Biodiversity

Source: Wikipedia, the free encyclopedia.

fungi in a forest in Northern Saskatchewan (in this photo, there are also leaf lichens and mosses
).

Biodiversity or biological diversity is the variety and variability of

ecological, and cultural processes that sustain life.[2]

More than 99.9% of all species that ever lived on Earth, amounting to over five billion species, are estimated to be extinct. Estimates on the number of Earth's current species range from 10 million to 14 million, of which about 1.2 million have been documented and over 86% have not yet been described. The total amount of related DNA base pairs on Earth is estimated at 5.0 x 1037 and weighs 50 billion tonnes. In comparison, the total mass of the biosphere has been estimated to be as much as four trillion tons of carbon. In July 2016, scientists reported identifying a set of 355 genes from the last universal common ancestor (LUCA) of all organisms living on Earth.

The

Western Greenland. More recently, in 2015, "remains of biotic life" were found in 4.1 billion-year-old rocks in Western Australia. According to one of the researchers, "If life arose relatively quickly on Earth...then it could be common in the universe."[3]

Since

mass extinction events. In the Carboniferous, rainforest collapse led to a great loss of plant and animal life. The Permian–Triassic extinction event, 251 million years ago, was the worst; vertebrate recovery took 30 million years. The most recent, the Cretaceous–Paleogene extinction event, occurred 65 million years ago and has often attracted more attention than others because it resulted in the extinction of the non-avian dinosaurs
.

Rapid

humans has displayed an ongoing biodiversity reduction and an accompanying loss of genetic diversity named the Holocene extinction, and often referred to as the sixth mass extinction. The reduction is caused primarily by human impacts, particularly habitat destruction. Conversely, biodiversity positively impacts human health
in many ways, although a few negative effects are studied.

History of the term

Definitions

"Biodiversity" is most commonly used to replace the more clearly-defined and long-established terms, species diversity and species richness.[15] Biologists most often define biodiversity as the "totality of

ecosystems of a region".[16][17]
An advantage of this definition is that it presents a unified view of the traditional types of biological variety previously identified:

Other definitions include (in chronological order):

Number of species

According to Mora and colleagues' estimation, there are approximately 8.7 million terrestrial species and 2.2 million oceanic species. The authors note that these estimates are strongest for eukaryotic organisms and likely represent the lower bound of prokaryote diversity.[25] Other estimates include:

  • 220,000
    vascular plants, estimated using the species-area relation method[26]
  • 0.7-1 million marine species[27]
  • 10–30 million insects;[28] (of some 0.9 million we know today)[29]
  • 5–10 million bacteria;[30]
  • 1.5-3 million
    cryptic speciation.[31] Some 0.075 million species of fungi had been documented by 2001;[32]
  • 1 million mites[33]
  • 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.[34] The findings may eventually cause a significant change in the way science defines species and other taxonomic categories.[35][36]

Since the rate of extinction has increased, many extant species may become extinct before they are described.

animals groups.[38]

Loss of biodiversity

During the last century, decreases in biodiversity have been increasingly observed. It was estimated in 2007 that up to 30% of all species will be extinct by 2050.

background extinction rates.[40][42][43] and expected to still grow in the upcoming years.[43][44][45] As of 2012, some studies suggest that 25% of all mammal species could be extinct in 20 years.[46]

In absolute terms, the planet has lost 58% of its biodiversity since 1970 according to a 2016 study by the World Wildlife Fund.[47] 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.[48]

A 2017 study published in

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."[50]

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.[51]

Distribution

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 interactions between other species.[52] The study of the spatial distribution of organisms, species and ecosystems, is the science of biogeography.[53][54]

Diversity consistently measures higher in the

Yasuní National Park in Ecuador, have particularly high biodiversity.[55][56]

