Global biodiversity is the measure of biodiversity on planet Earth and is defined as the total variability of life forms. More than 99 percent of all species [1] that ever lived on Earth are estimated to be extinct. [2] [3] Estimates on the number of Earth's current species range from 2 million to 1 trillion, but most estimates are around 11 million species or fewer. [4] About 1.74 million species were databased as of 2018, [5] and over 80 percent have not yet been described. [6] The total amount of DNA base pairs on Earth, as a possible approximation of global biodiversity, is estimated at 5.0 x 1037, and weighs 50 billion tonnes. [7] In comparison, the total mass of the biosphere has been estimated to be as much as 4 TtC (trillion tons of carbon). [8]
In other related studies, around 1.9 million extant species are believed to have been described currently, [9] but some scientists believe 20% are synonyms, reducing the total valid described species to 1.5 million. In 2013, a study published in Science estimated there to be 5 ± 3 million extant species on Earth although that is disputed. [10] Another study, published in 2011 by PLoS Biology, estimated there to be 8.7 million ± 1.3 million eukaryotic species on Earth. [11] Some 250,000 valid fossil species have been described, but this is believed to be a small proportion of all species that have ever lived. [12]
Global biodiversity is affected by extinction and speciation. The background extinction rate varies among taxa but it is estimated that there is approximately one extinction per million species years. Mammal species, for example, typically persist for 1 million years. Biodiversity has grown and shrunk in earth's past due to (presumably) abiotic factors such as extinction events caused by geologically rapid changes in climate. Climate change 299 million years ago was one such event. A cooling and drying resulted in catastrophic rainforest collapse and subsequently a great loss of diversity, especially of amphibians. [13]
Chapman, 2005 and 2009 [9] has attempted to compile perhaps the most comprehensive recent statistics on numbers of extant species, drawing on a range of published and unpublished sources, and has come up with a figure of approximately 1.9 million estimated described taxa, as against possibly a total of between 11 and 12 million anticipated species overall (described plus undescribed), though other reported values for the latter vary widely. In many cases, the values given for "Described" species are an estimate only (sometimes a mean of reported figures in the literature) since for many of the larger groups in particular, comprehensive lists of valid species names do not currently exist. For fossil species, exact or even approximate numbers are harder to find; Raup, 1986 [15] includes data based on a compilation of 250,000 fossil species so the true number is undoubtedly somewhat higher than this. The number of described species is increasing by around 18,000–19,000 extant, and approaching 2,000 fossil species each year, as of 2012. [16] [17] [18] The number of published species names is higher than the number of described species, sometimes considerably so, on account of the publication, through time, of multiple names (synonyms) for the same accepted taxon in many cases.
Based on Chapman's (2009) report, [9] the estimated numbers of described extant species as of 2009 can be broken down as follows:
Major/Component group | Described | Global estimate (described + undescribed) | ||
---|---|---|---|---|
Chordates | 64,788 | ~80,500 | ||
↳ | Mammals | 5,487 | ~5,500 | |
↳ | Birds | 9,990 | >10,000 | |
