In 1845, Belgian farmers discovered, too late, that a load of seed potatoes they had bought from America was contaminated with Phytophthora infestans, a Mexican fungus that had recently started infecting fields in the US. The blight caused by P. infestans rapidly spread all over the continent, triggering the European potato famine. Belgium and Prussia suffered over 40,000 hunger-related deaths each, and 10,000 died in France. But the worst impact was in Ireland, where a third of the population was entirely dependent on the potato for food. One million people out of a population of 8 million died of starvation and its side-effects between 1845 and 1850, and another million emigrated.
Like every famine since then, this wasn’t a “natural” catastrophe. Ireland continued to export food throughout the period, even echoing today’s biofuels debate on whether crops should be diverted to non-food uses by sending over 1.3 million gallons of cereal-derived alcohol to England in 1847, the worst year of the famine.
That said, the famine wouldn’t have happened without the spread of the Mexican fungus, an example of what we now call “invasive alien species” (IAS). The UN Convention on Biological Diversity (CBD) describes these as “… animals, plants, fungi and microorganisms entered and established in the environment from outside of their natural habitat. They reproduce rapidly, out-compete native species for food, water and space, and are one of the main causes of global biodiversity loss.”
Species are often introduced deliberately, through for example, fish farming, the pet trade, or horticulture; or unintentionally, through transportation, travel, and scientific research. According to the CBD, invasive alien species have contributed to nearly 40% of all animal extinctions for which the cause is known since the 17th century. Annual environmental losses caused by introduced pests in the US, UK, Australia, South Africa, India and Brazil have been calculated at over US$ 100 billion.
Economic costs are high too. The zebra mussel was unknown in North America until it was brought to the Great Lakes in a ship’s ballast water in the late 1980s. Since then, it has become a major macrofouler within North American freshwater conduits. Among other things, the mussels block the pipes that deliver water to cities and factories and cooling water to power plants. In the US, congressional researchers estimated the mussel cost the power industry alone $3.1 billion in 1993-1999, with its impact on industries, businesses, and communities estimated at over $5 billion. In Canada, Ontario Hydro reported zebra mussel impacts of $376,000 annually per generating station.
At the Rio+20 conference on sustainable development, the International Union for the Conservation of Nature argued that “IAS are one of the leading and most rapidly growing threats to food security, human and animal health, and biodiversity and, together with climate change, one of the most difficult to reverse.” An article in Science lists a number of threats, for example in sub-Saharan Africa, witchweed (Striga hermonthica) infects 20 million to 40 million hectares of corn, sorghum, sugarcane, millet, and native grasses, reducing yields by 20% to 100%. Losses total about $1 billion per year and affect 100 million people.
However, as another article in Science points out, although the invasion of alien species has started to change the whole food chain in the Mediterranean, there is a lack of knowledge on which to base relevant risk assessments. The IUCN stresses the importance of collecting relevant information and informing everybody concerned in time for effective prevention, early warning and rapid response.
Last month, an OECD-sponsored conference of the International Pest Risk Mapping Workgroup in Tromsø, Norway, presented new ideas about how to incorporate climate change, economics, and uncertainty into pest risk models and maps for invasive alien species, and how to communicate these improved results to biosecurity policymakers. Beyond the intrinsic importance of the issue, I was struck by how the conference illustrates the complexity of many problems facing decision makers. The way a threat evolves will be determined by factors ranging from the biology of microbes to the psychology of policymakers, and there are probably lessons for specialists in other domains from this approach that integrates uncertainties into both the analyses and the advice.
The full proceedings of the meeting will appear in an upcoming issue of the journal NeoBiota, but you can read a summary here.