19 septiembre 2013

Invasive Alien Species: Risks, Impacts and Solutions

Dreissena polymorpha

Invasive alien species (IAS) are a leading cause of biodiversity loss in Europe and across the globe. As plants or animals that are introduced, either accidentally or deliberately, into areas they would not otherwise have reached, IAS can cause substantial ecological damage, disrupting native ecosystems. This can lead to extinctions, loss of important ecosystem services and harm to human health. They can also result in significant economic losses; estimates indicate that IAS damage and control measures currently cost Europe at least €12 billion per year. In recognition of the serious and urgent nature of this threat, the EU Biodiversity Strategy to 20201 sets specific targets to tackle IAS. The strategy also includes the development of a dedicated legislative instrument focusing on early warning, rapid response and damage control, which was adopted on the 9th of September this year.

This Thematic Issue from Science for Environment Policy presents key pieces of research exploring risk assessments of IAS, surveillance methods, management practices and public perceptions of the problem.
The first article in this issue asks ‘What are the impacts of invasive alien species?’, presenting a study which reveals that beyond the immediate effects of IAS, more subtle changes can occur that affect an entire ecosystem. In the UK, for example, the predatory flatworm not only reduces numbers of native earthworms, but also increases waterlogging; in the absence of earthworms, the soil becomes less porous. This in turn affects conditions for plants and makes the habitat less suitable for moles. These diverse impacts must be carefully considered in risk assessments and management of IAS, the study’s authors note.

Risk assessments are a particularly important aspect of IAS research, as they can help set priorities and support effective surveillance and rapid response. Limited resources mean it is not possible to control every species that is alien to Europe, therefore risk assessments are needed which help us identify the species that are most likely to have ecological and economic impacts.

‘A new approach for evaluating alien species risk’ sets out a framework for best practice, defining risk in relation to transport (which includes introduction), establishment, abundance, spread, and impact. This, say the researchers, aids understanding of how invasion processes are linked and promotes a more effective, integrative approach to IAS risk assessments. The article ‘Socio-economic factors affect risk of alien species invasion’ examines the best ways of predicting locations most at risk from invasion by alien aquatic species. The study summarised in this article shows that basing risk assessments on environmental factors, such as temperature, and omitting socio-economic factors, such as distance to the nearest port, could result in serious underestimations of the areas at risk.

The importance of human influence is also highlighted by the article ‘Human population density explains alien species richness in protected areas’. This study shows that across the wide range of different habitats encompassed by South African national parks, local human population is the only characteristic that consistently reflects IAS abundance.

Risks of invasion can change over time, as the article ‘Mapping fish invasions in European freshwaters’ illustrates. Documenting pathways of fish invasion into Germany and Austria, the researchers demonstrated that although, in the past, the main driver of introductions has been commercial fisheries, the species currently showing the most rapid expansions have been introduced via trade in animals. The changing nature of IAS risk as a result of climate change is the focus of the article ‘Endangered species' response to the dual threat of climate change and invasive species’, which predicts that the invasive zebra mussel may benefit from climate change, negatively affecting native mussel populations.

Beyond the impacts and risks of IAS, this issue also explores how best to guard against future introductions and prevent the spread of newly introduced species. Good surveillance is particularly important and the article ‘Effective tools to predict spread and improve monitoring of invasive alien species’ considers how habitat suitability models can provide information for targeted sampling, providing much higher detection rates than random sampling.

Effective prevention can be achieved, however, as the article ‘Risks of invasion of alien marine species driven by global shipping’ illustrates. This study examined the risks of invasion of marine species spread by transportation in ballast water, and shows that treating this water before it is discarded could reduce the risk by as much as 82%.

One key factor influencing the success of management and eradication of IAS are the perceptions of different stakeholders, from the public to conservation managers and scientists. ‘Does the public’s view of invasive alien species differ from the professionals’?’ explores differing attitudes to IAS, and indicates that the general public feel that human responsibility for introduction is a key factor in whether to eradicate species, often not explicitly discussed by scientists. The study’s authors call for better communication, stressing that open discussion between scientists and the public could lead to a valuable increase in understanding of IAS.
The importance of an in-depth understanding of the risks of IAS is also highlighted in our last article, ‘Conservation managers and public unaware of invasive alien species’ true risks’, detailing a UK survey which finds, worryingly, that regardless of the amount of scientific research on a species, both the public and conservation managers are unaware of the full risks posed by IAS.

In conclusion, IAS present a severe threat to global biodiversity. To meet this challenge, prevention of new introductions, early warning of invasions and rapid response to such threats must be guiding principles. An effective system of prioritisation is also needed, to focus limited resources on key threats. Furthermore, good communication between scientists, the public and conservation managers would increase the chances of success in vital prevention, eradication and management efforts.
  1. http://ec.europa.eu/environment/nature/biodiversity/comm2006/2020.htm
Dr. Piero Genovesi
Chair, IUCN SSC Invasive Species Specialist Group
Senior Scientist, Institute for Environmental Protection and Research

Fuente: European Commission - Science for Environment Policy

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