Mass die-offs of birds, fish, and marine invertebrates have grown increasingly frequent and severe, hiking at a rate of approximately one major mortality event per year over the past seven decades, according to a new study published by Yale, UC Berkeley, and University of San Diego researchers.
“While this might not seem like much, one additional mass mortality event per year over 70 years translates into a considerable increase in the number of these events being reported each year,” said study co-lead author Adam Siepielski, an assistant professor of biology at the University of San Diego, in a statement about the study, which was published earlier this month in the Proceedings of the National Academy of Sciences.
“Going from one event to 70 each year is a substantial increase, especially given the increased magnitudes of mass mortality events for some of these organisms, Siepielski added.
The researchers define mass mortality events as “rapidly occurring catastrophic demographic events” that eliminate more than 90 percent of a population, kill more than a billion animals, or produce “700 million tons of dead biomass in a single event.” For the study, they evaluated 727 mass die-offs of almost 2,500 animal species since 1940.
“This is the first attempt to quantify patterns in the frequency, magnitude and cause of such mass kill events,” said study senior author Stephanie Carlson, an associate professor at the University of California, Berkeley’s Department of Environmental Science, Policy and Management.
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