Environmental changes and human activities have caused a growing number of mass die-offs for many species.

A new scientific study published in the Proceedings of the National Academy of Sciences says large-scale deaths of fish, birds and invertebrates increased over a 72-year period from 1940 to 2012. Researchers came to this conclusion after reviewing the records of 727 “mass mortality events.”

The “good news” is that the number of die-offs for mammals remained about the same, while those involving amphibians and reptiles actually went down during the period under study.

Researchers could not determine how much of the upswing in die-offs is because of increased awareness of the problem.

Just how big are mass die-offs? These events involve at least a billion deaths, or the destruction of 90% of a population or 700 million tons of animals.

Some of the causes of die-offs include disease, disturbances produced by humans, and biotoxins, Jane Lee noted at National Geographic.

-Noel Brinkerhoff

To Learn More:

Recent Shifts in the Occurrence, Cause, and Magnitude of Animal Mass Mortality Events (by Samuel B. Feya, Adam M. Siepielskic, Sébastien Nussléd, Kristina Cervantes-Yoshidad, Jason L. Hwand, Eric R. Huberd, Maxfield J. Feyb, Alessandro Catenazzie and Stephanie M. Carlson, PNAS) (pdf)

Mass Animal Die-Offs Are on the Rise, Killing Billions and Raising Questions (by Jane Lee, National Geographic)

Pesticides Suspected in Deaths of Birds and Bees (by Noel Brinkerhoff and Steve Straehley, AllGov)

7 Million Birds Die in U.S. and Canada Each Year because of Communication Towers (by Matt Bewig, AllGov)