↳ | Reptiles | 8,734 | ~10,000 | |
↳ | Amphibia | 6,515 | ~15,000 | |
↳ | Fishes | 31,153 | ~40,000 | |
↳ | Agnatha | 116 | unknown | |
↳ | Cephalochordata | 33 | unknown | |
↳ | Tunicata | 2,760 | unknown | |
Invertebrates | ~1,359,365 | ~6,755,830 | ||
↳ | Hemichordata | 108 | ~110 | |
↳ | Echinodermata | 7,003 | ~14,000 | |
↳ | Insecta | ~1,000,000 (965,431–1,015,897) | ~5,000,000 | |
↳ | Archaeognatha | 470 | ||
↳ | Blattodea | 3,684–4,000 | ||
↳ | Coleoptera | 360,000–~400,000 | 1,100,000 | |
↳ | Dermaptera | 1,816 | ||
↳ | Diptera | 152,956 | 240,000 | |
↳ | Embioptera | 200–300 | 2,000 | |
↳ | Ephemeroptera | 2,500–<3,000 | ||
↳ | Hemiptera | 80,000–88,000 | ||
↳ | Hymenoptera | 115,000 | >~1,000,000 [19] | |
↳ | Isoptera | 2,600–2,800 | 4,000 | |
↳ | Lepidoptera | 174,250 | 300,000–500,000 | |
↳ | Mantodea | 2,200 | ||
↳ | Mecoptera | 481 | ||
↳ | Megaloptera | 250–300 | ||
↳ | Neuroptera | ~5,000 | ||
↳ | Notoptera | 55 | ||
↳ | Odonata | 6,500 | ||
↳ | Orthoptera | 24,380 | ||
↳ | Phasmatodea (Phasmida) | 2,500–3,300 | ||
↳ | Phthiraptera | >3,000–~3,200 | ||
↳ | Plecoptera | 2,274 | ||
↳ | Psocoptera | 3,200–~3,500 | ||
↳ | Siphonaptera | 2,525 | ||
↳ | Strepsiptera | 596 | ||
↳ | Thysanoptera | ~6,000 | ||
↳ | Trichoptera | 12,627 | ||
↳ | Zoraptera | 28 | ||
↳ | Zygentoma (Thysanura) | 370 | ||
↳ | Arachnida | 102,248 | ~600,000 | |
↳ | Pycnogonida | 1,340 | unknown | |
↳ | Myriapoda | 16,072 | ~90,000 | |
↳ | Crustacea | 47,000 | 150,000 | |
↳ | Onychophora | 165 | ~220 | |
↳ | non-Insect Hexapoda | 9,048 | 52,000 | |
↳ | Mollusca | ~85,000 | ~200,000 | |
↳ | Annelida | 16,763 | ~30,000 | |
↳ | Nematoda | <25,000 | ~500,000 | |
↳ | Acanthocephala | 1,150 | ~1,500 | |
↳ | Platyhelminthes | 20,000 | ~80,000 | |
↳ | Cnidaria | 9,795 | unknown | |
↳ | Porifera | ~6,000 | ~18,000 | |
↳ | Other Invertebrates | 12,673 | ~20,000 | |
↳ | Placozoa | 1 | - | |
↳ | Monoblastozoa | 1 | - | |
↳ | Mesozoa (Rhombozoa, Orthonectida) | 106 | - | |
↳ | Ctenophora | 166 | 200 | |
↳ | Nemertea (Nemertina) | 1,200 | 5,000–10,000 | |
↳ | Rotifera | 2,180 | - | |
↳ | Gastrotricha | 400 | - | |
↳ | Kinorhyncha | 130 | - | |
↳ | Nematomorpha | 331 | ~2,000 | |
↳ | Entoprocta (Kamptozoa) | 170 | 170 | |
↳ | Gnathostomulida | 97 | - | |
↳ | Priapulida | 16 | - | |
↳ | Loricifera | 28 | >100 | |
↳ | Cycliophora | 1 | - | |
↳ | Sipuncula | 144 | - | |
↳ | Echiura | 176 | - | |
↳ | Tardigrada | 1,045 | - | |
↳ | Phoronida | 10 | - | |
↳ | Ectoprocta (Bryozoa) | 5,700 | ~5,000 | |
↳ | Brachiopoda | 550 | - | |
↳ | Pentastomida | 100 | - | |
↳ | Chaetognatha | 121 | - | |
Plants sens. lat. | ~310,129 | ~390,800 | ||
↳ | Bryophyta | 16,236 | ~22,750 | |
↳ | Liverworts | ~5,000 | ~7,500 | |
↳ | Hornworts | 236 | ~250 | |
↳ | Mosses | ~11,000 | ~15,000 | |
↳ | Algae (Plant) | 12,272 | unknown | |
↳ | Charophyta | 2,125 | - | |
↳ | Chlorophyta | 4,045 | - | |
↳ | Glaucophyta | 5 | - | |
↳ | Rhodophyta | 6,097 | - | |
↳ | Vascular Plants | 281,621 | ~368,050 | |
↳ | Ferns and allies | ~12,000 | ~15,000 | |
↳ | Gymnosperms | ~1,021 | ~1,050 | |
↳ | Magnoliophyta | ~268,600 | ~352,000 | |
Fungi | 98,998 (incl. Lichens 17,000) | 1,500,000 (incl. Lichens ~25,000) | ||
Others | ~66,307 | ~2,600,500 | ||
↳ | Chromista [incl. brown algae, diatoms and other groups] | 25,044 | ~200,500 | |
↳ | Protoctista [i.e. residual protist groups] | ~28,871 | >1,000,000 | |
↳ | Prokaryota [ Bacteria and Archaea, excl. Cyanophyta] | 7,643 | ~1,000,000 | |
↳ | Cyanophyta | 2,664 | unknown | |
↳ | Viruses | 2,085 | 400,000 | |
Total (2009 data) | 1,899,587 | ~11,327,630 |
However the total number of species for some taxa may be much higher.
