Use of native species to improve carbon sequestration and contribute towards solving the environmental problems of the timberlands in Biscay, northern Spain.

The rapid transformation of natural forest areas into fast-growing exotic species plantations, where the main objective is timber and pulp production, has led to a neglect of other services forests provide in many parts of the world. One example of such a problem is the county of Biscay, where the management of these plantations has negative impacts on the environment, creating the necessity to evaluate alternative tree species for use in forestry. The actual crisis in the forest sector of the region could be an opportunity to change to native species plantations that could help restore ecosystem structure and function. However, forest managers of the region are using the current interest on carbon sequestration by forest to persist with the "pine and eucalyptus culture", arguing that these species provide a big C sequestration service. Moreover, they are promoting the expansion of eucalyptus plantations to obtain biomass for the pulp and paper industry and for bioenergy. The aim of this paper is to answer the following questions: Is this argument used by the foresters well-founded? or, could the use of native species in plantations improve the C sequestration service in Biscay while avoiding the environmental problems the actual plantations cause? To answer these questions we created three alternative future scenarios: a) the Services scenario, where there is a substitution of fast-growing exotic plantations by native broadleaf species plantations; b) the Biomass scenario, where there is a bet on eucalyptus plantations; and c) the Business as usual scenario. The changes in the C stock in living biomass in these scenarios have been simulated by a hybrid approach utilising inventories and models, and the period considered was 150 years. Our results show that the substitution of existing exotic plantations by plantations of native species has the greatest potential for increasing C sequestration. Although short- and mid-term outcomes may differ, when the long-term (more than 50 years) is considered, the C stock in the living biomass in the Services scenario is the greatest, accumulating 38% more C than the Business as usual scenario and 70% more C than the Biomass scenario at the end of the study period. Thus, changing pine and eucalyptus by native species in plantations, while solving some of the environmental problems of the actual plantations, sequesters more C in the long-term. As C sequestration initiatives only make sense if there is a good chance of long-term persistence of the C stocks created, there is no C sequestration argument for the foresters to continue with the actual policy of the use of fast-growing exotic species.