Despite years of accumulating scientific evidence that fire is critical for maintaining the structure and function of grassland ecosystems in the US Great Plains, fire has not been restored as a fundamental grassland process across broad landscapes. The result has been widespread juniper encroachment and the degradation of the multiple valuable ecosystem services provided by grasslands. Here, we review the social–ecological causes and consequences of the transformation of grasslands to juniper woodlands and synthesize the recent emergence of prescribed burn cooperatives, an extensive societal movement by private citizens to restore fire to the Great Plains biome. We discuss how burn cooperatives have helped citizens overcome dominant social constraints that limit the application of prescribed fire to improve management of encroaching woody plants in grasslands. These constraints include the generally held assumptions and political impositions that all fires should be eliminated when wildfire danger increases.

Grasslands are the most threatened and least protected biome. Yet, no study has been conducted to identify the last remaining continuous grasslands on Earth. Here, we used World Wildlife Fund (WWF) and International Union for Conservation of Nature (IUCN) classifications to measure the degree of intactness remaining for the world's grassland ecoregions. This analysis revealed three findings of critical conservation importance. First, only a few large, intact grasslands remain. Second, every continent with a grassland ecoregion considered in this study contains at least one relatively intact grassland ecoregion. Third, the largest remaining continuous grasslands identified in this analysis have persisted despite last centuries anthropogenic pressures and have the best chance to withstand 21st century pressures of global change. We discuss how these regions are of critical conservation importance to global grassland conservation efforts under anthropogenically driven global change. They provide essential ecosystem services, play an important role in mitigating the effects of climate change, serve as critical repositories for grassland biodiversity, are foundational for continental migration pathways, hold unique cultural heritage, and people's livelihoods depend upon their persistence.

Summary: Restoration priorities are typically established without quantitative information on how to overcome the thresholds that preclude successful restoration of desirable ecosystem properties and services. We seek to demonstrate that quantifying ecological thresholds and incorporating them into management‐oriented frameworks provide a more comprehensive perspective on how the threshold concept can be applied to achieve restoration goals. As an example, restoration actions have been largely unsuccessful when based on prevailing ecological knowledge of fire‐based thresholds in nonresprouting Juniperus woodland. We build on previous threshold‐based research and link well‐established models from applied fire physics with a widely applied ecological positive feedback model of woody plant encroachment to introduce a more comprehensive understanding of the mechanism influencing fire intensity and juniper mortality. Our coupling of physical and ecological fire models revealed a critical knowledge gap, a lack of a quantitative estimate on the critical surface fire intensity required to cause mortality of Juniperus ashei trees, which limits the linking of scientific knowledge from these two disciplines. To quantify the relationship between fire intensity and J. ashei mortality, we input data from a previous experiment into Byram's fireline intensity model. This critical surface fire intensity–mortality threshold was estimated to be I_s > 160 kJ m⁻¹ s⁻¹. This value establishes a specific threshold that managers should target when attempting to use restoration to collapse J. ashei woodlands. Synthesis and applications. For scientific information associated with the threshold concept to be useful to practitioners, specific information is needed that demonstrates how to use restoration activities to overcome thresholds and collapse the current, degraded state in favour of a more desired ecological state. With this in mind, we present a broadly applicable decision support model within a state and transition framework that identifies the ecological states where the surface fire intensity–mortality threshold is most likely to meet restoration objectives and provides examples of how fuel properties that drive fire intensity should be targeted in restoration to surpass this threshold.