World Population And Health

Feeding the world's ever-increasing population has two separate components, which are largely based on the economies of the respective country. For developing countries, simply meeting the caloric intake on a daily basis will continue to

© 2002 by CRC Press LLC

be a challenge. Because the food supply of those living in technologically advanced countries has generally been accomplished, interest has turned to developing food with greater health benefits. Plant breeders have focused most of their efforts over the previous 5 decades into increasing the yield of staple crops, and these efforts have proven wildly successful as the number of people eating less than 2100 calories per day has fallen by 75%, largely as a result of the Green Revolution (Mann, 1999).

There are a number of factors, however, that portend trouble with our food supplies. First, the majority of the world's food is provided by only 20 crop species, and it is predicted that wheat and corn will provide 80% of the caloric needs in developing countries. Because of plant domestication and the tendency for breeders to use the same or similar germplasm, the genetic diversity within each crop is surprisingly narrow (Tanksley and McCouch, 1997). Second, the maximum yields of cereal crops have not increased in 25-30 years, an indication that the genetic yield potential has been reached. Third, average yields rarely meet the maximum (record) yields. According to Kramer and Boyer (1995), average yields of all major U.S. crops are only 22% of record yields.

Since 1929, U.S. farmers have harvested approximately 96% of the acreage planted (calculated from National Agricultural Statistics Service data); 70% of the loss in yield is attributed to unfavorable physical/chemical environments (e.g., water and nutrient availability, temperature, excessive salt, etc.), while 12% is due to biotic causes (diseases, insects, and weeds). Almost 90% of the land surface in the U.S. and world-wide is subjected to physical/chemical conditions that limit crop growth (Dudal, 1976). Fourth, productive land in the U.S. and abroad is being developed for other uses that decrease biodiversity and are largely incompatible with farming. In the U.S., for example, each year for the past 40 years, 1.5% of the total acreage of farmland was lost to urbanization (U.S. Census Bureau, 2000). Past trends have shown that the land for housing and other development has largely taken place on land that was previously farmed. Fifth, the unspoken reality caused by the lack of any comprehensive local, regional, and national farmland conservation policies is that our society expects advances in agriculture and biotechnology to outpace global demand of food.

The world's population is expected to increase by over 22% to 7.5 billion people by the year 2020, with most of the population growth occurring in developing countries (U.S. Census Bureau, 2000). The WHO has predicted that by 2020 rice, wheat, and maize production will have to increase by 40% to meet the caloric needs of the world (Pinstrup-Andersen et al., 1999). Thus, there are two approaches for ensuring that the world's caloric and nutritional needs are met in the upcoming decades. The first approach is obvious, but has been adopted by governments (India and China) only after a clear crisis has presented itself, and that is to restrict population growth. The second alternative is to increase, yet again, the Earth's carrying capacity by improving the nutritional content of food, effectively delivering more nutritional value with the same, or lower, level of production. Accomplishing this will be imperative, as the genetically controlled yield potential of the major food crops has apparently been reached using current levels of breeding and biotechnology. Any further increase in yield will likely include fundamental changes in a plant's ability to add biomass by improving carbon or water use efficiency. The purpose of this article is to review the current status and future prospects of improving the nutritional content of food, including vitamins, micronutrients, and phytochemicals using plant breeding and bioengineering methods.

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