Lake surface temperatures are rising globally and are expected to continue to increase due to climate change. New research indicates that lake temperatures could exceed natural variability within this century, especially in tropical lakes.
This unprecedented warming, and the disappearance of existing climates “could lead to the extinction of some species and the redistribution of others on a global scale,” the study warns.
Previous studies have investigated the emergence of unprecedented warming in both terrestrial and marine ecosystems. However, advanced modeling techniques to project how lakes will warm in the future haven’t been as widely used, the authors of the new study note. To fill this gap, the researchers employed a combination of historical records, remote sensing, and advanced modeling to compare natural variation in the past (1850-2014) to projected temperatures amid climate change in the future (2015-2100).
The analysis projected that many cool water lakes and those in northern latitudes would experience unprecedentedly high surface temperatures under a scenario in which climate change warms the Earth an extra 4°C (7.2°F) above pre-industrial levels. In warmer tropical regions, these extreme conditions will occur sooner at 2.4°C (4.3°F) of warming, that’s because warm, tropical lakes are more consistently the same temperature throughout the year and have no winter freeze. The low natural variation means that a sudden rise in heat from climate change can quickly push tropical lakes to unprecedented temperatures, Iestyn Woolway, second author of the study, explained in an email to Mongabay. Woolway is an independent research fellow with Bangor University in the UK.
High temperatures could also affect how water stratifies in tropical lakes. Warm water is less dense than cold water and tends to stay at the surface, while the colder water sinks deeper in the lake. Anyone who has been in a lake and noticed cold water by their feet while the surface is warm has experienced the natural phenomenon of stratification. As global temperatures rise, this thermal stratification is likely to become stronger in tropical lakes, Woolway said.
With temperature differences becoming greater, less mixing will occur. That will likely lead to a decline in fish populations and greater food insecurity for many communities that depend on freshwater fish for protein, Woolway said. Low-income communities such as those near Lake Victoria will be especially vulnerable, he added.
Warmer water may also favor the introduction of invasive species that can out-compete native species, Woolway said, such as the Baikal seal (Pusa sibirica), native to Russia’s cold Lake Baikal.
“The Baikal seal, adapted to cold water, might face challenges for survival as its habitat warms, potentially leading to its decline or extinction,” Woolway wrote in an email.
Many lake ecosystems are already threatened by human-caused stressors, such as overfishing and pollution. Extreme temperature increases can further degrade these ecosystems and likely create habitats unsuitable for many native aquatic organisms, especially in low latitudes, the researchers concluded.
Banner image: Baikal Seals by Sergio Tittarini via Visual hunt
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