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The mystery of global species numbers: From 100 million to 1 trillion, how do scientists estimate our planet's biodiversity?
In Earth's biodiversity, estimates of global species numbers are often confusing. According to scientists, the current number of species on Earth ranges from 2 million to 1 trillion, however most estimates put the number of existing species at about 11 million. These numbers come with a lot of uncertainty, especially since the species that have been described are still only a small part of the overall species.
More than 99% of all biological species have become extinct, and the number of species alive today is still not accurately known.
As of 2018, approximately 1.74 million species have been digitized, but more than 80% of species have yet to be described. According to estimates, the total amount of DNA on Earth is approximately 5.0 x 10^37 base pairs, weighing 50 billion tons. The mass of the entire biosphere is estimated to be up to 4 trillion tons of carbon, and the comparison highlights the sheer scale of biodiversity and Earth's ecosystems.
An estimated 1.9 million extant species are thought to have been described, but scientists suspect that 20% of species names are synonyms, reducing the number of validly described species to 1.5 million. A study published in Science magazine in 2013 estimated that there are approximately 5 million ± 3 million existing species on Earth. The controversial nature of this number has made scholars confused about biodiversity.
While understanding species diversity, scientists have also explored the mechanisms behind extinction and speciation. Background extinction rates vary among species, but are generally estimated to be approximately one species facing extinction per million species-years. Taking mammals as an example, the average survival time of these species is usually 1 million years. Both increases and decreases in biodiversity are closely related to extreme events that occurred on Earth in the past, such as the climate change event 299 million years ago, which led to the collapse of rainforests and the massive loss of amphibians.
Known species and statistics
Chapman attempted to compile the most detailed available species statistics in 2005 and 2009. Based on a variety of published and unpublished research results, he concluded that there are approximately 1.9 million described species and the predicted total number of species. The number is as high as 11 million to 12 million. Many of these figures are only conservative estimates, and the number of descriptive species will continue to increase in the future.
Currently, the number of newly described species each year is approximately 18,000 to 19,000, and the number of fossil species is close to 2,000.
According to the report of Chapman (2009), the estimated number of existing effective species in 2009 can be broken down into the following categories. Although the total number of species may be higher for some categories, such as insects with numbers ranging from 10 to 30 million, bacteria from 5 to 10 million, fungi from 1.5 million, and so on. In 1982, Terry Erwin calculated that the global species richness may be as high as 30 million species based on research on a tropical tree beetle.
Over time, however, scientific predictions of overall biological numbers have changed. A 2017 study estimated the current number of species to be between 1 billion and 6 billion, with 70 to 90 percent being bacteria. In addition, a study in May 2016 estimated that there are 1 trillion species on the earth based on the law of scale, the vast majority of which are microorganisms. Although this view is controversial, it has also ignited academic discussions.
Indicators and Trends
With the signing of the Convention on Biological Diversity in 1992, biological protection has become an important task for the international community. In order to describe changes in global biodiversity, various indicators have emerged, but currently there is no unified indicator for all valid species. Ecologists use different methods to measure changes in biodiversity.
For example, the "Living Body Index" (LPI) is a population-based indicator that combines data from multiple vertebrate species to generate a single index. The global LPI in 2012 showed a decrease of 28%.
In addition, changes in conservation status over time can be measured based on the Red List Index compiled by the International Union for Conservation of Nature (IUCN). Includes fully classified species: mammals, birds, amphibians and corals. However, these indices are limited due to data availability challenges, particularly the lack of data on rare species.
The Biodiversity Indicators Partnership was established in 2006 to promote the development and promotion of biodiversity indicators and increase their accessibility. These efforts hope to provide more comprehensive ecological and environmental indicators to capture the vast impression of biodiversity loss.
Biodiversity is the cornerstone of life on earth, but with species extinction and habitat loss, how humans protect and understand the diversity of life on earth remains an unsolved mystery, and this makes us wonder Think about where will biodiversity go in the future?
