Document: JUL-3-65-37

Documentation of land cover history of secondary forests of northeastern Costa Rica using time-series remote sensing data.

READ, J.M.* ¹, J.S.DENSLOW ^2,3 and S.M.GUZMAN ³

Syracuse University, Syracuse, NY, U.S.A. ¹
USDA Forest Service, Hilo, HI, U.S.A. ²
Louisiana State University, Baton Rouge, LA, U.S.A. ³

Abstract:
We reconstructed the land-cover and land-use history of a lowland tropical forest landscape to examine the spatial and temporal patterns of anthropogenic disturbance and forest regrowth. The study covered an area of ca. 20 by 30 km of the Caribbean lowlands of northeastern Costa Rica, including extensive forested and agricultural areas, as well as La Selva Biological Station and part of Braulio Carillo National Park. We identified and mapped land-cover using aerial photographs (1:60,000 for 1960, 1983, and 1992) and Landsat Thematic Mapper (TM) images (28.5 x 28.5 m pixels for 1986 and 1996-97). The aerial photograph-derived classifications were georeferenced and rectified to the Landsat-TM classifications. The resulting time-series consisted of medium-scale land-cover maps (min. mapping unit = 3 ha) suitable for analysis of forest, pasture, agricultural crops (including plantations) and scrub for 1960, 1983, 1986, 1992 and 1996. In 1960 the association between roads and rivers was strong, and most clearings were located along these routes. During 1960-1983, the annual rate of decrease in forest area was 1.43% of the 1960 forest area with 74% of the deforested area converted to pastures in response to strong economic incentives for beef export. The rate of deforestation slowed dramatically between 1983 and 1992, coinciding with a dramatic decline in beef exports. By 1996 forest remained on 61% of the landscape, reduced from 88% in 1960. Half of the landscape outside the La Selva-Braulio complex (20% of the study area) was forested in 1996. Of this forested area more than half (58%) had been in forest throughout the study period, although it is likely that much had been selectively logged. The remaining 42% was in young secondary vegetation (scrub and forest), only 4% of which was in forests older than 13 yrs. Unprotected forests were strongly fragmented; by 1996 almost half of all forests outside La Selva and Braulio Carrillo National Park lay within 100 m of a forest edge. Patterns of forest clearing and regrowth reflected the influence of road and river access, soil fertility, and topography. While the Sarapiqui basin continues to be a predominantly forested landscape, outside of protected areas, forests have been strongly affected by logging and agricultural activity.

Keywords: tropical rain forest, deforestation, remote sensing, landscape patterns

This abstract is being presented at: 10:30 AM in session:
Poster Session #5: Landscape Ecology.