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College Catastrophic Flooding Is Mitigated by Biodiversity, Says New Study Led by Bard College Biology Professor

Ecologists have hypothesized for 30 years that biodiversity could reduce the negative effects of extreme weather events.

Annandale-on-Hudson, N.Y. – The impact of catastrophic flooding can be mitigated by protecting biodiversity, suggests a new study led by Bard College biology professor Alexandra Wright and published this week in the journal Nature Communications.

In June 2013 a massive, 200-year flood hit much of eastern and central Europe; damages resulting from the event totaled more than €12 billion in losses. Flooding in Germany covered multiple river basins, including, in central Germany, the location of the Jena Experiment, one of the longest-running biodiversity experiments in the world. Some fields in this experiment grow monocultures similar to central European agricultural fields, while other fields grow multiple species of grasses together in a single field. These fields have been growing and establishing for 12 years.

Nico Eisenhauer, an ecologist at the German Centre for Integrative Biodiversity Research, and coauthor of the study, said the flood completely submerged some areas of the Jena Experiment for more than three weeks. “We worried that the effects on the experiment would be catastrophic.”

“We had no idea that flooding might have positive effects in these grasslands,” says plant ecologist and lead author Wright, who is visiting assistant professor of biology at Bard. “When we looked at the data, we saw that productivity skyrocketed in some of the highest diversity fields.”

Increased productivity following an extreme weather event was unprecedented. Ecologists have hypothesized for 30 years that biodiversity could reduce the negative effects of extreme weather events. In the case of droughts, this is because diversity may act similarly to the lottery. The more tickets you buy, the higher the likelihood that you’ll win. Higher-diversity fields are less negatively affected by droughts because there is a higher likelihood that the higher diversity field will contain the winning ticket. This resistance to negative drought effects results in higher-diversity communities being more stable over time. In the case of the flooding at the Jena site, productivity in the highest-diversity plots was more productive than in the past, but it was also less stable. In such cases, the inherent utility of monitoring stability is called into question.

In the next 100 years, rising atmospheric CO2 concentrations are predicted to increase the frequency and severity of extreme weather. In Europe, costs associated with flooding may double in frequency within just four decades. Mitigating these costs in Europe, as well as elsewhere in the world, will depend on our ability to maintain high-diversity ecosystems. In fact, future extreme-flooding events could temporarily increase productivity in areas where biodiversity has been protected.

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