Global biodiversity

[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.

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.

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perhaps the most comprehensive recent statistics on numbers of extant species, drawing on a range of published and unpublished sources, and has come up with a figure of approximately 1.9 million estimated described taxa, as against possibly a total of between 11 and 12 million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.

[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.

[33] Challenges to these indices due to data availability are taxonomic gaps and the length of time of each index.

The cause of most of the biodiversity loss is, generally speaking, human activities that push the planetary boundaries too far.

[41][42][43][44][45] Others disagree, saying that loss of habitat is caused mainly by "the growth of commodities for export" and that population has very little to do with overall consumption.

[49][50] Still, it is the general habitat destruction (often for expansion of agriculture), not climate change, that is currently the bigger driver of biodiversity loss.

These tend to be directly or indirectly connected to climate change and can cause a deterioration of forest ecosystems.

For example, the UN Convention on Biological Diversity aims to prevent biodiversity loss and to conserve wilderness areas.

However, a 2020 United Nations Environment Programme report found that most of these efforts had failed to meet their goals.

Examples of the multicellular biodiversity of the Earth.
Insects make up the vast majority of animal species. [ 14 ]
The distribution of numbers of known and undescribed (estimated) species on Earth, grouped by major taxonomic groups; according to Chapman 2009. Absolute number of species on the left (orange = estimated number of yet to be described species, blue = already described). Right: percentage of species already described (green) and estimated to be not yet known (yellow).
The distribution of numbers of known and undescribed (estimated) species on Earth, grouped by major taxonomic groups; according to Chapman 2009. Absolute number of species on the left (orange = estimated number of yet to be described species, blue = already described). Right: percentage of species already described (green) and estimated to be not yet known (yellow).
Summary of major environmental-change categories that cause biodiversity loss. The data is expressed as a percentage of human-driven change (in red) relative to baseline (blue), as of 2021. Red indicates the percentage of the category that is damaged, lost, or otherwise affected, whereas blue indicates the percentage that is intact, remaining, or otherwise unaffected. [ 34 ]