Trends in Ecology & Evolution
ReviewAlien species in a warmer world: risks and opportunities
Section snippets
Does climate change affect biological invasions?
Climate change and biological invasions are two important drivers affecting biodiversity and ecosystem services 1, 2. However, their effect on biodiversity has usually been assessed independently, despite good scientific reasons to expect the rate and extent of biological invasions to be influenced by climate change 3, 4, 5. The various pressures from global change in general, and climate change and biological invasions in particular, should therefore be considered in a more integrated manner.
Interplay of global warming and biological invasions
There is increasing evidence that global warming has enabled alien species to expand into regions where previously they were not able to survive and reproduce. Based on case studies of climate-mediated biological invasions that have been reported for plants, invertebrates, fishes and birds (see also Online Supplementary Material), we discuss the ways in which climate change influences the sequential stages of an invasion process.
Mechanisms underlying invasion success in the context of climate change
All these aforementioned examples (and for more case studies see Online Supplementary Material) suggest that changing climatic conditions, and warming in particular, appear to have had an increasingly important role in triggering increases in population abundance and distribution not only of native but also of alien species since the 1970s, when climatic conditions began to change. For many cases, an in-depth understanding of their ecological limits and how these have changed during the recent
Climate change blurs migration and invasion
The increasing number of colonization events and subsequent establishment of species originating from regions with a warmer climate than in the area of establishment and spread is remarkable (our (non-exhaustive) list provided in the Online Supplementary Material includes >100 taxa). Such species appear to have responded to the changed climatic conditions of the recent past, which enabled them to reproduce and establish in the presence of resident species. Simultaneously, native species have
Consequences of climate-mediated invasions
Alien species can be viewed as drivers and passengers of change in biological communities 69, 70. Many invasive species exert strong impacts on invaded communities and ecosystems [71] and transform ecosystem properties [10], which inevitably leads to changes in biological communities. The consequences of climate-mediated biological invasions are far-reaching and more controversial than those of past invasions not affected by climate change, where species typically originate from habitats with
Lack of knowledge and research needs
Most of the current information about range shifts and invasions comes from the plant and animal kingdoms, whereas little is known about invasions of alien microorganisms [85]. For example, modern forestry practice uses commercial mixtures of symbiotic ectomycorrhizal fungi for successful establishment of trees in silviculture [86], transporting them away from their native distribution range. The impacts of these alien fungi on local ecosystems are unknown, not to mention the impacts of the
Conclusions
In a changing world, it will be increasingly difficult to evaluate the impacts of alien species and prioritising species for removal, and it is likely that the increasing presence of ‘new’ species and the decline of ‘old’ ones will change successional patterns and ecosystem functioning 93, 94. With continued climate change and the resulting increasing discrepancy between the requirements of resident species and altered environmental conditions, one should take into account that some of the
Acknowledgements
This contribution results from the Integrated Project ‘ALARM: Assessing large-scale environmental risks for biodiversity with tested methods’ [97] funded by the European Commission (GOCE-CT-2003-506675). P.P. and V.J. were supported by grant numbers AV0Z60050516 and MSM0021620828; Z.B-D. and B.C. by grant number NKFP6/013/2005; W.T. by the ANR Biodiversité DIVERSITALP; A.R. and C.R. by the ANR Biodiversité URTICLIM; M.V. by CONSOLIDER CSD2008-00040 and M.Z. and M.M. were supported by the
Glossary
- Alien
- an organism occurring outside its natural past or present range and dispersal potential, whose presence and dispersal is due to intentional or unintentional human action.
- Apomictic/parthenogenic
- asexual form of reproduction without fertilization.
- Casual
- refers to organisms that do not form self-replacing populations and rely on repeated introductions for their persistence.
- Cryptogenic
- a term used for species of unknown origin or means of arrival, which cannot be ascribed as being native or alien
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