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Washington (AFP) – The decline of animal species that disperse seeds is hurting the ability of plants to move to more suitable habitats in a warming world, according to a new study published Thursday in the journal Science.
The findings illustrate a worrying feedback loop between biodiversity loss and the global climate crisis, with forests vital for sequestering carbon.
“When we lose birds and mammals, we don’t just lose the species themselves. We lose this important ecological function, which is seed dispersal,” lead author Evan Fricke told AFP. ‘Rice University.
The paper is the first to quantify the problem on a global scale and estimates that the ability of plants dispersed by animals to keep pace with climate change has already been reduced by 60% due to the loss of mammals and birds. .
Climate change is altering ecosystems around the world, meaning that an area hospitable to a given tree species today could be hostile in decades to come.
There are regions where the tree can move, with more welcoming conditions of precipitation and temperature, but to get there it must undertake a journey while it is still only a seed.
About half of all plants depend on animals to eat their fruits or nuts to transport their seeds, while some rely solely on the wind.
For their study, the Danish-American research team used data from thousands of field studies of animal traits, along with machine learning, to build a map of the contributions of seed-dispersing birds and mammals. in the world.
They also compared seed dispersal maps today to what things would have looked like without human-caused extinctions and shrinking ranges.
The models went into great detail, including “which animals eat the seeds of which fruits, how far the seeds go from the parent plant, and also how this passage impacts germination,” Fricke said.
This means that when an animal eats a fruit, it can destroy the seeds or scatter them meters and kilometers away.
Machine learning has been used to fill in the gaps of some animal species that have not been studied in depth.
For example, if a South American fox was not as well studied as a European fox, but had similar characteristics, the computer model predicted how it would interact with seeds.
The results were surprising, showing that seed dispersal losses were particularly severe in temperate regions of North America, Europe, South America and Australia, even though they had lost only a few percent of their mammal and bird species.
The disruption was less severe in tropical South America, Africa and Southeast Asia, but would accelerate if more iconic threatened species were lost, such as elephants.
Together, the research shows that efforts to conserve and restore animal species to their former ranges can help fight climate change.
“Animal decline can disrupt ecological networks in ways that threaten the climate resilience of entire ecosystems that people rely on,” Fricke said.
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