe most circumstances and presents a unified view of the traditional types of biological variety previously identified:

    (usually measured at the species diversity level) [59] (often viewed from the perspective of ecosystem diversity) [59]
  • morphological diversity (which stems from genetic diversity and molecular diversity[60] ) (which is a measure of the number of functionally disparate species within a population (e.g. different feeding mechanism, different motility, predator vs prey, etc.) [61] ) This multilevel construct is consistent with Datman and Lovejoy.

Wilcox 1982 Edit

An explicit definition consistent with this interpretation was first given in a paper by Bruce A. Wilcox commissioned by the International Union for the Conservation of Nature and Natural Resources (IUCN) for the 1982 World National Parks Conference. [62] Wilcox's definition was "Biological diversity is the variety of life forms. at all levels of biological systems (i.e., molecular, organismic, population, species and ecosystem). ". [62]

Genetic: Wilcox 1984 Edit

Biodiversity can be defined genetically as the diversity of alleles, genes and organisms. They study processes such as mutation and gene transfer that drive evolution. [62]

United Nations 1992 Edit

The 1992 United Nations Earth Summit defined "biological diversity" as "the variability among living organisms from all sources, including, inter alia, terrestrial, marine and other aquatic ecosystems and the ecological complexes of which they are part: this includes diversity within species, between species and of ecosystems". [63] This definition is used in the United Nations Convention on Biological Diversity. [63]

Gaston and Spicer 2004 Edit

Gaston & Spicer's definition in their book "Biodiversity: an introduction" is "variation of life at all levels of biological organization". [64]

Food and Agriculture Organization 2020 Edit

What is forest biological biodiversity? Edit

Forest biological diversity is a broad term that refers to all life forms found within forested areas and the ecological roles they perform. As such, forest biological diversity encompasses not just trees, but the multitude of plants, animals and microorganisms that inhabit forest areas and their associated genetic diversity. Forest biological diversity can be considered at different levels, including ecosystem, landscape, species, population and genetic. Complex interactions can occur within and between these levels. In biologically diverse forests, this complexity allows organisms to adapt to continually changing environmental conditions and to maintain ecosystem functions.

In the annex to Decision II/9 (CBD, n.d.a), the Conference of the Parties to the CBD recognized that: “Forest biological diversity results from evolutionary processes over thousands and even millions of years which, in themselves, are driven by ecological forces such as climate, fire, competition and disturbance. Furthermore, the diversity of forest ecosystems (in both physical and biological features) results in high levels of adaptation, a feature of forest ecosystems which is an integral component of their biological diversity. Within specific forest ecosystems, the maintenance of ecological processes is dependent upon the maintenance of their biological diversity.” [65]

Biodiversity is not evenly distributed, rather it varies greatly across the globe as well as within regions. Among other factors, the diversity of all living things (biota) depends on temperature, precipitation, altitude, soils, geography and the presence of other species. The study of the spatial distribution of organisms, species and ecosystems, is the science of biogeography. [66] [67]

Diversity consistently measures higher in the tropics and in other localized regions such as the Cape Floristic Region and lower in polar regions generally. Rain forests that have had wet climates for a long time, such as Yasuní National Park in Ecuador, have particularly high biodiversity. [68] [69]

Terrestrial biodiversity is thought to be up to 25 times greater than ocean biodiversity. [70] Forests harbour most of Earth's terrestrial biodiversity. The conservation of the world's biodiversity is thus utterly dependent on the way in which we interact with and use the world's forests. [71] A new method used in 2011, put the total number of species on Earth at 8.7 million, of which 2.1 million were estimated to live in the ocean. [72] However, this estimate seems to under-represent the diversity of microorganisms. [73] Forests provide habitats for 80 percent of amphibian species, 75 percent of bird species and 68 percent of mammal species. About 60 percent of all vascular plants are found in tropical forests. Mangroves provide breeding grounds and nurseries for numerous species of fish and shellfish and help trap sediments that might otherwise adversely affect seagrass beds and coral reefs, which are habitats for many more marine species. [74]

The biodiversity of forests varies considerably according to factors such as forest type, geography, climate and soils – in addition to human use. [75] Most forest habitats in temperate regions support relatively few animal and plant species and species that tend to have large geographical distributions, while the montane forests of Africa, South America and Southeast Asia and lowland forests of Australia, coastal Brazil, the Caribbean islands, Central America and insular Southeast Asia have many species with small geographical distributions. [75] Areas with dense human populations and intense agricultural land use, such as Europe, parts of Bangladesh, China, India and North America, are less intact in terms of their biodiversity. Northern Africa, southern Australia, coastal Brazil, Madagascar and South Africa, are also identified as areas with striking losses in biodiversity intactness. [75]

Latitudinal gradients Edit

Generally, there is an increase in biodiversity from the poles to the tropics. Thus localities at lower latitudes have more species than localities at higher latitudes. This is often referred to as the latitudinal gradient in species diversity. Several ecological factors may contribute to the gradient, but the ultimate factor behind many of them is the greater mean temperature at the equator compared to that of the poles. [76] [77] [78]

Even though terrestrial biodiversity declines from the equator to the poles, [79] some studies claim that this characteristic is unverified in aquatic ecosystems, especially in marine ecosystems. [80] The latitudinal distribution of parasites does not appear to follow this rule. [66]

In 2016, an alternative hypothesis ("the fractal biodiversity") was proposed to explain the biodiversity latitudinal gradient. [81] In this study, the species pool size and the fractal nature of ecosystems were combined to clarify some general patterns of this gradient. This hypothesis considers temperature, moisture, and net primary production (NPP) as the main variables of an ecosystem niche and as the axis of the ecological hypervolume. In this way, it is possible to build fractal hyper volumes, whose fractal dimension rises to three moving towards the equator. [82]

Biodiversity Hotspot Edit

A biodiversity hotspot is a region with a high level of endemic species that have experienced great habitat loss. [83] The term hotspot was introduced in 1988 by Norman Myers. [84] [85] [86] [87] While hotspots are spread all over the world, the majority are forest areas and most are located in the tropics.

Brazil's Atlantic Forest is considered one such hotspot, containing roughly 20,000 plant species, 1,350 vertebrates and millions of insects, about half of which occur nowhere else. [88] [ citation needed ] The island of Madagascar and India are also particularly notable. Colombia is characterized by high biodiversity, with the highest rate of species by area unit worldwide and it has the largest number of endemics (species that are not found naturally anywhere else) of any country. About 10% of the species of the Earth can be found in Colombia, including over 1,900 species of bird, more than in Europe and North America combined, Colombia has 10% of the world's mammals species, 14% of the amphibian species and 18% of the bird species of the world. [89] Madagascar dry deciduous forests and lowland rainforests possess a high ratio of endemism. [90] [91] Since the island separated from mainland Africa 66 million years ago, many species and ecosystems have evolved independently. [92] Indonesia's 17,000 islands cover 735,355 square miles (1,904,560 km 2 ) and contain 10% of the world's flowering plants, 12% of mammals and 17% of reptiles, amphibians and birds—along with nearly 240 million people. [93] Many regions of high biodiversity and/or endemism arise from specialized habitats which require unusual adaptations, for example, alpine environments in high mountains, or Northern European peat bogs. [91]

Accurately measuring differences in biodiversity can be difficult. Selection bias amongst researchers may contribute to biased empirical research for modern estimates of biodiversity. In 1768, Rev. Gilbert White succinctly observed of his Selborne, Hampshire "all nature is so full, that that district produces the most variety which is the most examined." [94]

Chronology Edit

Biodiversity is the result of 3.5 billion years of evolution. [12] The origin of life has not been established by science, however, some evidence suggests that life may already have been well-established only a few hundred million years after the formation of the Earth. Until approximately 2.5 billion years ago, all life consisted of microorganisms – archaea, bacteria, and single-celled protozoans and protists. [73]

The history of biodiversity during the Phanerozoic (the last 540 million years), starts with rapid growth during the Cambrian explosion—a period during which nearly every phylum of multicellular organisms first appeared. [96] Over the next 400 million years or so, invertebrate diversity showed little overall trend and vertebrate diversity shows an overall exponential trend. [59] This dramatic rise in diversity was marked by periodic, massive losses of diversity classified as mass extinction events. [59] A significant loss occurred when rainforests collapsed in the carboniferous. [35] The worst was the Permian-Triassic extinction event, 251 million years ago. Vertebrates took 30 million years to recover from this event. [36]

The fossil record suggests that the last few million years featured the greatest biodiversity in history. [59] However, not all scientists support this view, since there is uncertainty as to how strongly the fossil record is biased by the greater availability and preservation of recent geologic sections. [25] Some scientists believe that corrected for sampling artifacts, modern biodiversity may not be much different from biodiversity 300 million years ago, [96] whereas others consider the fossil record reasonably reflective of the diversification of life. [59] Estimates of the present global macroscopic species diversity vary from 2 million to 100 million, with a best estimate of somewhere near 9 million, [72] the vast majority arthropods. [97] Diversity appears to increase continually in the absence of natural selection. [98]

