Crop pests spreading polewards under global
warming
7 November 2013
Issue 349
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Source: Bebber, D. P.,
Ramotowski, M. A. T. &
Gurr, S. J. (2013). Crop
pests and pathogens move
polewards in a warming
world. Nature Climate
Change.
DOI:10.1038/NCLIMATE19
90.
Crop pests and pathogens are moving into new habitats, towards the North and
South Poles, as global warming progresses, new research suggests. Observation
records from around the world show that many crop pests, including insect and
bacterial pests, are moving towards the poles at an average rate of 2.7 km per
year.
Today, 10-16% of growing crops are lost to pests, with further losses occurring after
harvest. In our globally connected world, there is great opportunity for pests to be spread
across international borders. Indeed, it is estimated that more than half of plant diseases
are spread by human introduction. However, once introduced, weather conditions are
thought to be the main determinant of whether a pest or pathogen becomes established.
The importance of weather has led to speculation on how the effects of climate change
might affect pest distributions and, subsequently, food security.
Contact:
s.j.gurr@exeter.ac.uk,
d.bebber@exeter.ac.uk
This study suggests that the warming climate is allowing pests to become established in
regions that would have been previously unsuitable because they were cooler. The
researchers analysed 612 published records of where crop pests and pathogens have
occurred, including mites, aphids, fungi, bacteria, beetles, flies, butterflies and moths,
amongst others. The latitude of occurrences was then plotted to investigate how ranges of
these species have shifted since 1960.
Read more about:
Climate change and
energy, Agriculture
The results show that, although there was a large amount of variation between different
groups, on average, there was a shift of 2.7 km per year towards the poles, with significant
shifts for many important pest species. For example, fungi, bacteria, beetles, flies,
butterflies and moths have all clearly been moving towards the poles in the past 50 years.
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One important factor that the researchers investigate is the possibility of a bias in the
records of where pests and pathogens have occurred. They highlight the fact that scientific
techniques and equipment are typically more advanced in countries at higher latitudes, i.e.
closer to the poles. However, if such a bias existed it would lead to pests being first reported
in countries closer to poles and only later discovered nearer the Equator. The trend observed
in this study is that most pests are actually observed first nearer the equator and only later
at higher latitudes, suggesting that it is the result of global warming, not data bias.
In fact, the only groups that might appear as if they have moved towards the Equator,
according to the observation records, are nematode worms and viruses. These are often
both soil borne, and therefore more difficult to detect, especially in countries closer to the
Equator with less technical capacity. In these cases, it may be bias in the data that explains
the apparent ‘movement’, suggest the study’s authors.
Although global food security depends on a variety of different interconnected factors, plant
diseases and pests can have a drastic effect, especially in poorer countries. The findings in
this study suggest that, in the face of climate change, increased investment in monitoring
and preventing the spread of crop pests are needed.