Two major trends that will affect crop production and the global environment are the increases in human population and energy use. After two centuries of exponential growth, world population shows signs of stabilizing at about nine billion in 2050 (3). Energy use is projected to rise about twice as fast as population because of economic development. We are not sure whether the population graph is following the exponential model or whether the logistic model applies and we are approaching carrying capacity (33-19, 33-20). This leads to a range of estimates for population growth (2).

We saw earlier that it is possible to feed an adult on a plant diet from about 0.2 hectares of land and this is about what will be available on average when world population reaches 8 billion (19-20, 4). However the yields we achieve in industrial countries need to be achieved world-wide (57-04). This in turn requires that inputs, at least of fertilizer and probably pesticides have to rise in other countries to match those in North America and Europe (57-03). If the other countries mechanize crop production this will entail further energy consumption. This is likely because mass migration from rural areas to the cities is underway on all continents. While agriculture accounts for only about 2% of energy consumption in North America and Europe it would amount to about 10% of energy demand in the rest of the world.

A balance between agricultural energy consumption, food supply and population is achievable, but it depends on certain assumptions. The main assumption is that everyone in the world has equal access to the food supply. At the moment the supply and the ability to buy it are very unequally spread among the countries of the world (5). So many countries in Africa, South America and Asia would need to become much richer in order to develop their own agriculture or purchase the food that they need.

China alone represents a major challenge to the world’s food supply. It has about 20% of the world’s population but less than 10% of the world’s crop land. It had about 0.2 hectares per person in 1950 and now has about 0.1. It has managed to feed itself and actually improve people’s diet over the past decade. However, with its population set to increase by a further 20% before stabilizing at 1.5 billion it is doubtful that this can continue (6). Fertilizer use is high and further increases will not bring much additional yield. There are already problems of nutrient pollution and soil degradation and the area of agricultural land is shrinking because of urban development (13).

The USA has about twice as much cropland as China but a fifth of its population. It is one of a handful of countries with a relative excess of cropland in relation to population. Others include Canada, Australia and the Russian Federation (7). China is undergoing rapid industrial development and now supplies us with a wide range of the manufactured articles that used to be made here. In the future it is likely to be a major customer for US agricultural products. Other countries may try to follow China’s road to economic development. Even if they do not it is likely that China’s demand for food will raise prices of agricultural commodities and this could be good news for US producers. Of course US consumers are likely to be unhappy as food becomes more expensive after many years of falling prices.

Grain-fed meat production is increasing in China. This increases the land required to meet its dietary needs and cannot be sustained on a global scale. In order to provide an adequate diet for everyone cropland needs to be devoted to feeding people. Animal production needs to be based on more marginal land that will support grazing but not crops (19-31).  But over-grazing  and desertification are a constant threat in arid lands.

A 58% increase in global energy use is expected over the next 25 years and it seems likely that most of this energy will come as it does now from combustion of fossil fuels (8). The rate of discovery of new reserves has slowed down but for some reason the oil industry is confident that supplies will extend beyond the 40 years of known reserves at current rates of consumption. Gas reserves are a little higher at about 60 years (but little of this is in the US). Coal reserves are considerably higher at over 200 years (9). Coal is more evenly distributed and its consumption is rising faster than for gas and oil outside the US and Europe. So atmospheric carbon dioxide will go on increasing for the next 50 years and other gaseous pollutants will increase as coal consumption rises (10).

The argument about the connections between rising atmospheric CO₂ rising temperatures and other weather changes is almost over (11-07, 11-08). Crop productivity should increase with these changes, as long as rainfall patterns are not disrupted (41-10). However, the changes impose further stress on natural plant communities and there are doubts whether forest ecosystems can adapt fast enough to survive the changes. For example, American beech may become extinct over a large part of its present range and it will not be able to spread north fast enough to take advantage of new habitat (11). The other atmospheric pollutants that accompany CO₂ emissions from fossil fuels will cause more damage to crops and wild plants.

As we saw earlier, global energy demand is only a fraction of the energy captured in photosynthesis, and an even smaller fraction of solar radiation reaching the earth (22-02). About 40% of the world’s population relies on biomass as their primary energy source, but these are people who consume very little energy by our standards. Gathering fuel for firewood consumes more of these peoples’ time as it progressively degrades or eradicates native vegetation. Sustainable production of bio-fuels seems like the answer to problems of energy supply. However, this would require massive changes in land use, and large investment in equipment for conversion of biomass to usable fuels. The major growth in fuel requirements is predicted to be in transportation, but biomass to fuel conversion processes such as corn to ethanol will not generate enough of an energy profit to support this growth (20-11).

The demand for food and fuel is leading to deforestation in many tropical countries. The loss of biodiversity and environmental quality is unfortunate for the resident population but has implications for us as well. The tropical forests were a major sink for the carbon dioxide that we generate through our fossil fuel consumption (42-08).

In the US the prices of many agricultural commodities continued to fall in real terms in the last quarter of the 20^th century. Even though yields continued to increase, income per acre declined (12). So far it has not been possible to break away from the system of price support for selected commodities. In 2000 the payments amounted to half of farm income. The payments are supposed to help farms stay in business but end up as one more factor encouraging consolidation in the industry: large farms get more government assistance than small farms.

The number of farms decreased as individual holdings got larger in the second half of the century. The number of farm-workers also continued its long-term decline so that there is now a little more than one full-time worker for each farm. The numbers of farms and farm workers seem to have stabilized towards the end of the century and these may be minimum sustainable values (13). Most farms are run as part-time businesses and about 10% of the remaining farms account for 70% of production. The profitability of farming has been helped to some extent by diversifying the uses of staple crops (ethanol and syrup from corn and tofu from soybeans) and by adopting alternative crops. The area of farmland has also declined from its high point at the beginning of the 20^th century. In contrast to many other countries, the US has seen an increase in the area of woodland (14).

The increase in US population during the last century was mainly in urban areas so that rural population decreased in relative terms from 60% in 1900 to 25% in 2000 (15). In the upper Midwest rural population fell in absolute terms from the middle of the century (16). This was associated with a loss of economic and cultural vitality in rural communities. Such communities were more likely to survive where there were large towns that provided an economic stimulus to the surrounding areas. This may be the reason why rural populations persisted and grew in Ohio and surrounding states (17).

Urban populations have increased in every state of the Union.  The increases were most marked in the coastal states, east and west and along the shores of the Great Lakes (18). Although this is classed as urban development it is more accurate to call it suburban. Average lot sizes for new homes are about 0.15 hectare or 0.4 acre (64-06). The spacious lifestyle of the suburbs depends on personal transportation for access to work, shops and leisure and this accounts for much of our energy demand. Many people have criticized this and other aspects of suburban sprawl but it leads to new opportunities. The new homes are an expanding market for landscape supplies and services. Surviving farms can market directly to the surrounding population. Families can enjoy a visit to the local farm to buy or pick their own produce (19). This may help maintain contact and understanding between the mass of the population and the few remaining farmers.

Another related development is the growth of golf as an industry that is now equivalent to about two thirds of major crop sales and involves 12% of the US population. The number of golf-courses has increased threefold in the past 50 years (3435-72, 20).

©Michael Knee, Ohio State University, 2003

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