Diversification Edit

The existence of a global carrying capacity, limiting the amount of life that can live at once, is debated, as is the question of whether such a limit would also cap the number of species. While records of life in the sea show a logistic pattern of growth, life on land (insects, plants and tetrapods) shows an exponential rise in diversity. [59] As one author states, "Tetrapods have not yet invaded 64 percent of potentially habitable modes and it could be that without human influence the ecological and taxonomic diversity of tetrapods would continue to increase exponentially until most or all of the available eco-space is filled." [59]

It also appears that the diversity continues to increase over time, especially after mass extinctions. [99]

On the other hand, changes through the Phanerozoic correlate much better with the hyperbolic model (widely used in population biology, demography and macrosociology, as well as fossil biodiversity) than with exponential and logistic models. The latter models imply that changes in diversity are guided by a first-order positive feedback (more ancestors, more descendants) and/or a negative feedback arising from resource limitation. Hyperbolic model implies a second-order positive feedback. [100] Differences in the strength of the second-order feedback due to different intensities of interspecific competition might explain the faster rediversification of ammonoids in comparison to bivalves after the end-Permian extinction. [100] The hyperbolic pattern of the world population growth arises from a second-order positive feedback between the population size and the rate of technological growth. [101] The hyperbolic character of biodiversity growth can be similarly accounted for by a feedback between diversity and community structure complexity. [101] [102] The similarity between the curves of biodiversity and human population probably comes from the fact that both are derived from the interference of the hyperbolic trend with cyclical and stochastic dynamics. [101] [102]

Most biologists agree however that the period since human emergence is part of a new mass extinction, named the Holocene extinction event, caused primarily by the impact humans are having on the environment. [103] It has been argued that the present rate of extinction is sufficient to eliminate most species on the planet Earth within 100 years. [104]

New species are regularly discovered (on average between 5–10,000 new species each year, most of them insects) and many, though discovered, are not yet classified (estimates are that nearly 90% of all arthropods are not yet classified). [97] Most of the terrestrial diversity is found in tropical forests and in general, the land has more species than the ocean some 8.7 million species may exist on Earth, of which some 2.1 million live in the ocean. [72]

The balance of evidence Edit

"Ecosystem services are the suite of benefits that ecosystems provide to humanity." [105] The natural species, or biota, are the caretakers of all ecosystems. It is as if the natural world is an enormous bank account of capital assets capable of paying life sustaining dividends indefinitely, but only if the capital is maintained. [106]

These services come in three flavors:

  1. Provisioning services which involve the production of renewable resources (e.g.: food, wood, fresh water) [105]
  2. Regulating services which are those that lessen environmental change (e.g.: climate regulation, pest/disease control) [105]
  3. Cultural services represent human value and enjoyment (e.g.: landscape aesthetics, cultural heritage, outdoor recreation and spiritual significance) [107]

There have been many claims about biodiversity's effect on these ecosystem services, especially provisioning and regulating services. [105] After an exhaustive survey through peer-reviewed literature to evaluate 36 different claims about biodiversity's effect on ecosystem services, 14 of those claims have been validated, 6 demonstrate mixed support or are unsupported, 3 are incorrect and 13 lack enough evidence to draw definitive conclusions. [105]

Services enhanced Edit

Provisioning services Edit

Greater species diversity

  • of plants increases fodder yield (synthesis of 271 experimental studies). [67]
  • of plants (i.e. diversity within a single species) increases overall crop yield (synthesis of 575 experimental studies). [108] Although another review of 100 experimental studies reports mixed evidence. [109]
  • of trees increases overall wood production (Synthesis of 53 experimental studies). [110] However, there is not enough data to draw a conclusion about the effect of tree trait diversity on wood production. [105]
Regulating services Edit

Greater species diversity

  • of fish increases the stability of fisheries yield (Synthesis of 8 observational studies) [105]
  • of natural pest enemies decreases herbivorous pest populations (Data from two separate reviews Synthesis of 266 experimental and observational studies [111] Synthesis of 18 observational studies. [112][113] Although another review of 38 experimental studies found mixed support for this claim, suggesting that in cases where mutual intraguild predation occurs, a single predatory species is often more effective [114]
  • of plants decreases disease prevalence on plants (Synthesis of 107 experimental studies) [115]
  • of plants increases resistance to plant invasion (Data from two separate reviews Synthesis of 105 experimental studies [115] Synthesis of 15 experimental studies [116] )
  • of plants increases carbon sequestration, but note that this finding only relates to actual uptake of carbon dioxide and not long-term storage, see below Synthesis of 479 experimental studies) [67]
  • plants increases soil nutrientremineralization (Synthesis of 103 experimental studies) [115]
  • of plants increases soil organic matter (Synthesis of 85 experimental studies) [115]

Services with mixed evidence Edit

Provisioning services Edit
Regulating services Edit
  • Greater species diversity of plants may or may not decrease herbivorous pest populations. Data from two separate reviews suggest that greater diversity decreases pest populations (Synthesis of 40 observational studies [117] Synthesis of 100 experimental studies). [109] One review found mixed evidence (Synthesis of 287 experimental studies [118] ), while another found contrary evidence (Synthesis of 100 experimental studies [115] )
  • Greater species diversity of animals may or may not decrease disease prevalence on those animals (Synthesis of 45 experimental and observational studies), [119] although a 2013 study offers more support showing that biodiversity may in fact enhance disease resistance within animal communities, at least in amphibian frog ponds. [120] Many more studies must be published in support of diversity to sway the balance of evidence will be such that we can draw a general rule on this service.
  • Greater species and trait diversity of plants may or may not increase long term carbon storage (Synthesis of 33 observational studies) [105]
  • Greater pollinator diversity may or may not increase pollination (Synthesis of 7 observational studies), [105] but a publication from March 2013 suggests that increased native pollinator diversity enhances pollen deposition (although not necessarily fruit set as the authors would have you believe, for details explore their lengthy supplementary material). [121]

Services hindered Edit

Provisioning services Edit
  • Greater species diversity of plants reduces primary production (Synthesis of 7 experimental studies) [67]
Regulating services Edit
  • greater genetic and species diversity of a number of organisms reduces freshwater purification (Synthesis of 8 experimental studies, although an attempt by the authors to investigate the effect of detritivore diversity on freshwater purification was unsuccessful due to a lack of available evidence (only 1 observational study was found [105]
Provisioning services Edit
  • Effect of species diversity of plants on biofuel yield (In a survey of the literature, the investigators only found 3 studies) [105]
  • Effect of species diversity of fish on fishery yield (In a survey of the literature, the investigators only found 4 experimental studies and 1 observational study) [105]
Regulating services Edit
  • Effect of species diversity on the stability of biofuel yield (In a survey of the literature, the investigators did not find any studies) [105]
  • Effect of species diversity of plants on the stability of fodder yield (In a survey of the literature, the investigators only found 2 studies) [105]
  • Effect of species diversity of plants on the stability of crop yield (In a survey of the literature, the investigators only found 1 study) [105]
  • Effect of genetic diversity of plants on the stability of crop yield (In a survey of the literature, the investigators only found 2 studies) [105]
  • Effect of diversity on the stability of wood production (In a survey of the literature, the investigators could not find any studies) [105]
  • Effect of species diversity of multiple taxa on erosion control (In a survey of the literature, the investigators could not find any studies – they did, however, find studies on the effect of species diversity and root biomass) [105]
  • Effect of diversity on flood regulation (In a survey of the literature, the investigators could not find any studies) [105]
  • Effect of species and trait diversity of plants on soil moisture (In a survey of the literature, the investigators only found 2 studies) [105]

Other sources have reported somewhat conflicting results and in 1997 Robert Costanza and his colleagues reported the estimated global value of ecosystem services (not captured in traditional markets) at an average of $33 trillion annually. [122]

Since the Stone Age, species loss has accelerated above the average basal rate, driven by human activity. Estimates of species losses are at a rate 100–10,000 times as fast as is typical in the fossil record. [123] Biodiversity also affords many non-material benefits including spiritual and aesthetic values, knowledge systems and education. [123]

Agriculture Edit

Agricultural diversity can be divided into two categories: intraspecific diversity, which includes the genetic variation within a single species, like the potato (Solanum tuberosum) that is composed of many different forms and types (e.g. in the U.S. they might compare russet potatoes with new potatoes or purple potatoes, all different, but all part of the same species, S. tuberosum).

The other category of agricultural diversity is called interspecific diversity and refers to the number and types of different species. Thinking about this diversity we might note that many small vegetable farmers grow many different crops like potatoes and also carrots, peppers, lettuce, etc.

