Coastal impacts, adaptation, and vulnerabilities: a technical input to the 2013 National Climate Assessment

The coast has long provided communities with a multitude of benefits including an
abundance of natural resources that sustain economies, societies, and ecosystems.
Coasts provide natural harbors for commerce, trade, and transportation; beaches and
shorelines that attract residents and tourists; and wetlands and estuaries that are critical for fisheries and water resources. Coastal ecosystems provide critical functions to
cycle and move nutrients, store carbon, detoxify wastes, and purify air and water. These
areas also mitigate floods and buffer against coastal storms that bring high winds and
salt water inland and erode the shore. Coastal regions are critical in the development,
transportation, and processing of oil and natural gas resources and, more recently, are
being explored as a source of energy captured from wind and waves. The many benefits
and opportunities provided in coastal areas have strengthened our economic reliance on
coastal resources. Consequently, the high demands placed on the coastal environment
will increase commensurately with human activity. Because 35 U.S. states, commonwealths, and territories have coastlines that border the oceans or Great Lakes, impacts to
coastline systems will reverberate through social, economic, and natural systems across
the U.S.

Impacts on coastal systems are among the most costly and most certain consequences
of a warming climate (Nicholls et al., 2007). The warming atmosphere is expected to
accelerate sea-level rise as a result of the decline of glaciers and ice sheets and the thermal expansion of sea water. As mean sea level rises, coastal shorelines will retreat and
low-lying areas will tend to be inundated more frequently, if not permanently, by the
advancing sea. As atmospheric temperature increases and rainfall patterns change, soil
moisture and runoff to the coast are likely to be altered. An increase in the intensity of
climatic extremes such as storms and heat spells, coupled with other impacts of climate
change and the effects of human development, could affect the sustainability of many
existing coastal communities and natural resources.

This report, one of a series of technical inputs for the third NCA conducted under the
auspices of the U.S. Global Change Research Program, examines the known effects and
relationships of climate change variables on the coasts of the U.S. It describes the impacts
on natural and human systems, including several major sectors of the U.S. economy, and
the progress and challenges to planning and implementing adaptation options. Below
we present the key findings from each chapter of the report, beginning with the following key findings from Chapter 1: Introduction and Context.