How extensive are land cover changes? How fast are such changes taking place? What are the trends? What are the implications of current and projected land cover changes with regard to climate change, ecosystem health, biodiversity, and economic and human well being?

INTRODUCTION:

Dr. Anthony C. Janetos, Chief, Earth System Modeling and Ecological Processing Branch, Mission to Planet Earth, National Aeronautics and Space Administration, Washington, DC

SPEAKERS:

Dr. David Skole, Institute for the Study of Earth, Oceans, and Space, University of New Hampshire, Durham, NH

Dr. Thomas Loveland, US Geological Survey, EROS Data Center, Sioux Falls, SD

Over the next few decades the global effects of land use and cover change may be as significant, or more so, than those associated with climate change. In addition to playing a role in climate, changes in land use and land cover are direclty linked to many facets of human health and welfare, including biodiversity, food production, and the origin and spread of disease. Yet, we know very little about this important human-caused agent of global change. It is a testament to this paucity of information that there does not now exist an accurate global map of agriculture, nor do we have good global measurements on the rate of forest loss.

Tropics: Tropical forest loss contributes to global change in many ways: through the release of radiatively active gases such as carbon dioxide and methane, by affecting the latent and sensible heat flux through alteration in surface conditions, by altering flows of water due to changes in runoff and evaporation, and through large-scale losses in species as forests are fragmented. There is also compelling evidence for increased rates of infectious disease in tropical regions disturbed by deforestation.

Until only a few years ago the rate of forest loss in the Amazon had been largely unknown; estimates ranged from 20,000 to 80,000 square kilometers per year. However, new advances in information technology and methods using remote sensing have made it possible to make highly precise measurements of deforestation rates and patterns over very large areas. the rate of clearing in the Amazon is now well known through the use of satellite observations with spatial resolution of less than 100 meters. New estimates of Amazon clearing shows that, although the rate of deforestation in the Amazon has been less than previously thought, the impact of forest fragmentation on habitat has been significant. Results show that deforestation is non-linear, and that the rate of deforestation in the Amazon appears to have risen rapidly from the 1970s until the late 1980s, and then fallen off quite dramatically.

For the first time, satellite measurements provide accurate data on loss of forests for estimating the net emissions of greenhouse gases from the tropics. Moreover, these studies show that for assessments of habitat loss and biodiversity, it is not enough to know only aggregate rates of forest loss, since it is the spatial pattern that is critically important to understanding forest fragmentation.

New evidence from other regions, in particular the first-ever analysis for the whole of Indochina, is providing new insight into the global magnitude of tropical deforestation. At the same time new measurements provide answers to old questions, they raise a host of new and interesting ones as well. It appears from data for the Amazon that large areas of deforested land are in secondary growth; about 30% of the deforested land in the late 1980s appears to be in some stage of regrowth following abandonment of agricultural fields.

The availability of satellite data and an emerging view of deforestation as a dynamic and complex system have fostered the development and implementation of an international research program, The Land Use and Cover Change Core Project (LUCC). LUCC is a joint initiative of the International Geosphere-Biosphere Programme (IGBP) and the International Human Dimensions Programme (IHDP). Its aim is to develop a coordinated international research effort on the topic of global land use and cover change through the active involvement of both physical and social scientists.

North America: The U.S. Geological Survey (USGS), through the Global Land Data Management component of the U.S. Global Change Research Program and the Land Remote Sensing Policy Act (Public Law 102-555), ensures access to the nation's space and aerial Earth imagery archives. Over 11 million frames of data, including continuous near-global coverage of satellite imagery dating back to 1972, provide a unique resource for mapping the changes in contemporary global land cover.

The USGS and the University of Nebraska-Lincoln (UNL) researchers recently completed a new map of conterminous U.S. land cover patterns using. A comparison of the 1990 map to a map of pre-settlement vegetation reveals that more than 61% of the lower 48 states is covered by the same dominant vegetation as existed prior to settlement. Most of the changes have occurred in the central U.S. where only 29% of the nation's grasslands remain. Much of this change is attributed to the expansion of agriculture.

The USGS/UNL team is now expanding the U.S. land cover classification and is developing a global 1-km land cover data base from satellite imagery. The USGS/UNL land cover data are already contributing to many Earth systems modeling studies. The USGS/UNL global land cover data base will be completed by late 1997.

Detailed analyses of change can also be made using the 24 years of high resolution Landsat satellite imagery stored in the USGS archives. For example, the historical Landsat data provide a means to:

Understand the extent of land devastated by the eruption of Mount Saint Helens and other volcanoes, monitor the recovery of the region's forests, measure the growth of irrigated agriculture in the Great Plains, monitor the cyclic nature of the hydrology of lakes, document the rate of growth of the rapidly developing Sunbelt cities, and quantify the conversion of cropland in intensive urban activities.

Dr. David Skole is a Research Professor at the Institute for the Study of Earth, Oceans, and Space at the University of New Hampshire. He is a systems ecologist, with research interests in the role of land use and land cover change in the global carbon cycle, particularly in tropical forests. He is the Principal Investigator on NASA's Landsat Pathfinder Project, which is using satellite remote sensing and numerical models to study tropical deforestation in Southeast Asia and the Amazon. Dr. Skole is the Chairman of the Core Project on Land Use and Cover Change (LUCC), a joint effort of the International Geosphere-Biosphere Programme and the International Human Dimensions Programme. Dr. Skole serves on numerous committees in the U.S. relating to Global Change Research, and has worked for several years on national and international global change research projects.

Dr. Thomas Loveland is a remote sensing scientist for the U.S. Geological Survey's EROS Data Center (EDC) in Sioux Falls, SD. Dr. Loveland has been engaged in remote sensing research programs at EDC for over 15 years. His research has dealt with large area land cover mapping and vegetation monitoring in the Arctic, Africa, and the United States. Dr. Loveland currently leads EDC's land cover characterization research project. He has also served as the co-chair of the International Geosphere-Biosphere Programme's Land Cover Working Group. He recently received the 1994 USGS Mendenhall Lecturer Award for his scientific leadership. The American Society of Photogrammetry and Remote Sensing also awarded him the Alan Gordon Memorial Award for significant achievements in remote sensing. Dr. Loveland has also held positions in geographic information system and remote sensing applications and management with state governments in South Dakota and Arizona. He has degrees in Geography from South Dakota State University.