Biodiversity

Source: Wikipedia, the free encyclopedia.

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

Biodiversity (or biological diversity) is the variety and variability of

primary productivity in the region near the equator. Tropical forest ecosystems cover less than one-fifth of Earth's terrestrial area and contain about 50% of the world's species.[2] There are latitudinal gradients in species diversity for both marine and terrestrial taxa.[3]

Since

mass extinction events. In the Carboniferous, rainforest collapse may have 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.

Human activities have lead to an ongoing biodiversity loss and an accompanying loss of genetic diversity. This process is often referred to as Holocene extinction, or sixth mass extinction. For example, it was estimated in 2007 that up to 30% of all species will be extinct by 2050.[4] Destroying habitats for farming is a key reason why biodiversity is decreasing today. Climate change also plays a role.[5][6] This can be seen for example in the effects of climate change on biomes. This anthropogenic extinction may have started toward the end of the Pleistocene, as some studies suggest that the megafaunal extinction event that took place around the end of the last ice age partly resulted from overhunting.[7]

History of the term

Shown in a museum, various models of species across various taxa and orders visualize the variety of life on earth.
  • 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."[8]
  • 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.[9][10]
  • 1974 – The term natural diversity was introduced by John Terborgh.[11]
  • 1980 – Thomas Lovejoy introduced the term biological diversity to the scientific community in a book.[12] It rapidly became commonly used.[13]
  • 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".[14]
  • 1985 – The term "biodiversity" appears in the article, "A New Plan to Conserve the Earth's Biota" by Laura Tangley.[15]
  • 1988 – The term biodiversity first appeared in publication.[16][17]
  • 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

Biologists most often define biodiversity as the "totality of

ecosystems of a region".[18][19]
An advantage of this definition is that it presents a unified view of the traditional types of biological variety previously identified:

Biodiversity is most commonly used to replace the more clearly-defined and long-established terms, species diversity and species richness.[23] However, there is no concrete definition for biodiversity, as its definition continues to be defined. Other definitions include (in chronological order):

Number of species

Discovered and predicted total number of species on land and in the oceans

According to Mora and her 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.[28] Other estimates include:

  • 220,000
    vascular plants, estimated using the species-area relation method[29]
  • 0.7-1 million marine species[30]
  • 10–30 million insects;[31] (of some 0.9 million we know today)[32]
  • 5–10 million bacteria;[33]
  • 1.5-3 million
    cryptic speciation.[34] Some 0.075 million species of fungi had been documented by 2001;[35]
  • 1 million mites[36]
  • 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.[37] The findings may eventually cause a significant change in the way science defines species and other taxonomic categories.[38][39]

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

animals groups.[41]

Current biodiversity loss

The World Wildlife Fund's Living Planet Report 2022 found that wildlife populations declined by an average 69% since 1970.[42][43][44]

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.[45][47][48] and expected to still grow in the upcoming years.[48][49][50] As of 2012, some studies suggest that 25% of all mammal species could be extinct in 20 years.[51]

In absolute terms, the planet has lost 58% of its biodiversity since 1970 according to a 2016 study by the World Wildlife Fund.[52] 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.[53]

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."[55]

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.[56]

Of 70,000 monitored species, around 48% are experiencing population declines from human activity (in 2023), whereas only 3% have increasing populations.[57][58][59]

fossil record.[69] Biodiversity loss is in fact "one of the most critical manifestations of the Anthropocene" (since around the 1950s); the continued decline of biodiversity constitutes "an unprecedented threat" to the continued existence of human civilization.[70] The reduction is caused primarily by human impacts, particularly habitat destruction
.

Loss of biodiversity results in the loss of

ecosystem goods and services. Species today are being wiped out at a rate 100 to 1,000 times higher than baseline, and the rate of extinctions is increasing. This process destroys the resilience and adaptability of life on Earth.[71]

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.[72] As of late 2022 9251 species were considered part of the IUCN's critically endangered.[73]

Numerous scientists and the

overconsumption are the primary factors in this decline.[74][75][76][77][78] However, other scientists have criticized this finding and say that loss of habitat caused by "the growth of commodities for export" is the main driver.[79]

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.[5][6]

Distribution

Distribution of living terrestrial vertebrate species, highest concentration of diversity shown in red in equatorial regions, declining polewards (towards the blue end of the spectrum)

Biodiversity is not evenly distributed, rather it varies greatly across the globe as well as within regions and seasons. Among other factors, the diversity of all living things (

biota) depends on temperature, precipitation, altitude, soils, geography and the interactions between other species.[80] The study of the spatial distribution of organisms, species and ecosystems, is the science of biogeography.[81][82]

Diversity consistently measures higher in the

Yasuní National Park in Ecuador, have particularly high biodiversity.[83][84]

There is local biodiversity, which directly impacts daily life, affecting the availability of fresh water, food choices, and fuel sources for humans. Regional biodiversity includes habitats and ecosystems that synergizes and either overlaps or differs on a regional scale. National biodiversity within a country determines the ability for a country to thrive according to its habitats and ecosystems on a national scale. Also, within a country, endangered species are initially supported on a national level then internationally. Ecotourism may be utilized to support the economy and encourages tourists to continue to visit and support species and ecosystems they visit, while they enjoy the available amenities provided. International biodiversity impacts global livelihood, food systems, and health. Problematic pollution, over consumption, and climate change can devastate international biodiversity. Nature-based solutions are a critical tool for a global resolution. Many species are in danger of becoming extinct and need world leaders to be proactive with the Kumming-Montreal Global Biodiversity Framework.

Terrestrial biodiversity is thought to be up to 25 times greater than ocean biodiversity.[85] 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.[86] 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.[87] However, this estimate seems to under-represent the diversity of microorganisms.[88] 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.[86] 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.[89][90]

The biodiversity of forests varies considerably according to factors such as forest type, geography, climate and soils – in addition to human use.[86] 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.[86] 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.[86] 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.[91][92]

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 at the poles.[93]

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

marine ecosystems.[95] The latitudinal distribution of parasites does not appear to follow this rule.[81] Also, in terrestrial ecosystems the soil bacterial diversity has been shown to be highest in temperate climatic zones,[96] and has been attributed to carbon inputs and habitat connectivity.[97]

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.[99]

Biodiversity Hotspots

A biodiversity hotspot is a region with a high level of endemic species that have experienced great habitat loss.[100] The term hotspot was introduced in 1988 by Norman Myers.[101][102][103][104] While hotspots are spread all over the world, the majority are forest areas and most are located in the tropics.[105]

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.[106][107] 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.[108] Madagascar dry deciduous forests and lowland rainforests possess a high ratio of endemism.[109][110] Since the island separated from mainland Africa 66 million years ago, many species and ecosystems have evolved independently.[111] 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.[112] 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.[110]

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."[113]

Evolution over geologic timeframes