But the lifestyle won't be as wasteful of resources, either, the Cornell ecologist predicts. Some observers are seeing early signs that nature is taking a hand at reducing human populations through malnutrition and disease. According to the report, global climate change is beginning to contribute to the food and disease problems. Even if a worldwide limit of 2.1 children per couple were adopted tomorrow, Earth's human population would continue to increase before stabilizing at around 12 billion in more than 60 years. The US population has doubled during the past 60 years to 270 million and, at the current growth rate, is projected to double again, to 540 million, in the next 75 years.
Malnutrition increases the susceptibility to diseases such as diarrhea and malaria.
One reason for the increase in malnutrition is that per capita production of grain has been declining since 1983. Grains provide 80 percent to 90 percent of the world's food. Each additional human further reduces available food per capita. The reasons for this per capita decrease in food production are a 20 percent decline in cropland per capita, a 15 percent decrease in water for irrigation and a 23 percent drop in the use of fertilizers. Biotechnology and other technologies apparently have not been implemented fast enough to prevent declines in per capita food production during the past 17 years.