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Outbreaks of rodents following pulses of primary productivity are characteristic of many ecosystems.In New Zealand,synchronous high seed production (masts) by indigenous beech trees is positively correlated with the difference between average summer temperatures in successive years (ΔT model) .Also ΔT can predict directly the probability of outbreaks of invasive house mice (Mus musculus) after beech masts.Outbreaks of mice and other invasive mammals,including rats (Rattus spp.) and mustelids,require large expenditure on pest control to protect vulnerable native species.We used temperature data to calculate national ΔT surfaces for the last 4 decades.Based on ΔT models for beech seed and mouse abundance,western areas of New Zealands South Island experience the highest frequency of localised beech masts and rodent outbreaks,up to one every 2.6 years.Mega-masts (defined as years with >50% of beech forest predicted to experience a mast) have occurred sporadically at a rolling average of 5.2 per 25 years.The 2014 mega-mast is predicted to extend across 85%of beech forest,and the cost of pest control for the entire affected area would be >50 times the average annual expenditure on aerial baiting by the Department of Conservation.A regional climate model was downscaled to generate daily temperatures to 2100.For three greenhouse gas emission scenarios,SRES A2 (regionally oriented economic development) ,B1 (global environmental sustainability) and the intermediate A1B,the frequency of mega-masts and subsequent high-cost pest control is predicted to change to 5.75,4.5 and 5.5 events per 25 years,respectively.