Remote spatial analysis lacking ethnographic grounding mischaracterizes sustainability of Indigenous burning regime

Scientific research that purports to evaluate Indigenous fire regimes in the absence of ethnographically contextualized ecological data runs the risk of exacerbating the fire blame game and providing evidence to support distorted narratives advanced by anti-Indigenous advocates. Spatial analysis of fire scars in Indigenous territories can be an effective tool for characterizing cultural fire regimes in terms of distribution and frequency, especially when qualified by linkages to different local ecosystems. A recently published article drew on fire scar mapping from satellite imagery to assess anthropogenic fire distribution and frequency in the Pimentel Barbosa Indigenous Land, Central Brazil. The authors use their findings to characterize A'uwẽ (Xavante) use of fire as unmanaged and a model of unsustainable use of cerrado resources. In this article, we discuss Aguiar & Martins's recent paper in light of our long-term research on A'uwẽ hunting with fire in the Pimentel Barbosa Indigenous Land, arguing that A'uwẽ hunters do burn according to established cultural protocols, manage their use of fire for conservationist purposes, and do not cause environmental degradation by burning.

Contradictions and Continuities: A Historical Context to Euro-American Settlement Era Fires of the Lake States, USA.

BackgroundThe Lake States experienced unprecedented land use changes during Euro-American settlement (settlement) including large, destructive fires. Forest changes were radical in this region and largely attributed to anomalous settlement era fires in slash (cumulation of tops and branches) following cutover logging. In this study I place settlement era fires in a historical context by examining fire scar data in comparison to historical accounts and investigate fire-vegetation-climate relationships within a 400-year context.ResultsSettlement era fires (1851–1947) were less frequent than historical fires (1548–1850) with little evidence that slash impacted fire frequency or occurrence at site or ecoregion scales. Only one out of 25 sites had more frequent settlement era fires and that site was a pine forest that had never been harvested. Settlement era fires were similar across disparate ecoregions and forest types including in areas with very different land use history. Settlement fires tended to burn during significantly dry periods, the same conditions driving large fires for the past 400 years. The burned area in the October 8, 1871 Peshtigo Fire was comprised of mesic forests where fuels were always abundant and high-severity fires would be expected given the conditions in 1871. Furthermore, slash would not have been a major contributor to fire behavior or effects in the Peshtigo Fire.ConclusionsHistorical records, like written accounts of fires and settlement era survey records, provide a reference point for landscape changes but lack temporal depth to understand forest dynamics or provide a mechanistic understanding of changes. While settlement land use changes of Lake States forests were pervasive, fires were not the ultimate degrading factor, but rather likely one of the few natural processes still at work.

Effects of Wildfires and Ash Leaching on Stream Chemistry in the Santa Ynez Mountains of Southern California

Wildfires can change ecosystems by altering solutes in streams. We examined major cations in streams draining a chaparral-dominated watershed in the Santa Ynez Mountains (California, USA) following a wildfire that burned 75 km2 from July 8 to October 5, 2017. We identified changes in solute concentrations, and postulated a relation between these changes and ash leached by rainwater following the wildfire. Collectively, K+ leached from ash samples exceeded that of all other major cations combined. After the wildfire, the concentrations of all major cations increased in stream water sampled near the fire perimeter following the first storm of the season: K+ increased 12-fold, Na+ and Ca2+ increased 1.4-fold, and Mg2+ increased 1.6-fold. Our results suggested that the 12-fold increase in K+ in stream water resulted from K+ leached from ash in the fire scar. Both C and N were measured in the ash samples. The low N content of the ash indicated either high volatilization of N relative to C occurred, or burned material contained less N.