Agricultural diversity can also be divided by whether it is 'planned' diversity or 'associated' diversity. This is a functional classification that we impose and not an intrinsic feature of life or diversity. Planned diversity includes the crops which a farmer has encouraged, planted or raised (e.g. crops, covers, symbionts, and livestock, among others), which can be contrasted with the associated diversity that arrives among the crops, uninvited (e.g. herbivores, weed species and pathogens, among others). [124]

Associated biodiversity can be damaging or beneficial. The beneficial associated biodiversity include for instance wild pollinators such as wild bees and syrphid flies that pollinate crops [125] and natural enemies and antagonists to pests and pathogens. Beneficial associated biodiversity occurs abundantly in crop fields and provide multiple ecosystem services such as pest control, nutrient cycling and pollination that support crop production. [126]

The control of damaging associated biodiversity is one of the great agricultural challenges that farmers face. On monoculture farms, the approach is generally to suppress damaging associated diversity using a suite of biologically destructive pesticides, mechanized tools and transgenic engineering techniques, then to rotate crops. Although some polyculture farmers use the same techniques, they also employ integrated pest management strategies as well as more labor-intensive strategies, but generally less dependent on capital, biotechnology, and energy.

Interspecific crop diversity is, in part, responsible for offering variety in what we eat. Intraspecific diversity, the variety of alleles within a single species, also offers us a choice in our diets. If a crop fails in a monoculture, we rely on agricultural diversity to replant the land with something new. If a wheat crop is destroyed by a pest we may plant a hardier variety of wheat the next year, relying on intraspecific diversity. We may forgo wheat production in that area and plant a different species altogether, relying on interspecific diversity. Even an agricultural society that primarily grows monocultures relies on biodiversity at some point.

  • The Irish potato blight of 1846 was a major factor in the deaths of one million people and the emigration of about two million. It was the result of planting only two potato varieties, both vulnerable to the blight, Phytophthora infestans, which arrived in 1845 [124]
  • When rice grassy stunt virus struck rice fields from Indonesia to India in the 1970s, 6,273 varieties were tested for resistance. [127] Only one was resistant, an Indian variety and known to science only since 1966. [127] This variety formed a hybrid with other varieties and is now widely grown. [127] attacked coffee plantations in Sri Lanka, Brazil and Central America in 1970. A resistant variety was found in Ethiopia. [128] The diseases are themselves a form of biodiversity.

Monoculture was a contributing factor to several agricultural disasters, including the European wine industry collapse in the late 19th century and the US southern corn leaf blight epidemic of 1970. [129]

Although about 80 percent of humans' food supply comes from just 20 kinds of plants, [130] humans use at least 40,000 species. [131] Many people depend on these species for food, shelter and clothing. [ citation needed ] Earth's surviving biodiversity provides resources for increasing the range of food and other products suitable for human use, although the present extinction rate shrinks that potential. [104]

Human health Edit

Biodiversity's relevance to human health is becoming an international political issue, as scientific evidence builds on the global health implications of biodiversity loss. [132] [133] [134] This issue is closely linked with the issue of climate change, [135] as many of the anticipated health risks of climate change are associated with changes in biodiversity (e.g. changes in populations and distribution of disease vectors, scarcity of fresh water, impacts on agricultural biodiversity and food resources etc.). This is because the species most likely to disappear are those that buffer against infectious disease transmission, while surviving species tend to be the ones that increase disease transmission, such as that of West Nile Virus, Lyme disease and Hantavirus, according to a study done co-authored by Felicia Keesing, an ecologist at Bard College and Drew Harvell, associate director for Environment of the Atkinson Center for a Sustainable Future (ACSF) at Cornell University. [136]

The growing demand and lack of drinkable water on the planet presents an additional challenge to the future of human health. Partly, the problem lies in the success of water suppliers to increase supplies and failure of groups promoting the preservation of water resources. [137] While the distribution of clean water increases, in some parts of the world it remains unequal. According to the World Health Organisation (2018), only 71% of the global population used a safely managed drinking-water service. [138]

Some of the health issues influenced by biodiversity include dietary health and nutrition security, infectious disease, medical science and medicinal resources, social and psychological health. [139] Biodiversity is also known to have an important role in reducing disaster risk and in post-disaster relief and recovery efforts. [140] [141]

According to the United Nations Environment Programme a pathogen, like a virus, have more chances to meet resistance in a diverse population. Therefore, in a population genetically similar it expands more easily. For example, the COVID-19 pandemic had less chances to occur in a world with higher biodiversity. [142]

Biodiversity provides critical support for drug discovery and the availability of medicinal resources. [143] [144] A significant proportion of drugs are derived, directly or indirectly, from biological sources: at least 50% of the pharmaceutical compounds on the US market are derived from plants, animals and microorganisms, while about 80% of the world population depends on medicines from nature (used in either modern or traditional medical practice) for primary healthcare. [133] Only a tiny fraction of wild species has been investigated for medical potential. Biodiversity has been critical to advances throughout the field of bionics. Evidence from market analysis and biodiversity science indicates that the decline in output from the pharmaceutical sector since the mid-1980s can be attributed to a move away from natural product exploration ("bioprospecting") in favour of genomics and synthetic chemistry, indeed claims about the value of undiscovered pharmaceuticals may not provide enough incentive for companies in free markets to search for them because of the high cost of development [145] meanwhile, natural products have a long history of supporting significant economic and health innovation. [146] [147] Marine ecosystems are particularly important, [148] although inappropriate bioprospecting can increase biodiversity loss, as well as violating the laws of the communities and states from which the resources are taken. [149] [150] [151]

Business and industry Edit

Many industrial materials derive directly from biological sources. These include building materials, fibers, dyes, rubber, and oil. Biodiversity is also important to the security of resources such as water, timber, paper, fiber, and food. [152] [153] [154] As a result, biodiversity loss is a significant risk factor in business development and a threat to long-term economic sustainability. [155] [156]

Leisure, cultural and aesthetic value Edit

Biodiversity enriches leisure activities such as hiking, birdwatching or natural history study. Biodiversity inspires musicians, painters, sculptors, writers and other artists. Many cultures view themselves as an integral part of the natural world which requires them to respect other living organisms.

Popular activities such as gardening, fishkeeping and specimen collecting strongly depend on biodiversity. The number of species involved in such pursuits is in the tens of thousands, though the majority do not enter commerce.

The relationships between the original natural areas of these often exotic animals and plants and commercial collectors, suppliers, breeders, propagators and those who promote their understanding and enjoyment are complex and poorly understood. The general public responds well to exposure to rare and unusual organisms, reflecting their inherent value.

Philosophically it could be argued that biodiversity has intrinsic aesthetic and spiritual value to mankind in and of itself. This idea can be used as a counterweight to the notion that tropical forests and other ecological realms are only worthy of conservation because of the services they provide. [157]

Ecological services Edit

Biodiversity supports many ecosystem services:

"There is now unequivocal evidence that biodiversity loss reduces the efficiency by which ecological communities capture biologically essential resources, produce biomass, decompose and recycle biologically essential nutrients. There is mounting evidence that biodiversity increases the stability of ecosystem functions through time. Diverse communities are more productive because they contain key species that have a large influence on productivity and differences in functional traits among organisms increase total resource capture. The impacts of diversity loss on ecological processes might be sufficiently large to rival the impacts of many other global drivers of environmental change. Maintaining multiple ecosystem processes at multiple places and times requires higher levels of biodiversity than does a single process at a single place and time." [105]

It plays a part in regulating the chemistry of our atmosphere and water supply. Biodiversity is directly involved in water purification, recycling nutrients and providing fertile soils. Experiments with controlled environments have shown that humans cannot easily build ecosystems to support human needs [158] for example insect pollination cannot be mimicked, though there have been attempts to create artificial pollinators using unmanned aerial vehicles. [159] The economic activity of pollination alone represented between $2.1–14.6 billion in 2003. [160]

According to Mora and colleagues, the total number of terrestrial species is estimated to be around 8.7 million while the number of oceanic species is much lower, estimated at 2.2 million. The authors note that these estimates are strongest for eukaryotic organisms and likely represent the lower bound of prokaryote diversity. [161] Other estimates include:

  • 220,000 vascular plants, estimated using the species-area relation method [162]
  • 0.7-1 million marine species [163]
  • 10–30 million insects [164] (of some 0.9 million we know today) [165]
  • 5–10 million bacteria [166]
  • 1.5-3 million fungi, estimates based on data from the tropics, long-term non-tropical sites and molecular studies that have revealed cryptic speciation. [167] Some 0.075 million species of fungi had been documented by 2001 [168]
  • 1 million mites[169]
  • The number of microbial species is not reliably known, but the Global Ocean Sampling Expedition dramatically increased the estimates of genetic diversity by identifying an enormous number of new genes from near-surface plankton samples at various marine locations, initially over the 2004–2006 period. [170] The findings may eventually cause a significant change in the way science defines species and other taxonomic categories. [171][172]

Since the rate of extinction has increased, many extant species may become extinct before they are described. [173] Not surprisingly, in the animalia the most studied groups are birds and mammals, whereas fishes and arthropods are the least studied animals groups. [174]

A variety of objective means exist to empirically measure biodiversity. Each measure relates to a particular use of the data, and is likely to be associated with the variety of genes. Biodiversity is commonly measured in terms of taxonomic richness of a geographic area over a time interval.

