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How many species are there on Earth? New research suggests there may be more than 1 trillion. What does this mean?
Global biodiversity is a measure of the species richness on Earth, defined as the total variability of life forms. Scientists estimate that more than 99% of species are already extinct. Estimates of the current number of species on Earth range from approximately 2 million to 1 trillion, although most estimates focus on 11 million or fewer. Although approximately 1.74 million species have been catalogued in the database as of 2018, more than 80% have yet to be described.
A possible approximation of the total DNA base code on Earth for global biodiversity is estimated to be 5.0 x 1037, which would weigh up to 50 billion tons.
In comparison, the total mass of the biosphere is estimated to be about 4 TtC (teratonnes of carbon). In other related studies, there are currently about 1.9 million described species, but some scientists believe that 20% of species are actually synonyms, which reduces the number of effectively described species to 1.5 million. A 2013 study published in the journal Science estimated the number of living species on Earth to be 5 ± 3 million, although this conclusion has been questioned.
Another study published in PLoS Biology in 2011 estimated that there are 8.7 ± 1.3 million eukaryotic species on Earth. As for fossil species, the 250,000 active fossil species that have been described only slightly represent all species that have ever lived. Biodiversity is affected by extinction and speciation.
Background extinction rates vary across taxa but are estimated to be about one extinction per million species-years.
In the case of mammals, these species typically live for about a million years. Historically, the growth and decline of biodiversity has been influenced by extinction events caused by (presumably) abiotic factors such as rapid geological and climatic changes. One example is a climate change 299 million years ago that led to a catastrophic collapse of tropical rainforests and a consequent huge loss of amphibian diversity.
In recent years, many studies have attempted to more accurately assess the total number of species. Based on research by Chapman in 2005 and 2009, using various published and unpublished sources, he concluded that there are approximately 1.9 million living species, with an overall estimate of between 11 and 12 million species, although some reports vary greatly.
As for the number of described species, the count is updated every year at about 18,000 to 19,000 living species, plus descriptions of nearly 2,000 fossil species are gradually being added.
However, total species numbers may be higher for some taxa. Estimates of the number of insects range from 10 to 30 million, bacteria from 5 to 10 million, fungi 1.5 million, and mites and protists 1 million each. Additionally, in 1982 Terry Erwin proposed an estimate of global species richness of 30 million based on the number of beetles in tropical trees.
A study published in PLoS Biology in 2011 reaffirmed that there are approximately 8.7 ± 1.3 million eukaryotic species on Earth. By 2017, most estimates put the number of species on Earth at 11 million or fewer. Another 2017 study even estimated that there are at least 1 billion to 6 billion species on Earth, of which 70-90% are bacteria.
A May 2016 study estimated that there are currently 1 trillion species (mostly microorganisms) on Earth based on scaling laws, but only one thousandth of them have been described.
In response to changes in biodiversity, biological conservation became a priority after the international community signed the Convention on Biological Diversity in 1992. Several indicators have been developed to describe trends in global biodiversity, although no single indicator covers all existing species. The Living Planet Index (LPI) is a composite index created using data from multiple vertebrate species.
As knowledge of biodiversity becomes increasingly important, should we pay more attention to our protection and understanding of this earth's resource?
