1. Acknowledgement Will the Proposed Mesoamerican Biological Corridor Protect Biodiversity? Highlighting Potential Problems with Biological Corridors SYNOPSIS The proposed Mesoamerican Biological Corridor (MBC) is an ambitious effort to stem the erosion of biodiversity in one of the world’s biologically richest regions. The intent is to connect large existing parks and reserves with new protected areas by means of an extensive network of biological corridors within Mesoamerica/Central America to create an environment which provides better prospects for the long-term survival of native species while also addressing the region’s socioeconomic needs. Based upon climatological rainfall records at 266 stations in Guatemala and adjacent areas, dry season rainfall in March is markedly lower in deforested areas than in forested areas of the same life zone for each of the widespread life zones. In general, dry season deforested habitats have higher daytime temperatures, are less cloudy, have lower estimated soil moisture and lower values of Normalized Difference Vegetation Index (NDVI) than do forested habitats in the same life zone. The result is hotter and drier air over deforested regions, with lower values of cloud formation and precipitation. The data suggest that deforestation is locally intensifying the dry season, increasing the risk of fire, especially for the long corridor connecting regions. In addition, forest regeneration in some parts of the MBC 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. DATA SETS A. Togography Ronald M. Welch, Deepak K. Ray *, Udaysankar S. Nair and Robert O. Lawton B. Holdridge Life Zones C. Ecosystems D. Average GOES cloud frequency RESULTS CONCLUSIONS The Rainfall Deficiency Map is derived by subtracting the estimated rainfall from the rain gauge derived average rainfall for each Holdridge Life Zone. Areas shown in green in are those regions that have estimated March rainfall comparable to climatological values from forested areas within the same Holdridge Life Zone. In these areas there should be no dry season climatic obstacles to the preservation of existing forests or to forest recovery. In contrast, the narrow Pacific coastal regions have estimated rainfall deficits of between 15mm to greater than 25 mm. In the Maya Lowland region estimated March rainfall deficits are commonly >25 mm. This deficit is approximately one-third of the March rainfall over forested parts of those life zones. This suggests that deforestation can substantially intensify the dry season, and thus increase susceptibility to fires, slow forest regrowth, and shift forest composition toward that characteristic of drier sites. In such cases, corridors linking the large protected areas may not serve well those species which have difficulty adjusting to altered ecosystems. 1.Deforestation alters surface energy budgets and commonly decreases latent heat fluxes from the surface to the atmospheric boundary layer, while increasing sensible heat fluxes. The net result is hotter and drier air over deforested areas than over forested ones. 2.Dry season rainfall in March is markedly lower in deforested areas than in forested areas of the same life zone for each of the widespread life zones in Central America. In general, deforested habitats have higher daytime temperatures, are less cloudy, have lower estimated soil moisture and lower values of NDVI than do forested habitats in the same life zone. 3.In many deforested areas within the wet forest life zones, estimated March rainfall deficits are >25 mm. 4.The climatic consequences of deforestation for forest re-growth on connecting corridors may vary by life zone. 5.Forest regeneration in some parts of the Mesoamerican Biological Corridor 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 would depend upon the ecological requirements of the organisms concerned. Observed March rainfall differs among life zones, ranging from about 23mm/15mm for the forested/deforested regions of the relatively dry subtropical lower montane moist forests to 105mm for the forested regions of the subtropical rain forests. More importantly, in each of these life zones, the forested regions have larger March rainfall than do the corresponding deforested areas. Contact Information: Ronald M. Welch: Atmospheric Sciences, University of Alabama Huntsville, welch@nsstc.uah.eduwelch@nsstc.uah.edu Deepak K. Ray: Forestry and Natural Resources, Purdue University, dkray@purdue.edudkray@purdue.edu Robert O. Lawton: Biological Sciences, University of Alabama Huntsville, lawtonr@email.uah.edulawtonr@email.uah.edu Udaysankar S. Nair: National Space Science and Technology Center, nair@nsstc.uah.edunair@nsstc.uah.edu For one of the major Holdridge life zones, the Subtropical moist forest, average climatological cloud cover frequency of occurrence (CF) values for the forested regions (Evergreen Needleleaf, Evergreen Broadleaf, and Deciduous Broadleaf) ranging from 26.27% to 28.53%, whereas in the deforested regions (Woodlands, Wooded Grasslands and Grasslands) they range from 18.91% to 22.39%. Standard deviations range from about 6.5% to about 8.9%. The land surface temperatures (LST), similarly ranges from 303K to 304.6K over forested and 308K to 309.8K over deforested regions, respectively. The normalized difference vegetation index (NDVI) and estimated soil moisture (SLM) are also higher over the forested regions. This was observed in all the other Holdridge moist and dry life zones. Climatological Average Rainfall (    ) for March (mm) HOLDRIDGE LIFE ZONES Rainfall observed over Forested Areas Rainfall observed over Deforested Areas Subtropical Lower Montane Moist Forest 23.14  13.63 N=7 14.79  6.65 N=19 Subtropical Moist Forest 39.00  37.66 N=11 14.34  11.45 N=38 Subtropical Lower Montane Wet Forest 65.90  70.57 N=10 32.00  33.70 N=5 Subtropical Wet Forest 74.79  39.28 N=41 58.07  31.61 N=58 Subtropical Rain Forest 105.17  50.00 N=6-- Corridors and Protected Regions Corridors and Protected Regions With the wealth of knowledge and theory about fragmentation effects and ways to ameliorate them, those interested in preserving global biodiversity are pushing to create large-scale conservation or “ecological networks”. The key strategy to the ecological network is the use of corridors that eco- functionally and physically join habitats at local, regional, national and international levels. Ecological networks are characterized by the following elements: a) core areas: comparatively large areas of biodiversity, ecosystem, and landscape conservation with a high probability of sustainable survival of local populations; b) ecological corridors: linear elements which connect the core areas and serve as migrating and dispersal routes, i. e. as stepping stones; c) buffer zones: zones around the network which protect its basic elements from external impacts and support or enlarge the ecological capacity of the network; d) zones of ecological reconstruction: areas with current low nature conservation value but with potential in the course of the rehabilitation. The establishment of effective MBC corridors depends upon forest recovery, but deforestation like that in Central America has local climatic consequences that might influence forest regeneration. A serious concern is the drying of deforested regions. Closed-canopy tropical forests are effective in trapping transpired moisture, so that most of the ambient forest humidity is derived from the trees themselves. Anthropogenic disturbances to forest canopies locally decrease the ability of forests to maintain moisture. Deforestation also influences climates at the regional scale. Nair et al [2003] showed that cleared regions in lowland Costa Rica were warmer, had lower dew point temperatures, had altered sensible and latent heat fluxes, had fewer clouds and had altered cloud properties as compared to nearby forested regions. Similarly, deforested areas in Amazonia are hotter and drier, at least during the dry season]. Several studies suggest that land use changes may influence regional climate, which then enhance and sustain these changes. Thus, the current alterations of the natural landscape in Central America, coupled with continuing high rates of deforestation, may have climatic consequences that affect both the stability of the existing protected forests and the rate of regeneration on now deforested components of the MBC ACKNOWLEDGEMENTS This project was supported by NASA grant number NAG5-11941 We thank Conservation International for providing the Mesoamerican Biological Corridor Map and the National Institute of Seismology, Volcanology, Meteorology and Hydrology (INSIVUMEH), Guatemala, for providing the rainfall data set.