Agriculture Reference
In-Depth Information
Fig. 7.1
Crop-pest-environment triangle showing interactions between abiotic and biotic factors
• Rising winter temperatures reduce winter
mortality.
• Decreased
7.3
Elevated Temperatures
snow
cover
can
increase
mortality.
• Rising temperatures extend the growing
season.
• Greater nutrient demands coincide with plant-
ing and fruiting of many crops.
• Rising temperatures accelerate insect life
cycles - greater generation numbers.
• Earlier migration and maturation.
Climate change will also result in increased
problems with insect-transmitted diseases.
These changes will have major implications for
crop protection and food security, particularly in
the developing countries, where the need to
increase and sustain food production is most
urgent. Long-term monitoring of population
levels and insect behavior, particularly in identi-
fi ably sensitive regions, may provide some of
the fi rst indications of a biological response to
climate change. In addition, it will also be
important to keep ahead of undesirable pest
adaptations, and therefore, it is important to
carefully consider global warming and climate
change for planning research and development
efforts for pest management and food security in
the future.
Insects are cold-blooded organisms, the tempera-
ture of their bodies is approximately the same as
that of the environment. Therefore, temperature is
probably the single most important environmental
factor infl uencing insect behavior, distribution,
development, survival, and reproduction (Fig.
7.2
).
Insect life stage predictions are most often calcu-
lated using accumulated degree days from a base
temperature and biofi x point. Some researchers
believe that the effect of temperature on insects
largely overwhelms the effects of other environ-
mental factors (Bale et al.
2002
). It has been esti-
mated that with a 2 °C temperature increase,
insects might experience one to fi ve additional life
cycles per season (Yamamura and Kiritani
1998
).
In colder regions (higher latitudes) with dis-
tinctive seasons, insects have broader thermal tol-
erance and are living in climates that are currently
cooler than their optima (Deutsch et al.
2008
).
Global warming might therefore benefi t many
insect species in the temperate regions.
Reduced winter mortality of two insect pests
was observed in Japan, when mean temperature
in January was above 4 °C. Species which already
develop at low temperatures and need a smaller
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