Bats and rice: Quantifying the role of insectivorous bats as agricultural pest suppressors in rice fields

Abstract

Rice represents the main staple food for more than half of the world's population, playing an essential role in food security and economic growth. One of the major pests affecting this crop is the striped rice stem borer moth (Chilo suppressalis), a widespread species found in Australasia, Asia and southern Europe. Bats are paramount insect consumers and their role as natural pest controllers in agriculture has been increasingly acknowledged, including in rice paddies. In this study we quantify, for the first time in Europe, the economic value of the ecosystem services provided by insectivorous bats as suppressors of a rice pest through exclusion experiments in rice plantations in Spain. Our study design included exclosures that prevented bats from hunting over some experimental areas, combined with molecular analyses of bat guano. By assessing the crop damage levels caused by C. supressalis inside and outside the exclosures, we showed that pest impact almost doubled in the absence of bats (94.5 % of damage increase). We estimated that bats were preventing crop losses of almost 70 kg of rice per hectare on average, which in economic terms would imply savings of 56€/ha. If we extrapolate our results to the national level, these values could reach up to 7.6 tonnes of rice, or more than 6 million euros saved by bats per year in Spain. Our findings highlight the importance of implementing management measures that favour bat populations in agrosystems as part of the Integrated Pest Management strategies to fight harmful insects, thereby increasing yields and land productivity in a sustainable and environmentally friendly way.