Increase in Mass die-offs of fish and birds

Dead sunfish and large-mouth bass in April 2014, following a severe winter on Wintergreen Lake, Michigan. Credit: Gary Mittelbach, UC Berkeley
Date:13 January 2015 Author: William Horne Tags:, , , , ,

Scientists have found that mass die-off events are increasing rapidly for some species, and decreasing for others, threatening to disrupt fragile ecosystems across vast areas.

The study, published on Monday in the Proceedings of the National Academy of Sciences, looked at data from 727 mass die-off events, spanning 70 years and across 2500 different species.

Mass die-offs occur naturally and are distinct from extinction events. When these events are sufficiently dispersed in time, even if 90% of a particular species dies, they can often recover.

The study found that over the last 70 years these events have been increasing by about one event per year.

“While this might not seem like much, one additional event per year over 70 years translates to a considerable increase in the number of events being reported each year,” said study co-lead author Adam Siepielski, an assistant professor of biology at the University of San Diego.

The research shows, however, that these events have been increasing dramatically for birds, fish and invertebrates, while they have declined for reptiles and amphibians, and remained unchanged for mammals. This development can upset ecological balances beyond the potential disappearance of a specific species, then.

This study suggests that in addition to monitoring physical changes such as changes in temperature and precipitation patterns, it is important to document the biological response to regional and global environmental change.

The researchers highlighted ways to improve documentation of such events in the future, including the possible use citizen science to record mass mortality events in real-time.


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