Trends in Ecology & Evolution
ReviewInvasive species, ecosystem services and human well-being
Section snippets
Invasive species, ecosystem services and valuation
Invasive alien species (IAS), defined as those non-native species that threaten ecosystems, habitats or species [1], are key drivers of human-caused global environmental change [2]. Widely heralded as the second greatest agent of species endangerment and extinction after habitat destruction, particularly on islands [3], IAS are also inflicting serious impacts on the ecosystem processes that are fundamental to human well-being (defined as access to secure livelihoods, health, good social
Food, fiber and fuel
Introduced species are both a blessing and a curse for agriculture and food security. For instance, most food crops are deliberately introduced non-native species, yet other IAS can reduce crop yields by billions of dollars annually [10]. The impacts of several plant IAS on agriculture have recently been well documented. For instance, yellow star thistle (Centaurea solstialis), an invasive late-season annual in California that is unpalatable to cows, costs the state US$7.65 million annually in
Regulating services
Impacts of IAS on regulating services are relatively unknown but, because they interfere with basic ecosystem functions such as the provision of clean water and a stable climate, they might well dwarf the impacts on the better-understood provisioning services discussed previously. IAS could thus have underappreciated but widespread impacts on pollination, water purification, pest control, natural hazards and climate mitigation, services that are both the cornerstone of fisheries, agriculture
Cultural services
Impacts of IAS on cultural services, defined as those attributes of an ecosystem that are non-consumptive (i.e. hold value for recreation, tourism, history, education, science, heritage, inspiration, spirituality and aesthetics) [5], are difficult to assess because they are based on personal and local value systems. IAS usually alter cultural services, either negatively or positively, and sometimes in opposition to impacts on other services.
Future directions
Assessing the impacts of IAS on ecosystem services has only recently become an explicit focus of studies of invasion ecology [27], and certainly some ecosystem services are better understood than others. For example, the impacts of IAS on provisioning services (food, fiber and fuel) are frequently well quantified. Impacts on other life-supporting services, such as fresh water and most regulating services (pollination, disease and pest regulation and flood and fire control), are rarely
Acknowledgements
We thank the organizers and participants of the October 2007 Diversitas Meeting on the ecological and economic dimensions of invasive species for stimulating this review. The case studies benefited from comments by H. MacIsaac, B. van Wilgen, J. Jeffrey and L. Hadway, and an earlier version of the manuscript was much improved by comments from two anonymous reviewers.
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