Oct 30, 2009
Of mongooses and men: why aerosol geoengineering could prove risky
A growing number of scientists believe that dangerous climate change is inevitable, unless geoengineering solutions are applied. But what are the risks associated with geoengineering? Could it create more problems than it solves?
If ecological analogues are anything to go by, then the answer is a resounding yes. Damon Matthews from Concordia University and Sarah Turner from the University of Calgary, both in Canada, report on some of the human interventions that have been used to solve other environmental problems.
In many cases these interventions have resulted in unforeseen catastrophic outcomes. However, not all interventions were bad news. Matthews and Turner show that the most successful and low-risk interventions were those carried out on a small scale – something they believe would be worth heeding if we decide to employ geoengineering to reduce global warming.
Back in 1883, the Indian mongoose was introduced to the Hawaiian islands in order to bring down the population of rats (invaders that arrived with European settlers) and control damage to sugar cane crops. Unfortunately the mongooses, which hunt during the day, were not interested in catching the nocturnal rats, and instead became efficient killers of many native and endemic species, including ground-nesting birds, sea birds, snakes, lizards and sea turtles.
It is a classic case of a poorly designed biological intervention, with the damaging environmental impacts of the scheme far outweighing any economic or ecological benefit from the presence of the mongoose. Similarly, the 1929 introduction of cane toads to Queensland, Australia, in an effort to control the grey-backed cane beetle has resulted in an escalating ecological disaster. Today cane toads are a major pest, munching their way through native Australian species and spreading rapidly across Australia. To add insult to injury, the cane toad didn't control the beetle population.
Both of these schemes were crude, large-scale, irreversible projects. "They are examples of introducing a generalized predator into an open ecosystem in the presence of large scientific uncertainty," Matthews told environmentalresearchweb.
By contrast the most successful human interventions have tended to be carried out on a small scale in a highly controlled and well understood environment. For example, a number of acidified lakes and soils have been neutralized back to a more balanced and healthy state by applying neutralizing agents such as calcium carbonate. Meanwhile, cultivating seaweed in coastal regions has helped to combat eutrophication of coastal waters, caused by agricultural nutrient runoff.
Writing in Environmental Research Letters, Matthews and Turner suggest that there are a number of parallels between these human interventions in the past and potential geoengineering schemes of the future. "We think that large-scale interventions, which have potential high effectiveness, are more risky than small-scale interventions and most likely to have dramatic unforeseen consequences," said Matthews.
Firing reflective particles into the atmosphere could be a close analogue to the mongoose they think. "Based on past experience, the likelihood of something going wrong that was not anticipated is very high with something like stratospheric sulphate aerosol geoengineering," said Matthews.
And if we really must contemplate geoengineering, then they suggest we opt for the smaller-scale schemes, such as reforestation and direct air capture of carbon dioxide alongside sequestration in controlled locations.
About the author
Kate Ravilious is a contributing editor to environmentalresearchweb.