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InvaCost : Predicting the impact of invasive insects in a warmer world

  • 09.09.2015

While Man may be largely responsible for the current climate disturbances, he is not the only creature on the planet that is feeling the effects. All living organisms have to cope with the unprecedented global warming. While some species manage to adapt, through biological changes or by migrating to colder regions, others that are not able to keep up with the pace of change will see their numbers reduced or actually become extinct.

Some species are now raising particular concern among scientists – nuisance insects, i.e. those which transmit diseases or ravage farmers’ crops.

As the thermometer climbs higher, might we see a mass invasion by such insects? What might be their impact on the economy, public health and/or the environment within a few years from now? To answer these questions, a team of scientists from the University of Paris Sud and the French National Scientific Research Centre (CNRS) launched a project called InvaCost (Invasive Insects and their Cost Following Climate Change). 

"Most wanted"

The first step is to draw up a list of the worst insects, i.e. the ones that are likely to cause the most damage. Some are certain to feature on the list, such as the Asian hornet, which eats bees; fire ants, whose bites send thousands of people to hospital every year and cause heavy crop losses; and the Gambian mosquito, which transmits malaria.  But the novel feature of the project is that the researchers will not simply draw up the list themselves.

We want to give the project a participatory dimension by allowing the general public to guide our research with their questions and remarks. People will for instance be able to choose from among our proposals those insects which they regard as most in need of investigation and we’ll incorporate them in our final list of some twenty species,” promises Franck Courchamp. 

Modelling future distribution

The second step is to draw up probability charts for the distribution of these insects in 2050, 2080 and 2100.  To do so, it will first be necessary to list all the variables that govern the distribution patterns for each insect. For a dozen or so it is quite easy to precisely describe their distribution parameters, including rainfall levels, extreme temperature, plus land use and human population density. 

Next the researchers will need to run a number of climate models, based on the most optimistic and most pessimistic CO2 emission levels published by the Intergovernmental Panel on Climate Change (IPCC). It then remains to add various statistical models for extrapolating current data in order to assess the probability that invasive species will establish themselves in a given location, based on the local variables at each location studied. 

In total, no fewer than 120 models will be used to draw up future distribution maps.

According to our studies on ants, changes in distribution differ not only according to the actual species but also over time. Some insects will initially invade new areas but will then see their distribution area reduced, while other species will follow the opposite trend,” expects Franck Courchamp.  

According to our studies on ants, changes in distribution differ not only according to the actual species but also over time.

Forewarned is forearmed

The last step of the project will be to estimate the costs that insect invasions are likely to engender. In addition to economic costs arising for example from crop damage, there may also be public health costs due to illnesses transmitted by these invasive species and environmental costs, calculated on the basis of the impact the insects are likely to have on other living species and natural resources. 

We’re partnering with environmental economists and public health experts so as to be able to estimate these costs,” reveals the project coordinator.  

Prevention is always more effective and less expensive than cure. So these risk prediction charts should be used to help step up surveillance of species identified as likely to invade new territory and cause serious damage and losses there. 

“ Invasive insects constitute a major threat to agriculture and public health. The purpose of InvaCost is to facilitate the implementation of a targeted monitoring policy so that action can be taken as soon as an invasion occurs. ”

Franck Courchamp

University of Paris Sud

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Crédit Photos : Yann Stofer (2015)

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