Tolerance, the ability of populations to cope with the chemical stress resulting from toxic contaminants, has been described in many organisms from bacteria to fungi, from phytoplankton to terrestrial flowering plants, and from invertebrates such as worms to vertebrates like fish and amphibians. The building of tolerance, be it by physiological acclimation or genetic adaptation, can have great consequences for the local biodiversity, and hence the ecology and ecosystem functioning of many of the world's habitats. Understanding the frequency of the occurrence of tolerance has tremendous...