The occurrence of forest fires is a natural phenomenon in Mediterranean ecosystems. In recent decades the frequency and spread of fires have become prominent factors in the economics, social impact and conservation of biodiversity. The abandonment of traditional agricultural and grazing activities in forests has contributed in particular to the current pattern of forest fires, in as much as the total forest area is as large as it has even been in Catalonia and the flora it contains is highly flammable.
In order to ascertain the extent to which forest fires and common post-fire treatments affect key species like the European rabbit (Oryctolagus cuniculus), the researchers Joan Real and Alex Rollan, from the UB's Conservation Biology Group undertook a specific project recently reported in the European Journal of Wildlife Research.
The wood from Mediterranean forests in Catalonia is of little value and is rarely put to commercial use, so it often ends up being burned. As such, means of economic and social value must be found is forest areas are to be maintained. One alternative that could provide financial return would be licensed hunting, if practised sustainably. For example, the hunting of partridges and rabbits -- species that are increasingly scarce but also coveted by hunters -- could generate considerable income. With proper management, this could represent an important source of revenue for Mediterranean forest areas. Furthermore, rabbits and partridges are fundamental to forest ecosystems, as they support endangered predatory species such as the Iberian Lynx, the Spanish Imperial Eagle and Bonelli's Eagle. This means, of course, that the development and conservation of these species is also a key factor in the conservation of biodiversity.
The forest after a fire
After a fire it is standard practice to remove any timber from large burned trees with potential commercial value, leaving the burned branches in situ along with other burned vegetation of no commercial value, post-fire activities that are normally subsidized by the government. The extent to which this technique of leaving burned branches in situ influences the management of post-fire forest productivity and biodiversity conservation is unknown. It appears to be more a matter of intuitive action than a technique based on proven possible benefits. Indeed, the evidence suggests that this practice could well increase the risk of future fires. Additionally, there is no indication that the technique improves conditions for rabbits and partridges, key species in these ecosystems that could also provide significant economic return for forest farms.
Fires, forestry techniques and biodiversity
As detailed in a scientific paper published in the European Journal of Wildlife Research, the UB experts studied the rabbit populations in different areas of the Sant Llorenç del Munt i l'Obac natural park, which in August 2003 was hit by a forest fire that burned some 4,600 hectares. The basic objective was to study how forest fires and post-fire forest management affected the abundance and recovery of rabbit populations. The team looked at forty-one different plots of land to which different post-fire forest management techniques had been applied. Specifically, each of the plots studied corresponded to one of four different types of forest management: natural areas not burned, burned areas where burned branches were left in situ, burned areas where all burned wood was removed, and areas of low vegetation cover before the fire.
Interesting results were obtained. In the burned areas, rabbit populations recovered faster and reached high abundances five years after the fires had occurred, far surpassing population numbers in unburned areas. Additionally, in burned areas where the burned branches were removed, rabbit populations grew faster and reached higher abundances than in plots where the burned branches were left on the ground. Finally, close analysis taking into account the different layers of vegetation and burned wood showed a strong negative correlation between the amount of burned wood left on a plot and rabbit abundance and, in contrast, a positive correlation in the case of uncovered soil and the existence of herbs and grasses.
As Joan Real explains, "the reasons for these results lie, firstly, in the fact that fires 'open up the landscape', and that the early stages of regeneration after a fire encourage the growth of herbs and grasses of high nutritional value for rabbits, so the species can reproduce at an adequate rate. Secondly, burned branches left in situ are likely to prevent not only the movement and actions of rabbits but also the growth of these plants of high nutritional value. Therefore, this post-fire treatment is not favourable to rabbit abundance."
In the authors' opinion, removing burned wood left by forest fires is an alternative approach that increases the potential financial returns obtainable from Mediterranean forests, where the value of the wood is very low and could be surpassed by income from hunting. In addition, this forestry technique could contribute to the recovery of rabbit populations affected by inadequate habitats, viral diseases and overexploitation, and is essential for the conservation of highly endangered species and the future of Mediterranean biodiversity. Furthermore, the application of this technique paves the way for the use of controlled burning as a tool for the improvement and recovery of rabbit populations.
This research, published in the European Journal of Wildlife Research, received the support of organizations including the Barcelona Natural Park Service, the Sant Llorenç del Munt i l'Obac natural park and the Cercle d'Amics dels Parcs Naturals natural park support group. The UB's Conservation Biology Group, led by Joan Real of the Department of Animal Biology, carries out applied research into the conservation of endangered species, aimed at helping those responsible for conservation to apply effective measures. The research work carried out by the group in the field of conservation of birds of prey in Catalonia is also supported by the Fundació Miquel Torres, Barcelona Provincial Council, and the companies Fecsa-Endesa, Estabanell i Pahisa SA, Electra Caldense SA and Red Eléctrica de España SA.
- Àlex Rollan, Joan Real. Effect of wildfires and post-fire forest treatments on rabbit abundance. European Journal of Wildlife Research, 2010; 57 (2): 201 DOI: 10.1007/s10344-010-0412-y
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