* Purdue Department of Forestry and Natural Resources
* USDA Census of Agriculture
* USDA Natural Resources Conservation Service

December 9, 2008

Study: Data analysis influences farmland protection policy

WEST LAFAYETTE, Ind. - They might be neighbors geographically and agriculturally, but Indiana and Illinois are worlds apart when it comes to preserving farmland, said two Purdue University forestry and natural resources researchers.

Illinois takes an aggressive approach to protecting farmland from excessive development and urban sprawl, while Indiana is far less regulatory, said Linda Prokopy, an assistant professor in environmental and land-use planning. Part of the reason, Prokopy said, is because policy-makers in the two states interpret and apply U.S. Department of Agriculture farmland data differently.

"They use the data to justify distinctively different approaches to farmland protection," she said.

Prokopy and graduate student Aaron Thompson compared Indiana and Illinois farmland acreage losses and government responses in a study titled "Tracking Urban Sprawl: Using Spatial Data to Inform Farmland Preservation Policy." The study will appear in an upcoming issue of Land Use Policy.

The researchers delved into the farmland preservation issue in response to their own observations, Prokopy said.

"What we noticed is that Indiana and Illinois had very different policies related to farmland preservation but yet, driving around Indiana, we saw a lot of farmland being lost to urban sprawl," she said. "We wondered why Indiana wasn't being more proactive about addressing the issue, so we thought we'd look into the numbers and see what's really going on."

In their study, Prokopy and Thompson examined farmland losses between 1992 and 2002 using data from the USDA's Census of Agriculture and National Resources Inventory. They then collected the same information utilizing Geographic Information Systems (GIS) data sets - a process commonly known as spatial analysis.

GIS is a type of computer software that enables analysts to examine information that is linked to specific geographic locations to identify patterns and trends that are difficult to quantify without understanding their spatial characteristics.

"Our research showed that in the 10-year period we looked at in the study, Indiana lost the equivalent of Tippecanoe County in terms of acreage of farmland," Prokopy said. "That's a pretty startling statistic when you think about it."

Tippecanoe County is 503 square miles in size, or nearly 322,000 acres.

"In Illinois what we were finding in the Census of Agriculture was a net gain in farmland, somewhere just under 550,000 acres from 1992 to 2002," Thompson said. "What we reported in the spatial analysis was a significant decrease, so there were a lot of differences in the numbers there. Here in Indiana what we were seeing for the time period we were looking at supported what the Census of Agriculture was finding."

The USDA surveys U.S. farmers every five years for the Census of Agriculture. The survey asks questions about land use and ownership, production practices, income, expenses, general business characteristics and other areas. Data from the 2007 census will be released in February 2009.

The National Resources Inventory (NRI) tracks general land use and trends based on 800,000 randomly selected sample sites nationwide. Samples are compiled by the USDA's Natural Resources Conservation Service.

Both USDA data sources are helpful but might not give a completely accurate picture of farmland loss, Thompson said.

The Census of Agriculture is a voluntary survey sent to the nation's farms, defined by the USDA as any operation that sells at least $1,000 worth of agricultural commodities during a year, or would have sold those commodities under normal circumstances.

With the NRI, county-level data is not available for years after 1997, and the numbers don't always match up with those in the agricultural census, Thompson said.

"Using spatial analysis, we were able to look at the overall farmland patterns across the entire landscape," he said. "This eliminated some of the definitional issues we faced, especially in the Census of Agriculture."

Prokopy and Thompson found that Indiana policy-makers factored into their land-use decisions farmland acreage figures from Census of Agriculture reports as far back as the 1970s. Farmland has been converted to development purposes at a greater pace in recent years than in the earlier years of the past three decades, Thompson said.

The Purdue study doesn't make specific policy recommendations. It does, however, urge state- and county-level officials to look beyond USDA statistics when considering farmland preservation issues.

"One of the take-home messages from this research is that Indiana needs to pay more attention to the loss of farmland and how to protect farmland," Prokopy said.

"We're advocating for programs that allow farmers to maintain the value in their land and that also protects the nation's interest in having land that can be farmed."

Writer: Steve Leer, (765) 494-8415,

Sources: Linda Prokopy, (765) 496-2221,

Aaron Thompson, (765) 494-9598,

Ag Communications: (765) 494-2722;
Beth Forbes,
Agriculture News Page

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