Mitigating Adverse Impacts of Climate Change

It is now well understood that changes in the physical climate system over the last century have been driven in large part by human activities and that the human influence on climate is increasing. Future climate changes may be much more dramatic and dangerous. For example, rising sea levels will increase coastal flooding during storms, which may become more intense. Effective mitigation of dangerous future climate change and adaptation to changes that are certain to occur even with mitigation efforts require knowledge of how the climate is changing and why. But there is no well-developed climate-monitoring system, and fundamental changes are needed in the U.S. climate observing program. The United States does not have, nor are there clear plans to develop, a long-term global benchmark record of critical climate variables that are accurate over very long time periods, can be tested for systematic errors by future generations, are unaffected by interruption, and are pinned to international standards. Difficult climate research questions also remain, for example, the cloud-water feedback in climate models. Another example concerns the geographic distribution of the land and ocean sources and sinks of carbon dioxide, which do not simply map with geography, but rather display complex patterns and interactions. As nations seek to develop strategies to manage their carbon emissions and sequestration, the capacity to quantify the present-day regional carbon sources and sinks does not exist.

Protecting Ecosystems

Nearly half of the land surface has been transformed by direct human action, with significant consequences for biodiversity, nutrient cycling, soil structure and biology, and climate. The beneficial effects of these transformations—additions to the food supply, improved quality of human habitat and in some cases ecosystem management, large-scale transportation networks, and increases in the efficiency of movement of goods and services—have also been accompanied by deleterious effects. Morethan one-fifth of terrestrial ecosystems have been converted into permanent croplands, more than one-quarter of the world’s forests have been cleared, wetlands have shrunk by one-half, and most of the temperate old-growth forest has been cut. More nitrogen is now fixed synthetically and applied as fertilizers in agriculture than is fixed naturally in all terrestrial ecosystems, and far too much of this nitrogen runs off the ground and ends up in the coastal zone. Coastal habitats are also being dramatically altered; for example, 50 percent of the world’s mangrove forests, important tropical coastal habitats at the interface between land and sea, and coastal buffers of wave action, have been removed (Granek, 2005). That the world’s marine fisheries are either overexploited or, for some fish, already depleted is well known; one recent study even suggests the potential for their total collapse by the middle of this century (Worm et al., 2006). And yet there are no adequate spatially resolved estimates of the planet’s biomass and primary production, and it is not known how they are changing and interacting with climate variability and change.

Improving Human Health

Environmental factors have strong influences on a broad array of human health effects,including infectious diseases, skin cancers, or chronic and acute illnesses resulting from contamination of air, food, and water. Public health decision making has benefited from the continued availability of satellite-derived data on land use, land cover, oceans, weather, climate, and atmospheric pollutants. However, the stresses of global environmental change and growing rates of resource consumption now spur greater demands for collection and analyses of data that describe how environmental factors are related to patterns of morbidity and mortality. Further improvements in the application of remote sensing technologies will allow better understanding of disease risk and prediction of disease outbreaks, more rapid detection of environmental changes that affect human health, identification of spatial variability in environmental health risk, targeted interventions to reduce vulnerability to health risks, and enhanced knowledge of human health-environment interactions.

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