No longer do we have to justify the existence of humid tropical forests on the feeble grounds that they might carry plants with drugs that cure human disease. Gaia theory forces us to see that they offer much more than this. Through their capacity to evapotranspirate vast volumes of water vapor, they serve to keep the planet cool by wearing a sunshade of white reflecting cloud. Their replacement by cropland could precipitate a disaster that is global in scale.

During the last century, decreases in biodiversity have been increasingly observed. In 2007, German Federal Environment Minister Sigmar Gabriel cited estimates that up to 30% of all species will be extinct by 2050. [176] Of these, about one eighth of known plant species are threatened with extinction. [177] Estimates reach as high as 140,000 species per year (based on Species-area theory). [178] This figure indicates unsustainable ecological practices, because few species emerge each year. [ citation needed ] Almost all scientists acknowledge that the rate of species loss is greater now than at any time in human history, with extinctions occurring at rates hundreds of times higher than background extinction rates. [177] As of 2012, some studies suggest that 25% of all mammal species could be extinct in 20 years. [179]

In absolute terms, the planet has lost 58% of its biodiversity since 1970 according to a 2016 study by the World Wildlife Fund. The Living Planet Report 2014 claims that "the number of mammals, birds, reptiles, amphibians, and fish across the globe is, on average, about half the size it was 40 years ago". Of that number, 39% accounts for the terrestrial wildlife gone, 39% for the marine wildlife gone and 76% for the freshwater wildlife gone. Biodiversity took the biggest hit in Latin America, plummeting 83 percent. High-income countries showed a 10% increase in biodiversity, which was canceled out by a loss in low-income countries. This is despite the fact that high-income countries use five times the ecological resources of low-income countries, which was explained as a result of a process whereby wealthy nations are outsourcing resource depletion to poorer nations, which are suffering the greatest ecosystem losses. [180]

A 2017 study published in PLOS One found that the biomass of insect life in Germany had declined by three-quarters in the last 25 years. Dave Goulson of Sussex University stated that their study suggested that humans "appear to be making vast tracts of land inhospitable to most forms of life, and are currently on course for ecological Armageddon. If we lose the insects then everything is going to collapse." [181]

In 2020 the World Wildlife Foundation published a report saying that "biodiversity is being destroyed at a rate unprecedented in human history". The report claims that 68% of the population of the examined species were destroyed in the years 1970 - 2016. [182]

In 2006, many species were formally classified as rare or endangered or threatened moreover, scientists have estimated that millions more species are at risk which have not been formally recognized. About 40 percent of the 40,177 species assessed using the IUCN Red List criteria are now listed as threatened with extinction—a total of 16,119. [184]

Jared Diamond describes an "Evil Quartet" of habitat destruction, overkill, introduced species and secondary extinctions. [185] Edward O. Wilson prefers the acronym HIPPO, standing for Habitat destruction, Invasive species, Pollution, human over-Population and Over-harvesting. [186] [187]

According to the IUCN the main direct threats to conservation fall in 11 categories [188]

1. Residential & commercial development

  • housing & urban areas(urban area]s, suburbs, villages, vacation homes, shopping areas, offices, schools, hospitals)
  • commercial & industrial areas (manufacturing plants, shopping centers, office parks, military bases, power plants, train & shipyards, airports) & recreational areas (skiing, golf courses, sports fields, parks, campgrounds)
    (crop farms, orchards, vineyards, plantations, ranches)(shrimp or finfish aquaculture, fish ponds on farms, hatchery salmon, seeded shellfish beds, artificial algal beds)
    production (geothermal, solar, wind, & tidal farms) production (oil and gas drilling)
  • mining (fuel and minerals)

4. Transportation & service corridors

  • service corridors (electrical & phone wires, aqueducts, oil & gas pipelines)
  • transport corridors (roads, railroads, shipping lanes, and flight paths)
  • collisions with the vehicles using the corridors
  • associated accidents and catastrophes (oil spills, electrocution, fire)

5. Biological resource usages

    (bushmeat, trophy, fur)
  • persecution (predator control and pest control, superstitions)
  • plant destruction or removal (human consumption, free-range livestock foraging, battling timber disease, orchid collection) or wood harvesting (selective or clear-cutting, firewood collection, charcoal production)
  • fishing (trawling, whaling, live coral or seaweed or egg collection)

6. Human intrusions & activities that alter, destroy, simply disturb habitats and species from exhibiting natural behaviors

  • recreational activities (off-road vehicles, motorboats, jet-skis, snowmobiles, ultralight planes, dive boats, whale watching, mountain bikes, hikers, birdwatchers, skiers, pets in recreational areas, temporary campsites, caving, rock-climbing)
  • war, civil unrest, & military exercises (armed conflict, minefields, tanks & other military vehicles, training exercises & ranges, defoliation, munitions testing)
  • illegal activities (smuggling, immigration, vandalism)

7. Natural system modifications

  • fire suppression or creation (controlled burns, inappropriate fire management, escaped agricultural and campfires, arson)(dam construction & operation, wetland filling, surface water diversion, groundwater pumping)
  • other modifications (land reclamation projects, shoreline rip-rap, lawn cultivation, beach construction and maintenance, tree-thinning in parks)
  • removing/reducing human maintenance (mowing meadows, reduction in controlled burns, lack of indigenous management of key ecosystems, ceasing supplemental feeding of condors)

8. Invasive & problematic species, pathogens & genes

    (feral horses & household pets, zebra mussels, Miconia tree, kudzu, introduction for biocontrol)
  • problematic native species (overabundant native deer or kangaroo, overabundant algae due to loss of native grazing fish, locust-type plagues)
  • introduced genetic material (pesticide-resistant crops, genetically modified insects for biocontrol, genetically modified trees or salmon, escaped hatchery salmon, restoration projects using non-local seed stock) & microbes (plague affecting rodents or rabbits, Dutch elm disease or chestnut blight, Chytrid fungus affecting amphibians outside of Africa)
    (untreated sewage, discharges from poorly functioning sewage treatment plants, septic tanks, pit latrines, oil or sediment from roads, fertilizers and pesticides from lawns and golf courses, road salt)
  • industrial & military effluents (toxic chemicals from factories, illegal dumping of chemicals, mine tailings, arsenic from gold mining, leakage from fuel tanks, PCBs in river sediments)
  • agricultural & forestry effluents (nutrient loading from fertilizer run-off, herbicide run-off, manure from feedlots, nutrients from aquaculture, soil erosion)
  • garbage & solid waste (municipal waste, litter & dumped possessions, flotsam & jetsam from recreational boats, waste that entangles wildlife, construction debris)
  • air-borne pollutants (acid rain, smog from vehicle emissions, excess nitrogen deposition, radioactive fallout, wind dispersion of pollutants or sediments from farm fields, smoke from forest fires or wood stoves)
  • excess energy (noise from highways or airplanes, sonar from submarines that disturbs whales, heated water from power plants, lamps attracting insects, beach lights disorienting turtles, atmospheric radiation from ozone holes)

10. Catastrophic geological events

  • ecosystem encroachment (inundation of shoreline ecosystems & drowning of coral reefs from sea level rise, dune encroachment from desertification, woody encroachment into grasslands)
  • changes in geochemical regimes (ocean acidification, changes in atmospheric CO2 affecting plant growth, loss of sediment leading to broad-scale subsidence)
  • changes in temperature regimes (heat waves, cold spells, oceanic temperature changes, melting of glaciers/sea ice)
  • changes in precipitation & hydrological regimes (droughts, rain timing, loss of snow cover, increased severity of floods) events (thunderstorms, tropical storms, hurricanes, cyclones, tornadoes, hailstorms, ice storms or blizzards, dust storms, erosion of beaches during storms)

Habitat destruction Edit

Habitat destruction has played a key role in extinctions, especially in relation to tropical forest destruction. [189] Factors contributing to habitat loss include: overconsumption, overpopulation, land use change, deforestation, [190] pollution (air pollution, water pollution, soil contamination) and global warming or climate change. [191] [192]

Habitat size and numbers of species are systematically related. Physically larger species and those living at lower latitudes or in forests or oceans are more sensitive to reduction in habitat area. [193] Conversion to "trivial" standardized ecosystems (e.g., monoculture following deforestation) effectively destroys habitat for the more diverse species that preceded the conversion. Even the simplest forms of agriculture affect diversity – through clearing/draining the land, discouraging weeds and "pests", and encouraging just a limited set of domesticated plant and animal species. In some countries, property rights [194] or lax law/regulatory enforcement are associated with deforestation and habitat loss. [195]

