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Unit 13: Looking Forward: Our Global Experiment // Section 2: Measuring (and Reducing) the Human Footprint

Population growth and economic development over this century present many different environmental challenges. As described in previous units, some are local in scale, such as certain types of water pollution. Some are regional in scale, such as acid rain. And some are global, such as climate change. In all cases, one simple strategy to minimize harmful impacts on the natural environment is to reduce the human "footprint" on the environment—although this simple concept is sometimes quite complicated to apply to a specific environmental problem.

At some basic level, most of our environmental challenges are related to the rapid increase in human population. As discussed in Unit 5, "Human Population Dynamics," demographers estimate that global population will increase through the middle of this century to approximately 9 billion and may stabilize or even decrease after that. A simple way of thinking about how to solve environmental problems—from atmospheric pollution to climate change—is in the context of how an individual appropriates some of the natural environment for his or her own needs. Addressing climate change can be discussed in terms of how much carbon dioxide and other greenhouse gases are emitted by each person; habitat loss can be discussed in terms of how much land each person requires to extract food and other services; air pollution can be discussed in terms of the amount of pollutants each person emits, etc. In this framework, population growth can be seen as a primary driver of environmental degradation, as the footprint of human society will increase in direct proportion to the number of people. In the purest sense, one's ecological footprint refers to how much land is required to support one’s various activities (Fig. 1). However, the concept of a footprint is often used in a more general sense, applied not only to the amount of land, but also to water use, pollution emitted, etc.

Global footprint (hectares/person)

Figure 1. Global footprint (hectares/person)
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For some issues, like water resources, calculating one's footprint is relatively straightforward. Per capita water use depends on dietary choices as discussed in Unit 8, "Water Resources," as well as on water use for sanitation, drinking, and other purposes, so calculating the average water needs for a particular society is quite feasible.

Because there is more than one cause for biodiversity loss, quantifying one's footprint is more complicated. As discussed in Unit 9, "Biodiversity Decline," many fish species are declining in number because of human fishing (or overfishing). For other species, such as those that live in the tropical rainforest, a major threat is the destruction of habitat. Still other species are threatened by toxic pollution. Quantifying exactly how one person affects the decline in biodiversity is therefore a much more complicated affair.

Calculating the impact of the human footprint on climate change brings other complications. At a basic level, one can calculate how much fossil fuel an individual uses and therefore how much carbon dioxide is emitted. However, greenhouse gases are produced not only when we use energy directly but also when we buy products that require energy to make them, from a new house or car to fresh produce that require energy for transportation. This is also an issue at a national scale. For example, the carbon dioxide emission footprint of a country like the United States only includes the fossil fuel that is actually used in the United States, but excludes the energy that is used to make products in other countries that are then shipped to American consumers.

Considering one's environmental footprint—however it is calculated—leads to a fundamental tension between economic development and environmental impacts. As discussed above, population growth is at the root of many environmental problems. But population growth is not the only driver of environmental degradation, and perhaps not even the primary one. It is true that many environmental problems would be much easier to solve if the population were much smaller, but over the next 50 years, demographers predict that the world population will increase another only 50 percent or so and then will start to decline. In comparison, human consumption of goods and services—sometimes measured by economists as gross domestic product (GDP) per capita—is predicted to grow by a factor of ten or even more through this century (Fig. 2). What this means is that the footprint of human society is getting larger, partially because the human population is growing (i.e., more individual footprints), but mostly because humans are getting richer, appropriating more and more of the natural environment for their needs, impacting almost every environmental challenge discussed in this course.

Global GDP

Figure 2. Global GDP
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Some people believe a strategy for fixing environmental problems involves restraining economic growth, reducing the human footprint on the environment by using less of the natural world. In many cases, this can be accomplished without reducing the quality of human life. For example, there are many ways to conserve water or electricity that do not sacrifice quality of life. However, preserving the environment is unlikely to happen simply at the expense of economic development. Economic development leads to better quality of life for people all over the world; it raises people up from desperate poverty and gives our societies the capacity to fix many of the environmental challenges. So how can we increase the quality of human life, encourage economic development, and still protect the environment as human appropriation of the natural world becomes greater and greater? The answer may involve new technology. In some cases, new technologies allow us to reduce our environmental footprint while still providing the goods and services we need, allowing our economic well-being to flourish. A good example is the catalytic converter on automobiles that reduced air pollution, improving human health but still allowing us to drive our cars. New technology may not be a panacea for all environmental problems, but it can help societies balance their needs for economic development with their goals for protecting the environment.

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