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New Farm Maps Offer In-Depth Picture of Global Agricultureby Becky Oskin, Senior Writer   |   January 20, 2015 10:49am ET

All farmers on the ground know their land as well as their own wrinkled hands, but

totaling up all the world's cropland is a difficult task. Yet the competitively for land among

developers, growers and other parties makes getting an accurate count of the world's arable

acres especially important as the planet's population grows.

Two new maps released Friday (Jan. 16) considerably improve estimates of the amount

of land farmed in the world — one map reveals the world's agricultural lands to a resolution

of 1 kilometer, and the other  provides the first look at the sizes of the fields being used for

agriculture, the researchers said. Earlier studies estimated that the world's cropland may cover

an area between 1.22 billion and 1.71 billion hectares, a range that varies by more than 40

percent.

"The field-size map is really unique — no such global product currently exists," study

co-author Linda See, a researcher at the International Institute for Applied Systems

Analysis in Austria, said in a statement.

The researchers built the cropland database by combining information from several

sources, such as satellite images, regional maps, video and geotagged photos, which were

shared with them by groups around the world. Combining all that information would be an

almost-impossible task for a handful of scientists to take on, so the team turned the project

into a crowdsourced, online game. Voluntary logged into "Cropland Capture" on a computer

or a phone and determined whether an image contained cropland or not. Participants were

entered into weekly prize drawings.

The new global cropland map shows the extent of land dedicated to farming in 2005, and the

field-size map illustrates different approaches to farming. It turns out that medium and large

fields dominate in North America, central South America, Europe and Australia, while small

fields pepper the farming regions in Africa, India, Southeast Asia and China.

The researchers said they hope the global cropland map will becomes a reference map for

climate modelers, as well as agencies that monitor and report on agricultural development

worldwide. The field-size map is more a rough first step in looking at the world's fields, but

offers a new way to monitor global agriculture, the scientists said. For instance, a growth in

field sizes in a certain region could reflect a shift there toward development and

mechanization.

"Current sources of information on cropland extent are not accurate enough for most

applications," study lead author Steffen Fritz said in the statement. "The global cropland map

is a low-cost solution to fill this need."

Both maps are free to download from the "Cropland Capture" game host website, called Geo-

Wiki, with online registration. The researchers are now producing a new cropland map for

2010, and update the field-size map, they said.

The maps were also published in the journal Global Changes Biology.