Integrating ecology and economics: European honey buzzards as ecosystem service providers against yellow-legged hornets

The economic valuation of ecosystem services is an essential tool for integrating environmental considerations into decision-making processes. However, the valuation is challenging as many of these services lack formal market values. This study evaluates the role of the European honey buzzard in controlling the invasive yellow-legged hornet, quantifying the number of colonies destroyed per breeding pair of the raptor and assessing the economic and social value of this regulatory ecosystem service. We implemented a two-phase approach: 1) a biological phase, aimed to estimate the pest control in biological terms, and 2) an economic phase, focused on assessing the economic value of the pest control service using two complementary methods: the replacement cost and the contingent valuation. Results indicate that each honey-buzzard pair eliminates between 67.0 and 83.7 hornet colonies per breeding season. Honey-buzzards lead to colony collapse in at least 79.9% of attacked hornet nests, highlighting the bird's effectiveness. The estimated cost savings in hornet nest removal ranged from €2.6 to €6.4 million annually, while public willingness to pay for honey-buzzard protection reached €33.7 million, revealing strong social appreciation. Both estimations are much higher than the budget that official institutions target to manually eliminate hornet nests each year. Our findings emphasize the importance of integrating ecological and economic evaluations. While our approach does not capture all dimensions of nature's value, it offers a complementary perspective that can help inform practical conservation strategies and provide foundations to rationalize and justify the budget spent on pest control measures by public institutions.