In 1982, Terry Erwin published an estimate of global species richness of 30 million, by extrapolating from the numbers of beetles found in a species of tropical tree. In one species of tree, Erwin identified 1200 beetle species, of which he estimated 163 were found only in that type of tree. [26] Given the 50,000 described tropical tree species, Erwin suggested that there are almost 10 million beetle species in the tropics. [27] In 2011 a study published in PLoS Biology estimated there to be 8.7 million ± 1.3 million eukaryotic species on Earth. [11]
By 2017, most estimates projected there to be around 11 million species or fewer on Earth. [4] A 2017 study estimated there are around at least 1 to 6 billion species, 70-90% of which are bacteria. [4] A May 2016 study based on scaling laws estimated that 1 trillion species (overwhelmingly microbes) are on Earth currently with only one-thousandth of one percent described, [28] [29] though this has been controversial and a 2019 study of varied environmental samples of 16S ribosomal RNA estimated that there exist 0.8-1.6 million species of prokaryotes. [30]
After the Convention on Biological Diversity was signed in 1992, biological conservation became a priority for the international community. There are several indicators used that describe trends in global biodiversity. However, there is no single indicator for all extant species as not all have been described and measured over time. There are different ways to measure changes in biodiversity. The Living Planet Index (LPI) is a population-based indicator that combines data from individual populations of many vertebrate species to create a single index. [31] The Global LPI for 2012 decreased by 28%. There are also indices that separate temperate and tropical species for marine and terrestrial species.
The Red List Index is based on the IUCN Red List of Threatened Species and measures changes in conservation status over time and currently includes taxa that have been completely categorized: mammals, birds, amphibians and corals. [32] The Global Wild Bird Index is another indicator that shows trends in population of wild bird groups on a regional scale from data collected in formal surveys. [33] Challenges to these indices due to data availability are taxonomic gaps and the length of time of each index.
The Biodiversity Indicators Partnership was established in 2006 to assist biodiversity indicator development, advancement and to increase the availability of indicators.
