There are about 11,000 species of birds on Earth. And almost half of them suffer from sometimes very strong stock losses. By contrast, only six percent of all bird species are increasing in number. This is the startling result of a global study by Alexander Lees of Manchester Metropolitan University and his team in the "Annual Review of Environment and Resources". Birds living in the tropics, mountains and in the polar regions are particularly affected, the working group writes.
"We are now experiencing the first signs of a new wave of extinction of continental spreading bird species," says Lees: Earlier extinction events primarily affected island species, but the large -scale destruction of natural landscapes, especially in the tropics, is now also causing the extension of species. In Brazil, for example, at least three species have disappeared since the turn of the millennium. Many of the former very common bird species have also broken down in the existing inventory. Pastras, for example, were considered everyday birds in parts of Asia a few decades ago, but they were largely eaten.
North America and Europe are also affected: both continents have also lost billions of birds in recent decades. The cause here is mostly intensive agriculture, which deprives the animals of habitat and food. A similar pattern emerges in the tropics. "Bird diversity peaks in the tropics worldwide, and that's where the number of endangered species is highest," says Lees.
Habitat destruction, industrial agriculture and overhunting are the main causes, but climate change is also increasingly playing a role. This is especially true for species in the polar latitudes and in the high mountains, where global warming is progressing most strongly and leading to reduced habitats. The tropics seem to be just as affected as Costa Rica suggests. In the meantime, the rainforest area has increased again, but the number of birds has shrunk – possibly due to a lack of food: rising temperatures and shifting rainy and dry seasons make life difficult for local insects there - and thus also for the birds.
However, the inventory is made more difficult in the most species -rich regions because systematic records are missing or shorter periods include than in the moderate latitudes. However, since birds are the best examined animal group worldwide, there are still sufficient data for many types to provide reasonably secure statements about existing trends. And these are worried about Lees and Co: "Our estimates indicate an effective overall overall advisory rate that could be six times higher than the rate of extinction of Vogel species since 1500," writes the group.
They therefore urge us to finally get serious about protecting habitats. "The fate of bird populations depends heavily on us stopping habitat loss and degradation," says Lees. Lees and Co also write that it could be possible to reverse negative population trends: The restoration and better protection of wetlands such as animals have ensured that the number of waterfowl has risen sharply again in North America and Europe. So far, however, these cases are rather the exception.
