The Fertilizer Institute (TFI) and other members of the Agricultural Nutrient Policy Council (ANPC) on Dec. 9 said a new report raises serious questions about the data used by the U.S. Environmental Protection Agency (EPA) to set pollution limits for the Chesapeake Bay watershed.
The report, Comparison of Draft Load Estimates for Cultivated Cropland in the Chesapeake Bay Watershed, was commissioned by ANPC and prepared by LimnoTech, a water sciences and environmental engineering consulting firm based in Ann Arbor, Mich. The report compares EPA’s Total Maximum Daily Loads (TMDL) with those in the draft USDA report Assessment of the Effects of Conservation Practices on Cultivated Cropland in the Chesapeake Bay Region.
The report found inconsistencies in data and modeling between EPA and USDA in a range of areas, including land use and total acreage of the Chesapeake Bay watershed; hydrology; assumptions about conservation practices; and model frameworks and results. “The model results are substantially different and raise significant concerns that should be investigated and resolved before the TMDL is finalized,” the report said.
At a telephone news conference on Dec. 9, ANPC representatives said these substantial differences “have to be explained” before EPA proceeds with its Chesapeake Bay TMDL Rule. “They both can’t be right, and there is a lot at stake if we don’t get it right,” said Tom Hebert of the Washington-based Bayard Ridge Group.
Don Parrish, ANPC president and senior director of regulatory relations at the American Farm Bureau Federation, cautioned as well that the rule has “extremely broad implications” for more than just the Chesapeake Bay watershed, noting that EPA has requested to use the same modeling approach in the Midwest along the Mississippi River.
“Through the Bay TMDL, EPA is implementing a rule that will have significant impact on economic growth and development, including food production, in the watershed,” Parrish said. “It is critical for EPA to get the facts right, including providing an accurate accounting for existing management and conservation practices before it imposes potential economic disaster on agricultural producers in the Bay watershed.”
Among the many discrepancies, the report says EPA’s model estimates that there are 3.3 million acres of cropland in the Bay watershed, versus USDA’s estimate of 4.38 million acres. Total agricultural land estimates, which include pastures, hay, cropland under conservation tillage, and cropland under conventional tillage, also vary between the two models, with EPA at 9 million acres and USDA at 12.12 million acres.
USDA estimates that seven percent of cropped acres in the Bay watershed are under conventional tillage, five percent have a level of tillage between conservation tillage and conventional tillage, and 88 percent use conservation tillage practices such as mulch till or no-till. By contrast, EPA estimates that 50 percent of cropped acres are under conventional tillage and 50 percent are under conservation practices. “These differences in assumptions about total acres, land use, and conservation tillage versus conventional are significant when predicting different loading estimates,” the report said.
“In general, the cultivated cropland conservation practices incorporated in USDA’s model framework are documented and statistically valid in sufficient detail to allow a general understanding of practices accounted for in the modeling, the assumptions made regarding specific conservation practices, and the level of implementation,” the report continues. “A similar level of detail and documentation is not, however, available for the EPA model framework.” Without further documentation of the EPA model framework, the report said “it is not possible to evaluate the validity of EPA assumptions or conclusions.”
The report highlights many other differences as well. Regarding hydrology data, the report says USDA used 47 years of precipitation data in its calculations, versus just 10 years of data analyzed by the EPA model. Regarding total sediment loadings to the Bay watershed from agriculture, EPA’s figures show nearly 2.6 million tons of sediment versus USDA’s 930,000 tons.
EPA estimates that the total load of nitrogen delivered to the Bay from all sources is 249.3 million pounds, 64.7 million pounds (21 percent) less than the amount estimated by USDA. EPA estimates that the total load of sediment delivered to the Bay from all sources is 3.99 million tons, 2.865 million tons (42 percent) less than USDA’s estimate. EPA estimates that the total load of phosphorus delivered to the Bay from all sources is 16.5 million pounds, 1.8 million pounds (12 percent) more than USDA’s estimate.
“If USDA’s numbers are correct, agriculture has already significantly surpassed EPA targets for reductions in sediment and phosphorus,” said National Association of Corn Growers Director of Public Policy Rod Snyder. “It is crucial that farmers in the Bay watershed receive appropriate credit for their efforts to be good stewards of our land and water resources.”
The LimnoTech report also found that USDA and EPA make different assumptions about animal feeding operations (AFOs) and concentrated animal feeding operations (CAFOs). “Because the TMDL will have immediate economic consequences, the quest for more accurate data must begin immediately,” said National Pork Producers Council Chief Environmental Counsel, Michael Formica. “Should EPA proceed without an unassailable data set in hand, all stakeholders in the Bay should question not only EPA’s pollution assignments, but also its diet for cleanup.”
According to the LimnoTech study, the USDA model framework seems to more accurately represent real world, Chesapeake Bay watershed agricultural operations and management practices, including consideration of crop rotations, varying levels of tillage, and actual nutrient management practices.
“The ANPC wanted to know if the differences in EPA and USDA estimates were significant enough to call the draft TMDL into question,” said Lisa Kelley of the National Council of Farmer Cooperatives. “The LimnoTech study provides a resounding ‘yes’ to that question and we are urging EPA to step back and re-examine the precision and accuracy of its data.”
EPA released the draft Chesapeake Bay TMDL Rule on Sept. 24, 2010, and solicited public comment for 45 days. It has stated its intention to release the final TMDL Rule by Dec. 31, 2010. Environmental groups have largely endorsed the draft rule. The rule’s critics, who include local governments, waste water management agencies, builders, and agricultural groups, have faulted it for faulty science, inadequate cost assessments, and a rushed timeline to complete the Bay cleanup by 2025. Critics have also questioned EPA’s authority to enforce TMDLs under the Clean Water Act.
The LimnoTech report is available at http://nutrientpolicy.org/ANPC_News.html.