Europe have little cropland per person and few opportunities to open new lands for crops. Africa and South America have extensive unused areas, but much of this land has environmental constraints or harbors cultural and biological diversity that deserves protection.

The United States has some of the highest rates of soil erosion in the world. Soil erosion exceeds soil formation on at least 40 percent of U.S. cropland. About one-half of the topsoil that existed in North America before European settlement has been lost.

Other areas with high erosion rates are China, India, the former Soviet Union, and Ethiopia. Worldwide, about 25 percent of the land (about twice as much as we now use) has the potential for agricultural use. Putting much of that land into agricultural production would mean loss of valuable forests and grasslands and would cause loss of biodiversity and result in major ecological destruction. Large expanses of land, however, could be converted to agricultural use or could be used more intensively (but carefully) without causing great damage. It is possible that food production could be expanded considerably, even on existing farmland, given the proper inputs of fertilizer, water, high-yield crops, and technology. This will be essential if human populations continue to grow as they have during this century. Whether it will be possible to supply agricultural inputs and expand crop production remains to be seen. Global climate change could have devastating effects on world food supplies and might necessitate conversion of forests and grasslands to feed the world's population.

There are great differences in fertilizer use between the more-developed and less-developed countries. Many farmers in the developed countries use more fertilizer than is needed. Excess chemicals are a major source of water pollution and threaten health in some areas.

Many new and alternative methods could be used in farming to reduce soil erosion, avoid dangerous chemicals, improve yields, and make agriculture just and sustainable. Some alternative methods are developed through scientific research; others are discovered in traditional cultures and practices nearly forgotten in our mechanization and industrialization of farming. Some authors advocate returning to low-input, regenerative, "organic" farming that may be more sustainable and more healthful than our current practices. Growing your own food or buying locally grown food at co-ops, farmer's markets, or through a producers' or buyers' association can provide healthy, wholesome food and also support sustainable agriculture.