China has many times the human population of the U.S., and the same is true for pigs: It has 450 million of them, seven times the U.S. population.
That's one of the interesting things you can learn from a new set of maps that show the global distribution of livestock—all 1.4 billion cattle, 1.9 billion sheep and goats, 980 million pigs, and 19.6 billion chickens out there. Did you know that most of Argentina's land area is given over to cattle? Or that most U.S. chickens live in the south?
The maps were developed by researchers at International Livestock Research Institute, in Kenya, the UN's Food and Agriculture Organization, and other groups. They show data down to the square kilometer level, a higher resolution than available previously.
There are several good reasons for mapping livestock, says Tim Robinson, at the ILRI. One, doing so can help predict disease by showing when and where outbreaks are mostly likely to occur. Researchers recently linked the density of poultry markets to H7N9-strain avian flu incidents, for example. "The obvious use for such maps in the immediate future is to help target surveillance to areas most at risk, which could provide advance warning should the virus spread and allow authorities to move quickly to contain it," Robinson says. Areas in India, Bangladesh, Vietnam, Indonesia, and the Philippines could be vulnerable if the disease—which has killed at least 100 people so far—spreads beyond China, the research has shown.
Livestock production also impacts the environment. As the developing world becomes richer, it is likely to eat more meat, take up more land, and produce more pollution. The maps can help show which places might be most affected.
"Changes in production globally are driven by increasing wealth in the developing world, population growth and urbanization," Robinson says. "We can begin to predict how this will impact upon pandemic risk, pollution from highly concentrated production systems, and availability of cheaper protein."
You can find out more about the maps at the Livestock Geo-Wiki here.