STALLARD, R. F. 2001. Possible environmental factors
underlying amphibian decline in eastern Puerto Rico:
analysis of U.S. government data archives. Conservation
Biology 15:943–953.
Abstract:
The past three decades have seen major declines in populations of several species of amphibians at
high elevations in eastern Puerto Rico, a region unique in the humid tropics because of the degree of environmental
monitoring that has taken place through the efforts of U.S. government agencies. I examined changes
in environmental conditions by examining time-series data sets that extend back at least into the 1980s, a
period when frog populations were declining. The data include forest cover; annual mean, minimum, and
maximum daily temperature; annual rainfall; rain and stream chemistry; and atmospheric-dust transport. I
examined satellite imagery and air-chemistry samples from a single National Aeronautics and Space Administration
aircraftflight across the Caribbean showing patches of pollutants, described as thin sheets or lenses,
in the lower troposphere. The main source of these pollutants appeared to be fires from land clearing and deforestation,
primarily in Africa. Some pollutant concentrations were high and, in the case of ozone, approached
health limits set for urban air. Urban pollution impinging on Puerto Rico, dust generation from Africa
(potential soil pathogens), and tropical forest burning (gaseous pollutants) have all increased during
the last three decades, overlapping the timing of amphibian declines in eastern Puerto Rico. None of the data
sets pointed directly to changes so extreme that they might be considered a direct lethal cause of amphibian
declines in Puerto Rico. More experimental research is required to link any of these environmentalfactors to
this problem.