Challenges of the 21st Century - Science For Environmental Protection: The Road Ahead - page 15

increasing numbers of manufactured chemicals and products introduced into the
environment (EPA 2011a); and increased food and water demand and concomi-
tant changes in land use (NRC 2011). Those demographic, consumption, and
production changes contribute to the challenge of addressing environmental
problems and health outcomes as increasing amounts of land and resources are
demanded to meet human wants and needs.
Changes in Land Use
Land use is a major factor driving environmental quality. Land use
strongly influences water quality through runoff, water quantity through influ-
ence on the hydrologic cycle, air quality through emissions and deposition and
carbon storage in terrestrial landscapes, and biologic diversity through habitat
loss, disturbance, and resource availability. In the United States, changes in land
use result largely from expansion of urban and agricultural areas, energy devel-
opment, and changes in forestry practices.
Population growth and demographic transitions have increased the re-
quirement of land area for residential, commercial, and transportation activities
(Squires 2002). In the conterminous United States, it has been estimated that up
to 45.5 million acres (2.4%) of land is characterized by impervious surfaces (in-
cluding roads, building, sidewalks, and parking lots) (Nowak and Greenfield
2012). Impervious surfaces change the hydrology and ecology of rivers (higher
peak flows and scouring of habitat) and reduce the availability of groundwater
for agriculture and other human use. In addition, the interconnected effects of
urban sprawl are numerous and complex—greater automobile use in less-
densely populated communities can lead to increased air pollution and more
sedentary lifestyles, both of which are risk factors for heart disease. Less dense
housing also increases energy use per capita and contributes to increased air
pollution and climate change and potentially to such adverse health effects as
increased asthmatic attacks (Frumkin 2002; Younger et al. 2008; Brownstone
and Golob 2009).
Despite increased demand for food and fuel, the land area dedicated to ag-
riculture has not increased substantially over the last few decades. In the United
States, acreage devoted to corn has increased over the last 10 years, but total
agricultural acreage has been largely unchanged. Agricultural productivity has
increased as a result of major investments in research by both the public and
private sectors, but there is still uncertainty as to whether the increase can be
maintained and, if so, whether it would have associated environmental costs. For
example, without substantially increased nutrient-use efficiency, increased
amounts of fertilizers will be applied per acre of agricultural land, and therefore
increased amounts of those nutrients will be lost to the environment. If increased
productivity is not maintained, more acres will need to be devoted to agriculture,
probably at the expense of marginally productive lands and natural ecosystems.