It’s no longer just a question of whether the planet’s precious lakes are being affected by climate change. The evidence from observations is clear: changes in climate, especially in recent decades, have impacted lakes worldwide.
With warming trends expected to continue, researchers are now turning their attention to predicting how this will affect lakes in the future. A new study of lakes in Austria provides valuable insights.
Austrian Federal Forests, a government agency responsible for the management of 13 Austrian lakes, asked Martin Dokulil, a retired researcher at the University of Innsbruck, to forecast surface water temperatures in nine of the largest of these lakes and to advise about potential impacts.
Dokulil studied historical records and found a rise in summer surface water temperature parallel to air temperature since the mid-1960s. He estimates an average increase in annual lake temperature of about 1 degree Celsius (less than 2 degrees Fahrenheit) during this period. “Increases in air temperature as a result of climate change are mirrored in lake waters where temperatures are also on the rise,” he concluded.
He predicts that lake surface water temperatures are likely to rise by up to 3 degrees Celsius (5.4 degrees Fahrenheit) in Austrian Lakes by 2050, depending on the region.
What’s the big deal with seemingly small increases in water temperature? The scientific and conservation communities are concerned because water temperature is one of the key factors affecting vital lake functions, from mixing within the lake to ecological stability and the lake’s water budget.
The concern about warming lake temperatures is not limited to Europe. I’ve been writing a series of posts on the topic of warming lakes, including Lake Tahoe and the Great Lakes in North America, and Lake Tanganyika in Africa. Climate change is now considered a major driver affecting the way lake ecosystems function.
Two of the largest lakes in Austria, Bodensee (Lake Constance) bordering Germany and Neusiedler See (Fertö) bordering Hungary, were included in the study along with Attersee, the largest lake completely in Austria, and Traunsee, the deepest lake. The latter two, along with Mondsee and Wolfgangsee, are part of a lake district north of the Alps. The three largest lakes in a region south of the Alps were also included in Dokulil’s study published online in the journal Hydrobiologia.
Some of the lakes were more affected than others, basically because they are located in different sub-climate zones, Dokulil told me.
“The temperature trends I found are similar in many European lakes and with observations elsewhere in the world,” he explained. “However, lakes in the Alps are perhaps more affected than in other regions of Europe because the air temperature here is increasing at a higher rate.” His findings are consistent with warming trends found in global lake temperature assessments.
A member of the Global Lake Temperature Collaboration, Dokulil said that many of the consequences of the warming trend also correspond to lakes elsewhere. He participated in two European-wide studies, known as REFLECT (Response of European Lakes to Environmental and Climate Change) and CLIME (Climate and Lake Impacts in Europe), which documented the impacts to lakes as a result of climate change.
The ecological status of many lakes in Europe has changed dramatically over the last 20 years, according to the results of the CLIME study published in 2010.
Researchers acknowledged that many of the changes are the result of human activities in lake watersheds, but some are also driven by changes in the regional climate. Milder and wetter winters are causing increased runoff of nutrients (and other pollutants). When coupled with warmer and calmer European summers, these changes in climate create ideal conditions for promoting algal growth in lakes. Dokulil predicts that Austrian lakes will be affected in similar ways.
“Significant increases in summer temperatures will also affect the carbon cycling in lakes, with potential consequences on atmospheric carbon dioxide levels and the Earth’s climate,” he added.
The future challenge in Austria and elsewhere is figuring out how to protect and restore the health of lakes in a warming world. Forecasting potential increases in water temperature allows agencies like Federal Forests to better inform and adapt lake restoration and management efforts – an important step in the right direction for finding solutions.
Lisa Borre is a lake conservationist, freelance writer and avid sailor. With her husband, she co-founded LakeNet, a world lakes network, and co-wrote a sailing guide called “The Black Sea” based on their voyage around the sea in 2010. A native of the Great Lakes region, she served as coordinator of the Lake Champlain Basin Program in the 1990s. She is now an active member of the Global Lake Ecological Observatory Network.