Deforestation Rates and Trends in Costa Rica, 1940 to 1983

Forest area change associated with life zones, slope gradients, and transportation networks was examined within the framework of a geographically referenced data base for Costa Rica. Locations of forest boundaries and other landscape attributes were digitized from available map sources. Differential rates of primary forest clearing associated with these variables were derived for four reference periods between 1940 and 1983. Deforestation occurred predominantly in tropical dry and moist life zones during the early reference periods; in intermediate periods, tropical and premontane moist and wet zones were affected. By 1983, only the less accessible high-rainfall zones in rugged terrain retained relatively undisturbed forest. The relationship between total primary forest cleared and slope gradient began as inverse and did not approach linearity until the last reference period, when improved transportation routes had penetrated the northeastern lowland Atlantic region. Road development that provided access to the forest was an important agent of change in all reference periods. By 1977, all major regions of the country had been penetrated by roads, and only high mountain forests were relatively inaccessible. Significant gaps exist in the data base because forest maps represent only broad zones, and locations of regenerating forest were not available. The historical data will be used to direct satellite monitoring toward landscapes of predicted change to quantitatively assess forest change dynamics. SEVERAL REPORTS HAVE BEEN COMPILED to describe impacts and propose strategies to slow the advance of tropical forest destruction (U.S. Department of State 1978, 1980; World Bank 1978; Barney 1980; Zerbe et al. 1980; Office of Technology Assessment 1984). Although the seriousness of tropical deforestation at the global level is subject to disagreement (Myers 1980, Lanly 1982, Sedjo Revelle 1982; Houghton et al. 1983; Seidel & Keyes 1983). The range of global carbon flux estimates could be reduced by almost 60 percent with more reliable data on the rate and permanence of tropical deforestation (Houghton et al. 1983). Permanence of deforestation relates to how long the area stays in nonforest cover (i.e., agriculture) before it reverts back to successional forest following disturbance or land abandonment. Knowing the locations of areas susceptible to deforestation and agricultural areas more likely to come back in succession forest would help to direct sampling efforts and satellite monitoring to the landscapes of interest. Written records are often incomplete and do not include maps showing locations of forest coverage that are accurate enough to establish a baseline. Aerial photography and other remote-sensing techniques can provide a means by which present and past forest conditions can be compared (Williams & Miller 1979, Sader 1980, Green 1982, Woodwell et al. 1983, Tucker et al. 1984, Sader & Joyce 1985). Spatially and temporally coregistered data can be used to show geographically specific changes and trends for the time frames selected (Joyce et al. 1984).