To improve or not to improve? The dilemma of “bat-friendly” farmland potentially becoming an ecological trap

Abstract

Conventional agriculture occupies a substantial portion of Earth’s terrestrial surface and adversely affects biodiversity through pesticide spread, mechanisation, and loss of spatial and temporal heterogeneity of farmed landscapes. Consequently, conventional agriculture has become a primary target of many restoration projects operating at various scales, from habitat to landscape. While these restoration efforts aim to increase farmland biodiversity and promote the delivery of associated ecosystem services, unintended consequences may arise when important threats are not mitigated. For instance, animals may be led to make maladaptive choices, and lured to attractive sites with poor habitat quality (ecological traps), resulting in adverse effects on individual fitness and demography. We focus our review on European farmland as a case study because of its extensive presence on the continent and the particularly articulated legal framework regulating agriculture and biodiversity within the European Union. Europe's policy framework is dual-faced: one promotes farmland development regardless of management practices, while the other advocates for biodiversity protection measures that sometimes lack strong supporting evidence or overlook critical management aspects. Insectivorous bats contribute significantly to ecosystem service delivery through insectivory in agricultural landscapes, consuming large numbers of pest arthropods. However, when restoring habitats for bats in conventional farmland, potential unintended outcomes must be considered, particularly if restoration actions are not accompanied by mitigation of key threats. These threats include the persistent and widespread use of pesticides, road networks, the siting of wind turbines in farmed landscapes, and opportunistic predators, especially domestic cats. We argue that installing bat boxes and enhancing habitat and landscape features, such as increasing connectivity and diversity, potentially trap bats in attractive yet unsuitable environments if such threats are not mitigated. While environmental restoration in farmland is highly valued for supporting bat populations, it is crucial to avoid neglecting factors that could have the opposite effect, turning 'improved' farmland into a sink. Research is urgently needed to understand such potential unintended effects and inform farmland management and policymakers.