I don’t know Anne well but I already like her. She said that when she looks at the patch of grass out her office window in McGilvrey Hall at Kent State she sees, “Potential ecosystem services.” That’s my kind of attitude! (Although I’m also silently cursing her because she added that she was, “glad it’s not a parking lot,” and now I can’t get Big, Yellow Taxi out of my head.) As I sang to myself … they paved paradise and put up a parking lot… I started thinking about what happens when paving crews come rolling on in; when water can’t soak naturally into the ground, and it rushes across the landscape carrying whatever it picks up along the way and then dropping it into local creeks and rivers.
Hard surfaces like paved roads, parking lots, and roofs are called “impervious surfaces.” According to the USGS, “Impervious surfaces can be generally defined as any material of natural or anthropogenic source that prevents the infiltration of water into soil, thereby changing the flow dynamics, sedimentation load, and pollution profile of storm water runoff.”
There are three problems typically associated with our ever expanding rock-solid human landscape; there is too much water, moving too fast, and it’s polluted. According to Environmental Health Perspectives, “(In 2004) in the United States alone, pavements and other impervious surfaces covered more than 43,000 square miles—an area nearly the size of Ohio.” The water that fell on those surfaces didn’t have a chance to soak into the ground slowly and seep into streams, and that means several things – groundwater not being recharged, and storm drains delivering sudden large volumes of water to streams, physically impacting stream ecosystems and causing flooding and bank erosion. When particulate matter from the air, nitrogen oxides from car exhaust, rubber particles from tires, nutrients from fertilizers, and other pollutants that have collected on roads and parking lots are carried along with that water it can result in “urban stream syndrome.”
As if that’s not enough, another problem can occur during hot weather. If rain falls on impervious surfaces it can get superheated; when that hot water is added to a stream or river it can stress or kill aquatic life vulnerable to small increases in water temperature at different stages in their life cycle. According to the Environmental Health Perspectives article quoted above, “Increased temperature also decreases the water’s ability to hold oxygen, which has a further detrimental effect on the aquatic life. Warm temperatures can cause a variety of problems for fish, including decreased egg survival, retarded growth of fry and smolt, increased susceptibility to disease, and decreased ability of young fish to compete for food and to avoid predation. Especially affected are species that require cold water throughout most stages of their lives, such as trout and salmon.”
PS I found an excellent website with ideas to reduce impervious surfaces. I can attest to the effectiveness of some – I have a driveway of interlocking brick and a sidewalk of quarry stone. (Covered in snow right now though… heavy sigh…).