Mass animal deaths on the rise worldwideThousands of birds fall from the sky. Millions of fish wash up on the shore. Honey bee populations decimated. Bats overtaken by a deadly fungus. Piglets die in droves from a mysterious disease. It was tragic stories such as these that prompted a group of researchers from the University of San Diego, UC Berkeley and Yale to embark on a broad review of all the reports of large animal die-offs in the scientific literature since the middle of the last century. They turned up 727 such papers documenting “mass mortality events” (MME) of 2,407 global populations of mammals, birds, fish, reptiles, amphibians and marine invertebrates — like the thousands of starfish that perished in North America in 2014. Their analyses, published this week in the Proceedings of the National Academy of Sciences, revealed that not only are these events becoming more frequent, they’re also increasing in magnitude, with the number of fatalities higher for birds, fish and marine invertebrates. Thirty-five events completely or nearly wiped out an entire population.  Over the last 70-plus years — between 1940 and 2012, when the researchers ended their data collection — there has been about one more MME per year. “Going from one event to 70 each year is a substantial increase, especially given the increased magnitudes of MMEs for some of these organisms,” said Adam Siepielski, University of San Diego assistant professor of biology and the study’s co-lead author. The cumulative death toll reaches into the billions. The number one cause was disease, which was responsible for 26 percent of the mass killings, followed — no big surprise — by human activity, mostly traceable to environmental contamination. Toxic algal blooms, like the one that has plagued Lake Erie in recent years, have also emerged as a leading killer. “Mass die-offs result from both natural and human-driven causes,” said study coauthor Samuel Fey, a Yale researcher who studies how extreme temperatures can affect biological populations. More