The clearing of natural vegetation for agriculture results in erosion of topsoil, with billions of tons blowing in the wind or washing downriver to the ocean each year. Iowa has lost 50% of its richest resource in this manner. Overgrazing and intensive cultivation eventually lead to declining yields and desertification, to the tune of 15 million acres a year worldwide. And while fertilizers can increase yields, they, too, eventually wash into rivers and wetlands where they fuel an algal bloom that chokes out desirable species. In the seventies, the Potomic River in the U.S. became nearly devoid of fish in this manner. Even with corrective measures recovery has been slow.

There are hundreds of known food plants in the world, yet most of humanity depends on just three: corn, rice, and wheat. And only on a few varieties of these, a disaster in the making. The switch from hunting-gathering to farming traded a rich and varied diet for one that was plentiful but less balanced in nutrients. Nevertheless, our species can reproduce with a less than optimal diet. This much is clear. Agriculture provided enough energy to fuel the great proliferation of our species, which then spawned urbanization and the Industrial Revolution, with their own sweeping environmental impacts.

 

The villages around Lake Sentani in New Guinea are refreshingly simple and clean. Conspicuously absent are plastic bags, piles of garbage, and crowds. The people fish, raise pigs, and harvest the sago palm for food. They also have access to the markets of Jayapura where they purchase other agricultural products, mainly sweet potatoes. (next photo)