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Healthy lakes need
healthy forests
Why forests are important to lakes
Limiting runoff
Rain and snow melt can add nutrients, sediments, and other
pollutants to our lakes, causing decline in water
quality. Water that soaks or infiltrates into the ground is less likely
to damage lake quality.
 Forest
ecosystems, which include tree canopies, shrubs, young trees, and herbaceous
ground layer vegetation, effectively capture precipitation and limit runoff.
Rain that falls on a forest canopy is caught by leaves and drips to the
ground with much less force than raindrops hitting the ground. Snowfall
is similarly trapped, especially by coniferous trees, and much of the moisture
is released back to the atmosphere without ever touching the ground.
Spring snow melts are less extreme in watersheds with
a significant proportion of forest cover. Snow in the forest melts later
than snow on open land, and melt water input to streams is more evenly
distributed. Thus, peak flows are not as great and erosive force is reduced.
Plants on the forest floor are also important in intercepting
precipitation, slowing runoff, and contributing to infiltration by keeping
the soil's organic surface layer well-aerated and moist. Riparian forest
buffers slow down water flowing overland, often capturing its sediment
load before it can enter a lake or stream.
Providing nutrients and habitat
 Shoreland
forests act as filters, retainers, and suppliers of nutrients and organic
material to lakes. Shoreland trees grow, mature, and eventually fall into
lakes where they protect shorelines from erosion, and are an important source
of nutrients, minerals and wildlife habitat.
Invasive species in forests can harm lakes
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Buckthorn |
Invasive plant species are a
threat to Wisconsin's forest vegetation, and can reduce the amount of rainwater
and snow melt a forest infiltrate into the ground. Vines like oriental bittersweet
and black swallowwort can climb and kill mature trees. Species like garlic
mustard can affect regeneration of many tree species as well as choke out
native ground flora. Garlic mustard, like many aggressive plants, is a champion
at competing for light and nutrients. It even releases toxic chemicals to
poison its competitors.
Tall shrub species, including buckthorn and honeysuckle,
have also invaded many Wisconsin forests. These shrubs can form such dense
thickets that they interfere with tree regeneration.
Beneath the shrubs, soils are often bare and unprotected by herbaceous
flora. The lack of ground cover allows water to flow overland more easily,
picking up sediment and pollutants along the way. Bare soils also tend
to become hardened, so water does not infiltrate as readily.
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