Biodiversity loss happens when various species disappear completely from Earth (extinction) or when there is a decrease or disappearance of species in a specific area. This in turn leads to a reduction in biological diversity in that area. The decrease can be temporary or permanent. It is temporary if the damage that has led to the loss is reversible in time, for example through ecological restoration. If this is not possible then the decrease is permanent. This ongoing global extinction (also called the holocene extinction or sixth mass extinction) is a biodiversity crisis. The cause for most of the biodiversity loss are those human activities that push the planetary boundaries too far. [34] [35] [36]
The causes for current biodiversity loss are habitat loss, fragmentation and degradation; [37] land use intensification (and ensuing land loss/habitat loss), often for commercial and agricultural uses (specifically monoculture farming). [38] [39] Further causes include nutrient pollution and other forms of pollution (air and water pollution), over-exploitation and unsustainable use (related to human overpopulation), invasive species [40] and climate change. [37]
Many scientists, along with the Global Assessment Report on Biodiversity and Ecosystem Services , say that the main reasons for biodiversity loss are the growing human population and excessive consumption. [41] [42] [43] [44] [45] However other scientists have criticized this, saying that loss of habitat is caused mainly by "the growth of commodities for export". They also state that population has very little to do with overall consumption due to country wealth disparities. [46]
Climate change is another threat to global biodiversity. [47] [48] For example, coral reefs – which are biodiversity hotspots – will be lost within the century if global warming continues at the current rate. [49] [50] However, habitat destruction (often for the expansion of agriculture), is currently the more significant driver of biodiversity loss, not climate change. [51] [52] Invasive species and other disturbances have become more common in forests in the last several decades. These tend to be directly or indirectly connected to climate change and have negative consequences for forest ecosystems. [53] [54]
Groups that care about the environment have been working for many years to stop the decrease in biodiversity. Now, preventing biodiversity loss is often included in global policies. It can be part of the response to the triple planetary crisis. For example, the UN Convention on Biological Diversity aims to prevent biodiversity loss and to conserve wilderness areas. However, a report of the United Nations Environment Programme in 2020 found that most of these efforts had failed to meet their international goals. [55] For example, of the 20 biodiversity goals laid out by the Aichi Biodiversity Targets in 2010, only six were "partially achieved" by the deadline of 2020. [56] [57]The Holocene extinction, or Anthropocene extinction, is the ongoing extinction event caused by humans during the Holocene epoch. These extinctions span numerous families of plants and animals, including mammals, birds, reptiles, amphibians, fish, and invertebrates, and affecting not just terrestrial species but also large sectors of marine life. With widespread degradation of biodiversity hotspots, such as coral reefs and rainforests, as well as other areas, the vast majority of these extinctions are thought to be undocumented, as the species are undiscovered at the time of their extinction, which goes unrecorded. The current rate of extinction of species is estimated at 100 to 1,000 times higher than natural background extinction rates and is increasing. During the past 100–200 years, biodiversity loss and species extinction have accelerated, to the point that most conservation biologists now believe that human activity has either produced a period of mass extinction, or is on the cusp of doing so. As such, after the "Big Five" mass extinctions, the Holocene extinction event has also been referred to as the sixth mass extinction or sixth extinction; given the recent recognition of the Capitanian mass extinction, the term seventh mass extinction has also been proposed for the Holocene extinction event.
Biodiversity or biological diversity is the variety and variability of life on Earth. Biodiversity is a measure of variation at the genetic, species, and ecosystem level. Biodiversity is not distributed evenly on Earth; it is usually greater in the tropics as a result of the warm climate and high primary productivity in the region near the equator. Tropical forest ecosystems cover less than 10% of earth's surface and contain about 90% of the world's species. Marine biodiversity is usually higher along coasts in the Western Pacific, where sea surface temperature is highest, and in the mid-latitudinal band in all oceans. There are latitudinal gradients in species diversity. Biodiversity generally tends to cluster in hotspots, and has been increasing through time, but will be likely to slow in the future as a primary result of deforestation. It encompasses the evolutionary, ecological, and cultural processes that sustain life.
Extinction is the termination of a taxon by the death of its last member. A taxon may become functionally extinct before the death of its last member if it loses the capacity to reproduce and recover. Because a species' potential range may be very large, determining this moment is difficult, and is usually done retrospectively. This difficulty leads to phenomena such as Lazarus taxa, where a species presumed extinct abruptly "reappears" after a period of apparent absence.
Conservation biology is the study of the conservation of nature and of Earth's biodiversity with the aim of protecting species, their habitats, and ecosystems from excessive rates of extinction and the erosion of biotic interactions. It is an interdisciplinary subject drawing on natural and social sciences, and the practice of natural resource management.
