Archive for January, 2011

W&L Research Shows New “Adaptive” Fencing Reduces Pollution in Chesapeake Bay

Lexington, Virginia • November 29, 2010

A study by two Washington and Lee University undergraduates is investigating whether a new “adaptive” fencing program used to keep cattle out of streams that feed into the Chesapeake Bay watershed is as effective as state and federal cost-share fencing programs in reducing the in-stream concentration of harmful bacteria.

Peter O’Donnell and Thomas Jenkins hope that their research will encourage more farmers to participate in the farmer-friendly “Adaptive Streambank Fencing Program.” Established as a pilot in the Shenandoah Valley by the Shenandoah Resource Conservation and Development Council, the program is funded by private donations from the Chesapeake Bay Funders Network.

Jenkins, a senior environmental major with a focus on economics, also developed a computer economic model that is designed to help farmers make decisions about which types of fencing are most cost-effective for their individual circumstances.

“This research shows that adaptive fencing programs are effective for reducing bacteria and economically may be a better choice for certain situations,” said Robert Humston, assistant professor of biology at W&L and instigator of the research.

Some farmers have criticized the state and federal cost-share programs as too stringent in requiring high-cost conventional fencing and a 20- to 35-foot buffer between pasture and stream. The programs provide no funding for labor, maintenance or replacement of the fencing. Farmers usually must commit to maintaining all cost-share fencing for 10 to 15 years.

“With the possibility of increased pollution mandates for farmers to clean up the Chesapeake Bay, this is definitely a contentious issue,” said Humston.

“The government programs may work for some farmers, but it’s less appealing to those who have to bear the high costs of repairing fencing after flooding. Also, the large buffer area, impractical on some farms due to the topography, results in loss of pasture thus reducing herd numbers. Others aren’t comfortable taking money from the federal government. But as controversial as this issue is, when you talk to farmers they do all appreciate the value and importance of clean water in our streams.”

The pilot “Adaptive Streambank Fencing Program” originally provided up to 75 percent of the cost of minimum standard fencing-permanent posts, two-strand electrified wire-with no standard setback from the stream except that it needed to be “top of streambank.” Over the initial three years of the program, setbacks ranged from three feet to over 100 feet on some projects, with an average of 24 feet. Farmers commit to excluding their livestock from streams for at least five years.

The program has since been expanded to cover seven counties in the Shenandoah Valley and now provides reimbursement costs for materials only for the fencing, watering systems and livestock crossings.

“The program has become fairly popular,” said Humston. “Studies clearly show that conventional fencing greatly reduces bacteria in streams compared to no fencing at all. But before this research no one had studied the differences between adaptive fencing, conventional fencing and no fencing.”
O’Donnell, with a strong background in biology and biochemistry, led the research to test streams with different fencing for levels of e-coli, a bacteria found in high concentrations in cow feces. All samples were collected from streams with cattle feeding in adjacent pastures.

“If you see a problem with bacteria from cow feces then you can assume that there are also high inputs of nutrients since they also come from cow feces,” explained Humston. “While the bacteria will eventually die, the harmful nutrients go downstream and end up in the Chesapeake Bay.”

O’Donnell and Jenkins studied 15 streams-four with conventional fencing, six with adaptive fencing and five that were unfenced. While bacteria levels tended to increase in stream sections that were unfenced, the initial analyses suggest that bacteria decreased in stream sections protected by both conventional fencing, which reduced bacteria by a mean 32.6 percent, and adaptive fencing which reduced it by a mean of 20.9 percent.

Though a more thorough analysis needs to take into account other sources of variation between these study streams, Humston explained that the difference is probably attributable to the larger buffer area required by the federal programs. “Funding agencies have been hesitant to fund adaptive fencing programs because they would rather hold out for the better solutions provided by the large buffers that improve the health of streams as well as remove nutrients found in cow feces,” he said. “There are lots of things between cow feces on a pasture and a stream that will kill bacteria, whether it’s ultra violet radiation, small predators that eat bacteria or just drying out in the sun. Before this, no one had tested to see if the adaptive fencing program with its lower cost fencing and smaller or no buffers is just as effective,” he said.

“The students planned the entire experiment and executed it themselves, so it was the most hands-off experience I’ve ever had working with students. They did a fantastic job,” said Humston.

Jenkins used his strong background in economics to develop the economic model to look at the amount of time it would take a farmer to recover an investment in different types of fencing. “There are plenty of farm scale models,” he pointed out, “but none that directly addresses the problem of fencing streams to exclude cattle.”

He started by creating a basic model of a cow-calf farm, the predominant form of livestock agriculture in the area, and developed it further through talking with farmers, people at the Virginia Tech Extension Office and the Natural Resource Conservation Service, a division of the U.S. Department of Agriculture.

Jenkins assumed that the farm would have a completed fencing project with water troughs and stream crossings. All the details of the farm, such as acreage, fence distance, buffer width, stocking rate and beef prices etc., are input according to each farm. “The farmer can enter how much land he or she has, how many head of cattle, how much pasture would be lost by putting in different types of fencing, what the initial investment is, the annual cost of maintenance etc. It’s very easy,” he said.

“If the economic model shows there is a substantial time difference before a farmer realizes the economic benefits of a particular fencing program, it gives the farmer a quantitative basis to make a decision and feel comfortable about not having a high risk for long term economic loss,” he said.

Jenkins added that one benefit of excluding cattle from streams is that the farmer can use the fencing to divide pastures and set up a rotational grazing operation. “It’s good for the cows, good for the land and good for the stream because the cows are moved around and not concentrated in one area. The farmer can grow grasses throughout the year and move the cows around for feeding. The farmer often doesn’t have to buy additional feed which is a huge saving,” Jenkins said.

“When you look at some of the water these cows are drinking, it’s not nearly as clean as well water, so there is a real health benefit for the cows having access to clean water,” he said. “But that’s hard to capture statistically because every farmer I talked to had a different story. For example, one farmer had five cows die from the water-borne disease leptosporidium each year before he fenced them, but none died once they were excluded from the stream. Another farmer noticed less hoof-rot in his herd once they were fenced from the stream.”

But Jenkins could include cattle weight gain and beef prices in the model. “I found a study that showed that cattle tend to gain about 5 percent more weight when provided with an off-stream water source,” he said. “When the cost of installing the fencing, troughs and crossings, and yearly flood maintenance are balanced against increased income from selling heavier calves, the farmer’s costs are recovered over time.”

Jenkins designed the economic model to produce different results over time, even for the same farm. “I added a random component to reflect what happens when a variable portion of the fence is destroyed or damaged by flood each year. If you run repeated simulations with the model it will give you the average number of years to recover the initial cost of the fencing,” he said.

“His model is probably conservative,” said Humston. “That’s good because you can tell a farmer he or she will recover a fencing investment in a certain number of years, but it’s probably going to be sooner.”

O’Donnell and Jenkins hope to present their findings at the Virginia Water Conference in March 2011. “I’m also hoping they can publish a paper on their research before they graduate,” said Humston.

The Chesapeake Bay Funders Network is a funding collaborative of private non-profit foundations helping communities to initiate and sustain necessary changes to promote and protect the health of the Chesapeake Bay.

O’Donnell was funded through a Mellon Grant to W&L’s environmental studies program. Jenkins was funded through a private gift from the Lewis Legacy Foundation.

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