6. Bat conservation in the context of forest management

#### 6.1. The impacts of silviculture

Figure 1. The spatial distribution of foraging bats in a forest stand. Gleaners (Myotis and Plecotus) forage within the foliage of the trees and around shrubs and bushes in the understory, whereas hawkers (Nyctalus, Eptesicus, Barbastella and Pipistrellus) are distributed above and under the canopy (a). When a tree dies, (b) a space free of vegetation forms. This clearing is generally avoided by gleaners and possibly exploited by hawkers where the space is not too cluttered by dead branches. Barbastella barbastellus may take advantage of any peeling bark for potential diurnal roosts. Once the dead tree has fallen, (c) hawkers distribute at the top of the clearing. The forest gap allows light to penetrate to the ground level, favouring the development of low vegetation. Certain gleaners (Myotis nattereri and Plecotus auritus) take advantage of this opportunity by foraging in the understory while others (Myotis myotis) require bare ground, and Myotis bechsteinii continues to exploit the foliage of the canopy. Bb: Barbastella barbastellus; Es: Eptesicus serotinus; Mb: Myotis bechsteinii, mm: Myotis myotis; Mms: Myotis mystacinus; Mn; Myotis nattereri; Nl: Nyctalus leisleri; Nn: Nyctalus noctula; Pa: Plecotus auritus;

Pk: Pipistrellus kuhlii; Pp: Pipistrellus pipistrellus.

70 Bats

Regardless of the type of silvicultural practice undertaken in forests around the world, biodiversity will be affected. Harvest exclusion areas or setting aside reserves within production forests constitute sites that are richer in terms of species present, whereas timber plantations with more economically profitable methods employed, notably short rotation forestry, are the most impacting of approaches [1, 26, 71]. For bats, silvicultural logging reduces food resources, destroys breeding sites, and can kill individuals or colonies when trees are felled [2, 5, 6, 71]. Females of Plecotus auritus have been shown to entirely avoid forests recently logged during lactation periods even if mature trees have been preserved [32]. The same avoidance has also been observed in juveniles of Myotis bechsteinii and Myotis nattereri probably due to the decrease in the volume of foliage, which is an important source of insect production for these species [31]. More generally, logging forests for timber induces a net loss of prey-bearing mature broadleaves causing an immediate reduction in food resource. Therefore, bats are forced to move to new habitats next to their previous foraging grounds that are already occupied by other individuals, reducing the carrying capacity of the milieu. The silvicultural harvesting of mature trees that possess cavities inevitably leads to a reduction of the total number of roosts available to bats. Even if the natural ageing of trees continues and is accompanied by the gradual formation of new cavities, principally by woodpeckers, the setting aside of areas of unlogged mature forest to protect habitat diversity must still be maintained in order to ensure the temporal and spatial continuity of bat colonies [2, 6, 31]. Indeed, only harvest exclusion areas where the natural forest cycle is allowed to continue without the intervention of man represent truly ideal habitats for bats [80]. However, strict protection obviously remains an unrealistic measure across the European forest scale, implying a need for other forest management strategies.

maintain a group of trees, ensuring a forest ambience, around a cavity while, again, limiting the potential risk of injury to forestry workers or public. Maintaining quantities of deadwood, where possible both snags and ground-lying, should target the minimal threshold of

In Europe, the accumulation of knowledge over the last decade on the relationships between bats and forests has orientated programmes geared towards a greater consideration for bats. In addition, the Natura 2000 network has been adopted in the European Community making it possible to designate numerous sites considered as fundamental for these animals [2, 13]. Forests being a key issue for the conservation of bats need to be taken into account as part of regional planning and forest management policies [2]. However, even though the number of appropriate management recommendations has increased in recent years the implementation of concrete conservation strategies is challenging, and unfortunately slow. Furthermore, forest managers must meet society's growing demand for wood products among other objectives such as reducing fossil fuel consumption, curtailing the impacts of

