Feature: The Global Environment and Food Production
Contrary to popular fears of global warming and carbon dioxide levels, those changes may be a blessing, argues a noted MSU scientist. The popular media has led Americans to believe that global environmental changes are leading us to disaster. But beneath the rhetoric, the evidence is that the current changes--including the rising levels of atmospheric carbon dioxide--are very favorable for the most essential of human activities, namely, the production of food. Not many people think of it this way, but food, climate, and the rising levels of atmospheric carbon dioxide are uniquely interrelated.
Food production is the world's most important renewable resource. The production of this renewable resource, upon which all life depends, is possible only through photosynthesis, the most important biochemical process. An essential raw material, almost always in short supply, is the atmospheric carbon dioxide. For example, an acre corn crop must process over 40,000 tons of air to produce the record yield of 130 bushels per acre recorded in the U.S. for 1994.
Globally, some 25 crops stand between people and starvation. The largest single food group is the cereal grains, of which corn is a leading member. They provide approximately 60 percent of the calories and 50 percent of the protein consumed by the human race. The legumes provide about 20 percent of the world's protein. The balance of calories, protein and essential vitamins and minerals is obtained from tuber and root crops and various fruits, nuts and vegetables. Food animals, deriving their food either directly or indirectly from plants, provide 20 percent of the protein with 5 percent coming from fish. The most determinant factor in agricultural (food) production is weather or the climate. For agriculture, climate must be managed both as a resource to be used wisely on the one hand or a hazard to be dealt with on the other.
Food production is very much a function of climate, which in itself is unpredictable. In fact, the principal characteristic of climate is variability. From the perspective of food security, the stability of agricultural production is as important, if not more so, than the magnitude of output. Climate variability has a greater input on agricultural productivity -- both its magnitude and stability -- than does climate change. Extremes in weather, rather than averages, affect agriculture. Both crops and livestock are sensitive to weather over relatively short periods of time. Annual averages of temperature and rainfall do not convey short term deficiencies, which differences impact both the volume and stability of food output. History reveals that for food production, warming is better than cooling.
Of all the natural climatic hazards, drought is that which farmers fear most. The lack of water is the single greatest impediment to plant growth and global food production. This is illustrated by the fact that today irrigated cropland--about 17 percent of the world's cropland--produces one third of the agricultural output. For the United States, the 12 percent of the cultivated farm land that is irrigated, accounts for 37 percent of crop production. U.S. agriculture consumes, mostly through irrigation, 80 to 85 percent of the nation's fresh water resources. For the world it is more than 65 percent. The most readily identifiable potential climatic impact of significant magnitude on future living standards of the human race is in agriculture (food) production. The availability of the water resources and the efficiency of its use, will be a major key to future food security.
We now introduce the impacts of the rising level of atmospheric carbon dioxide. First, we have its effect on climate change, and second, its effect on food production. The climate change impact is characterized by the widely publicized global warming or the so-called 'greenhouse effect.' Presumably this also is causing an increased frequency of extreme or hazardous events. Conversely, elevated levels of atmospheric carbon dioxide have a decidedly beneficial effect on crop production through an enhancement of photosynthetic capacity and an increase in water use efficiency. Additionally, hundreds of experiments now show partial alleviation of the harmful effects of both marginally low and high temperatures, air pollutants, a lessening of the environmental stresses imposed by drought, alkalinity, and mineral stresses -- both excesses and deficiencies -- low light intensities and UV-B radiation.
Concerning changes in levels of atmospheric carbon dioxide, there are some well-known facts. First, there is a documented increase. The isolated test site at Mauna Loa in Hawaii shows more than a 12 percent increase in the mean annual concentration, from 316 ppm by volume of dry air in 1959 to the 1995 level of 360 ppm. The current annual rate of increase is about 0.5 percent or 1.6ppm. Carbon dioxide source sink models predict that the current level of atmospheric CO2 will be doubled by the latter part of the 21st century. Second, the increase is truly global. The earth's atmosphere is very effective in dispensing emissions from whatever the source, be it natural or man- made. Third, with the average level of CO2 rising, there is an annual oscillation of the earth's atmospheric CO2. The earth's atmospheric CO2 level begins to fall in the spring and continues through the summer months as it appears to be sequestered by the vegetation of the northern hemisphere. In late autumn, there is a resurgence of CO2 into the atmosphere. This results in new heights by mid- winter. With the amplitude increasing by about 0.5 percent each year, it appears the concentration or amount of the earth's biomass is either increasing or is steady. It is not decreasing. Thus there are two ongoing global experiments inadvertently being conducted by the worlds' people.
The outcomes of either we do not know. First is the so-called global warming resulting from increasing amounts of atmospheric CO2 and other radiatively active trace gases. Second is the magnitude of the stimulative effect of the earth's atmospheric CO2 enrichment on improved photosynthetic capacity, and its effects on plant growth and development. This in turn increases food production, forestry output, and global biological productivity with an improvement in water use efficiency.
Meanwhile, these two experiments will likely continue well into the 21st century with the final results not fully realized. The topics of food security, the magnitude of climate change (global warming), and the beneficial biological effects of the rising levels of atmospheric carbon dioxide are rent with both political and scientific controversy. There are those that advocate immediate action with accompanying costs of billions of dollars for reducing the worlds' output of CO2. Global initiatives concerning such were promoted at the Rio Earth Summit in 1992, and again in the recent Berlin Assembly in March 1995. To date, our knowledge of the climate effects of the rising CO2 content and other greenhouse gases in the atmosphere is inadequate for initiating any global attempt to change the climate.
If the climate does change some warming could be tolerated, and may even be beneficial with no reductions in food production. A warming trend would increase the lengths of the growing seasons, encourage farmer adaptations, and favor the introduction of new technologies and cultural practices. The result would be crops and food animals more resistant to environmental stresses. The prospects of climate change from increasing levels of atmospheric carbon dioxide do not frighten many agriculturists, farmers or foresters.