A Quantitative Graph-Based Approach to Monitoring Ice-Wedge Trough Dynamics in Polygonal Permafrost Landscapes

In response to increasing Arctic temperatures, ice-rich permafrost landscapes are undergoing rapid changes. In permafrost lowlands, polygonal ice wedges are especially prone to degradation. Melting of ice wedges results in deepening troughs and the transition from low-centered to high-centered ice-wedge polygons. This process has important implications for surface hydrology, as the connectivity of such troughs determines the rate of drainage for these lowland landscapes. In this study, we present a comprehensive, modular, and highly automated workflow to extract, to represent, and to analyze remotely sensed ice-wedge polygonal trough networks as a graph (i.e., network structure). With computer vision methods, we efficiently extract the trough locations as well as their geomorphometric information on trough depth and width from high-resolution digital elevation models and link these data within the graph. Further, we present and discuss the benefits of graph analysis algorithms for characterizing the erosional development of such thaw-affected landscapes. Based on our graph analysis, we show how thaw subsidence has progressed between 2009 and 2019 following burning at the Anaktuvuk River fire scar in northern Alaska, USA. We observed a considerable increase in the number of discernible troughs within the study area, while simultaneously the number of disconnected networks decreased from 54 small networks in 2009 to only six considerably larger disconnected networks in 2019. On average, the width of the troughs has increased by 13.86%, while the average depth has slightly decreased by 10.31%. Overall, our new automated approach allows for monitoring ice-wedge dynamics in unprecedented spatial detail, while simultaneously reducing the data to quantifiable geometric measures and spatial relationships.

Fire History (1896–2013) in an Abies religiosa Forest in the Sierra Norte of Puebla, Mexico

The oyamel forests, as Abies dominated forests are commonly known as, register their largest distribution (95% of their population) along the Trans-Mexican Volcanic Belt (TMVB). Although efforts have been made to study these forests with various approaches, dendrochronology-based studies have been limited, particularly in pure Abies forests in this region. The objective of this study was to reconstruct fire regimes in an Abies religiosa forest in the Sierra Norte in the state of Puebla, Mexico. Within an area of 50-ha, we collected 40 fire-scar samples, which were processed and analyzed using dendrochronological techniques to identify 153 fire scars. The fire history was reconstructed for a period of 118 years (1896–2013), with low severity surface fires occurring mainly during in the spring (92.8%) and summer (7.2%). Over the past century, fires were frequent, with an mean fire interval (MFI) and Weibull median probability of (WMPI) of five years when considering all fire scars and less than 10 years for fires covering larger areas (fires recorded by ≥25% of samples). Extensive fires were synchronized with drought conditions based on Ring Width Indexes, Palmer Drought Severity Index (PDSI) and El Niño Southern Oscillation (ENSO). After 1983, we observed a change in fire frequencies attributed to regulated management. Longer fire intervals within the last several decades are likely leading to increased fuel accumulations and could potentially result in more severe fires in the future, threatening the sustainability of these forests. Based on our finding, we recommend management actions (silvicultural or prescribed fire) to reduce fuels and the risk of severe fires, particularly in the face of climatic changes.

Thaw subsidence and frost heave caused by 2018-20 forest fires around Batagay: validation with multiple InSAR data and field observation

