Deforestation and dry season rainfall in northern Mesoamerica: Implications for forest sustainability

The forest types in northern Mesoamerica generally are those that require dry season rainfall for their survival. However it is not clear whether the current rainfall amounts are sufficient to maintain existing forests and regenerate the pristine forests in the deforested patches. The climatological rainfall records at 266 stations in Guatemala and adjacent areas show statistically significant (t-values) higher dry season rainfall over forested areas than deforested areas of the major Holdridge life zones. Climatological cloud cover also is often statistically significantly higher over forested regions (ANOVAS were significant). The rainfall predicted from the correlation (R=0.68; standard error = 0.8) of these two records for March shows rainfall deficiencies >25mm in several Holdridge life zones compared to the climatological rainfall observed by the rain gauges over the forested regions. With the onset of the wet season however, from April through June the observed rain gauge rainfall differences between forested and deforested regions becomes statistically insignificant and the estimated rainfall deficiencies are slowly removed based on the Holdridge life zones. This suggests the climatic consequences of deforestation for forest regrowth on connecting corridors may vary by life zone. In particular, reduced dry season precipitation in deforested areas of northern Mesoamerica originally occupied by wet forests might become a two-fold problem for the many connecting corridors of the MBC that lie within these life zones. The data suggest 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 of that life zone but rather in forest regeneration more typical of drier conditions. The extent to which this would influence the conservation utility of any given corridor depends upon the ecological requirements of the organisms concerned.