Diseases and pests that feed on crops are increasing at an alarming rate, decimating harvests in larger areas, adding to the long list of climate change factors that are threatening global food security, a study published this week in the journal Nature Climate Change warns.

According to the researchers, crop pests are spreading further towards the poles at an average rate of two miles per year.

Among the reasons for this trend, the researchers found that warmer temperatures towards the far north and south, and at higher altitudes, are creating conditions conducive to the crop killers in larger areas.

The researchers pointed to the global crop trade, which more easily spreads invasive species around the world as one of the main factors, but said that climate change has exacerbated the problem.

"The most convincing hypothesis is that global warming has caused this shift," Dr Dan Bebber from the University of Exeter and lead author of the study told BBC News. "We detect a shift in their distribution away form the equator and towards the poles."

"One example is the Colorado potato beetle. Warming appears to have allowed it to move northwards through Europe to into Finland and Norway where the cold winters would normally knock the beetle back," said Bebber.

BBC News reports:

To investigate the problem, the researchers looked at the records of 612 crop pests and pathogens from around the world that had been collected over the past 50 years.

These included fungi, such as wheat rust, which is devastating harvests in Africa, the Middle East and Asia; insects like the mountain pine beetle that is destroying trees in the US; as well as bacteria, viruses and microscopic nematode worms.

Each organism's distribution was different - some butterflies and insects were shifting quickly, at about 12 miles (20km) a year; other bacterium species had hardly moved. On average, however, the pests had been spreading by two miles each year since 1960.

"Global food security is one of the major challenges we are going to face over the next few decades," Bebber added. "We really don't want to be losing any more of our crops than is absolutely necessary to pests and pathogens."

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