Habitat conservation is a management practice that seeks to conserve, protect and restore habitats and prevent species extinction, fragmentation or reduction in range. It is a priority of many groups that cannot be easily characterized in terms of any one ideology.
The Anthropocene is a proposed geological epoch dating from the commencement of significant human impact on Earth's geology, landscape, limnology and ecosystems, including, but not limited to, anthropogenic climate change. The nature of the effects of human activities on Earth can be seen for example in biodiversity loss, climate change, biogeography and nocturnality parameters, changes in geomorphology and stratigraphy.
An ecological or environmental crisis occurs when changes to the environment of a species or population destabilizes its continued survival. Some of the important causes include:
Habitat destruction occurs when a natural habitat is no longer able to support its native species. The organisms once living there have either moved to elsewhere or are dead, leading to a decrease in biodiversity and species numbers. Habitat destruction is in fact the leading cause of biodiversity loss and species extinction worldwide.
Human impact on the environment refers to changes to biophysical environments and to ecosystems, biodiversity, and natural resources caused directly or indirectly by humans. Modifying the environment to fit the needs of society is causing severe effects including global warming, environmental degradation, mass extinction and biodiversity loss, ecological crisis, and ecological collapse. Some human activities that cause damage to the environment on a global scale include population growth, neoliberal economic policies and rapid economic growth, overconsumption, overexploitation, pollution, and deforestation. Some of the problems, including global warming and biodiversity loss, have been proposed as representing catastrophic risks to the survival of the human species.
Wildlife conservation refers to the practice of protecting wild species and their habitats in order to maintain healthy wildlife species or populations and to restore, protect or enhance natural ecosystems. Major threats to wildlife include habitat destruction, degradation, fragmentation, overexploitation, poaching, pollution, climate change, and the illegal wildlife trade. The IUCN estimates that 42,100 species of the ones assessed are at risk for extinction. Expanding to all existing species, a 2019 UN report on biodiversity put this estimate even higher at a million species. It is also being acknowledged that an increasing number of ecosystems on Earth containing endangered species are disappearing. To address these issues, there have been both national and international governmental efforts to preserve Earth's wildlife. Prominent conservation agreements include the 1973 Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) and the 1992 Convention on Biological Diversity (CBD). There are also numerous nongovernmental organizations (NGO's) dedicated to conservation such as the Nature Conservancy, World Wildlife Fund, the Wild Animal Health Fund and Conservation International.
In biology, a refugium is a location which supports an isolated or relict population of a once more widespread species. This isolation (allopatry) can be due to climatic changes, geography, or human activities such as deforestation and overhunting.
The Tropical Andes is northern of the three climate-delineated parts of the Andes, the others being the Dry Andes and the Wet Andes. The Tropical Andes' area spans 1,542,644 km2 (595,618 sq mi).
There are several plausible pathways that could lead to an increased extinction risk from climate change. Every plant and animal species has evolved to exist within a certain ecological niche. But climate change leads to changes of temperature and average weather patterns. These changes can push climatic conditions outside of the species' niche, and ultimately render it extinct. Normally, species faced with changing conditions can either adapt in place through microevolution or move to another habitat with suitable conditions. However, the speed of recent climate change is very fast. Due to this rapid change, for example cold-blooded animals may struggle to find a suitable habitat within 50 km of their current location at the end of this century.
Insect biodiversity accounts for a large proportion of all biodiversity on the planet—over half of the estimated 1.5 million organism species described are classified as insects.
Defaunation is the global, local, or functional extinction of animal populations or species from ecological communities. The growth of the human population, combined with advances in harvesting technologies, has led to more intense and efficient exploitation of the environment. This has resulted in the depletion of large vertebrates from ecological communities, creating what has been termed "empty forest". Defaunation differs from extinction; it includes both the disappearance of species and declines in abundance. Defaunation effects were first implied at the Symposium of Plant-Animal Interactions at the University of Campinas, Brazil in 1988 in the context of Neotropical forests. Since then, the term has gained broader usage in conservation biology as a global phenomenon.
