There's no easy way to track all of the world's crops. What's missing, among other things, is an accurate map showing where they are.

But the people behind Geo-Wiki are hoping to fix that, with a game called Cropland Capture. They're turning people like you and me into data gatherers, or citizen scientists, to help identify cropland.

Here's how it works: Go to the site, and you see a satellite image with the question, "Is there any cropland in this red box?" When I played it on my iPhone, it was pretty easy to tell whether I was looking at cornfields or a mountain range.

I swiped the picture to the green "yes" on the right, to the red "no" on the left or down to the blue "maybe." I'm up 213 points, meaning I've successfully validated 213 square kilometers of land — or, as the game tells me, a size bigger than the Marshall Islands.

There's also a leader board, and those at the top of it are entered into a drawing at the end of the game's 25-week tournament for prizes like a new Samsung Galaxy S4 smartphone.

Some crop maps do already exist, says Linda See with Geo-Wiki, but they aren't consistent or completely reliable. So rather than make another map, she and her colleagues are doing something different.

"We're taking the existing maps and arguing that they must be right somewhere," she says. "So by putting them together you get a better product. But then we need to improve and validate that product, and that's where the game comes in."

See and her colleagues have also discovered that non-experts are as good as experts at identifying these kinds of data. In the game's first week, players surveyed 65,000 square kilometers.

"We know, for example, in Africa, there are huge yield gaps. This means you could produce much more food in certain places in Africa, but we don't even know where exactly the cropland is," Geo-Wiki's project lead, Steffen Fritz, tells The Salt. "So because we don't know where the cropland is, we don't know where the best investments could be made in terms of increasing production. So the first step is a very good cropland map."

The map, he says, can then be used by organizations on the ground that work with farmers to manage their crops better and get more out of each harvest.

A tweet led to a conversation with fellow gamer and agricultural economist Ulrich Kleinwechter at the International Potato Center.

He's one of the people who will benefit from having a map like the one Fritz and his colleagues are trying to make with the game. He says the maps would supply good foundational data for the Potato Center's simulation models of agricultural land — but also, playing is just plain fun.

"I found it very entertaining," he says. "I wonder how it will continue — whether some people get demotivated or whether a lot of players continue."

That's something Fritz wants to address. He says he's got some big updates in mind to keep people more interested, with more ways to earn points and rewards — an incentives system similar to World of Warcraft's recruit-a-friend program.

The game is available through Geo-Wiki's website and on Apple and Android devices.

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