Worldwide land-cover and ecosystem changes have become especially pronounced in recent decades. As the rates of change in many places have accelerated, so also have the magnitude of those changes and their impacts. More than ever, a comprehensive view of land-cover and ecosystem change is needed. Fortunately, new techniques for acquiring and managing information about these elements have been developed. The science and new technologies for measuring and understanding the dynamics and consequences of land-use and land-cover change have improved dramatically in the last decade. Studies in both tropical and temperate regions using Landsat data have demonstrated that rates of deforestation can be documented, and regrowth and reclearing of secondary growth also can be measured. Satellite data can be combined with ground-based and airborne measurements to determine the influence of land-cover change on biological diversity, hydrologic processes, and the potential for future resource production and utilization of an area. Research results and methods for measuring large-area land-cover and land-use change are now being used by commercial interests to develop sustainable plans for the production of livestock and forest products and to manage public lands for multiple uses.
The increasing volume of data on land cover and related variables greatly facilitates analyses of the dynamics of land-cover change. USGCRP-sponsored research has examined the patterns and rates of land-cover change in a wide range of different areas, exploring different ways for classifying land cover and related land-use practices. These efforts have led to delineation of a set of land-cover regions for the globe. Regional case studies have begun in many of these regions using a common protocol developed by scientists involved in the Land-Use and Land-Cover Change (LUCC) project, a core project of both the International Geosphere-Biosphere Programme and the international Human Dimensions of Global Environmental Change Programme (HDP). Through the use of comparable approaches in the conduct of these regional case studies, analyses of the dynamics of land-cover change in each of the regions form the basis for more general advances in understanding the complex interactions among human and natural processes. In the next decade, major new advances in the capabilities for remote sensing of land-cover and land-use dynamics are expected, resulting in an even greater increase in data available for documenting the dynamics of land-cover change.
In addition to gaining a better understanding of changes associated with the land, changes affecting or affected by the oceans (which cover 70% of the Earth's surface) are also critical to understanding the dynamics of the total Earth system. Warmed by the Sun and driven by winds, this vast mass of flowing water regulates the planet's seasonal and interannual climate fluctuations. The oceans are home to diverse communities of plants and animals, which take in and release dissolved carbon, nitrogen, oxygen, and other elements. Marine organisms participate in the global cycles of such elements, affecting their concentrations in the oceans, atmosphere, and land. Studies of ocean biology and circulation are crucial to understanding these biochemical cycles and their role in the maintenance of life.
The oceans now are under increasing pressure from human activities. Industrial waste, synthetic fertilizers, and other pollutants are carried by rivers into the ocean, where they can injure life and cause radical changes in the composition of marine ecosystems. The species composition of algal blooms is shifting, and "red tides" of toxic algae are more common along the coasts of the world. Coral reefs, which support a wide variety of organisms in the tropical seas, have been particularly hard hit. Fish and shellfish have suffered as well, with heavy impacts on marine industries. Through significant new remote sensing capabilities and the use of other satellites, aircraft, and ground-based instruments on ships, buoys, and moorings, USGCRP-sponsored research is studying the responses of marine life to various kinds of natural and human-induced global environmental change.
Humans are placing increasing demands on terrestrial and marine ecosystems. The challenge is to understand the potential consequences of natural and human-induced transformations and the effects of industrial activity on the structure and function of terrestrial and marine and coastal ecosystems. Such understanding is essential to maintaining the goods and services essential for human life provided by ecological systems and for developing mitigation options. It is also essential that the potential benefits derived from human-induced land transformations and industrial processes be balanced against the potential costs associated with the reduction or loss of ecological goods and services which result from such activities.
PROPOSED FUTURE RESEARCH ON CHANGES IN LAND COVER AND IN TERRESTRIAL AND MARINE ECOSYSTEMS
- Classify and inventory North American land cover. Federal agencies are cooperating to analyze Landsat satellite data (with resolutions of less than 100 meters) and to classify and inventory the land cover of North America and the entire equatorial tropics from 1970 to the present. This effort will document changes that affect the functioning of ecological systems and provides the global change research community and policy makers with valuable and accurate estimates of changes such as deforestation. A program is being developed to study land-cover change in portions of Mexico in cooperation with the Mexican government. This research is aimed at identifying land-cover changes on decadal time scales, especially those related to the conversion from agricultural to urban land uses and from forest to agricultural land use. This research will enhance knowledge related to productivity changes.
- Participate in the international Land-Use and Land-Cover Change Programme. A comprehensive science plan has been developed for studying global land cover and land use to determine how these have varied over the past and to evaluate the current land-cover status. The program, which will aim for global coverage of land cover at 1 km spatial resolution, will examine the major human causes of land-use change in different geographical and historical contexts and project changes that may occur over the next few decades. Projecting the future responses of terrestrial ecosystems to land-cover change requires understanding the relationships between past changes in land cover and in the structure and function of ecosystems.
- Study how ecosystems react to change and influence global phenomena. The interagency program on Terrestrial Ecology and Global Change (TECO) will continue in 1996. New studies under the program will: (1) focus on improving the understanding of how species, ecological characteristics and processes, and ecosystems are related to land-cover change, and (2) enhance capabilities to predict consequences of multiple influences (e.g., when the physical environment and ecological parameters change simultaneously).
- Work with international partners throughout North and South America to understand the dynamics of land use and land-cover change. A comprehensive new project, building on research already underway, includes the development of a model of the deforestation process at work in the Amazon using demographic data linked to satellite observations.
- Study the response of marine life to global environmental change. A science plan has been developed to study the effects of natural and human-induced environmental changes on marine life. Research focuses on (1) the inputs of nutrients from land, the atmosphere, or the ocean interior via upwelling, (2) temperature changes that alter physiological states, (3) radiation (e.g., UV) changes that affect primary productivity or damage cells, and (4) changes in circulation patterns and other oceanic processes that affect ecosystem structure and function.
- Develop a system for tracking changes in carbon flux resulting from land-use change. A new research program has been initiated to quantify terrestrial carbon fluxes from changes in land use and land management. Information at both national and regional levels is being collected on the successional status of ecosystems, carbon densities, and carbon cycling, and their relationships to changes in land use. This information is needed to address scientific issues related to carbon sources and sinks, and to provide a scientific basis for developing response options to a CO2 enhanced greenhouse effect.
- Apply new satellite ocean color data to coastal problems. A coastal program will focus on: (1) distinguishing and tracking harmful algal blooms; (2) tracking coastal and estuarine sediments to determine the fate of suspended sediments and land runoff into coastal oceans; (3) tracking coastal dynamic processes (ocean circulation pattern) to determine dispersal patterns of pollutants and red tides; and (4) application to coastal fisheries and ecosystem management.