Climate change and insect pests.

Chapter 7 (Page no: 119)

Climate change and biological control in agricultural systems: principles and examples from North America.

Biological control of pests is a key feature of integrated pest management programmes in many agroecosystems. An assessment of the potential impacts of climate change on biological control is critical but challenging, because biological control depends on interspecific interactions, which are generally complex. This chapter considers the potential effects of projected climate change on the biological control of insect pests, focusing on North American agricultural systems but involving principles that apply globally. The drivers of importance are projected rising surface temperatures, increased atmospheric CO₂ concentrations and changes in the amount of and variability in precipitation. We consider how these climate change drivers could affect biological control by: (i) directly affecting the physiology or behaviour of biological control agents and/or pests; (ii) changing the overlap between species in space and time; and (iii) modifying interactions among multiple species involved in biological control within the agroecosystem. We illustrate with the few North American documented examples of the sensitivity of biological control to climate change, or with data that indicate such sensitivities exist. Effects of the first type include increases in the occurrence of temperatures that exceed the thermal optima of natural enemies, such as those that have been documented for coccinellids. Effects of the second type include changes in phenological overlap between insect pests and their natural enemies, illustrated best by a recent report involving the cereal leaf beetle and its principal parasitoid. Effects of the third type include climate-related changes in plant responses to herbivory that influence natural enemies, to the effects of climate on interacting predator assemblages and food webs. Although there is evidence for each of these types of effects, the literature remains sparse. More studies are needed, and we suggest a research agenda to improve understanding of the sensitivity of biological control to climate change.

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