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Freshwater Lakes are Warming at Surprising Rate

Wednesday, February 22, 2017
Stephen R. Dujack

Stephen R. Dujack

Editor, The Environmental Forum®

There is an alarming new study out, funded by NASA and the National  Science Foundation. It was published in Geophysical Research Letters and announced at the American Geophysical Union fall meeting. Together, these are the heavyweights in climate change research and analysis. Their findings: The world’s lakes are warming at an alarming rate, much faster than the oceans or the atmosphere. The study monitored 235 lakes, spanning six continents and representing half the world’s freshwater supply, for 25 years. The results should bring a fresh spur to the urgency of mitigating greenhouse gases for social survival.

“These results suggest that large changes in our lakes are not only unavoidable, but are probably already happening,” said lead author Catherine O’Reilly, associate professor of geology at Illinois State University, Normal, in a press release. As noted by the respected website phy.org, “Earlier research by O’Reilly has seen declining productivity in lakes with rising temperatures.”

The warming rate is .34 degree Celsius per decade. By point of comparison, total warming of the atmosphere since the industrial revolution began is only 1 degree Celsius. Lakes are warming that much every three decades. The findings forecast a tragedy in the making, as freshwater aquatic ecosystems are unable to migrate to more amenable climates as temperatures change. When it comes to lakes, organisms can be literally locked in place. As temperatures swing so quickly, aquatic organisms can be stressed or disappear.

“Society depends on surface water for the vast majority of human uses,” co-author Stephanie Hampton, director of Washington State University’s Center for Environmental Research, Education, and Outreach in Pullman, said on phy.org. “Not just for drinking water, but manufacturing, for energy production, for irrigation of our crops. Protein from freshwater fish is especially important in the developing world.”

Freshwater ecosystems will change as a result of the warming. For one thing, eutrophication will get worse, as algal blooms increase as temperatures increase. The study projected that blooms will increase 20 percent over the next century. One result of the blooms — some of which would be toxic to fish — is an increase in emissions of methane, a potent greenhouse gas, which will rise by 4 percent.

U.S. Great Lakes, NASA

“Our knowledge of how lakes are responding to global change has been lacking,” the NSF site quoted Henry Gholz, its program director in the Division of Environmental Biology. “That has made forecasting the future of lakes — and the life and livelihoods they support — very challenging. These newly reported trends are a wake-up call to scientists and citizens, including water resource managers and those who depend on freshwater fisheries.” That last category includes a large slice of humanity.

The NSF site explains further the calamity facing freshwater ecosystems: “Temperature is one of the most fundamental and critical properties of water. It acts like a strict referee, commanding a host of other properties that include intricate living processes that have evolved within strict boundaries.”

Lakes in different climate zones are warming for different reasons. Northern lakes are losing ice cover earlier, and open water absorbs solar radiation more than highly reflective frozen water, exacerbating the process. In other regions, cloud cover is decreasing, also allowing in more sunlight. In the tropics, warming air temperatures are an important driver of lake temperatures.

There is good news and bad news for warm-region lakes: they have experienced less of an increase, but they are already near the limit that can be tolerated by fish. That is of particular concern for the African Great Lakes, home to one quarter of humanity’s freshwater supply and an important source of food for the region. “Understanding the trajectories of temperature change in inland waters is a foundational step in advancing science on a broad diversity of societally important issues,” according to the study.

“The U.S. Great Lakes are experiencing some of the earliest warming because of earlier ice melt,” according to the Christian Science Monitor. And The Minneapolis Star Tribune notes, “Relatively small changes can lead to large changes in systems that define our region,” because a temperature shift of 2 degree Celsius in the Great Lakes can mean the difference between a Lake Superior that is iced-over in winter or one that is  ice free. Lake Superior is the largest freshwater lake in the world by surface area.

Humanity depends on lakes. It is time to turn off the warming threatening their and our future.

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