Are cattle just a scapegoat for water quality problems?

OKEECHOBEE — Has South Florida’s bovine population been cast as the scapegoats, unfairly blamed for the excess phosphorus in runoff that enters Lake Okeechobee?

In the early 1980s, dairy cattle were blamed for the high phosphorus levels in the Taylor Creek/Nubbin Slough waterway. In 1987, the Department of Environmental Regulation implemented the DEP Dairy Rule, restricting the phosphorus levels in runoff, and as a result, causing most of the dairies to move out of the watershed because they could not meet the new standards.

The few dairies that remain use costly systems of retention ponds and spray fields to retain runoff — and the phosphorus — on the dairy property.

But 30 years later, the phosphorus levels in Taylor Creek/Nubbin Slough have not declined.

With the dairies out of the equation, some have shifted blame for the phosphorus levels in the Kissimmee River watershed to the beef cattle.

Some researchers question that assumption.

In a December 2010 article “Impact of Cattle Grazing in South Florida,” Okeechobee County Extension Director & Extension Agent III Pat Hogue noted that cattle played an important part in the state’s history.

“We know that Florida has the oldest history of cattle grazing and production in the United States. Cattle were first introduced in the U.S., in Florida when they were brought from Spain by Juan Ponce De Leon and his crew in 1521, and later introductions came with Hernando DeSoto in the 1530s. Prior to that time there would have been no impact on the waters of Florida by cattle grazing, other than the periodic impact bison may have had as they ventured to the state periodically in their nomadic roaming of the states. However, we do not know, and could only hazard any guess, as to what the nutrient or other particulate loads were prior to these times. We know that the Native Americans in Florida at the time, and later settlers took up cattle grazing and production that were the precursors to the modern Florida beef cattle industry, and that Florida, since those times, has always been a cattle grazing state, and one of the leaders in this endeavor throughout U.S. history.

“What we also know is that even prior to cattle coming to Florida, there were huge deposits of phosphorus in the ground that later became a leading mining industry for the state, and Florida is one of the leading suppliers of phosphorus fertilizers not only to the U.S., but the rest of the agriculture producing world. Did these phosphorus deposits have any effect on waterways in Florida even prior to cattle coming to the state and before we mined it and produced huge quantities of fertilizers and applied to the soils?

“Again, we have no empirical data to prove this, yet there is evidence that the soils in South Florida are probably inherently high in phosphorus, and may have been even before man started using the nutrient as a means to increase agricultural production. It’s reasonable to assume, and a case could probably be made that with all the water raining down on and flowing through and interacting with all the land that may contain high phosphorus levels South Florida, water bodies such as Lake Okeechobee may have always contained large amounts of the nutrient,” he wrote.

Mr. Hogue also noted that the levels of phosphorus loading into the lake did not appear to be affected by the reduction in dairy cattle in the watershed in the 1980s. In addition, since the early 1990s there has been a greatly reduced amount of phosphorus applied to pastures in South Florida as a result of research studies that showed it wasn’t needed as often and in amounts previously applied.

Despite these changes, the phosphorus loading into the lake did not decline.

Research projects over the years would seem to indicate that cattle grazing in South Florida have little to no adverse effects on water quality, particularly in regard to phosphorus, Mr. Hogue stated.

“One important aspect to keep in mind is that plants and grazing animals are not sources of nutrients. They can recycle nutrients into the various ecosystem components (air-soil-plant-water) but they usually don’t add additional nutrients into the system,” explained Maria Lucia Silveira of the Soil and Water Science UF/IFAS Range Cattle Research and Education Center.

Ms. Silveria is one of the authors of the 2010 research paper, “The cow-calf industry and water quality in Florida.”

“Discrepancies in the literature suggest that there is a high degree of uncertainty associated with early estimates of the relative contribution of cow/calf operations to water quality problems in south Florida,” the researchers stated.

“Generating sound, science-based information about the real contribution of grazing lands to water quality issues is a key to promoting the benefits of forage-based beef operations and the important role the industry plays in protecting Florida’s environment.”

Phosphorus loading in the Okeechobee watershed.

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