The impacts of climate change on the summerfruit industry with respect to insect pest incursions

Abstract

It is now well established that climate change is causing a rise in surface air temperatures due to anthropgenic greenhouse gas emissions. Evidence suggests that warmer surface air temperatures are likely to have an impact on species distributions and climatic suitability, potentially resulting in an increase of tropical or sub-tropical insect pest establishments in areas with temperate climates such as New Zealand. The increased risk of these exotic insect pests establishments is likely to affect both native ecosystems and agricultural industries. The New Zealand summerfruit industry is the fourth largest horticulural industry in New Zealand with a valuable export market worth NZ$30 million per annum. New Zealand currently maintains a valuable fruit fly free status that is maintained by strict biosecurity procedures such as the treatment and inspection of imported fruit and a nationwide trapping grid. However climate change could improve the climatic suitability for particular fruit fly species in New Zealand and increase the risk of permanent establishment.. In the absence of more detailed biological data for target species, any assessment of establishment potential of species under changing conditions often means the use of a species distribution model (SDM) to project climatic suitability in the target area. This research aimed to predict and compare the climatic suitability of major summerfruit producing regions in New Zealand under current climatic conditions and future climate change conditions of Bactrocera dorsalis, B. tryoni, B. zonata, Ceratitis capitata and C. rosa. A common ecoclimatic assessment model known as CLIMEX and a correlative modelling system comprising multiple SDM models were used to estimate climatic suitability for each species. Climatic suitability predictions for New Zealand were generated for 2040 and 2090 emission scenarios that represented best case, intermediate and worse case scenarios per time frame. The results using CLIMEX indicated an increase in climatic suitability around the summerfruit producing Hawkes Bay and Marlborough regions for all fruit fly species under all climate change scenarios. High future emission scenarios resulted in a higher increase in climatic suitability. The results with the multiple model system indicated an increase in climatic suitability for C. rosa under all climate change scenarios and around all major summerfruit producing regions, an increase in climatic suitability for B. zonata only under 2090 climate change scenarios around the summerfruit producing regions, Marlborough and Central Otago and an increase in climatic suitability for B. dorsalis around the summerfruit producing region Central Otago. A decrease in climatic suitability for C. capitata was observed in all areas under all climate change scenarios and no change from low risk was observed for B. tryoni. These results indicate that warmer temperatures may increase or decrease the risk exotic summerfruit insect pest incursions and establishments. In the event of an incursion or outbreak, knowledge of climatic suitability for exotic fruit fly species that present a serious threat to our horticulture industry will increase the effectiveness of an incursion response by concentrating eradication and spread prevention protocols around locations that are more vulnerable, rather than expend resources and valuable time on locations with a low climatic suitability. Additionally, the industries at risk can use this information to be pro-active and plan for emerging threats.