We read and hear a lot of impervious surfaces on lake properties and why they are bad for our lakes. A paper from the University of Wisconsin-Stevens Point Center for Land Use Education puts the concern in clear perspective.
"Impervious surfaces" is basically a fancy phrase for rooftops, sidewalks, driveways, decks and other common lake home features that don't allow rainwater to soak into the soil, and so send it on to the lake, carrying sediment, nutrients, and other forms of pollution.
According to the paper written by land use specialist Lynn Markham, that is only part of the story; impervious surfaces and the loss of natural habitat that goes with it have multiple impacts. Moreover, those impacts are cumulative and increase in proportion to the number of homeowners who develop lake properties unwisely. An inch of rain falling on an acre of land delivers 27,152 gallons of water, enough to fill a backyard swimming pool 30 feet long, 20 feet wide, and six feet deep.
An important variable is how much of that water simply flows downhill to the lake instead of soaking into the soil.
The more impervious surfaces are added, the more the functions of natural shoreline are compromised. Traditional lawns, while not actually impervious, absorb much less water than land with forests and native vegetation. To no surprise, impervious surfaces closest to the water have the most impact.
"The quality of fish and wildlife habitat generally decreases as the density of development increases along shorelines. Changes in water quality, bottom sediment, water levels and terrestrial and aquatic vegetation all contribute to this decline," Markham's paper notes.
A study on three Minnesota lakes found that black crappies and smallmouth bass were far less likely to build spawning nests along developed shorelines than along natural shorelines.
More broadly, a study correlated increasing impervious surfaces in a watershed with fewer fish species in lakes and fewer fish overall.
Additional research found that as impervious surfaces increase and natural shoreland declines, bird nesting cover and foraging areas are degraded, fragmented, or eliminated. Native wildlife then declines in abundance and diversity.
"Fewer green frogs were found on lakes in Northern Wisconsin when the shorelines were developed," Markham's paper stated. Frogs disappeared from shorelines where lots had only 100 feet of lake frontage, probably because of declining habitat and conditions that made the frogs more vulnerable to predators.
There is more, of course, and not to be discounted is the effect of over-development on the scenic beauty that attracts people to the lake country: "In a Minnesota survey, waterfront property owners and lake users cited cabin and home development over 85% of the time as the cause when they perceived a decline in the scenic quality on the lake they used the most."
All these are reasons to think of the bigger picture when building and landscaping lake properties. And if we've already gone too far in the direction of urban-style landscapes, they are reasons to consider giving something back by restoring some native vegetation, especially in that critical strip of land closest to the water.
Posted: Monday, May 4, 2020
Article comment by:
the blue herons cranes and water rats ate all the frogs.
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