Impacts of climate change on tomato, a notorious pest and its natural enemy: small scale agriculture at higher risk

Climate change (CC) clearly impacts food production, but risks on the climatic suitability of agricultural areas for vegetable crops, their pests and associated natural enemies are largely unexplored. Tomato, one of the most important vegetables in the world, is grown mostly outdoors, and may be severely impacted by CC. Farmers cultivating tomatoes need to adapt to an increase in the potential for outbreaks of pests favoured by CC and disruption of biological control, yet, no attempt has been made to simultaneously evaluate CC effects on a crop-pest-natural enemy system for tomato or any other crop. Here, we modelled the suitability of areas equipped with irrigation facilities (AEI) in 2050 for tomato, the two-spotted spider mite, Tetranychus urticae, a mite pest of tomato among more than 200 crops, and its key predator Phytoseiulus persimilis. We evaluated the suitability of AEI for tomato production under a 1.6 degrees C warming by 2050, within the targets of the Paris agreement. Projections show that climatic conditions become unsuitable for tomato production on 30%-100% of AEI for seven out of the 29 top tomato producing countries of the world. Model predictions suggest that two-spotted spider mite potential for outbreaks would increase substantially in nine countries in Europe, Africa and Asia, while biological control failures would occur globally. Model results have a significant relationship with growth rates for the three species measured in outdoor experiments, and farmer/expert perceptions on two-spotted spider mite outbreak severity captured via interviews. The expansion of AEI in other agricultural areas in the sub-Saharan Africa may offset losses of suitable land. However, several nations in the Middle East and South Asia with prevalent small scale agriculture would experience devastating impacts because of the unsuitability of conditions for tomato production and the potential increase in two-spotted spider mite outbreaks.