Combining observations and experiments to quantify invasive species impacts.

Biological invasions have for long being considered a major threat to biodiversity and ecosystem services. However, measuring the magnitude of such impacts have remain elusive and most information remains very local or taxon-dependant. For plants, this is particularly critical because plants can have effects that may take years to actually become evident in the invaded ecosystem, depending on the type of invader and the ecosystem which they invade. For example, trees in open ecosystems such as grasslands may take decades before they reach a density that is able to affect species diversity or alter ecosystem cycles (e.g. fire regimes).

To quantify and understand impacts of plant invasions, a combined  experimental  observational approach may be particularly useful. In this recent paper lead by Jacob Barney, we have summarised a novel standardised protocol called Global Invader Impact Network (GIIN). We propose to take advantage of plant invasions that have already occurred and therefore provide a “natural experiment” and observe the changes they have cause by comparing invaded and non-invaded communities. Of course, there are caveats to this approach that need to be faced but that enough replication may solved. In addition, manipulative removal experiments may help us to understand the legacies of such invasions and identify which impacts can have lasting effects on the ecosystems. This approach requires an important component of monitoring in the long-term as well as a carefully selection of biotic and abiotic variables to be recorded.  Nonetheless, the most powerful tool of our approach is the potential to be replicated across multiple regions, multiple sites and multiple species. We believe that this global approach may shed light into the generalities, but also the peculiarities, on plant invasion impacts. Undoubtedly, this will improve our ability to prioritise the management of the most harmful invaders. I think this is good example of innovative approaches that use observations to capture nature complexities as we have promoted with Rafe in our book.

Please take a look at the new paper:


Barney, J.N., Tekiela, D.R., Barrios-Garcia, M.N., Dimarco, R.D., Hufbauer, R.A., Leipzig-Scott, P., Nuñez, M.A., Pauchard, A., Pyšek, P., Vítková, M. & Maxwell, B.D. (2015) Global Invader Impact Network (GIIN): toward standardized evaluation of the ecological impacts of invasive plants. Ecology and Evolution, early online.

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