In ecology, extinction debt is the future extinction of species due to events in the past. The phrases dead clade walking and survival without recovery express the same idea.
Biodiversity loss happens when various species disappear completely from Earth (extinction) or when there is a decrease or disappearance of species in a specific area. This in turn leads to a reduction in biological diversity in that area. The decrease can be temporary or permanent. It is temporary if the damage that has led to the loss is reversible in time, for example through ecological restoration. If this is not possible then the decrease is permanent. This ongoing global extinction is a biodiversity crisis. The cause for most of the biodiversity loss are those human activities that push the planetary boundaries too far.
Conservation paleobiology is a field of paleontology that applies the knowledge of the geological and paleoecological record to the conservation and restoration of biodiversity and ecosystem services. Despite the influence of paleontology on ecological sciences can be traced back at least at the 18th century, the current field has been established by the work of K.W. Flessa and G.P. Dietl in the first decade of the 21st century. The discipline utilizes paleontological and geological data to understand how biotas respond to climate and other natural and anthropogenic environmental change. These information are then used to address the challenges faced by modern conservation biology, like understanding the extinction risk of endangered species, providing baselines for restoration and modelling future scenarios for species range's contraction or expansion.
The Global Assessment Report on Biodiversity and Ecosystem Services is a report by the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services, on the global state of biodiversity. A summary for policymakers was released on 6 May 2019. The report states that, due to human impact on the environment in the past half-century, the Earth's biodiversity has suffered a catastrophic decline unprecedented in human history, as an estimated 82 percent of wild mammal biomass has been lost. The report estimates that there are 8 million animal and plant species on Earth, with the majority represented by insects. Out of those 8 million species, 1 million are threatened with extinction, including 40 percent of amphibians, almost a third of reef-building corals, more than a third of marine mammals, and 10 percent of all insects.
The Biodiversity of South Africa is the variety of living organisms within the boundaries of South Africa and its exclusive economic zone. South Africa is a region of high biodiversity in the terrestrial and marine realms. The country is ranked sixth out of the world's seventeen megadiverse countries, and is rated among the top 10 for plant species diversity and third for marine endemism.
Moreover, we have unleashed a mass extinction event, the sixth in roughly 540 million years, wherein many current life forms could be annihilated or at least committed to extinction by the end of this century.
For the first time at a global scale, the report has ranked the causes of damage. Topping the list, changes in land use—principally agriculture—that have destroyed habitat. Second, hunting and other kinds of exploitation. These are followed by climate change, pollution, and invasive species, which are being spread by trade and other activities. Climate change will likely overtake the other threats in the next decades, the authors note. Driving these threats are the growing human population, which has doubled since 1970 to 7.6 billion, and consumption. (Per capita of use of materials is up 15% over the past 5 decades.)
The overarching driver of species extinction is human population growth and increasing per capita consumption.
Conservation biologists standardly list five main direct drivers of biodiversity loss: habitat loss, overexploitation of species, pollution, invasive species, and climate change. The Global Assessment Report on Biodiversity and Ecosystem Services found that in recent decades habitat loss was the leading cause of terrestrial biodiversity loss, while overexploitation (overfishing) was the most important cause of marine losses (IPBES, 2019). All five direct drivers are important, on land and at sea, and all are made worse by larger and denser human populations.
Research suggests that the scale of human population and the current pace of its growth contribute substantially to the loss of biological diversity. Although technological change and unequal consumption inextricably mingle with demographic impacts on the environment, the needs of all human beings—especially for food—imply that projected population growth will undermine protection of the natural world.
Current generic extinction rates will likely greatly accelerate in the next few decades due to drivers accompanying the growth and consumption of the human enterprise such as habitat destruction, illegal trade, and climate disruption.
Through examining the drivers of biodiversity loss in highly biodiverse countries, we show that it is not population driving the loss of habitats, but rather the growth of commodities for export, particularly soybean and oil-palm, primarily for livestock feed or biofuel consumption in higher income economies.