<p>The Arctic has experienced numerous fires in last year, and from June to August 2020, satellite data showed record carbon dioxide emissions from forest fires. Peatland in the Arctic contains large amounts of organic carbon, and their release into the atmosphere can create positive feedbacks for further increase of air temperature. In addition, forest fires burn the surface vegetation layer that has been acting as a heat insulator, which will accelerate the thawing of permafrost on scales of years to decades. Although the thaw depth can recover together with the recovery of surface vegetation, the massive segregated ice is not recoverable once it melted. Our study area is around the Batagay, Sakha Republic, Eastern Siberia. In June 2020, Verkhoyansk, located about 55 km west of Batagay, recorded the highest daily maximum temperature of 38.0 degrees Celcius. The Sentinel-2 optical satellite images showed a number of forest fires in 2019-20. We detected the surface deformation signals at each fire site with the remote-sensing method called InSAR (Interferometric Synthetic Aperture Radar). Also, we conducted a field observation in September 2019 for validations: 1) installed a soil thermometer and soil moisture meter; 2) established a reference point for leveling and first survey; 3) measured the thawing depth with a frost probe.</p><p> For seasonal ground deformations immediately after the fire, we mainly analyzed Sentinel-1 images. Sentinel-1 is the ESA's C-band SAR satellite, which has a short imaging interval of 12 days. As the short wavelength, vegetation changes lost coherence, and some pairs failed to detect ground deformation signals immediately after the fire. However, after the end of September, we detected displacements toward the satellite line-of-sight direction at all the fire sites. It indicates uplift signals due presumably to frost heave at the fire scar. For long-term deformations over one year, we used ALOS2 imaged derived by JAXA's L band SAR satellite. In the previous studies in Alaska, the ground deformation signal immediately after a fire could not be detected due to the coherence loss in the pairs derived from pre-fire and post-fire SAR images. Indeed, we could not detect deformation signals at the fire scars from the June pairs derived before and after the fire. However, the January pairs and March pairs, both of which were acquired before and after the fire, showed relatively high coherence even in the fire scar and indicated clear subsidence signals by as much as 15 cm. We interpret that, because the studied Verkhoyansk Basin is very dry and has little snow cover, the microwaves could penetrate the snow layer, which allowed us to detect deformation signals even in winter. Yanagiya and Furuya (2020) validated the consistency of the winter uplift signal for the 2014 fire site. We also analyzed the SM1 high spatial resolution mode (3 m) ALOS2 InSAR to investigate the specific ground deformation at each fire site.</p>

Unveiling the diversity of regional burning patterns at the Brazilian savanna

<p>Fire is an integral and predictable component of ecological functioning and dynamics in fire-prone biomes. However, the relationships and potential feedback between fire and its drivers are complex, as they depend on the temporal and spatial scales adopted when analyzing the fire regime. A remote sensing approach allows the characterization of fire regimes with larger spatial coverage and temporal homogeneity, especially where fire records are rare, as in the Brazilian savannas (Cerrado). The Cerrado is a mosaic of soil types and topographic settings, with varying regional climate patterns, resulting in a variety of fire resistant/sensitivity vegetation types, and recent disturbances, mostly due to increasing economic and agricultural development, along with changes in climate, are disrupting its natural fire patterns. Most studies characterizing fire activity in Cerrado are either performed at the biome-level or focus on very specific locations with results then extrapolated over the whole biome, which may mask important regional patterns. Here, we aim to characterize the regional fire patterns into the Cerrado’s 19 ecoregions, previously defined based on biophysical parameters which do not include fire. </p><p>We use burned area (BA), fire radiative power and individual fire scar data based on MODIS products (respectively, MCD64A1, MCD14ML and Global Fire Atlas) to evaluate inter and intra annual cycles, spatial anomalies and trends of BA, fire intensity and fire size (small fires: <1000ha, medium: 1000-5000ha and large fires: >5000ha) in each ecoregion from 2001 to 2019. </p><p>Our results show a marked north-south BA gradient, with higher annual BA contributions from the northern ecoregions. These ecoregions are mainly located in the latest agricultural frontier, MATOPIBA, where there are more vegetation remnants that are under high anthropogenic pressure due to recent economic development. Conversely, ecoregions showing low BA are highly fragmented and  have been historically deforested for longer periods. Most fires are of low intensity and higher intensity fires occur towards the end of the dry season period (June to October). Moreover, there are considerable differences in extremely intense events, especially in the eastern ecoregions. We also found that temporal and spatial patterns are highly variable, depending on fire scars size. Infrequent medium and large scars account for most of BA compared to common very small and small scars. Overall, fire seasonality varies substantially depending on fire size class: larger scars occur over a 2-month period within the dry season, whereas the remaining classes are increasingly scattered along the year. BA is increasing and fire intensity decreasing over MATOPIBA’s ecoregions, while in southern ecoregions, is the opposite, with a decreasing over BA and an increase of fire intensity. Smaller scars are overall decreasing, whereas medium and larger scars show positive trends over central and northern ecoregions. </p><p>This study highlights the importance of understanding the diversity of fire dynamics in Cerrado to better inform and prepare refined-scale fire management strategies in light of current regional ecosystem disturbances and future climate change. </p><p>The study was funded by CNPQ (grant 441971/2018-0) and P. S. Silva is supported by FCT (grant SFRH/BD/146646/2019).</p>

