by Alicia Pimental
April 01, 2007
Centuries of population growth and landscape changes have taken their toll on the Bay's water quality, according to the recently released Chesapeake Bay 2006 Health and Restoration Assessment.
Part Two of the assessment, Restoration Efforts, explains that “progress” toward the Bay Program's goal to reduce nutrient and sediment pollution from urban/suburban lands and septic systems is negative due to the rapid rate of population growth in the watershed—and the residential and commercial development that has come with it. About 16.6 million people are estimated to live in the Bay watershed, with an additional 170,000 people moving in each year.
- 90 percent of the goal to reduce nitrogen from urban/suburban lands and septic systems has been achieved.
- 67 percent of the goal to reduce phosphorus from these lands has been achieved.
- 57 percent of the goal to reduce sediment from these lands has been achieved.
The pollution increases associated with land development—such as converting farms and forests to urban and suburban developments—have surpassed the gains achieved from improved landscape design and stormwater management practices. Pollution from urban and suburban lands is now the only pollution sector in the Bay watershed that is still growing.
Population growth and related commercial and residential developments cause significant amounts of nutrients, sediment and chemical contaminants to make their way into the Bay and its rivers, degrading water quality.
Homes, roads, parking lots and shopping centers cover once-natural lands with impervious—or hardened—surfaces, which prevent water from entering the ground. During the 1990s, the amount of impervious surface in the Bay watershed grew by 41 percent—but the population during that same time period only grew by about 8 percent.
When it rains or snows, stormwater runs across roads, rooftops and other hardened surfaces, carrying with it the harmful pollutants we contribute to the environment—from driving our cars to fertilizing our lawns to not picking up pet waste. All of this is washed into our nearest stormwater drain or stream, and eventually to the Bay.
Once in the water, excess nutrients fuel the growth of algae, which deplete the water of oxygen that all of the Bay's living things need to survive.
Excess nutrients and sediments also cloud the water, which decreases the amount of sunlight that reaches bay grasses. These underwater grass beds provide vital food and habitat for fish, birds, blue crabs and other Bay creatures, and also help oxygenate the water.
Scientists estimate that one-quarter to one-third of the nitrogen reaching the Bay and its rivers comes through the air. One of the primary sources of air pollution are mobile sources, which include vehicles, construction equipment and gas-powered lawn tools. Pollutants released into the air eventually fall onto water surfaces and the land, where they can be washed into local waterways.
Everything we do on the land has an impact on the Bay and the creatures that live in it. By making small changes in the way we live our lives , the Bay watershed's ever-growing population can take part in the Bay restoration effort, helping to reverse the trend of declining water quality to protect all that live in the Bay and preserve the nation's largest estuary for generations to come.