A 2007 study conducted by the National Science Foundation found that biodiversity and genetic diversity are codependent—that diversity among species requires diversity within a species and vice versa. "If anyone type is removed from the system, the cycle can break down and the community becomes dominated by a single species." [196] At present [update] , the most threatened ecosystems occur in fresh water, according to the Millennium Ecosystem Assessment 2005, which was confirmed by the "Freshwater Animal Diversity Assessment" organised by the biodiversity platform and the French Institut de recherche pour le développement (MNHNP). [197]

Co-extinctions are a form of habitat destruction. Co-extinction occurs when the extinction or decline in one species accompanies similar processes in another, such as in plants and beetles. [198]

A 2019 report has revealed that bees and other pollinating insects have been wiped out of almost a quarter of their habitats across the United Kingdom. The population crashes have been happening since the 1980s and are affecting biodiversity. The increase in industrial farming and pesticide use, combined with diseases, invasive species, and climate change is threatening the future of these insects and the agriculture they support. [199]

In 2019, research was published showing that insects are destroyed by human activities like habitat destruction, pesticide poisoning, invasive species and climate change at a rate that will cause the collapse of ecological systems in the next 50 years if it cannot be stopped. [200]

Introduced and invasive species Edit

Barriers such as large rivers, seas, oceans, mountains and deserts encourage diversity by enabling independent evolution on either side of the barrier, via the process of allopatric speciation. The term invasive species is applied to species that breach the natural barriers that would normally keep them constrained. Without barriers, such species occupy new territory, often supplanting native species by occupying their niches, or by using resources that would normally sustain native species.

The number of species invasions has been on the rise at least since the beginning of the 1900s. Species are increasingly being moved by humans (on purpose and accidentally). In some cases the invaders are causing drastic changes and damage to their new habitats (e.g.: zebra mussels and the emerald ash borer in the Great Lakes region and the lion fish along the North American Atlantic coast). Some evidence suggests that invasive species are competitive in their new habitats because they are subject to less pathogen disturbance. [201] Others report confounding evidence that occasionally suggest that species-rich communities harbor many native and exotic species simultaneously [202] while some say that diverse ecosystems are more resilient and resist invasive plants and animals. [203] An important question is, "do invasive species cause extinctions?" Many studies cite effects of invasive species on natives, [204] but not extinctions. Invasive species seem to increase local (i.e.: alpha diversity) diversity, which decreases turnover of diversity (i.e.: beta diversity). Overall gamma diversity may be lowered because species are going extinct because of other causes, [205] but even some of the most insidious invaders (e.g.: Dutch elm disease, emerald ash borer, chestnut blight in North America) have not caused their host species to become extinct. Extirpation, population decline and homogenization of regional biodiversity are much more common. Human activities have frequently been the cause of invasive species circumventing their barriers, [206] by introducing them for food and other purposes. Human activities therefore allow species to migrate to new areas (and thus become invasive) occurred on time scales much shorter than historically have been required for a species to extend its range.

Not all introduced species are invasive, nor all invasive species deliberately introduced. In cases such as the zebra mussel, invasion of US waterways was unintentional. In other cases, such as mongooses in Hawaii, the introduction is deliberate but ineffective (nocturnal rats were not vulnerable to the diurnal mongoose). In other cases, such as oil palms in Indonesia and Malaysia, the introduction produces substantial economic benefits, but the benefits are accompanied by costly unintended consequences.

Finally, an introduced species may unintentionally injure a species that depends on the species it replaces. In Belgium, Prunus spinosa from Eastern Europe leafs much sooner than its West European counterparts, disrupting the feeding habits of the Thecla betulae butterfly (which feeds on the leaves). Introducing new species often leaves endemic and other local species unable to compete with the exotic species and unable to survive. The exotic organisms may be predators, parasites, or may simply outcompete indigenous species for nutrients, water and light.

At present, several countries have already imported so many exotic species, particularly agricultural and ornamental plants, that their indigenous fauna/flora may be outnumbered. For example, the introduction of kudzu from Southeast Asia to Canada and the United States has threatened biodiversity in certain areas. [207] Nature offers effective ways to help mitigate climate change. [208]

Genetic pollution Edit

Endemic species can be threatened with extinction [209] through the process of genetic pollution, i.e. uncontrolled hybridization, introgression and genetic swamping. Genetic pollution leads to homogenization or replacement of local genomes as a result of either a numerical and/or fitness advantage of an introduced species. [210] Hybridization and introgression are side-effects of introduction and invasion. These phenomena can be especially detrimental to rare species that come into contact with more abundant ones. The abundant species can interbreed with the rare species, swamping its gene pool. This problem is not always apparent from morphological (outward appearance) observations alone. Some degree of gene flow is normal adaptation and not all gene and genotype constellations can be preserved. However, hybridization with or without introgression may, nevertheless, threaten a rare species' existence. [211] [212]

Overexploitation Edit

Overexploitation occurs when a resource is consumed at an unsustainable rate. This occurs on land in the form of overhunting, excessive logging, poor soil conservation in agriculture and the illegal wildlife trade.

About 25% of world fisheries are now overfished to the point where their current biomass is less than the level that maximizes their sustainable yield. [213]

The overkill hypothesis, a pattern of large animal extinctions connected with human migration patterns, can be used to explain why megafaunal extinctions can occur within a relatively short time period. [214]

Hybridization, genetic pollution/erosion and food security Edit

In agriculture and animal husbandry, the Green Revolution popularized the use of conventional hybridization to increase yield. Often hybridized breeds originated in developed countries and were further hybridized with local varieties in the developing world to create high yield strains resistant to local climate and diseases. Local governments and industry have been pushing hybridization. Formerly huge gene pools of various wild and indigenous breeds have collapsed causing widespread genetic erosion and genetic pollution. This has resulted in the loss of genetic diversity and biodiversity as a whole. [215]

Genetically modified organisms contain genetic material that is altered through genetic engineering. Genetically modified crops have become a common source for genetic pollution in not only wild varieties, but also in domesticated varieties derived from classical hybridization. [216] [217] [218] [219] [220]

Genetic erosion and genetic pollution have the potential to destroy unique genotypes, threatening future access to food security. A decrease in genetic diversity weakens the ability of crops and livestock to be hybridized to resist disease and survive changes in climate. [215]

Climate change Edit

Global warming is a major threat to global biodiversity. [221] [222] For example, coral reefs – which are biodiversity hotspots – will be lost within the century if global warming continues at the current rate. [223] [224]

Climate change has proven to affect biodiversity and evidence supporting the altering effects is widespread. Increasing atmospheric carbon dioxide certainly affects plant morphology [225] and is acidifying oceans, [226] and temperature affects species ranges, [227] [228] [229] phenology, [230] and weather, [231] but, mercifully, the major impacts that have been predicted are still potential futures. We have not documented major extinctions yet, even as climate change drastically alters the biology of many species.

In 2004, an international collaborative study on four continents estimated that 10 percent of species would become extinct by 2050 because of global warming. "We need to limit climate change or we wind up with a lot of species in trouble, possibly extinct," said Dr. Lee Hannah, a co-author of the paper and chief climate change biologist at the Center for Applied Biodiversity Science at Conservation International. [232]

A recent study predicts that up to 35% of the world terrestrial carnivores and ungulates will be at higher risk of extinction by 2050 because of the joint effects of predicted climate and land-use change under business-as-usual human development scenarios. [233]

Climate change has advanced the time of evening when Brazilian free-tailed bats (Tadarida brasiliensis) emerge to feed. This change is believed to be related to the drying of regions as temperatures rise. This earlier emergence exposes the bats to greater predation increased competition with other insectivores who feed in the twilight or daylight hours. [234]

Human overpopulation Edit

The world's population numbered nearly 7.6 billion as of mid-2017 (which is approximately one billion more inhabitants compared to 2005) and is forecast to reach 11.1 billion in 2100. [235] Sir David King, former chief scientific adviser to the UK government, told a parliamentary inquiry: "It is self-evident that the massive growth in the human population through the 20th century has had more impact on biodiversity than any other single factor." [236] [237] At least until the middle of the 21st century, worldwide losses of pristine biodiverse land will probably depend much on the worldwide human birth rate. [238] Biologists such as Paul R. Ehrlich and Stuart Pimm have noted that human population growth and overconsumption are the main drivers of species extinction. [239] [240] [241]

According to a 2020 study by the World Wildlife Fund, the global human population already exceeds planet's biocapacity – it would take the equivalent of 1.56 Earths of biocapacity to meet our current demands. [242] The 2014 report further points that if everyone on the planet had the Footprint of the average resident of Qatar, we would need 4.8 Earths and if we lived the lifestyle of a typical resident of the US, we would need 3.9 Earths. [180]

Rates of decline in biodiversity in this sixth mass extinction match or exceed rates of loss in the five previous mass extinction events in the fossil record. [243] [244] [245] [246] [247] [248] [249] Loss of biodiversity results in the loss of natural capital that supplies ecosystem goods and services. From the perspective of the method known as Natural Economy the economic value of 17 ecosystem services for Earth's biosphere (calculated in 1997) has an estimated value of US$33 trillion (3.3x10 13 ) per year. [250] Species today are being wiped out at a rate 100 to 1,000 times higher than baseline, and the rate of extinctions is increasing. This process destroys the resilience and adaptability of life on Earth. [251]

In 2019, a summary for policymakers of the largest, most comprehensive study to date of biodiversity and ecosystem services, the Global Assessment Report on Biodiversity and Ecosystem Services, was published by the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES). The main conclusions:

1. Over the last 50 years, the state of nature has deteriorated at an unprecedented and accelerating rate.

2. The main drivers of this deterioration have been changes in land and sea use, exploitation of living beings, climate change, pollution, and invasive species. These five drivers, in turn, are caused by societal behaviors, from consumption to governance.

