Nutrients from industrial swine and poultry farms are showing up in streams in coastal North Carolina, the U.S. Geological Survey says in a new report.
USGS scientists took water samples from 54 agricultural sites to find the differences between those with and without concentrated animal feeding operations (CAFOs).
They found that 58 percent of the watersheds with CAFOs had water quality that reflected the presence of swine or poultry farms. Twenty-eight percent showed no effects.
Watersheds where farms are present had higher concentrations of nutrients such as ammonia and nitrogen. Excess nutrients can cause algal blooms that lead to fish kills.
Nutrients have been particular problems in the Tar-Pamlico and Neuse River basins of the coastal plain, particularly in the estuaries that serve as nurseries for fish and other sea life.
Hog and poultry farms pack thousands of animals into barns, flushing wastes into open pits called lagoons. Nutrient-rich water from the lagoons is sprayed to fertilize nearby fields.
The North Carolina Pork Council notes that the USGS study didn’t show exceedances of state water quality standards.
“While the USGS noted that some surface water around large swine and poultry farms shows differences in water quality, none of the findings suggest these differences are impacting either the health of local streams or humans using those streams,” it said.
The council called the study flawed and unlikely to reach reliable conclusions. A consultant’s analysis found the amount of wetlands in a watershed more significant than the number of animals in it.
Still, the findings could add to growing pressure on the 2,100 hog farms that make North Carolina the nation’s second-largest swine producer.
Neighbors of the farms have filed two dozen lawsuits in federal court, claiming odors, flies and drifting lagoon spray make their lives miserable.
In February, the Environmental Protection Agency agreed to investigate claims that North Carolina’s regulation of the farms violates the civil rights of minority neighbors.
This post was modified on Thursday, June 25, to add the North Carolina Pork Council’s response.