Their ability to track climate change is being squeezed on all sides
An American Robin forages for berries from a winterberry holly. Credit: David Stephenson/ZUMAPRESS.com/Alamy Live News
” The study’s really interesting,” said Alexa Fredston (a Rutgers University quantitative ecologist who was not involved in the new research). She adds that it is surprising “how substantially plants have already lost their ability to track climate change.” That also underscores how deeply intertwined biodiversity loss is with the climate crisis now facing the planet.
” “We are trying to understand, if we lose biodiversity, how does that affect the ecosystems that these species are lost from,” says Evan Fricke, an ecologist at Rice University and co-author of this new study.
For decades, scientists have tracked which birds and animals eat fruits, the seeds inside them, and how far they travel to germinate. These are what ecologists refer to as mutualistic interactions. Fricke says, “The animal gets some fruits and the plant gets moving.” He claims that he spent hours in a hammock with his eyes fixed on a piece fruit to see if any local birds stopped by for a snack.
Ecologists have found that deforestation has reduced the ability of trees to spread their seeds. This is evident in the case of the Atlantic Forest in Brazil. Fricke states that “but zooming out to global scale, there hadn’t been an analysis.” He and his colleagues “were trying to understand the size of this problem .”
He and his co-authors gathered data from thousands upon thousands of studies over many decades around the globe and fed it into a machine learning model. Researchers focused on plants that produce fleshy fruits. They taught the model how the model can recognize relationships between species traits, such as whether a bird lives in the canopy or the understory of the forest. Also, which animals and plants have mutualistic interactions. The researchers also considered how far animals could carry seeds and whether they produced seedlings. The model allowed researchers to predict mutualistic interactions between species that they didn’t have data on, such as rare or extinct species.
The model was used by researchers to compare where specific plant and animal species were found today with what they would expect to find if there had been no extinctions, changes in the climates of animals, or the introduction of new species. They found that all of these pressures have stymied plants’ seed-dispersal abilities, reducing thus their capacity to keep pace with climate change by 60 percent. Fricke states that this number is greater than the loss of biodiversity in birds and mammals. It clearly shows that as we lose mammals, we are often losing the best seeds dispersers .
Fredston states that the study is “really impressive” from a modeling perspective. Fredston says that the model and the data it contains are more than their parts because they “really impressive from a modeling standpoint.”
Climate change and biodiversity loss have caused the largest reductions in seed-dispersal capacity in regions like North America and Europe where climate shifts occur over greater distances. These regions are known for their large areas of flat terrain. Different climate conditions may exist in mountainous areas. Large mammals are less able to transport seeds long distances. This has also been a contributing factor.
Fricke, along with his colleagues, also looked at what would happen to birds and mammals currently listed as endangered or vulnerable by the International Union for Conservation of Nature. These losses would have the largest impact on seed dispersal and were most noticeable in Southeast Asia, Madagascar, and other parts of Asia. This suggests that remaining seed dispersal from these regions is being done by threatened species.
Fricke believes that his and his colleagues’ estimates of seed dispersal are likely conservative, as they didn’t consider other barriers like roads or infrastructures that could impede animals’ movement.
Overall Fricke believes that the new study gives a realistic picture of how climate change affects plants. Fricke says that the study shows that humans are forcing plants to travel longer distances in order to maintain comfortable climate conditions. However, it also slows down their ability to adapt to our impact on animals who rely on them to transport their seeds.
ABOUT THE AUTHOR(S)
Andrea Thompson, an associate editor at Scientific American, covers sustainability. Follow Andrea Thompson on Twitter Credit: Nick Higgins