3. Damage to ecosystems undermines 35 of 44 selected UN targets, including the UN General Assembly's Sustainable Development Goals for poverty, hunger, health, water, cities' climate, oceans, and land. It can cause problems with food, water and humanity's air supply.

4. To fix the problem, humanity will need a transformative change, including sustainable agriculture, reductions in consumption and waste, fishing quotas and collaborative water management. On page 8 the report proposes on page 8 of the summary " enabling visions of a good quality of life that do not entail ever-increasing material consumption" as one of the main measures. The report states that "Some pathways chosen to achieve the goals related to energy, economic growth, industry and infrastructure and sustainable consumption and production (Sustainable Development Goals 7, 8, 9 and 12), as well as targets related to poverty, food security and cities (Sustainable Development Goals 1, 2 and 11), could have substantial positive or negative impacts on nature and therefore on the achievement of other Sustainable Development Goals". [252] [253]

The October 2020 "Era of Pandemics" report by IPBES asserted that the same human activities which are the underlying drivers of climate change and biodiversity loss are also the same drivers of pandemics, including the COVID-19 pandemic. Dr. Peter Daszak, Chair of the IPBES workshop, said "there is no great mystery about the cause of the COVID-19 pandemic – or of any modern pandemic . . . Changes in the way we use land the expansion and intensification of agriculture and unsustainable trade, production and consumption disrupt nature and increase contact between wildlife, livestock, pathogens and people. This is the path to pandemics." [254] [45]

Conservation biology matured in the mid-20th century as ecologists, naturalists and other scientists began to research and address issues pertaining to global biodiversity declines. [256] [257] [258]

The conservation ethic advocates management of natural resources for the purpose of sustaining biodiversity in species, ecosystems, the evolutionary process and human culture and society. [244] [256] [258] [259] [260]

Conservation biology is reforming around strategic plans to protect biodiversity. [256] [261] [262] Preserving global biodiversity is a priority in strategic conservation plans that are designed to engage public policy and concerns affecting local, regional and global scales of communities, ecosystems and cultures. [263] Action plans identify ways of sustaining human well-being, employing natural capital, market capital and ecosystem services. [264] [265]

In the EU Directive 1999/22/EC zoos are described as having a role in the preservation of the biodiversity of wildlife animals by conducting research or participation in breeding programs. [266]

Protection and restoration techniques Edit

Removal of exotic species will allow the species that they have negatively impacted to recover their ecological niches. Exotic species that have become pests can be identified taxonomically (e.g., with Digital Automated Identification SYstem (DAISY), using the barcode of life). [267] [268] Removal is practical only given large groups of individuals due to the economic cost.

As sustainable populations of the remaining native species in an area become assured, "missing" species that are candidates for reintroduction can be identified using databases such as the Encyclopedia of Life and the Global Biodiversity Information Facility.

    places a monetary value on biodiversity. One example is the Australian Native Vegetation Management Framework. are collections of specimens and genetic material. Some banks intend to reintroduce banked species to the ecosystem (e.g., via tree nurseries). [269]
  • Reduction and better targeting of pesticides allows more species to survive in agricultural and urbanized areas.
  • Location-specific approaches may be less useful for protecting migratory species. One approach is to create wildlife corridors that correspond to the animals' movements. National and other boundaries can complicate corridor creation. [270]

Protected areas, including forest reserves and biosphere reserves, serve many functions including for affording protection to wild animals and their habitat. [271] Protected areas have been set up all over the world with the specific aim of protecting and conserving plants and animals. Some scientists have called on the global community to designate as protected areas of 30 percent of the planet by 2030, and 50 percent by 2050, in order to mitigate biodiversity loss from anthropogenic causes. [272] In a study published September 4 in Science Advances researchers mapped out regions that can help meet critical conservation and climate goals. [273]

Protected areas safeguard nature and cultural resources and contribute to livelihoods, particularly at local level. There are over 238 563 designated protected areas worldwide, equivalent to 14.9 percent of the earth's land surface, varying in their extension, level of protection, and type of management (IUCN, 2018). [274]

Forest protected areas are a subset of all protected areas in which a significant portion of the area is forest. [65] This may be the whole or only a part of the protected area. [65] Globally, 18 percent of the world's forest area, or more than 700 million hectares, fall within legally established protected areas such as national parks, conservation areas and game reserves. [65]

The benefits of protected areas extend beyond their immediate environment and time. In addition to conserving nature, protected areas are crucial for securing the long-term delivery of ecosystem services. They provide numerous benefits including the conservation of genetic resources for food and agriculture, the provision of medicine and health benefits, the provision of water, recreation and tourism, and for acting as a buffer against disaster. Increasingly, there is acknowledgement of the wider socioeconomic values of these natural ecosystems and of the ecosystem services they can provide. [276]

Forest protected areas in particular play many important roles including as a provider of habitat, shelter, food and genetic materials, and as a buffer against disaster. They deliver stable supplies of many goods and environmental services. The role of protected areas, especially forest protected areas, in mitigating and adapting to climate change has increasingly been recognized over the last few years. Protected areas not only store and sequester carbon (i.e. the global network of protected areas stores at least 15 percent of terrestrial carbon), but also enable species to adapt to changing climate patterns by providing refuges and migration corridors. Protected areas also protect people from sudden climate events and reduce their vulnerability to weather-induced problems such as floods and droughts (UNEP–WCMC, 2016).

National parks Edit

National park is a large natural or near natural areas set aside to protect large-scale ecological processes, which also provide a foundation for environmentally and culturally compatible, spiritual, scientific, educational, recreational and visitor opportunities. These areas are selected by governments or private organizations to protect natural biodiversity along with its underlying ecological structure and supporting environmental processes, and to promote education and recreation. The International Union for Conservation of Nature (IUCN), and its World Commission on Protected Areas (WCPA), has defined "National Park" as its Category II type of protected areas. [277]

National parks are usually owned and managed by national or state governments. In some cases, a limit is placed on the number of visitors permitted to enter certain fragile areas. Designated trails or roads are created. The visitors are allowed to enter only for study, cultural and recreation purposes. Forestry operations, grazing of animals and hunting of animals are regulated and the exploitation of habitat or wildlife is banned.

Wildlife sanctuary Edit

Wildlife sanctuaries aim only at the conservation of species and have the following features:

  1. The boundaries of the sanctuaries are not limited by state legislation.
  2. The killing, hunting or capturing of any species is prohibited except by or under the control of the highest authority in the department which is responsible for the management of the sanctuary.
  3. Private ownership may be allowed. and other usages can also be permitted.

Forest reserves Edit

There is an estimated 726 million ha of forest in protected areas worldwide. Of the six major world regions, South America has the highest share of forests in protected areas, 31 percent. [278]

The forests play a vital role in harboring more than 45,000 floral and 81,000 faunal species of which 5150 floral and 1837 faunal species are endemic. [279] In addition, there are 60,065 different tree species in the world. [280] Plant and animal species confined to a specific geographical area are called endemic species. In forest reserves, rights to activities like hunting and grazing are sometimes given to communities living on the fringes of the forest, who sustain their livelihood partially or wholly from forest resources or products. The unclassed forests cover 6.4 percent of the total forest area and they are marked by the following characteristics:

  1. They are large inaccessible forests.
  2. Many of these are unoccupied.
  3. They are ecologically and economically less important.

Steps to conserve the forest cover Edit

  1. An extensive reforestation/afforestation programme should be followed.
  2. Alternative environment-friendly sources of fuel energy such as biogas other than wood should be used.
  3. Loss of biodiversity due to forest fire is a major problem, immediate steps to prevent forest fire need to be taken. by cattle can damage a forest seriously. Therefore, certain steps should be taken to prevent overgrazing by cattle.
  4. Hunting and poaching should be banned.

Zoological parks Edit

In zoological parks or zoos, live animals are kept for public recreation, education and conservation purposes. Modern zoos offer veterinary facilities, provide opportunities for threatened species to breed in captivity and usually build environments that simulate the native habitats of the animals in their care. Zoos play a major role in creating awareness about the need to conserve nature.

