Rodent outbreaks and extreme weather events: a southeast Asian perspective

In recent reviews of rodent outbreaks (Singleton et al., 2010a,b), three general systems were identified that influence the food supply of rodents in significantly different ways. One is life-cycle- or evolutiondriven in the form of plant masting events. Outbreaks triggered by masting, including bamboo and beech forests, are examples of this system. The second is climatic; these include outbreaks driven by changes in abiotic conditions alone (aseasonal or unusual rainfall events, or major climatic events such as El Niño or La Niña). These are irregular and rodent populations respond rapidly to the peaks in increased food availability. The third is anthropogenic responses associated with extreme climate events or market forces with outbreaks driven by changes in cropping systems. These are driven directly by anthropogenic responses to calamitous events such as cyclones, high rainfall, and drought, or responses to shortfalls of production of staple crops.In Southeast Asia a massive outbreak of rodents in the Ayeyarwaddy delta in 2009 and 2010 was associated with a calamitous weather event, cyclone Nargis, which occurred 15 months prior to the outbreak. We present findings that support the association between the effects of cyclone Nargis and the subsequent rodent outbreaks. These rodent populations response appeared to be associated with an extended period of available high quality food, which was caused by asynchronous and aseasonal planting of rice during the 2008 monsoon season. We contend that climate change and extreme climatic events will increase the impacts of rodents on agricultural production in coming years.

Abstract licence: CC BY

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