Climatic change
Climatic change causes increased atmospheric pressure in the Atlantic and decreased pressure in the Pacific. These winds
decrease the amount of rain falling on the Pacific-facing slopes and see an increase in temperatures during the dry season.
In addition to the warmer, drier climate, the golden toad was
susceptible to disease and there's a hypothesis that
atmospheric contaminants reach critical levels when conditions are warm and dry.
Pollution
Recent research shows that common pesticides found in the environment had serious effects on the
sexual development of frogs. The pesticides make frogs sterile. Because large amounts of pesticides
are used in Costa Rican agriculture, it's believed that pollution might be one
of the possible reasons for the rapid decline of amphibians.
Ultraviolet radiation
Solar ultraviolet (UV) radiation has been identified as the reason for
declines in larvae and fungus. The exposure to UV
limits the function of the immune system. It is believed that the golden toad, in addition to the above stresses, may
have been exposed to UV and caused the population to crash.
Disease
There's a fungal disease known as chytridiomycosis which has caused the decline of many amphibians. This disease causes
skin damage and skin thickens which leads to dehydration and suffocation.
While visiting Monteverde, there's an opportunity to see amphibians in the park. If you don't succeed in
finding them in nature, try visiting the Ranario
frog ponds.
For a discussion
on this topic, Britton Windeler provides some great insight and further readings.
