Climate change is turning up the heat on lakes

Not for nothing, but when it comes to bodies of water and climate change, the ocean gets the (sea) lion's share of attention. But on land, around 117 million admittedly smaller bodies of water play necessary ecological, social, and economic roles. Lakes are relatively tiny, but "relative" is a key term there—for instance, the Great Lakes of North America account for 20 percent of the Earth's surface freshwater. We also rely on them for food, fresh water, transportation, and more.

New research identifies the interrelated challenges that the world's lakes face. According to Sapna Sharma, co-author of the research and an associate professor of York University's biology department, many of the climate change-related impacts that these watering holes remain relatively hidden despite these waters potentially facing an extensive collection of problems. "I hope that people get a sense of how widespread the effects of climate change on lakes are," she told Ars. "If you just go look out at a lake, you might not know all the changes it's experiencing."

To study this, Sharma and colleagues at different universities around the world pored over hundreds of research papers about lakes. These papers came from across the globe, and some date back to the 1930s, she said. Sharma and her fellow researchers all have differing areas of expertise, allowing them to review and synthesize the existing literature.

Sharma noted that there are a good number of other papers out there all focusing on different aspects of climate change's impact on lakes, but they tend to focus on particular niches, rather than the phenomenon as a whole. "To put it in a single document, in a single paper, was the novelty," she said.

Smoke on (or sometimes near) the water

The hundreds of papers painted a complex picture of lakes' past, present, and future under a rapidly changing climate. On a purely mechanical level, a warmer planet means less ice cover. More and more, ice is taking longer to grow on lakes in the fall and winter, and it leaves sooner in the spring and summer.

The heat also causes the waters to stratify sooner—meaning that the colder, heavier water will sink below the warmer, lighter water. Further, a changing climate can mean lakes experience more droughts or floods due to increased numbers of storms.

These mechanical phenomena can wreak havoc on life that relies on the lake for sustenance or their livelihoods (in the case of humans). For instance, a beefed-up seasonal stratification process can increase the likelihood of harmful algal blooms that can use up the oxygen in a lake and kill its other occupants. Algal blooms can also impact water quality for humans. Some lake fish prefer living in colder, deeper waters, so a warming lake could encroach on their habitats.

The human element

All of this, in turn, can impact humans on a cultural and economic level, Sharma said. In some cases, a decrease in yearly lake ice can mean cancellations of ice fishing tournaments, skiing races, and similar events. These events can be a big draw for small communities and bring in a great deal of tourism money.

Regular algal blooms on a lake can also decrease the property values of homes or cottages nearby. Around the world, these issues are more likely to impact marginalized people, Sharma added. For instance, algal blooms can make local water undrinkable for some Indigenous communities in Canada. "There are a bunch of economic, and social, and cultural consequences as well," she said.

Sharma said that new technologies like remote sensing and testing for biodiversity and the presence of species of flora and fauna using environmental DNA, or eDNA, will help researchers understand, and possibly address, the challenges lakes face going forward. The research notes that helping lakes thrive during climate change will involve bringing new and diverse perspectives into the conversation, including those of researchers from myriad fields and those of people living in countries outside North America and Europe.

BioScience, 2022. DOI: 10.1093/biosci/biac052 (About DOIs)