(Paris) Preserving forests will not be enough: tropical bird populations have greatly fell due to extreme heat linked to climate change, according to a study published Monday in the journal Nature Ecology & Evolution.
The intensification of extreme heat “caused a reduction of 25-38 %” of tropical bird populations between 1950 and 2020, compared to a situation where there would have been no climate change, concluded these scientists based in Europe and Australia.
“The conclusions are quite severe,” comments for AFP the main author of the study, Maximilian Kotz, the National Center for Supercalculators of Barcelona and the Potsdam climate research institute (PIK).
He notes that birds in the tropics are now confronted with 30 days of extreme heat per year against only 3 during the period 1940-1970. Climate change of human origin makes heat waves stronger and more likely in the world, estimates the scientific community.
“This has very important consequences on the way in which the conservation of biodiversity is thought: protecting immaculate habitats is crucial, but without attacking climate change, it will not be enough for birds,” he said.
“Close to the limits”
“This study underlines how complex it is to alleviate climate change and losses of biodiversity,” said AFP Aimae Van Tatenhove, of the ornithology laboratory of the American University of Cornell, “surprise” of the extent of the figures announced.
“This is an important reminder of the fact that we must continue to examine the various causes of population declines and apply these conclusions to conservation initiatives,” said the researcher who did not participate in the study.
To reach this conclusion, scientists have analyzed observation data of more than 3000 populations of birds around the world and used statistical models to isolate the effects of extreme climates of other factors.
Almost half of the bird species are in the tropical regions rich in biodiversity. These animals with colorful plumages also make services essential to ecosystems, for example by dispersing the seeds of plants.
But those who live in these regions may well already be “close to the limits” of tolerance at high temperatures, likely to cause heat strokes (hyperthermia) or dehydration, underline the authors.
They do not provide figures by species of birds, but cite for example a previous study, which has documented the decline of some of them in a forest of Panama: the King’s event holder and its red hoopoe, the two-color martin or even the Aurore trogon.
A study published in 2017 had also shown how some tropical hummingbirds were now forced to seek shadow to regulate their temperature in the face of extreme heat, when they should especially look for nectar essential for their survival.
Many factors
Extreme heat episodes, the frequency of which increases, therefore represent the main threat, more than the average increase in temperatures or precipitation, other aspects of climate change of human origin, notes the study.
The decline of bird populations in the world is also linked to other factors already highlighted in many scientific studies, such as invasive species, loss of habitat under the effect of deforestation for intensive agriculture, the use of pesticides or hunting.
But the conclusions of the study “question the vision that direct human pressures have so far been the dominant cause of the negative impacts on bird populations, rather than climate change, in tropical regions”, insist the authors.
“Deforestation has an obvious impact”, while it is “more difficult to see the immediate effects of extreme temperatures”, which require the analysis of long -term datasets, explains Aimee Van Tatenhove.
But all these phenomena deserve to be understood, underlines the specialist: “Why focus on a single factor when many of them lead the species to extinction?” »»
