Edited by: Rodrigo Medellin, National Autonomous University of Mexico, Mexico
Reviewed by: Mariana M. Vale, Federal University of Rio de Janeiro, Brazil; Tigga Kingston, Texas Tech University, USA
*Correspondence: Danilo Russo
This article was submitted to Conservation, a section of the journal Frontiers in Ecology and Evolution
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Bats are a biodiverse mammal order providing key ecosystem services such as pest suppression, pollination, and seed dispersal. Bats are also very sensitive to human actions, and significant declines in many bat populations have been recorded consequently. Many bat species find crucial roosting and foraging opportunities in European forests. Such forests have historically been exploited by humans and are still influenced by harvesting. One of the consequences of this pressure is the loss of key habitat resources, often making forests inhospitable to bats. Despite the legal protection granted to bats across Europe, the impacts of forestry on bats are still often neglected. Because forest exploitation influences forest structure at several spatial scales, economically viable forestry could become more sustainable and even favor bats. We highlight that a positive future for bat conservation that simultaneously benefits forestry is foreseeable, although more applied research is needed to develop sound management. Key future research topics include the detection of factors influencing the carrying capacity of forests, and determining the impacts of forest management and the economic importance of bats in forests. Predictive tools to inform forest managers are much needed, together with greater synergies between forest managers and bat conservationists.
Bats are one of the most diverse mammal groups featuring over 1300 species worldwide (Fenton and Simmons,
Although bats often roost in caves or buildings, many species inhabit forests and exhibit wing morphology and echolocation calls tailored to life in this cluttered habitat (Norberg and Rayner,
Forests have vital economic and social importance for humans, as a source of timber as well as other products (FAO,
Most European forests have been exploited by humans for centuries and are still strongly influenced by harvesting (Kirby and Watkins,
Europe is home to 53 bat species (Table
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Most European bats use forests for roosting and/or foraging (Table
If trends in European forest management are not reversed, we foresee a bleak future for bat species. How can the gap between forest management and the needs of forest dwelling bats be reconciled? In this paper we present the outcome of a workshop held in the Netherlands in November 2015 in which we identified knowledge gaps and collected suggestions for future research directions needed to balance forest productivity and bat conservation in European forestry practice. Although much is known about the basic ecology of some forest-dwelling species (e.g., Dietz,
Forestry alters forest stand age and composition, both key elements in determining foraging and roosting opportunities for bats (Figure
Frequently, management will affect different bat species in different ways by influencing the availability of roosting or foraging habitat. Thinning may make forest more suitable for foraging by edge or open space specialists, but be detrimental for species that hunt in clutter (Patriquin and Barclay,
Felling of a single roost tree can kill or harm individuals directly. Killing individuals may have legal implications, particularly if protected species are affected, although population-level effects are unknown. While appropriate measures could be planned to mitigate direct mortality, such as avoiding forest operations at critical times of year (e.g., the reproductive and hibernation seasons), the spatial patterns of habitat change resulting from logging may have considerable implications for bat conservation and in theory can be planned
Large-scale harvesting or thinning of woodland may lead to roost loss and induce changes in the availability of foraging habitat. Changes in forest structure caused by logging may increase the extent of edges or clearings, favoring bat species that use edge habitats, while affecting core habitat specialists detrimentally. Harvesting regimes that influence habitat availability as well as prey diversity or abundance may affect foraging success, body condition, survival, and reproductive success, translating into fitness consequences that affect demographic trends. Whether such effects are positive or not depends on the management choices adopted.
Bats are legally protected in the EU (corresponding to ca. 43% of European continent's landmass) and their deliberate killing or destruction of their habitat are legal offenses. The Habitats Directive enlists all species in Annex IV and 13 species under Annex II. Conserving Annex II species requires the designation of Special Areas of Conservation (The Council of European Communities,
Most European states participate into Bern Convention and the UNEP/EUROBATS Agreement and therefore have binding obligations to protect all bat species within their territories. EUROBATS (
In all cases the relevant international legal regulations have to be implemented under national law, but the interpretation in particular of Article 12 of the Habitats Directive, and the measures to fulfill the obligations vary strongly across the EU. Article 12 prohibits the deliberate capture, killing or disturbance of bats particularly during breeding, hibernation, and migration. Deterioration or destruction of breeding or roosting sites is also forbidden (EU Commission, 2007).
