Biodiversity
Biodiversity or biological diversity is the variety and variability of
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
Since
Rapid
History of the term
- 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."[5]
- 1967 - Raymond F. Dasmann used the term biological diversity in reference to the richness of living nature that conservationists should protect in his book A Different Kind of Country.[6][7]
- 1974 – The term natural diversity was introduced by John Terborgh.[8]
- 1980 – Thomas Lovejoy introduced the term biological diversity to the scientific community in a book.[9] It rapidly became commonly used.[10]
- 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".[11]
- 1985 - The term "biodiversity" appears in the article, "A New Plan to Conserve the Earth's Biota" by Laura Tangley.[12]
- 1988 - The term biodiversity first appeared in publication.[13][14]
- 1988 to Present - The United Nations Environment Programme (UNEP) Ad Hoc Working Group of Experts on Biological Diversity in began working in November 1988, leading to the publication of the draft Convention on Biological Diversity in May 1992. Since this time, there have been 15 Conferences of the Parties (COPs) to discuss potential global political responses to biodiversity loss. Most recently COP 15 in Montreal, Canada in 2022.
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
An advantage of this definition is that it presents a unified view of the traditional types of biological variety previously identified:- taxonomic diversity (usually measured at the species diversity level)[18]
- ecological diversity (often viewed from the perspective of ecosystem diversity)[18]
- morphological diversity (which stems from genetic diversity and molecular diversity[19])
- functional diversity (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.)[20]) This multilevel construct is consistent with Datman and Lovejoy.
Other definitions include (in chronological order):
- 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.[21] 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)...".[21]
- A publication by Wilcox in 1984: Biodiversity can be defined genetically as the diversity of alleles, genes and gene transfer that drive evolution.[21]
- 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".[22] This definition is used in the United Nations Convention on Biological Diversity.[22]
- Gaston and Spicer's definition in their book "Biodiversity: an introduction" in 2004 is "variation of life at all levels of biological organization".[23]
- The Food and Agriculture Organization of the United Nations (FAO) defines biodiversity in 2019 as "the variability that exists among living organisms (both within and between species) and the ecosystems of which they are part."[24]
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
- 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.
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.
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
In 2020 the
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 (
Diversity consistently measures higher in the
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
Even though terrestrial biodiversity declines from the equator to the poles,
In 2016, an alternative hypothesis ("the
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
Karoo ice age* |
| ← |
| ← |
The history of biodiversity during the
The biodivertisy of the past is called Paleobiodiversity. The
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
Most biologists agree however that the period since human emergence is part of a new mass extinction, named the
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
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:
- Provisioning services which involve the production of renewable resources (e.g.: food, wood, fresh water)[100]
- Regulating services which are those that lessen environmental change (e.g.: climate regulation, pest/disease control)[100]
- 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
- of fish increases the stability of fisheries yield (Synthesis of 8 observational studies)[100]
- of natural pest enemies decreases herbivorous pest populations (Data from two separate reviews; Synthesis of 266 experimental and observational studies;[106] Synthesis of 18 observational studies.[107][108] 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[109]
- of plants decreases disease prevalence on plants (Synthesis of 107 experimental studies)[110]
- of plants increases resistance to )
- 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)[54]
- plants increases remineralization (Synthesis of 103 experimental studies)[110]
- of plants increases soil organic matter (Synthesis of 85 experimental studies)[110]
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
Agricultural diversity can be divided into two categories:
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
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[119]
- When rice grassy stunt virus struck rice fields from Indonesia to India in the 1970s, 6,273 varieties were tested for resistance.[122] Only one was resistant, an Indian variety and known to science only since 1966.[122] This variety formed a hybrid with other varieties and is now widely grown.[122]
- 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.[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.
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
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]
Ecological services
Biodiversity supports many
"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."[100]
It plays a part in regulating the chemistry of our
Measuring biodiversity
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. In order to calculate biodiversity, species evenness, species richness, and species diversity are to be obtained first. Species evenness[157] is the relative number of individuals of each species in a given area. Species richness[158] is the number of species present in a given area. Species diversity[159] is the relationship between species evenness and species richness. There are many ways to measure biodiversity within a given ecosystem. However, the two most popular are Shannon-Weaver diversity index,[160] commonly referred to as Shannon diversity index, and the other is Simpsons diversity index.[161] Although many scientists prefer to use Shannon's diversity index simply because it takes into account species richness.[162]
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Analytical limits
Taxonomic and size relationships
Less than 1% of all species that have been described have been studied beyond noting their existence.
Current biodiversity loss
Rates of
The emergence of the sixth mass extinction is considered by conservation biologists, including Rodolfo Dirzo and Paul R. Ehrlich, to be "one of the most critical manifestations of the Anthropocene" and the continued decline of biodiversity constitutes "an unprecedented threat" to the continued existence of human civilization.[180]
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.[181] As of late 2022 9251 species were considered part of the IUCN's critically endangered.[182]
According to the
Numerous scientists and the
Global warming is a major threat to global biodiversity.[191][192] For example, coral reefs – which are biodiversity hotspots – will be lost within the century if global warming continues at the current rate.[193][194] Climate change has proven to affect biodiversity and evidence supporting the altering effects is widespread. Increasing atmospheric carbon dioxide certainly affects plant morphology[195] and is acidifying oceans,[196] and temperature affects species ranges,[197][198][199] phenology,[200] and weather.[201]
Some studies have however pointed out that habitat destruction for the expansion of agriculture and the overexploitation of wildlife are the more significant drivers of contemporary biodiversity loss, not climate change.[202][203]
Biodiversity changes
Introduced and invasive species
Barriers such as large
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.[204] Others report confounding evidence that occasionally suggest that species-rich communities harbor many native and exotic species simultaneously[205] while some say that diverse ecosystems are more resilient and resist invasive plants and animals.[206] An important question is, "do invasive species cause extinctions?" Many studies cite effects of invasive species on natives,[207] 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,[208] 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,[209] 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
Finally, an introduced species may unintentionally injure a species that depends on the species it replaces. In
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.[210] Nature offers effective ways to help mitigate climate change.[211] Another example may be ignored is the pines, most pines origin in the north hemisphere and the pines were introduced into South hemisphere as the landscape plants.[212]
Hybridization and genetic pollution
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.[215][216]
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.[217]
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.[218][219][220][221][222]
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.[217]
Conservation
The conservation ethic advocates management of
Conservation biology is reforming around strategic plans to protect biodiversity.
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.[234]
Protection and restoration techniques
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
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.
- Biodiversity banking places a monetary value on biodiversity. One example is the Australian Native Vegetation Management Framework.
- Gene banks are collections of specimens and genetic material. Some banks intend to reintroduce banked species to the ecosystem (e.g., via tree nurseries).[237]
- 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.[238]
Priorities for resource allocation
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.[239]
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.[240]
Protected areas
Protected areas, including forest reserves and biosphere reserves, serve many functions including for affording protection to wild animals and their habitat.[241] 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.[242][243] The target of protecting 30% of the area of the planet by the year 2030 (30 by 30) was adopted by almost 200 countries in the 2022 United Nations Biodiversity Conference. At the moment of adoption (December 2022) 17% of land territory and 10% of ocean territory were protected.[244] In a study published 4 September 2020 in Science Advances researchers mapped out regions that can help meet critical conservation and climate goals.[245]
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).
Forest protected areas are a subset of all protected areas in which a significant portion of the area is forest.[58] This may be the whole or only a part of the protected area.[58] 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.[58]
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