Many people (including national leaders) worry that population growth depletes resources and can trigger social or economic catastrophe if it is not contained. As discussed in the preceding section, most of the projected population growth during this century will take place in developing nations. These countries have faced many challenges in recent decades, including low levels of education, poor health standards, poverty, scarce housing, natural resource depletion, wars, and economic and political domination by other countries. In Sub-Saharan Africa industrial development has stalled and most workers still make a living from subsistence agriculture.
Countries in this situation generally have devoted less energy to addressing environmental issues than their wealthier neighbors, so these problems have intensified. Especially in the poorest countries, therefore, future population growth is likely to make environmental deterioration worse (although it does not automatically follow that countries with low population growth rates will have cleaner environments).
However, the relationship between population and the environment is complex. As noted in section 1, human societies’ impacts on the environment are a function of three major, interconnected elements: population size, affluence or consumption, and technology. An expanded version of the IPAT equation separates technology into two factors: resource-intensity (how many resources are used to produce each unit of consumption) and waste-intensity (how much waste each unit of consumption generates), and also considers the sensitivity of the environment (footnote 11).
Societies’ environmental impacts take two major forms. First, we consume resources such as land, food, water, soils, and services from healthy ecosystems, such as water filtration through wetlands. (For more on ecosystem services, see Unit 9, “Biodiversity Decline.”) Over-consumption uses up or severely depletes supplies of non-renewable resources, such as fossil fuels, and depletes renewable resources such as fisheries and forests if we use them up faster than they can replenish themselves (Fig. 11).
