FIGURE 7.2 SeaWiFS captured these images of the Florida coast on September 17, 2001. In the left image, the colors red, green, and blue have been assigned to what the naked eye would see as green, blue-green, and blue. Clear blue offshore seawater appears blue, coastal water that is typically green appears red, and water with high levels of suspended sediment appears white. Water dominated by red tide appears dark gray. The right image is a false-color image showing milligrams of chlorophyll per cubic meter of seawater. SOURCE: E.Yohe, NASA Earth Science Enterprise, “Hunting dangerous algae from space,” NASA Distributed Active Archive Center (DAAC) Alliance, July 9, 2002. Available at http://earthobservatory.nasa.gov/Study/Redtide/.

Conversion of lands for human use is essential for the human enterprise to grow food, build cities, and obtain other essential services. The increasing intensity and extent of human land-use are as global as is changing climate. Harvesting of fisheries from the ocean and water quality impacts from coastal development are also leading to massive alteration of ocean ecosystems. Changing land and ocean use may increase the vulnerability of human populations and ecosystems to changing climate, moving ecosystems closer to thresholds beyond which there is no recovery. Each land-use and ocean-use decision is unique, but there are regional and even global trends that have cumulative effects. The effects of changing land and ocean use vary widely—they include the formation of large sources and sinks of CO₂, changes in hydrology and geomorphology, changes in landscape patterns that affect biodiversity, and a host of other effects (DeFries et al., 2004; Foley et al., 2005).

Remote sensing of land-cover and ocean-biomass change is crucial both for observing environmental change and as input in individual, local, national, and transnational decision making. Satellite