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Global biodiversity

Global biodiversity is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Global biodiversity rather than just read about it. In short: Global biodiversity is the measure of biodiversity on Earth and is defined as the total variability of life forms. More than 99 percent of all species that ever lived on Earth are estimated to be extinct.

Global biodiversity — main illustration
Global biodiversity — illustration

Key takeaways

  • Global biodiversity belongs to science; place it in that map before memorising details.
  • Learn the definition first, then one example that makes the definition concrete.
  • Connect Global biodiversity to a quantity you can measure, compute or draw — that is where exam questions come from.
  • Reproduce the core statement of Global biodiversity from memory before moving on to harder problems.

Reference excerpt

Global biodiversity is the measure of biodiversity on Earth and is defined as the total variability of life forms. More than 99 percent of all species that ever lived on Earth are estimated to be extinct. 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. About 1.74 million species were databased as of 2018, and over 80 percent have not yet been described. The total amount of DNA base pairs on Earth, as a possible approximation of global biodiversity, is estimated at 5.0 × 1037, and weighs 50 billion tonnes. In comparison, the total mass of the biosphere has been estimated to be as much as 4 TtC (trillion tons of carbon). In other related studies, around 1.9 million extant species are believed to have been described currently, 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. Another study, published in 2011 by PLoS Biology, estimated there to be 8.7 million ± 1.3 million eukaryotic species on Earth. 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. 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.

Known species

Chapman, 2005 and 2009 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 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. 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, the estimated numbers of described extant species as of 2009 can be broken down as follows:

Estimates of total number of species However the total number of species for some taxa may be much higher.

10–30 million insects; 5–10 million bacteria; 1.5 million fungi; ~1 million mites ~1 million protists 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. Given the 50,000 described tropical tree species, Erwin suggested that there are almost 10 million beetle species in the tropics. In 2011 a study published in PLoS Biology estimated there to be 8.7 million ± 1.3 million eukaryotic species on Earth. By 2017, most estimates projected there to be around 11 million species or fewer on Earth. A 2017 study estimated there are at least 1 to 6 billion species, 70-90% of which are bacteria. 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, 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.

Indices to describe trends 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. 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. 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. 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

See also

Global Species Database Measurement of biodiversity

References

External links Biodiversity A-Z Archived 2020-09-19 at the Wayback Machine Wikispecies Biodiversity—Global issues Category natural environment Category biology

Illustrations

Global biodiversity: Examples of the multicellular biodiversity of the Earth.
Examples of the multicellular biodiversity of the Earth.
Global biodiversity: Insects make up the vast majority of animal species.[14]
Insects make up the vast majority of animal species.[14]
Global biodiversity: 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).
Global biodiversity: 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]
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]

Worked examples

Example 1 — a first encounter with Global biodiversity

Start with the simplest possible case. Write down what Global biodiversity claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Global biodiversity before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Global biodiversity ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Global biodiversity

In research
Global biodiversity appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry
Engineering practice reuses Global biodiversity in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom
Global biodiversity is common in secondary-school and first-year university syllabi. It links to neighbouring topics Biodiversity, so understanding it makes those chapters shorter.
In everyday life
Look for Global biodiversity outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.
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How to study Global biodiversity in 20 minutes

  1. Read the reference excerpt below once, without taking notes.
  2. Close the page and write down what Global biodiversity means in your own words.
  3. Compare your version with the excerpt and mark what you missed.
  4. Work through the three examples above with pen and paper.
  5. Explain Global biodiversity out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Global biodiversity in simple terms?

Global biodiversity is the measure of biodiversity on Earth and is defined as the total variability of life forms. More than 99 percent of all species that ever lived on Earth are estimated to be extinct.

Why does Global biodiversity matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Global biodiversity?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Global biodiversity.

Tags

  • Biodiversity

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