Surprising discovery: The number of species has not declined

(variety) The variety of life forms on earth - from corals to carnivores - has been attacked. Decades of scientific research have documented the disruption of ecosystems leading to extinction of species due to destruction of habitats, pollution, climate change, encroachment and over-exploitation. .

This made a recent report in the journal Science shocking.

Nick Gotelli, a University of Vermont professor, along with colleagues from Saint Andrews University, Scotland, and the University of Maine, reviewed data from a hundred authentic long-term monitoring studies. all over the world - from the polar regions to the tropics, under the sea and on the ground. They found that the number of species in many places has not changed much - or has actually increased.

Now wait a bit. A global extinction crisis will show in the extent of local biodiversity decline, is that true? However, that is not what scientists have noticed. Instead, the researchers found that, on average, the number of recorded species remained the same over time. 59 out of 100 bio-communities show an increase in abundance and 41 communities. In all these studies, the rate of transformation is very small.

However, researchers have also found that something is changing quickly: the species are living in the studied areas. Nearly 80% of the community considered by the research team showed significant changes in species composition, averaging about 10% of variation over a decade - significantly higher than the predicted rate of change by Models.

In other words, this report shows the huge number of alternative species in the global habitat that are taking place, leading to the creation of new bio-communities . 'Right in front of us, the same place where the research team might have observed a decade earlier, or even just a year ago, a new set of plants and animals may be taking over. keep, ' Gotelli said.

A soft world

The cause of this change is still not completely clear, but its impacts on conservation and policy can be significant. Historically, conservation and planning science has focused on protecting more threatened species, compared with the change in which plant and animal species are gathered together.'A policy application of this study is that we will need to focus on identifying species as well as the number of species , ' Gotelli said . 'The number of species in a position may not be our best record for environmental changes'.

For example, scientists have written that disturbed coral reefs can be replaced by a group of algae-dominated organisms. This alternative can keep the number of species constant, but does not provide fisheries or tourism (diving to see unattractive algae such as diving to see coral reefs) or protect the coast that coral reefs were at did.

Almost unrecognizable

This new study, led by Maria Dornelas at Saint Andrews University in Scotland, has carefully reviewed previous studies that have been monitoring and counting species over the years. The team selected 100 studies that included 6 million observations on more than 35,000 different species - including data from 1874 and over the past 40 years. Widely observed about habitat changes and declining species - and know that extinction rates are many times higher than usual - scientists have predicted the number of species observed in most studies. Save decline over time.

But why did they not find that the decline could be dominated by many factors. One of them relates to what science writer David Quammen calls 'planet of weeds'. In other words, invasive species or successful newcomers or common creatures - such as kudzu and mice - can spread new places, keeping the number of local species unchanged, even if the overall biodiversity of the earth is degraded.

'We have moved around species , ' Gotelli said. 'There is a huge diversity of ants in Florida, and about 30% of ants in Florida are not native. They were unintentionally introduced into this area, most of which originated in the rainforests of the old world, and now they are part of the local biological complex. Therefore, there may be increased biodiversity in local populations for global identity. "

And sampling problems can also hide important facts: some species may have become too rare - such as white rhinos, for example - it's hard to find them in a comprehensive survey. that, and therefore, does not appear in the original results and does not disappear in subsequent surveys.

Changes in scope related to climate change may also have affected, pushing species into new terrain quickly. On May 6, 2014, the White House released a National Climate Assessment that emphasizes, as a result of artificial warming , 'species, including many species. iconic, can disappear from the area where they used to live or become extinct, changing some areas so much that the combination of these areas of plants and animals is close as unrecognizable. '

The study, published April 18 in the journal Science, underscores this emerging reality, Nick Gotelli and co-authors conclude : 'need to expand the focus of research and planning from biodiversity loss to biodiversity change '.