Sustainable rice production is critical to food security especially in Asia. Effective biocontrol of major rice pests such as the White-Backed Planthopper (Sogatella furcifera, Horváth; WBP) is, hence, of eminent importance. We use newly compiled data from Thailand on the Wrinkle-Lipped Bat (Tadarida plicata, Buchanan), WBP distributions and an iterative modelling approach to quantify the importance of biological pest control by a common bat species on WBP. In Thailand, this single species interaction may prevent rice loss of almost 2,900 tons per year, which translates into a national economic value of more than 1.2. million USD or rice meals for almost 26,200 people annually. For the first time, our results show not only the critical importance of bat pest control services in economic terms, but also for sustaining food security. Thus, bat population decline as currently observed in Southeast Asia, will directly affect people by food and money. Functionally important populations, not just rare and endangered species, should be included in conservation management of human-dominated landscapes.