Lost birds and mammals spell doom for some plants

In one of the first studies of its kind, researchers have gauged how the biodiversity loss of birds and mammals will impact plants' chances of adapting to human-induced climate warming. The research was funded in part by the U.S. National Science Foundation.

More than half of plant species rely on animals to disperse their seeds. In a study published in Science, researchers showed that the ability of animal-dispersed plants to keep pace with climate change has been reduced by 60% due to the loss of mammals and birds that help such plants adapt to environmental change.

Researchers at Rice University, the University of Maryland, Iowa State University and Aarhus University in Denmark used machine learning and data from thousands of field studies to map the contributions of seed-dispersing birds and mammals worldwide. 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 is during the short period when they're a seed moving across the landscape," said Rice University ecologist Evan Fricke, the study's first author.

As climate changes, many plant species must move to a more suitable environment. Plants that rely on seed dispersers can face extinction if there are too few animals to move their seeds far enough to keep pace with changing conditions.

"If there are no animals available to eat their fruits or carry away their nuts, animal-dispersed plants aren't moving very far," Fricke said. And many plants people depend on, both economically and ecologically, rely on seed-dispersing birds and mammals.

Fricke said the study is the first to quantify the scale of the seed-dispersal problem globally and identify the regions most affected. The authors used data synthesized 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 dispersal caused by animal declines.

"In addition to the wake-up call that declines in animal species have vastly limited the ability of plants to adapt to climate change, this study demonstrates the power of complex analyses applied to publicly available data," said Doug Levey, a program director in NSF's Division of Environmental Biology.