Tuesday, October 4, 2016

Global costs of invasive insects

Tetropium fuscum
For thousands of years, insects have been responsible for the spread of diseases in humans and livestock. They caused considerable damage on many levels: from attacks on crops and stocks, through the destruction of infrastructure, to the devastation of forests, thereby altering and weakening ecosystems. Among all living things, insects alone are probably the group responsible for the greatest costs. In addition, they are among the most aggressive invasive species. About 87% of 2500 terrestrial invertebrates that have colonized new territories are in fact insects.

The question remains - just how big is the economic damage insects are currently causing? In an attempt to answer this question an international team of researchers build a comprehensive database on economic damage attributable to invasive insects worldwide. Their data covered damage to goods and services, health care costs and agricultural losses and although we are looking at invasive species alone the authors came up with an estimated minimum economic damage of US$70 billion per year. 

Globally insects are taking a heavy toll on agriculture by consuming 40% of the harvest which would be enough to feed one billion people. 

Total health care costs attributable to invasive insects exceed US$6.9 billion (without counting malaria, Zika, or economic impacts on tourism or productivity, etc.). Among the diseases that have the greatest economic impact, dengue fever ranks first with costs accounting for 84% of the total.

Of the insects studied by the colleagues, the Formosan termite (Coptotermes formosanus) ranks as the most destructive, allegedly causing over US$30.2 billion of damage per year in the world. However, according to the research group, this estimate is based on a study that was insufficiently documented. Studies that were based on more sound data show other species at the top, e.g. the cabbage moth (Plutella xylostella), with a cost of US$4.1 billion per year, and the brown spruce longhorn beetle (Tetropium fuscum), which annually costs US$4 billion in Canada alone.

According to this study, North America suffers the largest financial losses, at US$27.3 billion annually, while Europe is currently listed at only US$3.6 billion per year. This difference, however, can be explained rather by the lack of evaluation sources than by a difference in exposure to these dangers. Thus, the total annual cost estimation is a real minimum likely representing a large underestimate of the real costs. Many parts of the world do not offer enough economic data to produce an accurate estimate. In addition, the research team focused on the study of the ten most costly invasive species, not counting the very large number that cause less damage. Finally, considering the estimated values of ecosystem services on a global scale (hundreds of billions of dollars for crop pollination alone), the disruption caused by invasive insects could reach a level far beyond the current estimate.

Some very scary numbers indeed. Keep in mind we are looking at lowest estimates using the most conservative approach to extrapolate them. I am not saying that DNA barcoding would be the ultimate solution to the problem of invasive species but it would certainly make a big contribution by helping to identify potential invaders early enough. Given the immense sums I was just talking about it seems rather modest if somebody asks for $2 billion to barcode all species (not only insects) of planet Earth.

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