Warming Lake Waters Disrupting Fishing
About 40 kilometers off Michigan’s Keweenaw Peninsula, in the waters of Lake Superior, rises the stone lighthouse of Stannard Rock. Since 1882, it has warned sailors in Great Lakes shipping lanes away from a dangerous shoal. But today, Stannard Rock also helps scientists monitor another danger: climate change.
Since 2008, a meteorological station at the lighthouse has been measuring evaporation rates at Lake Superior. And while weather patterns can change from year to year, Lake Superior appears to be behaving in ways that, to scientists, indicate long-term climate change: Water temperatures are rising and evaporation is up, which leads to lower water levels in some seasons. That’s bad news for hydropower plants, navigators, property owners, commercial and recreational fishers and anyone who just enjoys the lake.
When most people think of the physical effects of climate change, they picture melting glaciers, shrinking sea ice or flooded coastal towns (SN: 4/16/16, p. 22). But observations like those at Stannard Rock are vaulting lakes into the vanguard of climate science. Year after year, lakes reflect the long-term changes of their environment in their physics, chemistry and biology. “They’re sentinels,” says John Lenters, a limnologist at the University of Wisconsin–Madison.
Globally, observations show that many lakes are heating up — but not all in the same way or with the same ecological consequences. In eastern Africa, Lake Tanganyika is warming relatively slowly, but its fish populations are plummeting, leaving people with less to eat. In the U.S. Upper Midwest, quicker-warming lakes are experiencing shifts in the relative abundance of fish species that support a billion-dollar-plus recreational industry. And at high global latitudes, cold lakes normally covered by ice in the winter are seeing less ice year after year — a change that could affect all parts of the food web, from algae to freshwater seals.
