Climate change is a factor of climbing towards extinction for mountain birds

Scientists have brought new evidence that climate change is leading to the extinction of tropical bird species living near the summit of a mountain.

Researchers have long predicted that many creatures would seek to escape a warmer world by heading to the heights.

However, those who live at the highest levels can not go higher and are expected to decrease.

This study revealed that eight species of birds that once lived near a Peruvian mountain top have now disappeared.

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Researchers are particularly concerned about tropical mountain ranges and the impacts of climate change.

"Tropical mountain areas are hotspots for biodiversity, they harbor more species than any other place on Earth," BBC News, chief author Benjamin Freeman told BBC News. from the University of British Columbia.

"It's a bit warmer in the tropics and tropical plants and animals seem to live a little higher than before."

Species living in these areas are also extremely vulnerable because the difference in temperature between the lowest and highest altitudes in the tropics is not as great as in other parts of the world. This means that climbing on slopes may not be as effective for tropical species as for other regions.

To test these ideas, scientists conducted a survey in 2017 on the species of birds living on an isolated Peruvian mountain top.

The team covered the same field, at the same time of the year, and used the same methods as a previous survey, conducted in 1985.

They found that, on average, the species' ranges had climbed between the two surveys. Most of the species found at the highest altitudes experienced a significant decline in their range and abundance.

Researchers say that recent warming is an "extinction extinction factor" for some of these species, with temperatures in the region increasing by almost half a degree Celsius between the two surveys.

Of the 16 species restricted to the top of the ridge, eight had completely disappeared in the last survey.

"These birds climbed the mountain as much as you wanted if the temperature was the main switch that controlled their place of residence," said Dr. Freeman.

"Those who lived near the summit of 30 years ago are gone."

The authors warn that rising temperatures will continue to cause widespread "extirpations and extinctions" of animals and high altitude plants in the tropical Andes.

On the other hand, scientists have discovered that lowland bird species are benefiting from climate change, expanding their range, and moving their upper limits higher up in the mountains.

However, even species that are currently moving may be short of options over time.

The authors say that if global temperatures increase by 2.6 to 4.8 ° C during this century, tropical species could be pushed 500 to 900 m higher up the slopes. This could prove to be too far for some.

Another problem is that many mountains have been cleared of their forests, which limits the ability of the species to move.

"You really can not ignore this process if you are thinking about biodiversity and long-term conservation in these areas," said Dr. Freeman.

"The solution is to maintain protected habitat corridors that span large gradients of altitude."

The study was published in the Proceedings of the National Academy of Sciences.