Farmers know just about every square foot of their fields. Farmers with small plots of land will know their fields down to the square inch. They know what parts of the field have richer soil, what parts have better drainage, and where water tends to accumulate. Farmers know what parts of the field need a bit more fertilizer, and where they’ll have to watch for rocks or over-watering. They know what crops grow best on their land, and about how much they can produce each year. And they know exactly how much farmland they have.
Although each farmer knows how much land they have, globally, we do not have a completely accurate total of farmland world-wide. Estimates ranged from 1.22 and 1.7 billion hectares (1 hectare = 2.5 acres), a difference of more than 40%! And since it would be impossible to ask every farmer in the world the size of their farm, obtaining a better estimate of cropland coverage was just about impossible.
Impossible, that is, until a team from the International Institute for Applied Systems Analysis (IIASA) took on the job in 2010. They combined satellite images, regional maps, geo-tagged photos and video to create maps of farmland around the world. They then used the power of the masses to verify the information. They turned their project into a game, where participants from anywhere could log in, look at an image to see whether it contained cropland or not, and submit that information to the IIASA.
It took five years to develop two maps from all the data. The first map shows the concentration of farmland around the world, while the second map reflects field size. These maps can be used by scientists, academics, and other individuals to evaluate land use policies, explore sustainability issues, track deforestation and loss of cropland, and more.
The maps can be accessed for free by anyone by visiting http://www.geo-wiki.org/, and registering for an account.