Terrestrial biodiversity is thought to be up to 25 times greater than ocean biodiversity.[57] 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.[58] 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.[59] However, this estimate seems to under-represent the diversity of microorganisms.[60] 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.[58] Forests span around 4 billion acres (nearly a third of the earth's land mass) and are home to approximately 80% of the world's biodiversity. About 1 billion hectares are covered by primary forests. Over 700 million hectares of the world's woods are officially protected.[61][62]

The biodiversity of forests varies considerably according to factors such as forest type, geography, climate and soils – in addition to human use.[58] 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.[58] 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.[58] European forests in EU and non-EU nations comprise more than 30% of Europe's land mass (around 227 million hectares), representing an almost 10% growth since 1990.[63][64]

Latitudinal gradients

Generally, there is an increase in biodiversity from the

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.[65][66][67]

Even though terrestrial biodiversity declines from the equator to the poles,

marine ecosystems.[69] The latitudinal distribution of parasites does not appear to follow this rule.[53]

In 2016, an alternative hypothesis ("the

hypervolume. In this way, it is possible to build fractal hyper volumes, whose fractal dimension rises to three moving towards the equator.[71]

Biodiversity Hotspot

A biodiversity hotspot is a region with a high level of endemic species that have experienced great habitat loss.[72] The term hotspot was introduced in 1988 by Norman Myers.[73][74][75][76] 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.[77][78] 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.[79] Madagascar dry deciduous forests and lowland rainforests possess a high ratio of endemism.[80][81] Since the island separated from mainland Africa 66 million years ago, many species and ecosystems have evolved independently.[82] Indonesia's 17,000 islands cover 735,355 square miles (1,904,560 km2) 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.[83] 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.[81]

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."[84]

Evolution

History

Biodiversity is the result of 3.5 billion years of

protozoans and protists.[60]

Apparent marine fossil diversity during the Phanerozoic[86]

The history of biodiversity during the

Permian-Triassic extinction event, 251 million years ago. Vertebrates took 30 million years to recover from this event.[89]

The biodivertisy of the past is called Paleobiodiversity. The

fossil record suggests that the last few million years featured the greatest biodiversity in history.[18] 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.[90] Some scientists believe that corrected for sampling artifacts, modern biodiversity may not be much different from biodiversity 300 million years ago,[87] whereas others consider the fossil record reasonably reflective of the diversification of life.[18] Estimates of the present global macroscopic species diversity vary from 2 million to 100 million, with a best estimate of somewhere near 9 million,[59] the vast majority arthropods.[91] Diversity appears to increase continually in the absence of natural selection.[92]

Diversification

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.[18] 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."[18]

It also appears that the diversity continues to increase over time, especially after mass extinctions.[93]

On the other hand, changes through the

end-Permian extinction.[94] 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.[95] The hyperbolic character of biodiversity growth can be similarly accounted for by a feedback between diversity and community structure complexity.[95][96] 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.[95][96]

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.[97] It has been argued that the present rate of extinction is sufficient to eliminate most species on the planet Earth within 100 years.[98]

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).[91] 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.[59]

Role and benefits of biodiversity

Summer field in Belgium (Hamois). The blue flowers are Centaurea cyanus and the red are Papaver rhoeas
.

General ecosystem 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 (3.3x1013) per year.[99]

"Ecosystem services are the suite of benefits that ecosystems provide to humanity."[100] 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.[101] These services come in three flavors:

  1. Provisioning services which involve the production of renewable resources (e.g.: food, wood, fresh water)[100]
  2. Regulating services which are those that lessen environmental change (e.g.: climate regulation, pest/disease control)[100]
  3. Cultural services represent human value and enjoyment (e.g.: landscape aesthetics, cultural heritage, outdoor recreation and spiritual significance)[102]

There have been many claims about biodiversity's effect on these ecosystem services, especially provisioning and regulating services.[100] 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.[100]

Services enhanced

Provisioning services

Greater species diversity

  • of plants increases fodder yield (synthesis of 271 experimental studies).[54]
  • of plants (i.e. diversity within a single species) increases overall crop yield (synthesis of 575 experimental studies).[103] Although another review of 100 experimental studies reports mixed evidence.[104]
  • of trees increases overall wood production (Synthesis of 53 experimental studies).[105] However, there is not enough data to draw a conclusion about the effect of tree trait diversity on wood production.[100]
Regulating services

