| The proposed Mesoamerican Biological Corridor (MBC) is an ambitious effort to stem and turn back the erosion of biodiversity in one of the world's biologically richest regions. Two broad categories of forests, based on their hydrometeorological dependence, are identified in Mesoamerica: (1) those requiring sufficient dry season rainfall; and (2) those requiring frequent immersion in clouds in the dry season (e.g., cloud forests).; In the absence of a high-resolution rainfall data set, a statistical method is used to estimate rainfall from climatological cloud cover and rain gauge rainfall in northern Mesoamerica. Rainfall estimated from this method show deficits >25mm in the peak dry season month of March at several locations when compared to the climatologically occurring rainfall over forests. Numerical modeling analysis shows that future deforestation would lead to spatially widespread decreases in rainfall up to 100mm at certain locations like those in the Peten region of Guatemala. Even forested corridor regions would suffer rainfall decreases. The data suggests that deforestation is locally intensifying the dry season, so that forest regeneration in some parts of the MBC, particularly in the central Peten of Guatemala, may not result in second-growth forest that is characteristic, but rather in forests more typical of drier conditions.; New techniques for cloud forest mapping are developed and tested in Costa Rica that could be potentially useful for cloud forest biogeographers. Numerical modeling studies conducted for the Monteverde cloud forests of Costa Rica show that if the lowland and premontane regions were completely forested, the orographic cloud banks would have intersected the mountains at the lowest elevations, covered the largest land surface area, and remained longest on the ground in the montane regions. Deforestation has decreased the area immersed in orographic clouds in the montane regions by around 5--13% and raised the bases of the orographic cloud deck by about 25--75m in the afternoon. Results show that further deforestation in the lowland and premontane regions would lead to around 15% decrease in the cloud forest area immersed in orographic clouds and also raise the bases of the orographic cloud deck by up to 125m in the afternoon. |
