Global climate change and risk assessment: Invasive species
Article first published online: 19 DEC 2011
Copyright © 2011 SETAC
Integrated Environmental Assessment and Management
Volume 8, Issue 1, pages 199–200, January 2012
How to Cite
Chapman, P. M. (2012), Global climate change and risk assessment: Invasive species. Integr Environ Assess Manag, 8: 199–200. doi: 10.1002/ieam.1253
- Issue published online: 19 DEC 2011
- Article first published online: 19 DEC 2011
Invasive (i.e., nonnative) species are considered the second greatest agent of change to ecosystems after habitat change (Pejchar and Mooney 2009). They can have both direct and indirect effects, resulting in ecosystem impacts defined as substantial impacts to species composition, relative abundances, nutrient pools and fluxes, and disturbance cycles such as terrestrial fire regimes (Simberloff 2011). They can also change contaminant cycling and contaminant residues in top predators (Kwon et al. 2006) while adapting to contaminants (McKenzie et al. 2011). All of these affect ecosystem services.
Invasive species impacts are expected to increase as a result of global climate change. For instance, increased water temperature will alter thermal habitats and the potential range expansion of aquatic species, e.g., northern fish populations may be threatened by range expansions of warm water, southern fish populations (Sharma et al. 2007). Some aquatic habitats, such as alpine lakes, where resident communities would have to disperse northward over vast differences to colonize colder alpine lakes, may see complete replacement of aquatic communities after extinction events (Holzapfel and Vinebrooke 2005).
Changes in parasitic infestations will also occur as range extensions follow warming trends. For instance, the relatively recent (early 1990s) expansion of the eastern oyster (Crassostrea virginica) parasite, Perkinsus marinus, into the northeastern United States appears to be due to warming trends (Ford and Chintala 2006). Invasive species can also be disease vectors (Pejchar and Mooney 2009).
Successful invasions will change trophic interactions, which may have positive or negative effects on such invasions, with additional effects related to climate change. For instance, the native Atlantic crab, Carcinus maenas, preferentially feeds on the native mussel, Mytilus galloprovincialis, rather than on the New Zealand invasive mussel Xenostrobus securis, because it is easier to handle and break and thus energetically more favorable; this preference only increases with increased temperature (Veiga et al. 2011).
Determining the ability of invasive species to not only colonize different habitats but also to cause ecosystem impacts as defined by Simberloff (2011), above, requires consideration of 4 factors: arrival, survival, establishment, and spread. Risk assessments of invasive species must consider each of these factors, including environmental variability that can lead to microhabitats, which can support invasive species when the majority of available habitat cannot.
As mentioned previously, habitat change is arguably a greater agent of change than species invasions. Together, these 2 stressors result in complex nonadditive effects that will change ecosystem structure and function. For instance, loss of native habitat will favor invasive species over native species; even a comparatively small increase in habitat change over time can lead to an abrupt increase in invader abundance (Didham et al. 2007). However, the effects of invaders can change over time, modulated by 4 factors (Strayer et al. 2006): changes in the invasive species (e.g., changes in tolerance to physicochemical factors or to life history traits); changes in the biological community that is invaded (e.g., changes in community composition and in individual species characteristics); cumulative changes in the biotic environment that is invaded (e.g., via feeding or engineering activities); and, interactions between the invading species and other variables that control the ecosystem (e.g., fire regime in terrestrial ecosystems, hydrology in aquatic ecosystems).
Both positive and negative changes are possible. The following examples are provided by Pejchar and Mooney (2009). An invasive tree in Florida (Melaleuca quinquenervia) has a positive effect on honey production but a negative effect on tourism. The introduction of brush-tailed possums (Trichosurus vulpecula) to New Zealand resulted in massive defoliation but was highly profitable to the “eco-friendly” fur industry. In South Africa, invasive Acacia and Pinus species have resulted in reduced stream flow and increased fire intensity, but they have also been positively incorporated into local livelihoods, providing materials for thatching, timber, medicine, charcoal, and firewood. Carbon storage capacity has been lost from the Brazilian Amazon as fire-prone nonnative pasture grasses have replaced rainforest; however, locals have benefited economically in the short term. Thus, apparently harmful effects to biodiversity may not similarly translate into universally negative effects on the well being of humans, particularly over different time scales.
Ecosystems will change as a direct (e.g., warming) and indirect (e.g., invasive species) result of global climate change. Such change is inevitable and will occur as organisms adapt to and cope with changing environmental conditions. In the context of global climate change, irreversible changes will become the norm. Risk assessments of invasive species and of other changes enhanced by global climate change should not be based on comparisons to the “status quo,” but rather comparisons to the optimum level of ecosystem services possible under changing climatic conditions resulting in changing ecosystems. They should also be based on both negative and positive impacts over different time scales.
This Learned Discourse originated from material prepared in advance of the Pellston Workshop on The Influence of Global Climate Change on the Scientific Foundations and Applications of Environmental Toxicology and Chemistry. The workshop, sponsored by the Society of Environmental Toxicology and Chemistry (SETAC), was held July 16–21, 2011, at the Johnson Foundation at Wingspread (Racine, WI). Papers originating from that workshop are expected to be published in the SETAC journal Environmental Toxicology and Chemistry, in late 2012.
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