What is harmful to lakes?

Climate change, loss of habitat, invasive species, pollution, and human activity are all threats to lake ecosystems. None of these threats exist independently, and some of them enable others.

Pollution brings excess nutrients or pathogens into a lake, which impacts the broader ecosystem, leading to algae blooms and the loss of life in the lake. A variety of human activities pollute lakes, and some are a little less direct than you might expect.

Point source pollution is a direct outfall into a lake, such as a pipe carrying wastewater or a motorized boat leaking oil. Non-point source pollution exists over a lake’s broader watershed and includes runoff of fertilized lawns, soap used to wash cars, storm water runoff, and seepage from septic systems.

Forestry operations impact lakes because forests absorb precipitation, and removing trees or plants causes increased inflows to a lake. This alters its shoreline and depth, while also adding more sediment and phosphorus to the water. When agriculture is improperly managed, nutrients and pathogens from manure can seep into a lake and livestock can damage shorelines.

Invasive species are also harmful to lakes. Bits of aquatic plants can catch on a boat and then establish themselves in a new lake when that boat is launched elsewhere. Introduced species of fish, frogs, or turtles can directly kill indigenous species or compete with them for food and habitat.

Even low-impact recreation such as swimming, hiking, or paddling can have an impact on lakes. Sunscreen, lotions, and hair products can dissolve in the water. Animals may seek out litter or may be frightened away from their water source due to human presence or noise such as music.