Anticipating B. sempervirens viability in front of C. perspectalis outbreaks, fire, and drought disturbances.

Forest ecosystems face an increasing pressure of insect pest outbreaks due to changes in land-use, new climatic conditions, and the arrival of new invasive alien species. Also, insect outbreaks may interact with other shifting disturbances such as fire and drought, that eventually may boost the impacts of pests on forest ecosystems. In the case of alien species, the lack of long-term data and their rapid spread challenges their study and require appropriate new management strategies to cope with them. Here we studied the case of boxwoods (Buxus sempervirens) in Southern Pyrenees under the pressure of the invasive insect box tree moth (Cydalima perspectalis), fire, and drought events. We projected the future of boxwoods through the development of a spatially explicit simulation model and its implementation under different climatic and ecological scenarios. The results showed an initial boxwood decline due to C. perspectalis fast spread but a later stabilization of the population resulting from a fluctuating dynamic. Climate change is expected to reduce overall insect habitat suitability and future negative impacts on boxwoods. Furthermore, boxwood drought-induced mortality and burning will increase under new climatic conditions. Interaction between drought and insect pest conditioning regeneration after defoliation were negligible in our analyses. Boxwood decline was anticipated to be more notorious in locations under 800 m a.s.l. and in habitats where the species dominates the forest understory, while boxwood in open shrub forest types typical of higher elevations will be less endangered. Our results provide valuable information for boxwood and C. perspectalis management in a context of joint disturbance impacts and contribute to a better identification of the role of forest disturbances and their interactions.

Predicting the potential distribution and forest impact of the invasive species Cydalima perspectalis in Europe.

Invasive species have considerably increased in recent decades due to direct and indirect effects of ever-increasing international trade rates and new climate conditions derived from global change. We need to better understand how the dynamics of early species invasions develop and how these result in impacts on the invaded ecosystems. Here we studied the distribution and severe defoliation processes of the box tree moth (Cydalima perspectalis W.), a tree defoliator insect native to Asia and invasive in Europe since 2007, through the combination of species distribution models based on climate and landscape composition information. The results showed that the combination of data from the native and the invaded areas was the most effective methodology for the appropriate invasive species modeling. The species was not influenced by overall landscape factors, but only by the presence of its host plant, dispersal capacity, and climate suitability. Such climate suitability was described by low precipitation seasonality and minimum annual temperatures around 0°C, defining a continentality effect throughout the territory. We emphasize the need of studying distribution and severe defoliation processes separately because we identified that climate suitability was slightly involved in limiting species spread processes but strongly constrained ecosystem impact in terms of defoliation before the species reaches equilibrium with the new environment. New studies on habitat recovery after disturbance, ecological consequences of such impact, and community dynamics in a context of climate change are required for a better understanding of this invasive species.

Fire and biodiversity in the Anthropocene.

Fire has been a source of global biodiversity for millions of years. However, interactions with anthropogenic drivers such as climate change, land use, and invasive species are changing the nature of fire activity and its impacts. We review how such changes are threatening species with extinction and transforming terrestrial ecosystems. Conservation of Earth's biological diversity will be achieved only by recognizing and responding to the critical role of fire. In the Anthropocene, this requires that conservation planning explicitly includes the combined effects of human activities and fire regimes. Improved forecasts for biodiversity must also integrate the connections among people, fire, and ecosystems. Such integration provides an opportunity for new actions that could revolutionize how society sustains biodiversity in a time of changing fire activity.

Adapting prescribed burns to future climate change in Mediterranean landscapes.

Fire regimes are shifting or are expected to do so under global change. Current fire suppression is not able to control all wildfires, and its capability to do so might be compromised under harsher climate conditions. Alternative fire management strategies may allow to counteract predicted fire trends, but we lack quantitative tools to evaluate their potential effectiveness at the landscape scale. Here, we sought to quantify changes in fire regimes induced after the implementation of different fire management strategies. We developed and applied a new version of the model MEDFIRE in Catalonia (Mediterranean region of ~32,000 km2 in NE Spain). We first projected burnt area from 2016 to 2100 resulting from climate change under the Representative Concentration Pathway 8.5 scenario of HadGEM-CC model and under current fire suppression levels. We then evaluated the impacts of four fire management strategies: 'Let it burn', fixed effort of prescribed burning with two different spatial allocations, and adaptive prescribed burning dynamically adjusting efforts according to recent past fires. Results predicted the emergence of novel climates associated with similar barometric configurations to current conditions but with higher temperatures (i.e. hot wind events). These novel climates led to an increase in burnt area, which was partially counteracted by negative fire-vegetation feedbacks. All prescribed burning scenarios decreased the amount of high-intensity fires and extreme fire events. The 'Let it burn' strategy, although less costly, was not able to reduce the extent of high-intensity fires. The adaptive prescribed burning scenario resulted in the most cost-efficient strategy. Our results provide quantitative evidence of fire management effectiveness, and bring to light key insights that could guide the design of fire policies fit for future novel climate conditions. We propose adaptive landscape management focused on the reduction of fire negative impacts rather than on the elimination of this disturbance from the system.