induces the search for alternatives and new ways of making more from less. Looking back at agricultural development over thousands of years, there is evidence to suggest that this happens all the time in the provision of food. This is because historically food was produced using extensive production techniques – meaning large areas of land were used for the production of limited amounts of food. Environmental systems (especially soil fertility) impose such limits on production because it is typically the case that the amount of food that can be grown on the same land after a season or two of cropping tends to decrease. The simplest remedy for such soil exhaustion is fallowing of land, meaning that the field is left to rest for a season or more. During the time that the field is at rest, land is cultivated elsewhere.
Such a system is perfectly straightforward and feasible for a limited population. But as human numbers grow and demand for food increases, either the number of fields must be increased (making the production system more extensive – that is, using more land) or the population will have to rotate through their fallow land more quickly, resting the land less often, if at all. If the latter decision is made, then some way of maintaining the fertility of the soil and therefore growing more food on the same amount of land must be devised. The history of agriculture is replete with such innovations, from soil fertilization using manure and more modern inputs to complex systems of intercropping where different crops are used together or in rotation to maintain soil fertility, rather than continuously cropping the same food plant. As explained in Ester Boserup’s (1965) now-classic analysis, Conditions of Agricultural Growth, over long periods of history the amount of food produced on the same amount of land has increased exponentially, because demands for food rise with increases in population. More people means more food. This thesis is referred to as induced intensification and can be extended to all kinds of other problems and natural resources (see Chapter 3).
Owing to new cultivation techniques and input-heavy systems of agricultural production, the so-called Green Revolution, food production has boomed worldwide. Wheat production in India tripled between 1965 and 1980, for example, far outpacing the rate of population growth. In Indonesia during the 1970s, rice production increased by 37%. In the Philippines it increased by more than 40%. The period from the middle 1960s to the present in fact has been a period in which more food has been produced than consumed, and in which more people have been moved above the level of starvation than in the century prior.
Green Revolution A suite of technological innovations, developed in universities and international research centers, which were applied to agriculture between the 1950s and 1980s and increased agricultural yields dramatically, but with a concomitant rise in chemical inputs (fertilizers and pesticides) as well as increased demands for water and machinery
Induced Intensification A thesis predicting that where agricultural populations grow, demands for food lead to technological innovations resulting in increased food production on the same amount of available land
Nevertheless, a number of other environmental problems came with the Green Revolution and the expansion of food production, including the loss of unbroken soils across the prairies and rainforests of the Earth, and a concomitant loss in biodiversity. Where new land is not used to increase food supplies, increased intensity of production has also meant a massive input of fertilizers and pesticides. These chemicals take a toll on the land and are themselves made from petrochemicals, meaning that they depend upon petroleum extraction and manufacturing, with all of the environmental implications of that system. Energy is necessary, moreover, to produce farm equipment (like tractors, and harvesters), and to power that equipment. All of this energy comes from the ongoing exploitation of increasingly scarce petroleum resources, the production of which is costly and environmentally devastating. Each calorie of food in the years following the Green Revolution has become far more ecologically expensive. There appears to be no such thing as a free lunch.
These outcomes also raise questions about the problem of scale in assessing the impact of population. Agriculture might expand dramatically in a densely populated part of Brazil, for example, to produce soybeans for both consumption and industrial applications, with serious implications for the forest these crops replace. The “population” that drives this demand, however, lives thousands of miles away in Europe and the United States, and thrives in a high-impact lifestyle under conditions of low population density and growth. The circulation of agricultural products makes assessing the impact of local, regional, and global populations extremely difficult.
Nor is any of this to say that unlimited numbers of people lead to unlimited productive capacity and endless plenty, although the view has been described as “cornucopian” (literally “horn of plenty” from the Greek) by its critics. It does raise serious questions, however, about the problems of assuming natural limits. If population growth does not always lead to scarcity, or if it sometimes even results in increased resources, how useful is a Malthusian perspective?
Limits to Population: An Effect Rather than a Cause?
Beyond this, recent trends in population have made some of the pronouncements and assumptions of population-centered thinking moot. Specifically, the rate of population growth around the world has fallen precipitously in the past few years. Some areas are indeed experiencing negative growth. This should be encouraging for Malthusians. But more profoundly, it raises a basic question about population: Is population a social driver of environmental change or is it actually the product or outcome of social and environmental circumstances and conditions?
Consider the following: Population growth rates, which measure (as a percentage) the rate of natural increase of the total number of people on the Earth, peaked in the period between 1960 and 1970 (Figure 2.3). In the period since, they have only declined, slowly approaching a rate below 1%, nearing a state of zero population growth (ZPG). Whatever one might think about the danger that population (versus affluence, for example) presents for the environment, one must wonder what causes such a change.
Figure 2.3 Global population growth rates. Population growth rates peaked in the 1960s and have steadily and continuously declined since then.
Zero Population Growth A condition in a population where the number of births matches the number of deaths and therefore there is no net increase; an idealized condition for those concerned about overpopulation
What makes population growth decline? What are the implications for human–environment relations in a world where population, while continuing to grow, is likely to reach stability in the next 50 years?
Development and Demographic Transition
The most obvious precedent for this global shift comes from the demographic history of Europe in the nineteenth and early twentieth centuries. There, population went from a relatively stable state before 1800 to very high levels of growth in the 1800s, followed by a leveling off, and indeed a current state of population decline in many countries. The drivers of this trend can be broken down more carefully. We can examine the specific rate of births and deaths in Europe (or anywhere else) to provide clues as to what happened.
In traditional agrarian societies, the death rate (typically measured in numbers of deaths per 1000 people in a population in a year) and the birth rate (births per 1000 people per year) vary somewhat, but are both relatively high (around 40 or 50 per thousand). They also typically offset each other so that annually no more people are born than die, leading to low or negligible population growth.
In
