Impacts of low land use on a Tropical Montane Cloud Forest under a Changing Coastal Climate

Tropical Montane Cloud Forest (TMCF) are a primary source of fresh water in tropical locations and are highly sensitive to climate changes. Climatological analysis for El Yunque Rain Forest, located in North Eastern of the Island of Puerto Rico 40km south-east of the coastal city of San Juan, reflects changes in the regional meteorological response reflected by increasing moisture content and surface air temperatures within this forest. This TMCF is the main water resource of San Juan, one of the largest cities in the Caribbean, and it is surrounded by increasing urban sprawl in the lower elevations that is suspected to have contributed to modify the climate of the forest. These changes in the low lands of the TCMF may have affected atmospheric and surface variables such as latent and sensible heat fluxes, surface albedo and surface roughness, and the overall energy budget within the forest. It is also hypothesized that increases in sea surface temperatures are also influencing the climate of the forest.

The focus of the present research is to quantify the impacts of changes in land use close to coastal TMCFs, characterized by the case of El Yunque in the north-eastern coast of Puerto Rico during the dry season.

A climatological and numerical analysis is presented to characterize these land use processes under a changing coastal climate. The research makes use of a high resolution visible imagery from the NASA ATLAS sensor to characterize the current land–use condition of the area. Surface parameters such as albedo and land classes were introduced into a Mesoscale Model RAMS (Regional Atmospheric Modeling System). The atmospheric model was calibrated favorably against a high density network of surface temperature sensors located in and around the TMCF. The coupled and decoupled effects of land use and Green House Gases (GHG, represented by SSTs) is investigated in detail by organizing an ensemble of simulation runs that include reconstructed past land–use, present land use, reconstructed atmospheric variables and present climate.

Results indicate significant impacts in surface temperatures due to increases of SSTs and increases in cloud cover and cloud base due to low land development. A net reduction on the primary productivity of the forest is observed reflected in decreases of fresh water production.