Fire is an integral component of ecosystems globally and a tool that humans have harnessed for millennia. Altered fire regimes are a fundamental cause and consequence of global change, impacting people and the biophysical systems on which they depend. As part of the newly emerging Anthropocene, marked by human-caused climate change and radical changes to ecosystems, fire danger is increasing, and fires are having increasingly devastating impacts on human health, infrastructure, and ecosystem services. Increasing fire danger is a vexing problem that requires deep transdisciplinary, trans-sector, and inclusive partnerships to address. Here, we outline barriers and opportunities in the next generation of fire science and provide guidance for investment in future research. We synthesize insights needed to better address the long-standing challenges of innovation across disciplines to (i) promote coordinated research efforts; (ii) embrace different ways of knowing and knowledge generation; (iii) promote exploration of fundamental science; (iv) capitalize on the “firehose” of data for societal benefit; and (v) integrate human and natural systems into models across multiple scales. Fire science is thus at a critical transitional moment. We need to shift from observation and modeled representations of varying components of climate, people, vegetation, and fire to more integrative and predictive approaches that support pathways toward mitigating and adapting to our increasingly flammable world, including the utilization of fire for human safety and benefit. Only through overcoming institutional silos and accessing knowledge across diverse communities can we effectively undertake research that improves outcomes in our more fiery future.

Aims: We attempt to review the conceptualisation, science and classification of biomes and propose to limit the definition of a biome to potential natural vegetation as determined by general environmental variables.Results: Classifying the distribution and abundance of vegetation types on earth has been a central tenet of vegetation science since Humboldt’s classic studies in the early 1800s. While the importance of such classifications only grows in the wake of extreme changes, this review demonstrates that there are many fundamentally different approaches to define biomes, hitherto with limited efforts for unifying concepts among disciplines. Consequently, there is little congruence between the resulting maps, and widely used biome maps fail to delimit areas with consistent climate profiles.Conclusions: Gaps of knowledge are directly related to research avenues, and suggestions for defining and classifying biomes, as well as modelling their distributions, are provided. These suggestions highlight the primary importance of the climate, argue against using anthropogenic drivers to define biomes and stabilize the concept of biome to escape from the current polysemy. The last two decades have seen an emergence of new approaches, e.g., using satellite imagery to determine growth patterns of vegetation, leading to defining biomes based on the objective, observable qualities of the vegetation based on current reality.

Aspen forests and woodlands are some of the most species‐rich forest communities in the northern hemisphere. Changing climate, altered disturbance regimes, land use, and increased herbivore pressure threaten these forests both in Eurasia and North America. In addition, rapid mortality dubbed “Sudden Aspen Decline” is a concern for aspen's long‐term presence in the western United States, especially Colorado and Utah. Yet it is still unclear whether aspen is persistent or declining at the landscape scale. We assessed aspen persistence at different spatial scales in the Colorado Front Range by resampling 89 plots containing aspen from among 305 vegetation plots sampled by Robert Peet during 1972–1973. We hypothesized that aspen density and basal area had decreased at the landscape scale, with notable variability in change depending on the forest community type, and that this overall decrease has been more pronounced at lower elevations. We also assessed elevational range shifts of the major species in these forests. Aspen were no longer present in 22 of the 89 plots and aspen density for stems less than 2.5 cm diameter at breast height (DBH) had declined significantly overall, although density of medium (2.5–10 cmDBH) and large (>10 cmDBH) trees, as well as basal area, had not changed significantly. A comparison between montane (<2700 m elevation) and subalpine (2700–3500 m elevation) plots revealed that the decrease was more pronounced at higher elevations and was mostly the result of substantial decreases of stems in the eleven plots that were part of Peet's aspen‐dominated “Populus tremuloidesseries.” In these plots, aspen basal area decreased significantly whereas basal area ofAbies bifolia,Picea engelmannii,Pinus contorta, andPseudotsuga menziesiiincreased substantially. Upslope shifts were observed for most species, especially on northeast facing slopes, suggesting climate‐related responses. In summary, aspen have been resilient in mixed forests and may be beneficiaries of recent bark beetle epidemics, but have decreased and been subject to successional transitions in previously aspen‐dominated stands. Our results confirm the importance of region‐specific, multiple‐scale assessments of species persistence to make best management recommendations.