Researchers have identified a link between the diversity of crops grown in farmlands and the pollution they create in lakes and rivers. In a Frontiers in Ecology and the Environment e-View paper, ecologists show that when the biodiversity of crops is high, less dissolved nitrogen is found exiting the surrounding watersheds.
Nitrogen from agricultural fertilizers leaches through soils to groundwater and runs off into rivers and lakes, increasing aquatic dissolved nitrate. Too much nitrate in the water can lead to prolific growth of aquatic algae, which can use up most of a water body's oxygen when they die and are decomposed, creating "dead zones" that cannot support life.
Whitney Broussard of the University of Louisiana at Lafayette and R. Eugene Turner of Louisiana State University at Baton Rouge compiled data from the past 100 years on watersheds varying in size from the Illinois Cache River basin (400 square miles) to the Mississippi River Basin (more than a million square miles). The researchers compared this watershed data with land-use practices since the early 1900s.
The results show that since the beginning of the last century, the average farm size in the United States has doubled and the number of farms has fallen by almost two-thirds. Broussard also says that a shift from farm animals and simple plows to the use of machines to till croplands has changed not only the culture but the environmental impact of farming.
"With the growing American farm comes the necessity to use more industrialized means of farming," says Broussard. "Our agricultural practices have always impacted water quality, but over the past century the mechanization of agriculture and the use of more potent fertilizers has caused a greater effect: the nitrogen leakage rate is higher."
Modern farms tend to produce fewer crop varieties; this lower crop biodiversity can negatively impact surrounding watersheds. According to the stud
|Contact: Christine Buckley|
Ecological Society of America