Impact of land management on fire resilience and carbon fate in blanket bogs: The FireBlanket project

<p>Maintenance and enhancement of peatland carbon storage is a major policy objective towards meeting greenhouse gas (GHG) targets. Management interventions can influence both the storage capacity and the vulnerability of the stock to climate-change induced increases in drought frequency and severity, and incidence of wildfires. Quantification of these interactions is vital in informing best management practice, but is also challenging, given the ephemeral nature of climatic extremes and the usual paucity of high-quality ground-based observations within an area of interest capable of providing the necessary pre-impact and control data.</p><p>Following a dry and warm spell in spring 2019, a large wildfire burnt approximately >60 km<sup>2</sup> of blanket bog and wet heath within the Flow Country peatlands of Caithness and Sutherland, North Scotland. While the Flow Country is a site of global significance currently under consideration for UNESCO World Heritage Site Status, it has also been substantially modified in places by drainage and notably forestry (670 km<sup>2</sup>) and is now undergoing rapid and large-scale restoration. Serendipitously, the fire scar impacted the whole range of land-uses and occurred in an area actively used for research, and therefore where some baseline datasets were available.</p><p>The NERC funded FireBlanket project used this opportunity to investigate how land-uses interacted with wildfire in terms of 1) InSAR-derived “bog breathing” patterns exhibited during the 2018 drought 2) immediate and longer-term effects on vegetation communities 3) export and fate of organic carbon from land to ocean. By understanding how different management strategies of forestry and forest-to-bog restoration influence fire risk and damage, we hope to inform decision-making in the future.</p><p>Our preliminary results show that in near-natural and restored (drain-blocked) blanket bogs, the drought of 2018 led to a rapid surface compression that maintained near-surface moisture until 2019, in turn reducing the severity of the wildfire. In drained and degraded blanket bogs, this mechanical feedback is absent, due to higher bulk density and differences in vegetation assemblages, notably reduced cover of Sphagnum mosses. In those areas, the 2018 drought led to a rapid and sustained loss of moisture in the upper peat layers, associated with higher burn severity and more pronounced fire damage on vegetation. Furthermore, while DOM concentrations increased post-fire in streams receiving water from all burnt areas compared to unburnt ones, the changes were more pronounced in catchments with man-made drains.</p><p>Whilst further data processing and analysis is still underway, our study currently suggests that restoration is likely to increase wildfire resilience and reduce wildfire severity. When taking management decisions at the landscape scale, strategic re-wetting around vulnerable areas (e.g. highly degraded or undergoing forest-to-bog management leading to large volumes of brash on the ground) may help reduce the risks of occurrence of large catastrophic wildfires, and help minimise the carbon losses associated with these events.</p>

Fire-scarred fossil tree from the Late Triassic shows a pre-fire drought signal

Exploring features of wood anatomy associated with fire scars found on fossil tree trunks is likely to increase our knowledge of the environmental and ecological processes that occurred in ancient forests and of the role of fire as an evolutionary force. In Petrified Forest National Park, Arizona, where Late Triassic fossil trees are exposed, we found 13 examples of fossil logs with external features resembling modern fire scars. One specimen with the unambiguous external features of a fire scar was collected for analysis of its fossilized wood. A light-colored band composed of compressed and distorted tracheids was associated with the scarring event. Cell lumen diameter and cell wall thickness in the pre-scarring fossilized wood show a response similar to that described in modern trees experiencing drought conditions. Tracheids in the post-scarring wood are initially smaller, and then become larger than average following a recovery period, as is often observed in modern conifers following fire. The responses in external morphology and wood anatomy to drought and fire were similar to those of some modern trees and support the view that some forests may have experienced conditions favoring the evolution of fire-adapted traits for more than 200 million years.