Rising demand for animal protein is now conflicting with three main limits on its production: (a) Marine protein production, having risen by 5% per year since about 1950, is now very close to its sustainable limit. This was formerly thought to be perhaps 100 to 120 million tonnes per year but, in the wake of the catastrophic drop in the Peruvian anchovy catch in 1972, it is now widely estimated to be about 70 million tons per year, and prices are higher. (b) Beef production, already limited by the fertility of cattle, has now encountered the sustainable limit of grazing and in many areas exceeded it. Further increases, therefore, depend on intensive feed-stock agriculture - at an energy cost of about 12 pounds of coal equivalent per pound of beef protein. (c) The increase in soybean production in the past few decades has in most cases been due to increased planting; no significant intensification of yields is in sight, and demand continues to rise much faster than supply.
According to a 1995 report, world population growth was putting severe pressure on fish stocks and endangering the nutrition of nearly one billion people in developing countries. An expected fall in availability of fish threatened to deprive many of the world's poorest people of their principal source of animal protein.
According to a 1995 report, fish accounted for only just over 5 per cent of the average individual's intake of protein. But 640 million people in 39 countries relied on fish to provide more than 10 per cent of their total protein intake. For nearly 1 billion people, fish provided more than a third of their animal protein.
Consumption of fish caught in the wild was expected to fall worldwide by 25-50 per cent by 2050 from 10.2 kg per person a year in 1993. Catches, and consumption, in poorer countries were expected to decline even more steeply.
According to a 1995 report, per capita fish consumption in Tanzania could fall by 70 per cent by 2050 unless the country can increase imports or domestic catches. This would force Tanzanians to replace fish protein with less nutritious plant proteins, or to reduce overall protein intake.
In the 21st century, many species of fish will become luxuries only the well-to-do can afford.
As population pressures on fish stocks grow, fish prices will continue to climb, further reducing consumption among the poor. It is virtually impossible to increase fish-farming enough to maintain current rates of fish consumption in the face of forecast population growth.
Rising international demand has led developing countries to sell increasing proportions of their catch for foreign exchange.