Long-term developments in carbon dioxide emissions have tracked the middle of projected emission scenario ranges over the past three decades. If this tendency continues, it seems increasingly less likely that future emissions will follow current high-emission scenarios. However, in the past, periods of slow and fast global emissions growth was observed, which have led to previous critiques of scenarios being too low or too high. In the light of such unpredictability and since scenarios are meant to explore plausible futures, we here argue that a broad range of emission scenarios continue to be considered input in scenario-based analyses of future climate change. Furthermore, we find substantial regional differences in emissions trends. Territorial emissions in OECD countries fall on the low side of emission scenario ranges, whereas non-OECD territorial emissions fell closer to the medium or high-end. Since non-OECD emissions will become increasingly important, we recommend further exploring the relationships between regional and global emissions to support scenario assumptions and climate policymaking.

The impacts of wildfires are increasing in the Mediterranean Basin due to more extreme fire seasons featuring increasingly fast and high-intensity fires, which often overwhelm the response capacity of fire suppression forces. Fire behaviour is expected to become even more severe due to climate change. In this study, we quantified the effect of climate change on fire danger (components of the Canadian FWI System) and wildfire behaviour characteristics (rate of spread and fireline intensity) for the four major Mediterranean forest ecosystems located in the Transboundary Biosphere Reserve of Meseta Ibérica under RCP4.5 and RCP8.5 scenarios. The effect of climate change on wildfire behaviour was supplemented by taking into account net primary production (NPP), hence fuel load. Our results show that the meteorological fire season will start earlier and end later, leading to a significant increase in the number of days with weather conditions that promote high-intensity wildfires, for both climate scenarios. Fuel type shapes how wildfire spread characteristics will unfold. The most relevant changes are projected to occur in pine forests, where a wildfire with median fireline intensity will offer serious resistance to control from spring to autumn. The severity of fire behaviour in shrublands also increases substantially when considering climate change, with high-intensity wildfires potentially occurring in any time of the year. Both deciduous and evergreen broadleaf forests are predicted to typically generate wildfires with low enough intensity to remain within suppression capability. By adjusting fuel load to future climate conditions, our results highlight that fireline intensity in deciduous and evergreen broadleaf forests may not increase during summer, and can even be significantly reduced in shrublands. This study suggests that improved fire planning and management of wildfire-prone landscapes will counteract the effect of climate change on fire behaviour and impacts.

This study aims to assess wildfire hazard in northern Portugal by combining landscape-scale wildfire spread modeling and connectivity analysis to help fuel management planning. We used the Minimum Travel Time (MTT) algorithm to run simulations under extreme (95th percentile) fire weather conditions. We assessed wildfire hazard through burn probability, fire size, conditional flame length and fire potential index wildfire descriptors. Simulated fireline intensity (FLI) using historical fire weather conditions were used to build landscape networks and assess the impact of weather severity in landscape wildfire connectivity (Directional Index of Wildfire Connectivity, DIWC). Our results showed that 27 % of the study area is likely to experience high-intensity fires and 51 % of it is susceptible to spread fires larger than 1000 ha. Furthermore, the increase in weather severity led to the increase in the extent of high-intensity fires and highly connected fuel patches, covering about 13 % of the landscape in the most severe weather. Shrublands and pine forests are the main contributors for the spread of these fires, and highly connected patches were mapped. These are candidates for targeted fuel treatments. This study contributes to improving future fuel treatment planning by integrating wildfire connectivity in wildfire management planning of fire-prone Mediterranean landscapes.

Methods and models to design, prioritize and evaluate fuel break networks have potential application in many fire-prone ecosystems where major increases in fuel management investments are planned in response to growing incidence of wildfires. A key question facing managers is how to scale treatments into manageable project areas that meet operational and administrative constraints, and then prioritize their implementation over time to maximize fire management outcomes. We developed and tested a spatial modeling system to optimize the implementation of a proposed 3,538 km fuel break network and explore tradeoffs between two implementation strategies on a 0.5 million ha national forest in the western US. We segmented the network into 2,766 treatment units and used a spatial optimization model to compare linear versus radial project implementation geometries. We hypothesized that linear projects were more efficient at intercepting individual fire events over larger spatial domains, whereas radial projects conferred a higher level of network redundancy in terms of the length of the fuel break exposed to fires. We simulated implementation of the alternative project geometries and then examined fuel break-wildfire spatial interactions using a library of simulated fires developed in prior work. The results supported the hypothesis, with linear projects exhibiting substantially greater efficiency in terms of intercepting fires over larger areas, whereas radial projects had a higher interception length given a fire encountered a project. Adding economic objectives made it more difficult to obtain alternative project geometries, but substantially increased net revenue from harvested trees. We discuss how the model and results can be used to further understand decision tradeoffs and optimize the implementation of planned fuel break networks in conjunction with landscape conservation, protection, and restoration management in fire prone regions.