A bird eats a berry. Small birds like the robins can spread seeds over a long distance. Credit: Paul D.
Researchers gauged how the loss of birds and mammals will affect plants' chances of adapting to climate warming in one of the first studies of its kind.
Plants rely on animals to spread their seeds. The ability of animal-dispersed plants to adapt to climate change has been reduced by 60% due to the loss of mammals and birds.
Machine learning and data from thousands of field studies were used by researchers from Rice University and the University of Maryland. To understand the severity of the declines, the researchers compared maps of seed dispersal today with maps showing what dispersal would look like without human-caused extinctions or species range restrictions.
"Some plants live hundreds of years, and their only chance to move is during the short period when they're a seed moving across the landscape," said Rice ecologist Evan Fricke, the study's first author.
Many plant species have to move to a more suitable environment as climate changes. Plants that rely on seed dispersal can face extinction if there aren't enough animals to move their seeds far enough.
He said that if there were no animals available to eat their fruits or carry away their nuts, animal-dispersed plants wouldn't move very far.
Many plants people rely on, both economically and ecological, are reliant on birds and mammals, according to research conducted by the University of Maryland's National Socio-Environmental Synthesis Center.
The study is the first to quantify the scale of the seed-dispersal problem, and to identify the regions most affected. The authors used data from field studies around the world to train a machine-learning model for seed dispersal, and then used the model to estimate the loss of climate- tracking dispersal caused by animal declines.
Two significant technical advances were required to develop estimates of seed-dispersal losses.
"First, we needed a way to predict seed dispersal between plants and animals at any location around the world."
The researchers were able to model data on networks of species interactions from over 400 field studies.
He said that they needed to model how each interaction affected seed dispersal. When an animal eats a fruit, it can destroy the seeds or spread them a few meters away.
The researchers used data from thousands of studies to figure out how many seeds specific species of birds and mammals have.
The National Science Foundation's program director said that the study shows the power of complex analyses applied to huge, publicly available data, in addition to the wake-up call that declines in animal species have vastly limited the ability of plants to adapt to climate change.
The study showed that seed-dispersal losses were more severe in some parts of the world. Tropical regions in South America, Africa and Southeast Asia would be most affected by extinction.
Even though they lost a few percent of their mammal and bird species, the regions where climate- tracking seed dispersal declined by 95 percent were found.
A bear eats fruit. Many large seed dispersalrs are extinct or in decline. Credit: Paul D.
The intersection of the climate and biodiversity crises is highlighted by the seed-disperser declines.
The ability of plants to continue storing carbon and feeding people is dependent on the diversity of seed-dispersing animals.
Some declines in seed dispersal can be counteracted by restoration of the natural habitats.
The study's senior author, a professor and director at the Center for Biodiversity Dynamics in a Changing World, said that large mammals and birds are important as long-distance seed dispersal. The need to restore faunas to ensure effective dispersal in the face of rapid climate change was highlighted in the research.
When mammals and birds are lost from the environment, we don't just lose species. Ecological networks are damaged by extinction and habitat loss. The study shows that animal declines can disrupt ecological networks in ways that threaten the climate resilience of the entire ecosystems.
The effects of defaunation on plants' capacity to track climate change is information provided by Evan C. Fricke. www.science.org/doi/10.1126/science.abk3510
Science journal information.
Some plants are doomed by lost birds and mammals.
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