Air travel poses major threat to biodiversity, say scientists

Global air travel has become one of the greatest threats to biodiversity and public health by driving the spread of alien species and infectious diseases to new habitats, scientists report today.

The explosive growth of worldwide airlines has seen passenger numbers rise 8% a year in the past three years, creating travel networks that link remote and isolated ecosystems for the first time, boosting the spread of micro-organisms and insects to unprecedented levels, the scientists claim. The introduction of insects and other organisms from foreign regions has triggered ecological disasters around the globe. Many have no natural predators and thrive at the expense of native species which have not had time to evolve defences against the invaders.

Researchers at Oxford University analysed records for more than 3m scheduled flights between 3,570 airports around the world between May 2005 and April 2006 and calculated the most heavily-used routes. They then overlaid global climate maps, revealing the times of year different parts of the world experienced the best conditions for alien species to survive. By combining the information Andrew Tatem and Simon Hay at the university's spatial ecology and epidemiology group highlighted "invasion hotspots", the destinations most at risk from insects and micro-organisms being carried into the countries throughout the year.

The scientists found that the greatest threat to any country occurred from June to August, when many regions experienced similar climatic conditions and passenger numbers peaked. But closer inspection revealed specific routes that were at high risk of transferring organisms between distant countries. In January the greatest risk to Britain and other parts of Europe was found to come from air travel links with east China and Japan, while in July the risk shifted to routes servicing the east coast of South America. The analysis showed that the isolated Hawaiian islands, widely regarded as suffering the worst ecological damage from invasive species, were at risk from several countries within the space of a few months, as the climate varied to match that of east Asia, Central America and the Caribbean.

The wide-ranging climate and large number of airports put the US at greatest risk, with eastern US airports strongly linked to Mediterranean and Asia airports in January, and west coast airports most at risk from incoming flights from the Middle East and southern Africa in April