Droughts may benefit biodiversity in long run, study shows

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Droughts may even the playing field for marginalized species, according to a newly released study co-authored by UC Berkeley researchers.

The project was started in 2007 by Justin Brashares, a campus professor of environmental science, policy and management, and former campus postdoctoral researcher Laura Prugh, and many of the samples from the project were studied in UC Berkeley, according to co-author Joshua Grinath, a postdoctoral researcher at Middle Tennessee State University. He added that UC Berkeley was “hugely involved” in the study.

The researchers focused on the Carrizo Plain, a California semiarid grassland and national monument home to many threatened and endangered species, for their study. They examined the drought’s impact on hundreds of species on the plain.

The researchers found that dominant species on the Carrizo Plain suffered most during the drought, while rarer species increased in abundance, according to Grinath. He added that this trend was true for all animal and plant groups, with plants being hit first and carnivores responding later.

For example, the giant kangaroo rats that once thrived on the Carrizo Plain saw their population decline. This dominant species was replaced by the rarer short-nosed kangaroo rat and southern grasshopper mouse.

Grinath said the study had plenty of new findings, as it examined an extreme example of drought — the worst one in California in 1,200 years — and it studied the entire ecosystem rather than just plants.

“Drought episodes could be important for maintaining biodiversity,” Grinath said.

According to another co-author, Nicolas Deguines, a postdoctoral researcher from the University of Paris-Sud, the severity of the drought made it relevant to predicting the effects of climate change, as such droughts are predicted to occur more frequently.

Previous studies mainly focused on plants, but this one was more comprehensive — involving traps to catch and study insects, rodents and other small mammals, as well as the volunteer-run Carrizo Plain Christmas Bird Count, Grinath said. He added that they shined flashlights at night to catch reflections of nocturnal animals’ eyes and counted antelope and elk from airplanes.

Deguines said that fewer species decreased in number than expected. Of the 336 species studied, only 25 percent decreased significantly, according to Deguines.

The study is ongoing and the recovery from the extreme drought is still being monitored, according to Grinath. He said there are still many questions to be answered by studying the region’s development.

“Will the once dominant species come back at the same position? Will the ecosystem function differently after the drought?” Deguines said in an email.

Yao Huang is the lead research and ideas reporter. Contact him at [email protected] and follow him on Twitter at @Yhoneplus.