Grazers hasten ecosystem collapse from drought

 

 

Pressures from grazers hastens ecosystem collapse from drought

Experiments show grazing pressures compound drought stress, delay recovery

Date:

January 11, 2017

Source:

Duke University

Summary:

Ecosystem collapse from extreme drought can be significantly hastened by pressures placed on drought-weakened vegetation by grazers and fungal pathogens, a new study finds. The study’s experimental evidence shows that the natural enemies of plants play a major role in lowering resilience to drought and preventing recovery afterward. The finding may be applicable to a wide range of ecosystems now threatened by climate-intensified drought, including marshes, mangroves, forests and grasslands.

 

A new study by scientists at Duke University and Beijing Normal University may hold the answer why.

The researchers found that these tipping points can happen much sooner than current models predict because of the added pressures placed on drought-weakened plants by grazing animals and fungal pathogens.

“Our work provides the first real-world experimental evidence that these natural enemies of plants can play a dramatic role in lowering ecosystems’ tipping point by killing drought-weakened vegetation and preventing plants from recovering,” said Brian R. Silliman, Rachel Carson Associate Professor of Marine Conservation Biology at Duke’s Nicholas School of the Environment.

Ecologists have long known that drought can stimulate this type of attack on plants, he said, but they mostly discounted it as a secondary stress and not a main cause of ecosystem collapse.

“What we found is the opposite,” Silliman said. “Grazers have a strong compounding effect. This means these ecosystems are far more vulnerable to drought than the current models predict. With grazers present, they can handle much less drought stress.”

Read the full story: Science Daily