A team of researchers from the universities of Exeter and Oxford in the UK finds that many crop pests are spreading away from the tropics towards the north and south poles at an average rate of about two miles (3 kilometers) a year. While the spread is mostly facilitated by human transportation, the new study suggests that warming temperatures are allowing these organisms to flourish in regions that were once too cold for them to survive. The research was published Sept. 1 online in the journal Nature Climate Change.
To arrive at their results, the team looked at records of 612 crop pests and pathogens from around the globe that had been collected over the past 50 years. These included insects, such as the mountain pine beetle that is killing trees in the U.S., fungi, bacteria, viruses, moths, and microscopic nematode worms. The researchers found that, in general, the pests were moving closer to the north and south poles each decade. Adding to the problem is that pests are spreading faster than their predators, putting delicately-balanced ecosystems at risk.
“We believe the spread is driven to a large degree by global warming,” lead author Daniel Bebber of Exeter University told Reuters. “However, interactions between climate change, crops, and pests are complex, and the extent to which crop pests and pathogens have altered their latitudinal ranges in response to global warming is largely unknown,” he added.
Scientists estimate that between 10 and 16 percent of the world’s crops is damaged or destroyed by pests and disease. This makes safeguarding the global agricultural food supply one of the major challenges over the coming decades, the authors write. And although the trade in crops is mainly responsible for transporting pests around the globe, they cannot take hold unless conditions are suitable. According to Bebber, the most convincing hypothesis for the spread of crop-threatening pests is climate change.
“One example is the Colorado potato beetle. Warming appears to have allowed it to move northwards through Europe into Finland and Norway where the cold winters would normally knock the beetle back,” Bebber told BBC News. Another example is the mountain pine beetle, which has moved north into the U.S. Pacific Northwest where it has destroyed large areas of pine forest.
To fully understand the scale of the problem, the researchers said more and better information about the movement of pests and pathogens is needed. They also emphasized that border protection and the use of quarantines are important measures for reducing the chances that pests and disease-spreading organisms will invade our agricultural systems.