The proposed study integrates archaeological and paleoecological research to examine the mechanisms through which the pre-Hispanic Andean state of Tiwanaku generated extensive land-use changes that altered local ecosystems in such a way that renewable resource production, particularly agriculture and possibly fisheries, was sustained for nearly a millennium. Five research objectives converge on the issue of changing human environment interactions in the study area adjacent to Lake Titicaca: 1. to describe lake-level variation during the past 5000 years, the major period of human occupation; 2. to analyze Holocene climate variation in the altiplano both by using lake- level variation as input to water- and energy-budget (climatinomy) models, and by using stratigraphic variations of stable oxygen and carbon isotopes to measure the region's hydrological balance; 3. to reconstruct the spatial and temporal dynamics of raised-field agriculture in the study area by topographic mapping, systematic test excavations and ground penetrating radar; 4. to model agricultural space-time systematics in the context of explicit hypotheses regarding hydrological and climatic control of raised fields with Geographic Information Systems (GIS) techniques; and 5. to determine changes of erosion and deposition processes and soil nutrient loss coincident with distinct types of farming practices. The results of this research may hold broad implications for understanding the ecological and organizational bases of resource sustainability in harsh environments. This long-term view of different nutrient-retaining capacities of at least two different kinds of agricultural practices, raised fields (which are found throughout the tropics in inundated areas) and traditional dry-farmed fields may be useful in agronomy and agroecology. Finally, studies of global climate change may benefit form a finer-scaled picture of the past several thousand years in the Lake Titicaca basin, as well as from the attempt to separate, in the paleoecological record, effects of human activities from natural climatic variation.