Of the 15 million hectares of forests in France (including overseas territories), 4.5 million hectares are managed by the French Forest Office who are mainly financed by timber production. This management body has integrated key conservation issues for biodiversity at various spatial scales within production forest systems. First, a number of harvest exclusion areas, whereby no silvicultural intervention occurs, have been created, each area ranging in size from ten to hundreds of hectares, totalling nearly 50,000 ha. Second, 3% of managed forests are "habitat islands" (generally ranging from 1 to 10 ha in size) where a true naturalness approach allows the natural cycle of forests to ensue ageing and decomposition of trees. Third, three microhabitat-bearing trees or dead trees are systematically protected per hectare. Fourth, at least one-third of a mature broadleaved forest's area is maintained in each forest canton as often as possible. The exploitation by clearcutting cannot exceed a few dozen hectares for any single block and the natural regeneration of the ecosystem is favoured, which is thus less degrading to biodiversity than plantations. Lastly, a team of 45 conscientious forest engineers, technicians and ecologists set up in 2004 carry out forest inventories and studies to improve knowledge on the relations between bats and forests and to evaluate the impact of forestry in this Office. They convert the collected information into management guidelines that favour bat conservation. These people are trained in forestry and have years of experience in managing forest plots, and can use the technical terminology required when communicating appropriate strategies to silviculture. The internalisation of these issues by teams dedicated to the preservation of bats within forest management organisations is the best assurance of successful bat conservation within exploited forest systems

/ha. Finally, diversity in tree species, a diversity in the vertical stratification and structure of a forest stand can only further support a diversity and abundance of food resources

Bat Conservation Management in Exploited European Temperate Forests

http://dx.doi.org/10.5772/intechopen.73280

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25m<sup>3</sup>

climate change.

worldwide.

for the various species of bats.

7. The involvement of forest managers in France

#### 6.2. Forest management orientations in favour of bats

Given the major differences in the ecological functioning of forest habitats, i.e. different compositions and structures, combined with a diverse range of silvicultural techniques employed to manipulate growth conditions, it becomes difficult for the conservation biologists to propose bat-friendly management measures [2, 81]. The growing literature comparing managed and non-managed forests demonstrates that bats do have the ability to occupy exploited forest systems, which gives hope for improving the conservation status of many species throughout European forests [1]. However, so as to implement effective conservation measures for bats, it is vital to know what habitat parameters to conserve and balance this with appropriate silvicultural treatments that ensure the continuing exploitation of wood while assuring the safety of the loggers themselves and the public who use the forests for recreational purposes. Although it is necessary to further improve knowledge on the relationship between bats and forest management [2], some recommendations can already be put forward. In order to conserve both roosts and foraging habitats, it is imperative that the manager ensures the temporal and spatial continuity of mature broadleaved stands composed of native species by maintaining at least 35% of the surface area of each forest (about 1000 ha). One way of maintaining suitable habitats for bats in forests would be by setting aside a number of small sites of no more than a few hectares in size, leaving the forest within each site to complete its natural cycle. By doing so, this would assure the presence of tree cavities, deadwood, and certain heterogeneity to naturally occur across an entire forest mosaic. In addition, within production forest plots, maintaining a small number of live or dead trees possessing cavities even after felling treatments have been carried out can ensure a minimum continuation of usable roosts. This can be of particular ecological interest: live trees possessing cavities surrounding a dead tree form a group of trees representing a particularly attractive habitat for bats. Also, a tree possessing a large voluminous cavity at a high position can accommodate certain species for an extended period of time such as Nyctalus noctula. Because isolated trees are at a greater risk of falling (due to abiotic factors) it is possible and recommended to

maintain a group of trees, ensuring a forest ambience, around a cavity while, again, limiting the potential risk of injury to forestry workers or public. Maintaining quantities of deadwood, where possible both snags and ground-lying, should target the minimal threshold of 25m<sup>3</sup> /ha. Finally, diversity in tree species, a diversity in the vertical stratification and structure of a forest stand can only further support a diversity and abundance of food resources for the various species of bats.
