A wide range of environmental contaminants (e.g. road salt, fertilizers, dioxin, PCB,
pesticides and herbicides) pose threats to reptiles and amphibians. With the latter
group, life cycles that straddle both aquatic and terrestrial habitats make them
particularly vulnerable. For instance, in the late 1990s, a Canadian study conducted
in Quebec was the first to link physical deformities and genetic damage in frogs to
pesticide use in agricultural settings; during snowmelt and spring rains, the influx
of field-applied substances into surrounding aquatic habitats used by breeding
amphibians results in “toxic shock” to eggs and larvae. As we now know,
such stressors have both acute and chronic effects that can also make amphibians more
vulnerable to parasites and opportunistic diseases such as chytrid fungus and
ranaviruses.