Changes In Land Cover And In Terrestrial And Marine Ecosystems

Human-induced changes in land cover have occurred throughout human history. Large tracts of land have been cleared for agriculture, forestry, the collection of fuelwood, and for urban and industrial growth. Ecosystems have been transformed both in response to land-cover change and as the result of the inadvertent and intentional introduction of plants and animals from outside their normal habitats, thereby introducing new pests, diseases, and competitive species. The damming, diversion, and rechanneling of rivers, the development of intensive agricultural irrigation systems, and the dramatic increases in the consumption of water for urban and industrial purposes have altered the natural water cycles of many regions, the impacts of which were often felt in remote locales because of the far-reaching character of hydrologic systems.

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.


Highlights of USGCRP research in FY 1996 include programs to:

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Last updated 04/10/96