Land-Use Dynamics in a Post-Agricultural Puerto Rican Landscape (1936-1988)

Anthropogenic alteration of the landscape is a long-term disturbance both in duration and consequences. This study addresses land-cover responses to a history of human land use in northeastern Puerto Rico. Analysis of aerial photographs indicated that the pattern of land use in the municipality of Luquillo changed dramatically between 1936 and 1988. In 1936, sugar cane and pasture were the dominant land uses, occupying about one third of the study area each, while dense forest was rare. Pasture still occupied about a quarter of the area by 1988, but the area of sugai cane had declined to zero. Most sugar cane land was transformed to pasture after abandonment, while much of the pasture at higher elevations reverted to forest. More than half the study area in 1988 was occupied by dense forest, and the degree of forest regeneration was greatest adjacent to the Luquillo Experimental Forest and around patches that were dense forest remnants in 1936. The overall trend was from high-intensity agriculture to dense forest, but urban areas increased more than 2000 percent between 1936 and 1988 and are presently encroaching on forested areas. It is unclear from one study whether the same pattern would hold true at other sites in the tropics, but our study indicates the importance of preserving remnants of mature forest as sources of forest regeneration. In addition, the nature of the patches in the Luquillo landscape has changed as the land use has changed. In 1936, dense forest was highly fragmented, the patches were small and many of them had linear configurations (riparian corridors and hedgerows). By 1988, the average patch size of dense forest had increased greatly, although with one exception the patches were still small relative to other land-cover types.