Modelando los efectos del manejo de tierras en los asentamientos de la Amazonia Brasilera de Rondônia

The socioeconomic and ecological aspects of landuse change are interrelated, especially in the Brazilian Amazon, where immigrants are rapidly cutting the forest to establish farms. A computer simulation has been developed that projects land‐use changes, carbon release, and the time a family can remain on a farm lot as a function of initial soil and vegetation conditions, market and road infrastructure, and decision variables. The model simulates extremes of land‐use practices and typical land‐use conditions for central Rondônia, Brazil. Typical land‐use practices in Rondônia are based on published accounts of farmers’ activities. The most severe practices are defined based on extreme land management conditions along the Transamazon Highway. The best land‐use practices are innovative farming techniques that use a diversity of perennial crops. Model projections using the typical land‐use scenario produce changes in land cleared, carbon release, and farmer turnover rates representative of central Rondônia, based on interviews with 87 farmers. Results from both the model projections and the interview data show that farmers who have been on the lots a decade have cleared about half of the lot. The most striking result is the similarity in the typical and worst‐case scenarios over the 40‐year projection period in the percentage of land cleared and carbon released and in the number of families on the farm lots and abandoning the lots over time. Model results from the best‐case scenario compare well to the three farmers out of 87 interviewed who practice innovative farming. In both cases, farmers who have been on their land an average of eight years have deforested less than 20% of the lot. Spatial indices of fractal dimension and contagion are used to quantify the effects of the different land‐management practices. Changes in the fractal index over the 40 years of projected land management demonstrate the decrease in complexity as a forested region becomes dominated by agriculture for the typical and worst‐case scenarios. Low values of the contagion index indicates that a heterogeneous mix of land uses is retained with the best‐case scenario. These results suggest that crop diversity and nontraditional techniques provide both a social and environmental improvement over the other scenarios: the people are able to maintain themselves on the land, less carbon is released, and the land maintains a mix of habitat types. The model results illustrate that both social and environmental effects of land‐management practices need to be considered.