Increasing forestry contributions to maintain and enhance biodiversity is one of the targets of the 2020 EU Biodiversity Strategy to fulfill commitments to the Convention on Biological Diversity. Action 12 of the strategy makes provisions to integrate biodiversity measures in forest management plans, which will be implemented into national legislation and regulations. Nevertheless, bats are often disregarded when it comes to forestry practices in reality.
For instance, although the Habitat Directive prohibits any deliberate killing of bats or deterioration of their habitats, this is seldom applied to forestry operations. According to the Guidance document (EU Commission,
Thus, it is necessary to alert foresters about the legislation that applies to bats and their habitats. Information about the importance of forests and trees for bats has been distributed in some European countries, including national and multinational guidance. In Germany, recommendations for forest managers were published in 2000 following a nationwide 3-year research and development project on bats in forests (Meschede and Heller,
However, impacts on bats are still often neglected. European, as well as national legal obligations are regularly not complied with in forest management, and destruction of important bat forest habitats or roosts by logging still occurs.
There are few studies on the impacts of forestry on bats in Europe, and good practice examples including post-operation monitoring are rare (Berthinussen et al.,
Although research has been done elsewhere, especially in North America, we lack long-term longitudinal studies monitoring bat population trends after logging (Law et al.,
Quantification of direct mortality caused by forest operations is needed: if such mortality has consequences for populations, it would turn many managed forests into ecological traps (Russo et al.,
Much information on bat ecology in forests exists, but critical practical questions posed by forest managers are left unanswered (e.g., how many suitable roost trees/ha should be saved from logging?). We need to identify factors influencing the carrying capacity of forests for bats. Best estimates, or expert judgment are often adopted in management but their consequences are rarely monitored.
Several studies have surveyed bat activity by using bat detectors in logged vs. unlogged forest plots (Berthinussen et al.,
Ideally, practices that enhance economic performance but also improve forests for bats should be identified and promoted. Management needs to move beyond mere mitigation and mimic the spatial and temporal heterogeneity of “optimal” bat habitat at multiple scales (tree cavity, tree, immediate tree surroundings, general forest habitat, and landscape). For instance, maintaining diversity in forest structure by adopting
Comparative studies on how bats exploit differently managed or unmanaged forest are important, but selecting appropriate variables to assess bat activity and fitness proxies under different conditions is not trivial. Ideally, reproductive output or fitness should be measured, but this is difficult for bats in general and especially forest species, given their elusiveness and high mobility. High-quality, long-term individual data collected by radiotracking are valuable, but such studies are still constrained by the short lifespan of the batteries in small radio-transmitters. Tag performances will hopefully improve in the future perhaps by further miniaturization or by using inter-connected data networks (Ripperger et al.,
We also argue that research results should eventually lead to predictive tools to inform forest managers. For instance, an applied tool based on statistical models might support foresters in selecting the most “bat-friendly” forestry options. This might be developed employing state-of-art modeling, and models should be trained and validated with high quality data.
Several studies—geographically biased toward temperate countries, especially North America (Maine and Boyles,
Forestry can lead to dramatic changes in forest structure, creating both problems but also opportunities for bat conservation. Overall, a potentially positive future for the management of bats that simultaneously benefits forestry is foreseeable, provided some fundamental steps in research and subsequent management recommendations are taken. These include a quantitative assessment of factors influencing the carrying capacity of forests for bats, as well as the development of management strategies benefitting both conservation and production. A better understanding of the economic importance of bats in suppressing insects harmful to forestry is urged, as it would also provide effective arguments to facilitate acceptance among foresters of management measures aimed at conserving bats. Finally, we highlight that although scarce, there are examples of good management of bats in forest, yet many of these examples are known by bat experts but not by practitioners who implement them. A better dialogue between these two professional groups will bridge this information gap with substantial improvement of bat conservation in managed forests.
DR conceived the paper. All authors contributed equally to writing up and revising the manuscript.
The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
EUROBATS kindly sponsored the workshop on sustainable forest management for bats held in The Netherlands in November 2015 from which this paper arose. Thanks to Tony Mitchell-Jones for contributing important information from the EUROBATS Intersessional Working Group on Bats and Forestry which helped to stimulate the workshop's discussion on knowledge gaps and future objectives for research on bats and forestry. The Editor and the reviewers made very useful comments which greatly helped us to improve this article.