Invasive Species: The Importance of Distinguishing Harm from Change

Non-native species, like native species, can impact human health, national and local economies, and the ecosystems and ecological communities in which they reside.   A small proportion of non-native species are considered harmful.  In some instances, the harmful impacts can be dire.  Introduced pathogens can threaten human health, crops, and livestock. Other introductions can cause great economic harm, including seriously disrupting valuable ecosystem services, such as the provisioning of fresh water and timber, and some can cause extinctions of other species.  Few would disagree with efforts to manage these species and to mitigate the harm caused by them.  However, there may be some sense in questioning the control and management efforts involving non-native species producing other ecological impacts that have been deemed undesirable by some people.  These would include species that are altering the composition of historical communities, changing disturbance regimes, decreasing the size of native populations, and/or affecting ecosystem processes, but that are not seriously threatening our health, economies, ecological services, or causing other types of great ecological harm such as driving other species to extinction.  We need to be careful not declare mere change as harm.  Given the scarce human and financial resources available to manage environments and species, we do not have the luxury to devote resources to concerns that are fundamentally “claims of personal preference”.  Like other species, we need to adapt to the new environments and ecological communities being  created in the 21^st century by the global redistribution of species.  In instances where non-native species, even widespread nonnative species, are not causing economic harm or threatening human health, we may be wise to resist inclinations to declare such species as invasive, since once declared as invasive we oblige society to spend resources to manage them and the environments they inhabit.   In these cases, a more pragmatic and socially responsible response is called for.  In many cases, rather than trying to manage these species, we would do better to try to manage our attitudes toward them.