Greater species diversity

Services with mixed evidence

Provisioning services
  • None to date
Regulating services
  • 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;[112] Synthesis of 100 experimental studies).[104] One review found mixed evidence (Synthesis of 287 experimental studies[113]), while another found contrary evidence (Synthesis of 100 experimental studies[110])
  • Greater species diversity of animals may or may not decrease disease prevalence on those animals (Synthesis of 45 experimental and observational studies),[114] 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.[115] 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)[100]
  • Greater pollinator diversity may or may not increase pollination (Synthesis of 7 observational studies),[100] 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).[116]

Services hindered

Provisioning services
  • Greater species diversity of plants reduces primary production (Synthesis of 7 experimental studies)[54]
Regulating services
  • 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[100]
  • Effect of species diversity of plants on biofuel yield (In a survey of the literature, the investigators only found 3 studies)[100]
  • 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)[100]
Regulating services
  • Effect of species diversity on the stability of biofuel yield (In a survey of the literature, the investigators did not find any studies)[100]
  • Effect of species diversity of plants on the stability of fodder yield (In a survey of the literature, the investigators only found 2 studies)[100]
  • Effect of species diversity of plants on the stability of crop yield (In a survey of the literature, the investigators only found 1 study)[100]
  • Effect of genetic diversity of plants on the stability of crop yield (In a survey of the literature, the investigators only found 2 studies)[100]
  • Effect of diversity on the stability of wood production (In a survey of the literature, the investigators could not find any studies)[100]
  • 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)[100]
  • Effect of diversity on flood regulation (In a survey of the literature, the investigators could not find any studies)[100]
  • Effect of species and trait diversity of plants on soil moisture (In a survey of the literature, the investigators only found 2 studies)[100]

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.[117]

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.[118] Biodiversity also affords many non-material benefits including spiritual and aesthetic values, knowledge systems and education.[118]

Agriculture

Amazon Rainforest in South America

Agricultural diversity can be divided into two categories:

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).[119]

Associated biodiversity can be damaging or beneficial. The beneficial associated biodiversity include for instance wild pollinators such as wild bees and

ecosystem services such as pest control, nutrient cycling and pollination that support crop production.[121]

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.

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.[124]

Although about 80 percent of humans' food supply comes from just 20 kinds of plants,[125] humans use at least 40,000 species.[126] 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.[98]

Human health

Biodiversity's relevance to human health is becoming an international political issue, as scientific evidence builds on the global health implications of biodiversity loss.

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.[131]

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.[132] 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.[133]

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.[134] Biodiversity is also known to have an important role in reducing disaster risk and in post-disaster relief and recovery efforts.[135][136]

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.[137] A broad literature review published in 2010 by Nature (journal), Impacts of biodiversity on the emergence and transmission of infectious disease, found this to be broadly true within real environments.[138] Although some small population exceptions were found to exist, on average a collapse in biodiversity significantly increased the spread & spillover of infectious diseases.

Biodiversity provides critical support for drug discovery and the availability of medicinal resources.[139][140] 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.[128] 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;[141] meanwhile, natural products have a long history of supporting significant economic and health innovation.[142][143] Marine ecosystems are particularly important,[144] although inappropriate bioprospecting can increase biodiversity loss, as well as violating the laws of the communities and states from which the resources are taken.[145][146][147]

Business and industry

Agriculture production, pictured is a tractor and a chaser bin

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.[148][149][150] As a result, biodiversity loss is a significant risk factor in business development and a threat to long-term economic sustainability.[151][152]

Leisure, cultural and aesthetic value

Biodiversity enriches leisure activities such as birdwatching or natural history study.

Popular activities such as gardening and fishkeeping 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.[clarification needed]

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.[153]

Eagle Creek
, Oregon hiking