Botanical gardens Edit

In botanical gardens, plants are grown and displayed primarily for scientific and educational purposes. They consist of a collection of living plants, grown outdoors or under glass in greenhouses and conservatories. Also, a botanical garden may include a collection of dried plants or herbarium and such facilities as lecture rooms, laboratories, libraries, museums and experimental or research plantings.

Focusing on limited areas of higher potential biodiversity promises greater immediate return on investment than spreading resources evenly or focusing on areas of little diversity but greater interest in biodiversity. [281]

A second strategy focuses on areas that retain most of their original diversity, which typically require little or no restoration. These are typically non-urbanized, non-agricultural areas. Tropical areas often fit both criteria, given their natively high diversity and relative lack of development. [282]

In society Edit

In September 2020 scientists reported that "immediate efforts, consistent with the broader sustainability agenda but of unprecedented ambition and coordination, could enable the provision of food for the growing human population while reversing the global terrestrial biodiversity trends caused by habitat conversion" and recommend measures such as for addressing drivers of land-use change, and for increasing the extent of land under conservation management, efficiency in agriculture and the shares of plant-based diets. [283] [284]

International Edit

  • United Nations Convention on Biological Diversity (1992) and Cartagena Protocol on Biosafety
  • Convention on International Trade in Endangered Species (CITES) (Wetlands) on Migratory Species
  • United Nations Convention concerning the Protection of the World's Cultural and Natural Heritage (indirectly by protecting biodiversity habitats)
  • Regional Conventions such as the Apia Convention
  • Bilateral agreements such as the Japan-Australia Migratory Bird Agreement.

Global agreements such as the Convention on Biological Diversity, give "sovereign national rights over biological resources" (not property). The agreements commit countries to "conserve biodiversity", "develop resources for sustainability" and "share the benefits" resulting from their use. Biodiverse countries that allow bioprospecting or collection of natural products, expect a share of the benefits rather than allowing the individual or institution that discovers/exploits the resource to capture them privately. Bioprospecting can become a type of biopiracy when such principles are not respected. [285]

Sovereignty principles can rely upon what is better known as Access and Benefit Sharing Agreements (ABAs). The Convention on Biodiversity implies informed consent between the source country and the collector, to establish which resource will be used and for what and to settle on a fair agreement on benefit sharing.

European Union Edit

In May 2020, the European Union published its Biodiversity Strategy for 2030. The biodiversity strategy is an essential part of the climate change mitigation strategy of the European Union. From the 25% of the European budget that will go to fight climate change, large part will go to restore biodiversity and nature based solutions.

  • Protect 30% of the sea territory and 30% of the land territory especially Old-growth forests.
  • Plant 3 billion trees by the year 2030.
  • Restore at least 25,000 kilometers of rivers, so they will become free flowing.
  • Reduce the use of Pesticides by 50% by the year 2030.
  • Increase Organic farming. In linked EU program From Farm to Fork it is said, that the target is making 25% of EU agriculture organic, by the year 2030. [286]
  • Increase Biodiverisity in agriculture.
  • Give €20 billion per year to the issue and make it part of the business practice.

Approximately half of the global GDP depend on nature. In Europe many parts of the economy that generate trillions of euros per year depend on nature. The benefits of Natura 2000 alone in Europe are €200 - €300 billion per year. [287]

National level laws Edit

Biodiversity is taken into account in some political and judicial decisions:

  • The relationship between law and ecosystems is very ancient and has consequences for biodiversity. It is related to private and public property rights. It can define protection for threatened ecosystems, but also some rights and duties (for example, fishing and hunting rights). [citation needed]
  • Law regarding species is more recent. It defines species that must be protected because they may be threatened by extinction. The U.S. Endangered Species Act is an example of an attempt to address the "law and species" issue.
  • Laws regarding gene pools are only about a century old. [citation needed] Domestication and plant breeding methods are not new, but advances in genetic engineering have led to tighter laws covering distribution of genetically modified organisms, gene patents and process patents. [288] Governments struggle to decide whether to focus on for example, genes, genomes, or organisms and species. [citation needed]

Uniform approval for use of biodiversity as a legal standard has not been achieved, however. Bosselman argues that biodiversity should not be used as a legal standard, claiming that the remaining areas of scientific uncertainty cause unacceptable administrative waste and increase litigation without promoting preservation goals. [289]

India passed the Biological Diversity Act in 2002 for the conservation of biological diversity in India. The Act also provides mechanisms for equitable sharing of benefits from the use of traditional biological resources and knowledge.

Taxonomic and size relationships Edit

Less than 1% of all species that have been described have been studied beyond simply noting their existence. [290] The vast majority of Earth's species are microbial. Contemporary biodiversity physics is "firmly fixated on the visible [macroscopic] world". [291] For example, microbial life is metabolically and environmentally more diverse than multicellular life (see e.g., extremophile). "On the tree of life, based on analyses of small-subunit ribosomal RNA, visible life consists of barely noticeable twigs. The inverse relationship of size and population recurs higher on the evolutionary ladder—to a first approximation, all multicellular species on Earth are insects". [292] Insect extinction rates are high—supporting the Holocene extinction hypothesis. [293] [294]

The number of morphological attributes that can be scored for diversity study is generally limited and prone to environmental influences thereby reducing the fine resolution required to ascertain the phylogenetic relationships. DNA based markers- microsatellites otherwise known as simple sequence repeats (SSR) were therefore used for the diversity studies of certain species and their wild relatives.

In the case of cowpea, a study conducted to assess the level of genetic diversity in cowpea germplasm and related wide species, where the relatedness among various taxa was compared, primers useful for classification of taxa identified, and the origin and phylogeny of cultivated cowpea classified show that SSR markers are useful in validating with species classification and revealing the center of diversity. [295]

This article incorporates text from a free content work. Licensed under CC BY-SA 3.0 License statement/permission on Wikimedia Commons. Text taken from Global Forest Resources Assessment 2020 Key findings, FAO, FAO. To learn how to add open license text to Wikipedia articles, please see this how-to page. For information on reusing text from Wikipedia, please see the terms of use.

This article incorporates text from a free content work. Licensed under CC BY-SA 3.0 License statement/permission on Wikimedia Commons. Text taken from The State of the World’s Forests 2020. Forests, biodiversity and people – In brief, FAO & UNEP, FAO & UNEP. To learn how to add open license text to Wikipedia articles, please see this how-to page. For information on reusing text from Wikipedia, please see the terms of use.

How to Measure Species Diversity?

Any measure of species diversity, by itself, does not convey much information we appreciate its significance only when we compare with any other measure.

Measures of species diversity can be divided into three categories (Magurran, 1988).

(i) Species richness indices,

(ii) Species abundance models, and

(iii) Species proportional abundance based indices

Species Richness Indices:

Species richness, as measure of diversity, has been used by ecologists. Species density or the number of species per m 2 is most commonly used to measure species richness. However, species richness increases with sample size. The smallest sample size may be 1 km^ and the largest may be the entire region or country.

As the sample sizes are always unequal, Sanders technique called Rarefaction is used to cope with this difficulty.

Sanders’s formula, as modified by Hurlbert (1971) is as follows:

The simplest approach is to take the number of individuals in the smallest sample as the standardized sample size.

This may be explained with the help of the following example:

If in one catch of fish we obtain 9 species with 23 individuals, and in another catch from the same area made for the same duration we obtained only 13 individuals belonging to 6 species, Hurlberts’ formula may be used to find out the number of species we would have expected in the first catch if it too had only 13 individuals. Thus, expected number of species for the first catch x is 6.6 species (Table 7.4).

This index is based on the ratio of number of species (S) and the square root of the total number of individuals (N).

It is claimed that this index may be used to compare samples of different sizes and that the effect of the number of individuals is reduced. However, some authors have shown that this index is not independent of sample size.

Using the data given in Table 7.4, the value of IMn for catch x and catch y will be 1.88 and 1.66 respectively.

This index also relates the number of species to the number of individuals.

The index is influenced by sample size. However, some authors have demonstrated that both this and Manhinick’s index are insensitive to changes in community structure.

Using the data given in Table 7.4, the value of for sample x and sample y will be 2.55 and 1.95 respectively.

Species Abundance Models:

No community has species of equal abundance. Some species are very abundant, others may have medium abundance and still others may be rare or represented by only a few individuals. This observation led to the development of species abundance models.

Species diversity data is frequently described by one or more patterns of distribution (Piclou, 1975), diversity is usually examined in relation to the following four models:

(b) The log normal distribution

(d) The broken stick model (the random niche boundary hypothesis)

When plotted on a rank abundance graph, the four models represent a progression ranging from the geometric series where a few species are dominant with the remaining fairly uncommon, through the log series and log normal distributions where species of intermediate abundance become more common and ending in the conditions represented by the broken stick model in which species are equally abundant as may be hardly observed.

