Long-spined sea urchins, which have nearly vanished from the Caribbean, march across a seabed.
Photograph by Vilainecrevette, Alamy
What’s New
We’re not talking about a few dead fish littering your local beach. Mass die-offs are individual events that kill at least a billion animals, wipe out over 90 percent of a population, or destroy 700 million tons—the equivalent weight of roughly 1,900 Empire State Buildings—worth of animals.
And according to new research, such die-offs are on the rise.
The study, published this week in the Proceedings of the National Academy of Sciences, is the first to examine whether mass die-offs have increased over time.
Researchers reviewed historical records of 727 mass die-offs from 1940 to 2012 and found that over that time, these events have become more common for birds, marine invertebrates, and fish. The numbers remained unchanged for mammals and decreased for amphibians and reptiles. (See “What’s Killing Bottlenose Dolphins? Experts Discover Cause.”)
Disease, human-caused disturbances, and biotoxins—like the red tides caused by algae that are prevalent along American coastlines—are three major culprits.
Why It Matters
Big die-offs can permanently change food webs. Ninety-nine percent of the sea urchin Diadema antillarum disappeared from the Caribbean in 1983 thanks to a pathogen. The herbivore’s vanishing act paved the way for an algal invasion of reefs, smothering corals…..More Here