Integrating species distribution models at forest planning level to develop indicators for fast-growing plantations. A case study of Eucalyptus globulus Labill. in Galicia (NW Spain)

Abstract

Abstract Planting eucalypt stands in the Iberian Peninsula is controversial. In Galicia (NW Spain) the area covered by eucalypts and the intensity of eucalypt timber harvesting are among the highest in Europe. In this region, management plans for forest resources are intended for relatively homogeneous territorial units, smaller than the province, called forest districts (ForDis). The status of eucalypt plantations in ForDis is usually assumed to be highly variable, although this has not yet been quantified. Within this framework, the present study aimed to integrate an existing Eucalyptus globulus distribution model for current conditions and two different climate change scenarios with current forest cover (including eucalypt plantations) to provide quantitative and spatially-explicit information for identifying ForDis where eucalypt plantations may become problematic. Four parameters (suitability, importance, potential expansion and fragmentation) comprising 13 related indicators were calculated for eucalypt plantations in each of the 19 ForDis in the region. The findings show that more than 44% of the afforested area is covered by eucalypts in the province of A Coruna and in forest districts VI and XVIII (in Lugo and Pontevedra, respectively). A huge continuous patch of eucalypt, of more than 35,000\xa0ha, was detected across two ForDis (I and VI). The potentially high ecological and financial risks associated with this vast area of monoculture would negatively affect the sustainability and multifunctionality of these forest ecosystems. Analysis of the expected suitability of areas for E. globulus in forthcoming climate change scenarios identified four inland ForDis (IX, X in Lugo, XVI in Pontevedra and XI in Ourense) where an important increase in cover by this species may occur if no action is taken. Moreover, these areas overlap with the large ongoing expansion already observed for the more productive and frost-resistant E. nitens. The findings also revealed edge-dominated native broadleaved forest patches in the habitat suitable for E. globulus in the provinces of A Coruna and Lugo. Although the current level of occupancy of eucalypt within natural protected areas (NPAs) is moderate, the suitability of these areas for eucalypt plantations will increase in the predicted climate change scenario, possibly leading to aggravation of potential conflicts in these biodiversity hotspots. Regional forest agencies should therefore increase monitoring efforts to prevent further impacts on native forest and natural protected areas. The proposed quantitative indicators and methodology used are intended to be useful for forest planners and policy decision-makers in other regions where current and future conflicts related to exotic tree plantations are expected.