Species Proportional Abundance Based Indices:

These indices provide an alternative approach to the measurement of diversity. These indices are called heterogeneity indices (Peet 1974) as they take both species richness and evenness into consideration. South wood (1978) called them nonparametric indices in view of the fact that no assumptions are made about the shape of the underlying species abundance distribution. The following indices are used.

This index relates the contribution made by each species to the total number of individuals present.

Where pi is the proportion of individuals in the ith species. The equation given by Wilhm (1967) is the following:

Where pi = the number of individuals in the ith species and N= the total number of individuals. The values of Simpson’s index range from zero to 1 (unity) and are inversely proportional to the wealth of species (As I increases, diversity decreases). Pielou (1969) has given the following form of equation.

Therefore, index is usually expressed as 1 – I or l/I. The reciprocal form of Simpson’s index ensures that the value of the index increases with diversity.

The index independently derived by Shannon and Wiener from the application of information theory is known as the Sharmon index of diversity. It is sometimes incorrectly referred to as the Shannon – weaver index (Krebs, 1985).

The index assumes that:

(a) All species are represented in the sample, and

(b) Individuals are randomly sampled from an ‘indefinitely large’ population (Pielou, 1975).

It is calculated from the equation:

Where pi is the proportion of individuals found in the ith species. It is estimated as (ni/N). N is total number of individuals in S species. The value of Shannon index usually varies between 1.5 and 3.5 and rarely exceeds 4.5. The value of H’ is related to species richness but is also influenced by the underlying species abundance distribution. May (1975) has shown that if the underlying distribution is log normal, 10 species will be required to give a value of H’ < 5.0. Log2 is often used to calculate Shannon index. Usually the index is obtained from the series.


@. Biodiversity- definition: “variability among living organisms”
@. Biodiversity is the variety and variability of genus, species and ecosystem between and within
@. It is the number of different organisms & their relative frequency in an ecosystem
@. The term Biodiversity is coined by Walter Rosen, 1985
@. About 50 million sps. of plants, animals & microbes are existing in the world
@. Among this only 2 million are identified so far

@. Biodiversity also includes: Variability of genus, Variability of varieties, Variability of species, Variability of populations in different ecosystems, Variability in relative abundance of species
@. Knowledge of biodiversity is essential for sustainable utilization of resources
@. Biological resources provide us: Nourishment, Clothing, House, Fuel, Medicine and Revenue

Levels of biodiversity:

@. Biodiversity can be considered in THREE levels

(1). Genetic diversity: Genetic variation within species, both among individuals within single population and among geographically separated populations

(2). Species diversity: Biodiversity covers the full range of species on earth. Includes all the species, microbes, viruses, bacteria to animals and plants

(3). Ecosystem / community diversity: Biodiversity also includes variations in the geographical communities. This includes: Variations in the community in which the species lives, The ecosystem in which the community exists, Interaction within and between biotic and abiotic components

Types of biodiversity:

There are different types of biodiversity can be observed in nature, they are

(1). Genetic diversity: diversity in the alleles of a single gene

(2). Organismal diversity: differences in morphology, anatomy, behaviour of organisms

(3). Population diversity: variations observed quantitative ecological parameters such as frequency, density, abundance etc.

(4). Species diversity: Measures the species number variations in different genera at a particular habitat

(5). Community diversity: variability among community composition of and ecosystem and variations in the ecological interactions

(6). Ecosystem diversity: deals with the variations of interdependence of biotic and abiotic factors in the ecosystem

(7). Landscape diversity: measures the species composition in different landscapes

(8). Biogeographic diversity: diversity observed in geological and geographic history over a large period of time

Measuring biodiversity:

Ø. At simplest level: biodiversity is the species richness

Ø. Various levels/parameters of measuring the biodiversity are:

(1). Alpha diversity

(2). Beta diversity

(3). Gamma diversity

(1). Alpha diversity:

Ø Alpha diversity refers to number of species in a single community at a particular time

Ø Alpha diversity is better called as species richness

Ø Alpha diversity is used to compare number of species in different communities

(2). Beta diversity:

Ø It is the measure of degree of change in species composition along with an environmental gradient

Ø Example: Beta diversity is high, if the species composition of moss communities changes successively at higher elevations on a mountain slope. Beta diversity is low if same species of moss occupy the whole mountain side

(3). Gamma diversity:

Ø Gamma diversity applies to large geographic scale

Ø Gamma diversity is the rate at which additional species are encountered as geographical replacements within a habitat type in different localities

Ø Gamma diversity is a species turnover rate with distance between sites of similar habitat or with expanding geographic areas”

Uses of biodiversity:

Ø Biodiversity, besides its ecological significance, provides a socio-economic asset to the nation

Ø Uses related to biodiversity can be grouped into three categories:

(1). Productive use

(2). Consumptive use

(3). Indirect use

(1). Productive use:

Ø Products commercially harvested from biodiversity for exchange in market

Ø Productive value of biodiversity is concerned with national income

Ø Biodiversity provides: fuel, timber, fish, fodder, fruits, honey, cereals, medicinal plants etc.

Ø In India, income from biodiversity is nearly 30% (736.88 billion rupees, 1994-95)

(2). Consumptive use:

Ø Consumptive use of biodiversity deals with natural products that are consumed directly

Ø They are goods which do not come under normal circulation of trade

Ø Example: non timber forest products, Honey collected from forests, Medicine collected from forests

(3). Indirect use:

Ø Indict use is the most significant us of biodiversity

Ø This value is related primarily with functions of ecosystem

Ø Biodiversity is very essential for: Ecological balance, Constancy of climatic features and Soil maintenance

Importance/Significance of biodiversity:

Ø Biodiversity indicates variations of life forms (species, ecosystem, biome)

Ø Biodiversity indicate the health of ecosystem

Ø Biodiversity is in part a functioning of climate

Ø Biodiversity provides services like: Air quality and purity, Climate and seasons, Water purification, Pollination and seed dispersal, Prevention of erosion

Ø Non material benefits of biodiversity are: Spiritual values, Aesthetic values, Education and knowledge systems

Ø In agriculture biodiversity assist in the recovery of major cultivar when it is under sever attack of disease or pests

Ø Biodiversity also act as a store house of germplasm of commercially important plants

Ø About 80% of humans’ food supply comes from 20 kinds of plants, but human uses at least 40,000 species, all of them are the part of biodiversity

Ø There are more plant products to be discovered from diversity, they are kept hidden in the depth of species richness

Ø Biodiversity also support in drug discovery for modern diseases

Ø Most of the drugs which are now in commercial trade are derived directly or indirectly from biological resources

Ø About 50% of drugs used in US are derived from biodiversity

Ø According to WHO, 80% of world population depends on medicines from nature (biodiversity is the integral part of nature)

Ø Many industrial materials are deriving from biological sources. These include building materials, fibbers, dyes, rubber and oil

Ø Biodiversity provide security of resources such as water, timber, paper, fibre and food

Ø Biodiversity support leisure activities such bird watching and trucking

Ø Biodiversity also inspires musicians, painters and writers

Ø Gardening, fishing & specimen collecting are depends on biodiversity

Ø Biodiversity supports many ecosystem services that are not readily visible

Ø Biodiversity has immense role in the regulation of the chemistry of our atmosphere and water supply

Ø Biodiversity Helps in water purification, recycling nutrients and providing fertile soil

Definitions for ecosystem diversity ecosys·tem di·ver·si·ty

Ecosystem diversity deals with the variations in ecosystems within a geographical location and its overall impact on human existence and the environment. Ecological diversity is a type of biodiversity. It is the variation in the ecosystems found in a region or the variation in ecosystems over the whole planet. Biodiversity is important because it clears out our water, changes out climate, and provides us with food. Ecological diversity includes the variation in both terrestrial and aquatic ecosystems. Ecological diversity can also take into account the variation in the complexity of a biological community, including the number of different niches, the number of trophic levels and other ecological processes. An example of ecological diversity on a global scale would be the variation in ecosystems, such as deserts, forests, grasslands, wetlands and oceans. Ecological diversity is the largest scale of biodiversity, and within each ecosystem, there is a great deal of both species and genetic diversity.

Freebase (3.66 / 24 votes) Rate this definition:

Ecosystem diversity refers to the diversity of a place at the level of ecosystems. The term differs from biodiversity, which refers to variation in species rather than ecosystems. Ecosystem diversity can also refer to the variety of ecosystems present in a biosphere, the variety of species and ecological processes that occur in different physical settings.

N.A.S. led the field work, analysis, and writing. S.M.M. assisted with field work, data collection and organization for trait databases, and analysis. J.R.B. and P.L.L. led field work and provided feedback on experimental design and manuscript preparation. B.M.S. and R.J.S. led experimental design, funded efforts, and actively advised all stages of project development.

All authors and contributors to this work have followed the Committee on Publication Ethics (COPE) code of conduct and ethics.

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