sticides multiplied by a factor of 32 between 1950 and 1986, with developing countries now accounting for a quarter of the world's pesticide use. However, inappropriate and excessive use can cause contamination of both food and environment and, in some cases, damage the health of farmers. Pesticides also kill the natural enemies of pests, allowing them to multiply; meanwhile the number of pest species with resistance to pesticides has increased from a handful 50 years ago to over 700 now.
Crops and foods can produced using recombinant DNA techniques which enhance their agronomic potential, nutritional characteristics, or one or more features of pest protection (insect and viruses) and tolerance to herbicides. More than 40 such transgenic crop varieties have been cleared through the federal review process. New varieties of plants are being developed using genes from wild varieties with inbuilt disease resistance. Genes from the wild have been used to protect Brazil's coffee plantations; while a Mexican wild maize confers resistance to seven major diseases. According to the American Medical Association, these foods are "substantially equivalent to their conventional counterparts," and no long-term side effects have yet been detected.
While it is difficult to estimate the gains in food production that we may obtain from exploring new crop species, this could make a large contribution. Ninety percent of the world's food is derived from just 15 plant and 8 animal species. Wheat, rice, maize (corn), millet, and sorghum provide nearly all (70%) the food energy (calories) and up to 90% of all protein consumed by the world's people. Cereal grains are humankind's major food, contributing more than two-thirds of the world production of edible dry matter and half of the world's protein.
What Fraction of the World's NPP do Humans Appropriate
In order to determine how much food the world can produce, and what fraction of that production is captured by humans, we will re-visit a topic discussed in Global Change I: The Flow of Energy: Higher Trophic Levels
On land, one species, Homo sapiens, commands about 40% of the total terrestrial NPP. This has probably never occurred before in earth's history. Human "carrying capacity" on earth is hard to estimate, because it depends upon affluence of a population and the technology supporting that population. But at present levels of affluence and technology, a population 50 to 100% larger than we have today would push our use of terrestrial NPP to well over 50% of the available production, and the attending degradation of ecosystems on earth (e.g., air and water pollution) would be of major concern.
The Food and Agriculture Organization of the United Nations (FAO) has published a study on the food production outlook through the year 2010. The FAO forecasts that production increases can, in fact, accommodate effective demand and rising world population, although malnutrition will become an increasing problem in developing countries. It is also assumed that continuing substantial investments in agricultural research are essential.
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