Climate change increases frequency of fish mass extinction

(ORDO NEWS) — Using data collected from more than 500 previous fish die-offs in lakes in Wisconsin and Michigan, researchers use simulations to predict an increase in the frequency of fish mass die-offs as a result of climate change.

As the climate on the planet warms, the prevalence of fish extinction, or mass death, increases. These extinctions can have a major impact on ecosystem functioning, endanger existing fish populations and reduce the global food supply.

And the frequency of these events appears to be accelerating, with dire consequences for the world if global carbon emissions are not substantially reduced over the course of the 21st century.

These are the findings of a recent paper co-authored by two members of the University of Arkansas Department of Biological Sciences, PhD student Simon Taye and Associate Professor Adam Sipielski, and several of their colleagues.

The article “Climate warming increases the frequency of massive fish deaths in lakes of the northern temperate zone” collected 526 documented cases of fish deaths that occurred in lakes in Minnesota and Wisconsin between 2003 and 2013.

The researchers identified three main causes of these events: infectious diseases, summer deaths, and winter deaths.

The researchers then focused their attention on summer deaths, fish deaths associated with warm temperatures. They found a strong relationship between local air and water temperatures and the occurrence of these events, meaning their frequency increased as temperatures rose.

Moreover, their models using air or water temperature produced similar results, which is important because air temperature data is more readily available than global water temperature data.

Finally, after establishing a historical baseline, the team used models based on air and water temperature to predict future summer homicide rates.

The results were sobering. Based on local water temperature predictions, the models predicted an approximately six-fold increase in fish mortality rates by 2100, while local air temperature predictions predicted a 34-fold increase.

It is important to note that these projections were based on temperature projections for the most severe climate change scenario, which was the only scenario for which data were available for analysis.

As Tai explained, “If there are now eight summer kills per year, then according to the models, we could have about 41 per year based on water temperature estimates, or about 182 per year based on air temperature estimates.”

“We believe that the forecasts obtained from the water temperature model are more realistic, while the forecasts obtained from the air temperature model indicate that we need to better understand how and why regional air and water temperature estimates differ in time to predict how many deaths might occur.”

However, their models show strong associations between rising temperatures and the frequency of environmental disasters.

While the study used data related to northern temperate lakes, Ty said the study is relevant to Arkansas as well. “One of the conclusions of the work is that similar temperature fluctuations affect all fish species, so that regional heat can lead to the death of both cold-water and warm-water fish,” he said.

“In particular, climate change is not only a gradual increase in temperature, but also an increase in its fluctuations, as it was this summer,” he explained. “In turn, our results show that these rapid temperature changes affect a wide range of fish, regardless of their heat tolerance.”

Zipielski added: “This work is important because it demonstrates the ability to use readily available data to predict fish extinction.”

“Like many other examples of how a warming climate is negatively impacting wildlife populations, this work shows that extreme temperatures can be especially detrimental.”

“Particularly impressive is the scale of the project, which uses thousands of lakes and over a million air and temperature data points,” Sipielski added. “Lakes outside of the study area, including lakes in Arkansas and adjacent areas, are not likely to be immune to an increasing frequency of such events.”

Sipielski urged the people of Arkansas to help document these events when they find evidence of them, even on their own territory, by contacting the appropriate authorities.

The work was published in Limnology and Oceanography Letters. Taya and Sipielsky were joined by co-authors Andrew Bray, Andrew L. Ripel, Nicholas B.D. Phelps and Samuel B. Fey.

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