Sat. Jul 20th, 2019

Human advance threatens to leave thousands of species without space | Science

Human advance threatens to leave thousands of species without space | Science



Humans have needed 500 years of expansion, advance and, sometimes, progress to exterminate some 900 species of animals. The next wave of extinctions, already in march, can be carried ahead almost to the double. A study shows that, by 2070, changes in land use will endanger some 1,700 new species that until now have not experienced difficulties. But whether they disappear or not will depend on the choices made by humans.

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Ecologists from Yale University have started from the present situation of some 19,000 species of amphibians, birds and mammals to determine their geographic range or current habitat and what space they will have left in little more than 50 years, in 2070. As you do not know what the future will look like, they have used four possible scenarios related to the intensity and scope of climate change in progress: the resources available and necessary (and the depredation of the environment) will not be the same in a context of low or high CO emissionstwo.

The study, published in Nature Climate Change, shows that in the two intermediate scenarios, up to 1,698 species will see their habitats reduced significantly. Most of them will see their territories contracted by up to 50%, with an average reduction of 10% per decade although for many the worst will come in the next two. By taxonomic groups, the most affected are the amphibians, with almost 900 species that will see their situation worsen in the Red List of the International Union for Conservation of Nature.

At least 1,700 species not threatened today, will be in five decades if the pace of appropriation of natural resources is maintained

The crucifix frog of Lombok, for example, today inhabits the rain forests of the islands of Bali and Lombok (Indonesia). Although limited to these two islands, it still has a relatively large joint habitat of 403 square kilometers (kmtwo). In 2070, you will have to make do with just 190 km2. Worse will be the Nile cobo, a kind of African antelope that survives in a few areas of South Sudan. Of less than 20,000 kmtwo of current habitable range, will go to just 5,000 kmtwo in five decades.

"The change in land use with a greater expected impact on biodiversity is the transformation of wild lands into agricultural land, such as crops or pastures," the Yale ecologist and co-author of the study said in an email. Walter Jetz. "This includes the conversion of primary forests [sin apenas marcas humanas] in secondary, arboreal plantations or crops, and the modification of savannahs and grasslands in cropland and pasture, "he adds.

The work also allows us to anticipate which regions or countries are on track to lose more wildlife. The most pronounced reductions of available habitat will occur where there is still greater biodiversity: South and Central America, Southeast Asia and the central and eastern parts of Africa. These are the regions where the greatest changes in land use are occurring (and could follow).

"In East Africa, for example, major changes in land use are expected due to anticipated economic growth and regional and international demand for land for agriculture, and there is a significant number of species already threatened or limited to agriculture. these areas, which makes it a region very sensitive to the impacts of land-use change on biodiversity, also in Brazil, a considerable change in land use is anticipated and hosts an even greater number of rare species [en número]. It is the combination of large expected changes in land use and the prevalence of species with a limited geographical distribution which makes a region a great risk for conservation, "explains the US ecologist.

The conversion of forests, savannas and parederas into land for cultivation and livestock, main cause

The researchers also modeled two other possible scenarios. On the one hand, one in which humans continue as before, using fuels and emitting greenhouse gases at the same rate as in 2015. In this future between pessimistic and realistic, the species that would aggravate their situation would be counted by thousands and hundreds of those that are already threatened would be in critical danger, the stage prior to extinction.

But if emissions began to be reduced by 2030 and the Paris Agreements were fulfilled, which foresee maintaining temperatures between 1.5º and 2º above those of the 19th century, human pressure on nature would be reduced, and even , there would be slight improvements for amphibians, birds and mammals, which would recover up to a third of their territories. This is the optimistic scenario.

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