Climate change is altering species’ range limits and transforming ecosystems. For example, warming temperatures are leading to the range expansion of tropical, cold-sensitive species at the expense of their cold-tolerant counterparts. In some temperate and subtropical coastal wetlands, warming winters are enabling mangrove forest encroachment into salt marsh, which is a major regime shift that has significant ecological and societal ramifications. Here, we synthesized existing data and expert knowledge to assess the distribution of mangroves near rapidly changing range limits in the southeastern USA. We used expert elicitation to identify data limitations and highlight knowledge gaps for advancing understanding of past, current, and future range dynamics. Mangroves near poleward range limits are often shorter, wider, and more shrublike compared to their tropical counterparts that grow as tall forests in freeze-free, resource-rich environments. The northern range limits of mangroves in the southeastern USA are particularly dynamic and climate sensitive due to abundance of suitable coastal wetland habitat and the exposure of mangroves to winter temperature extremes that are much colder than comparable range limits on other continents. Thus, there is need for methodological refinements and improved spatiotemporal data regarding changes in mangrove structure and abundance near northern range limits in the southeastern USA. Advancing understanding of rapidly changing range limits is critical for foundation plant species such as mangroves, as it provides a basis for anticipating and preparing for the cascading effects of climate-induced species redistribution on ecosystems and the human communities that depend on their ecosystem services.

Prescribed fire is an important land conservation tool to meet ecological, cultural, and public safety objectives across terrestrial ecosystems. While estimates of prescribed burning in the U.S.A. exceed 4.5 million hectares annually, tracking the extent of prescribed fire is problematic for several reasons and prevents an understanding of spatial and temporal trends in landscape patterns of prescribed fires. We developed a regional prescribed fire database from 12 state forestry agencies in the southeastern U.S. using records of burn location, size, and calendar days and evaluated spatial and temporal patterns in burning from 2010 to 2020. Over half of all prescribed fires in the U.S. occur in the Southeast, with five states (Florida, Georgia, Alabama, South Carolina, and Mississippi) comprising over ninety percent of the burned area over a decade. We identified hot spots of concentrated prescribed fire activity on both public and private forestlands across the region, as well as regions of less burning, which often occurred in close proximity to hot spots. Temporally, most prescribed fires occurred in March and February across the region; the least activity was recorded between May and November. Our database reveals that burning is highly concentrated within the region, presumably reflecting local land ownership categories and associated land management objectives. This database and these analyses provide the first region-wide summary of fine-scale patterns of prescribed fire in the U.S. and demonstrate the potential for various analyses beyond this work for air quality modeling and remote sensing, as well as the potential impacts of demographic and land use changes.

Wildfires are integral for western US forests that have evolved with fire. Here we define “good wildfire” as areas that burn in an ecologically beneficial way, with a severity and return interval analogous to their historical fire regimes prior to European settlement. When severities match what an ecosystem historically experienced they can regulate forest structure while promoting regeneration, even in a warming climate ¹ . We quantified the amount of forested area (i.e., deciduous, conifer, or mixed forest types) burned with a severity and frequency matching its regime, and compared that to the area of prescribed burns in forests (2010-2020). Of forests that burned in the western US, 49% of the area burned as low-moderate severity good wildfire. High severity good wildfire (in systems that historically experienced this type of fire) represented an additional 9% of forest area burned, bringing the total area of good wildfire to 58% of forested area burned. The low-moderate severity good wildfires burned 3.1 million forest ha (N = 18,061 events), more than double the 1.4 million ha of prescribed burning (N = 24,817 events on federal land) over the same period. Knowing that fires are likely going to increase in frequency and area with warming ² , our key challenge will be promoting good wildfire while still protecting lives and property.