Prospects for Circa Situm
Tree Conservation in Mesoamerican
David H. Boshier, James E. Gordon, and Adrian J. Barrance
DRY FOREST ONCE STRETCHED almost continuously along the Mesoamerican (Central American/Mexican) Pacific coast, from Sonora in Mexico to Guanacaste in Costa Rica (area of 550,000 km2). Conditions suitable for dry forest also exist on the Yucatán Peninsula, the coast of the Mexican states of Puebla and Tamaulipas, with significant inland areas in dry valleys (e.g., Motagua Valley, Guatemala) throughout the region (see Graham and Dilcher 1995 and Murphy and Lugo 1995 for the distribution and origins of this forest type). Human preference for the seasonally dry tropical environment (Murphy and Lugo 1995) and the ease of clearing its vegetation have, however, led to the destruction and fragmentation of much of its forest. Janzen (1988: 130) estimated that less than 2 percent of the original forest is in a state “sufficiently intact to attract the attention of the traditional conservationist, ” with only 0.09 percent having official reserve status. Only on the Pacific Mexican coast are there significant areas of mature, possibly primary, dry forest. Even in these areas it is rare to find a forest with no evidence of occasional timber and firewood extraction, extensive livestock browsing, or hunting. In Central America the dry-forest zone is reduced to a patchwork of various types of agricultural land and small forests of secondary origin. Unregulated selective felling of economically important tree species continues, resulting in the commercial extinction of timber species in some areas (e.g., Astronium graveolens Jacq., Guaiacum sanctum L.). Reserve selection is often opportunistic, determined more by political, social, and economic constraints than by optimal biological criteria. Consequently the location of reserves may bias floristic composition (at species and gene pool levels), limiting their overall value for biodiversity conservation (Ledig 1988).
Any conservation initiative requires consideration of the extent and value of and threat to the resource to be targeted. Tropical dry forests are species-rich in comparison with most of the