Loss of animal biodiversity spells doom for some plants

More bad news for flora, with research indicating that even a small drop in wildlife can have dramatic effects on botanical distribution. A new study has shown how the biodiversity loss of birds and mammals will impact plants’ chances of adapting to human-induced climate warming.

More than half of plant species rely on animals to disperse their seeds, but the results of new research indicate that the ability of animal-dispersed plants to keep pace with climate change has reduced by 60% due to a loss of animal biodiversity.

Published in Science, it is the first study to calculate the scale of the seed-dispersal problem globally, and to identify the regions most affected: North America, Europe, South America, and Australia.

“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,” says lead author Dr Evan Fricke, of Rice University in the US.

As the climate changes in their region, many plant species need to move to a more suitable environment. However, if there are not enough animals to move their seeds – far enough to keep pace with changing conditions – plants that rely on seed dispersers can face extinction.

“If there are no animals available to eat their fruits or carry away their nuts, animal-dispersed plants aren’t moving very far,” says Fricke.

Which is worrying, given that many plants we rely on – both economically and ecologically – are reliant on seed-dispersing animals.

The researchers used data from more than 400 global field studies to train a machine-learning model for seed dispersal – using it to estimate the loss of tracking dispersal caused by animal declines.

Researchers used data on using data on plant traits and seed-dispersing animal traits. “to predict seed-dispersal interactions occurring between plants and animals at any location around the world,” says Fricke. 

“Second, we needed to model how each plant-animal interaction actually affected seed dispersal,” says Fricke. “For example, when an animal eats a fruit, it might destroy the seeds, or it might disperse them a few metres away or several kilometres away.”

The results spelled bad news for temperate regions across North America, Europe, South America, and Australia where seed-dispersal losses were especially severe.

“We found regions where climate-tracking seed dispersal declined by 95%, even though they’d lost only a few percent of their mammal and bird species,” says Fricke. 

According to senior author, Professor Jens-Christian Svenning of Aarhus University in Denmark, this research highlights an important intersection between the climate and biodiversity crises, and the need to restore birds and mammals in the face of rapid climate change.

“Biodiversity of seed-dispersing animals is key for the climate resilience of plants, which includes their ability to continue storing carbon and feeding people,” says Fricke.

“When we lose mammals and birds from ecosystems, we don’t just lose species. Extinction and habitat loss damage complex ecological networks. This study shows animal declines can disrupt ecological networks in ways that threaten the climate resilience of entire ecosystems that people rely upon.”