Geographical separation between the cause and the effect is another inherent problem of indirect effects. For economic and societal reasons, it is particularly well documented in studies and practical applications of pollution and biological control, but numerous examples are readily available from virtually any areas of ecology and environmental sciences. As regards pollution damage, the well-known examples relate to coastal and benthic effects of oil spills, consequences of lake acidification in Scandinavia due to the transboundary transfer of sulphur dioxide since the beginning of industrial revolution, bioaccumulation of radionuclides in the food webs of, for example, British pastures following the Chernobyl fallout, etc.
In ecology, there is a growing awareness of placing the dynamics of a local biological community in the broader landscape and biogeocoenological context. For example, in biocontrol applications, failure to anticipate indirect effects resulting from the community openness and exchange between localized subpopulations has led to a number of costly failures and unexpected outcomes. Following introduction, migrations of biocontrol agents were shown to be capable of suppressing nontarget species in spatially removed areas. Certain traits of the agent were shown to be related to elevated risks of nontarget species extinction, for example, the risk of extinction of a nontarget species increases with the decrease of its growth rate and the increase of the agent's attack rate compared to the target species. Hence the threat of extinction appears to be particularly acute for a nontarget species occupying habitat fragments co-mingled with the habitats occupied by target species, and when the target species is relatively productive and the agent is only moderately efficient at limiting the target species numbers.
Was this article helpful?