Researchers and farmland protection advocates for years have thought that areas needed a “critical mass” of farmland for agriculture to survive in a region.

Once farm acreage falls below a certain level, critical support services begin to leave, and farmers—faced with increased costs and complaints from new suburban neighbors—are more willing to allow rows of crops to be turned into rows of homes.

That, at least, was the theory.

But a new study that examined Mid-Atlantic farming trends over the past 50 years found there is no magic number that signals agriculture is on its way out of a county.

“We certainly went into this project thinking we were going to find a critical mass, and be able to say how much acreage you had to preserve to ensure that agriculture remains viable,” said Lori Lynch, an associate professor of agricultural and resource economics at the University of Maryland. “Theoretically, that makes sense.”

But what the study showed makes sense, too, Lynch said. It suggests that farmers are highly adaptive, and can thrive even in metropolitan counties.

“It shows they are a pretty creative group,” said Russell Brinsfield, executive director of the Maryland Center for Agro-Ecology, which funded the research.

It also means, Lynch said, that farming is not doomed in a particular county if it falls below a certain threshold. “It’s a really hopeful message about how farmers can adapt,” she said.

Preserving farmland, forests and other open spaces were among the key goals of the Chesapeake 2000 agreement, which called for a 30 percent reduction in the rate of sprawl, and for permanently preserving 20 percent of the watershed as open space. Farmland and other undeveloped areas typically have less of an impact on streams than developed lands.

The findings of the study indicate that the key to protecting farms and stemming sprawl may be less dependent on the amount of agricultural land in a region than it is on maintaining the income of farming households.

In some cases, farmers are more likely to remain in agriculture in metropolitan areas where there is a healthy economy than in rural areas with poor economies.

“Anything that we can do to help the economic stability of the farming community is probably the most important thing we can do to stop the conversion of farm land,” Brinsfield said. “Most farmers, if they can make a decent living farming their land, are certainly less likely to sell off development rights.”

The study by Lynch and a colleague, Janet Carpenter, reviewed historical data for Maryland, Virginia, Pennsylvania, New York, Delaware and New Jersey over a 50-year period. At one point, the study found the region did have a critical threshold of 189,240 acres per county. When counties fell below that level of agricultural land, the rate of farm loss began to increase.

But that trend halted by the late 1970s. From 1978 through 1997, the study found no relationship between the amount of harvested agricultural land and the rate of farmland loss.

In another surprising find, the study also found that the overall rate of farmland loss has decreased in recent decades.

Lynch said after the midpart of the century—when the amount of agricultural land nationwide was at an all-time high—the region’s most marginal farmland probably become uncompetitive and was abandoned.

Also, most counties by the early 1980s had adopted preferential taxation programs which reduced property taxes on farms. The study found that counties with preferential taxation lost farms at half the rate—4 percent over a five year period—of counties without such programs.

Brinsfield cautioned that the study only used data through 1997, and it was possible the rate of farmland loss may have accelerated since then. It was also hard to gauge the impact of farmland preservation programs, which have become more active in recent years.

Unemployment rates in a county are strongly related to greater farmland loss, and counties with healthy economies have a slower rate of loss.

In fact, the study said farmers in metropolitan areas could be better off financially than other farmers, in part because they—or members of their family—can more easily supplement their income from other jobs.

Conversely, rural counties with high unemployment rates can lose farmland at a faster pace than some metropolitan counties. Lynch said that might signal that many farm families in those areas can no longer supplement their income with outside employment.

“It’s not enough to look at the farm sector by itself,” Lynch said. “You want the economy around the farm sector to be strong.”

Adapting to change was also an important factor in the retention of agriculture. Of the 269 counties studied, the report said that 42 percent had shifted in the type of crop or animal products responsible for most of its income between 1949 and 1997.

Lynch and Brinsfield said the research indicates that the key to maintaining farming was helping farmers continue to find ways to diversify in the future by growing new, more-profitable crops. “The take-home message is figuring out how we can diversify farming operations and work with farmers and and foresters and others to make sure that their operations are more profitable,” Brinsfield said.

While Lynch found no critical mass for the region as a whole, she said it is possible that some individual farming sectors may have a critical mass.

“What we found may not be the whole story,” she said. “You might stop being a dairy-producing region or you might stop being a hog region because you lose a certain number of acres. But that doesn’t mean you have to go out of agriculture entirely.”

Brinsfield said that may mean that some regions tied to particular industries — such as poultry on the Eastern Shore—may need to consider more aggressive actions to make sure agriculture remains a viable industry for the long-term.

“Counties have economic development folks, but most of the time their focus is on manufacturing or business or those kinds of things,” he said. “They pay less attention to agriculture.”

Brinsfield’s organization recently made a grant to the Eastern Shore Land Conservancy for it to work with counties on the Delmarva peninsula to develop an agriculture-oriented economic development strategy.

The conservancy recently worked with Maryland’s six Eastern Shore counties to sign develop an Eastern Shore 2010 agreement that set a number of regional land use goals, including the promotion and protection of agriculture.

Rob Etgen, executive director of the conservancy, said counties may want to boost agriculture by trying to attract new canning operations to the Eastern Shore, which would allow farmers to grow and sell a greater variety of crops. The area may want to try growing vegetables, which would be marketed as a specific Eastern Shore brand and sold around the state, he said.

“We think the secret is certainly supporting the bottom line for agriculture,” Etgen said. “But we also need to preserve as much land as possible, and have good land use and comprehensive plans in counties. We think all of these things are important tools in sustaining rural agriculture and sustaining our rural landscape.”