Climate change 'driving spread of crop pests'

Climate change is helping pests and
diseases that attack crops to spread around
the world, a study suggests.
Researchers from the universities of Exeter
and Oxford have found crop pests are moving
at an average of two miles (3km) a year.
The team said they were heading towards the
north and south poles, and were establishing in
areas that were once too cold for them to live
in.

The research is published in the journal
Nature Climate Change .
Currently, it is estimated that between 10%
and 16% of the world's crops are lost to
disease outbreaks. The researchers warn that
rising global temperatures could make the
problem worse.
Dr Dan Bebber, the lead author of the study
from the University of Exeter, said: "Global
food security is one of the major challenges
we are going to face over the next few
decades.
"We really don't want to be losing any more of
our crops than is absolutely necessary to pests
and pathogens."

Trade transport
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.
"We detect a shift in their distribution away
form the equator and towards the poles,"
explained Dr Bebber,
The researchers believe that the global trade in
crops is mainly responsible for the movement
of pests and pathogens from country to
country.
However, the organisms can only take hold in
new areas if the conditions are suitable, and
the researchers believe that warming
temperatures have enabled the creature to
survive at higher latitudes.
Dr Bebber said: "The most convincing
hypothesis is that global warming has caused
this shift.
"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."
The researchers said that better information
about where the pests and pathogens were and
where they were moving was needed to fully
assess the scale of the problem.
"We also need to protect our borders, we have
to quarantine plants to reduce the chances
that pests and pathogens are able to get into
our agricultural systems," added Dr Bebber.