Early‐successional forest ecosystems that develop after stand‐replacing or partial disturbances are diverse in species, processes, and structure. Post‐disturbance ecosystems are also often rich in biological legacies, including surviving organisms and organically derived structures, such as woody debris. These legacies and post‐disturbance plant communities provide resources that attract and sustain high species diversity, including numerous early‐successional obligates, such as certain woodpeckers and arthropods. Early succession is the only period when tree canopies do not dominate the forest site, and so this stage can be characterized by high productivity of plant species (including herbs and shrubs), complex food webs, large nutrient fluxes, and high structural and spatial complexity. Different disturbances contrast markedly in terms of biological legacies, and this will influence the resultant physical and biological conditions, thus affecting successional pathways. Management activities, such as post‐disturbance logging and dense tree planting, can reduce the richness within and the duration of early‐successional ecosystems. Where maintenance of biodiversity is an objective, the importance and value of these natural early‐successional ecosystems are underappreciated.

Roads fragment landscapes and trigger human colonization and degradation of ecosystems, to the detriment of biodiversity and ecosystem functions. The planet's remaining large and ecologically important tracts of roadless areas sustain key refugia for biodiversity and provide globally relevant ecosystem services. Applying a 1-kilometer buffer to all roads, we present a global map of roadless areas and an assessment of their status, quality, and extent of coverage by protected areas. About 80% of Earth's terrestrial surface remains roadless, but this area is fragmented into ~600,000 patches, more than half of which are <1 square kilometer and only 7% of which are larger than 100 square kilometers. Global protection of ecologically valuable roadless areas is inadequate. International recognition and protection of roadless areas is urgently needed to halt their continued loss.

Summary 1.The earliest examples of alternative community states in the literature appear to be descriptions of natural vegetation said to both depend on and promote fire. Nonetheless, alternative community states determined by fire have rarely been documented at landscape scales and in natural vegetation. This is because spatial autocorrelation may confound analyses, experimental manipulations are difficult and a long-term perspective is needed to demonstrate that alternative community states can persist for multiple generations. 2. We hypothesized that alternative community states occur in a largely forested landscape in the Klamath Mountains, north-western California, USA, where shrub-dominated sclerophyllous vegetation establishes after fire that is lethal to forests. Forests redevelop if succession is not arrested by fire. Our hypothesis would require that sclerophyll and forest vegetation states each be maintained by different self-reinforcing relationships with fire. 3. To test this hypothesis, we examined pyrogenicity of forest and sclerophyll vegetation as a function of time since the previous fire, accounting for spatial autocorrelation. Fire exclusion served as a de facto experimental treatment. Areas where fire had proceeded to occur served as controls. 4. Our findings are consistent with the occurrence of alternative community states established and maintained by different self-reinforcing feedbacks with fire. Sclerophyll vegetation was more pyrogenic, especially where time-since-fire (TSF) was relatively short, a favourable relationship for this fire-dependent vegetation. Forests were much less pyrogenic, especially where TSF was long, favouring their maintenance. Fire exclusion therefore has led to afforestation and rapid retreat of fire-dependent vegetation. 5. Synthesis: We have documented how different self-reinforcing combustion properties of forest and sclerophyll vegetation can naturally produce alternative states coexisting side-by-side in the same environment. Such fire-mediated alternative states may be underappreciated, in part, because they are difficult to demonstrate definitively. In addition, the dynamics they exhibit contrast with common perceptions that fire hazard increases deterministically with TSF in forests and shrublands. Addressing the impacts of fire exclusion will probably require a management shift to better allow fire to perform its ecological role in shaping landscape diversity and maintaining firedependent biota.