Chapter 2 discusses major factors that lead to environmental change and some of the persistent challenges that EPA will likely continue to face in the coming decades. The committee cannot predict with certainty what new environmental problems EPA will face in the next 10 years or more, but it can identify some of the common drivers and common characteristics of problems. The specific topics discussed in this chapter were identified based on committee expertise and a review of the scientific literature. This chapter is not meant to be an exhaustive list of all factors leading to environmental changes or of all persistent and future environmental challenges. Instead, the chapter is meant to provide some illustrative examples of the types of problems facing EPA today and some of the factors that create and influence those problems.


Major socioeconomic factors are directly and indirectly driving environmental changes and are increasing the imperative for EPA to maintain and strengthen its environmental research efforts. Those socioeconomic factors are often reflected in population growth and migration, demographic shifts, land-use change and habitat loss, increasing energy demand and shifting energy supplies, new consumer technologies and consumption patterns, increasing emissions of greenhouse gases, and movement of organisms beyond their traditional ranges, which in turn have implications for the scientific knowledge that is required to inform policy decisions at EPA effectively. EPA will be challenged in coming years to adapt to rapid changes in scientific knowledge, society, and the environment. An increased awareness of the effects of human activity on human health and the environment has raised people’s concern regarding the issues that the agency is charged with addressing.

Population Growth

It took until 1800 AD for mankind to reach a population of 1 billion people, but only required 123 more years to reach 2 billion, 33 more years to reach 3 billion, and about 13–14 more years for each additional billion people thereafter (UN 1999). In October 2011, the worldwide population hit 7 billion (UN 2011). With the dramatic increase in population, human activities have altered and will continue to alter an ever-increasing portion of Earth’s surface (Wulder et al. 2012). Such activities have diminished natural ecosystems and the benefits that they provide, including water purification, flood control, climate moderation, and new crop plants.

In the United States, the population continues to increase at approximately 1% per year (US Census Bureau 2012). This population growth contributes to such environmental effects as increased emissions of greenhouse gases due to energy use, transportation demand, and residential and commercial activities (EPA 2011a); increased consumption of resources (Worldwatch Institute 2011);

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