Ladder fuels rather than canopy volumes consistently predict wildfire severity even in extreme topographic-weather conditions
Year: 2024
Type: article
Abstract: Drivers of forest wildfire severity include fuels, topography and weather. However, because only fuels can be actively managed, quantifying their effects on severity has become an urgent research priority. Here we employed GEDI spaceborne lidar to consistently assess how pre-fire forest fuel structure affected wildfire severity across 42 California wildfires between 2019-2021. Using a spatial-hierarchical modeling framework, we found a positive concave-down relationship between GEDI-derived fuel structure and wildfire severity, marked by increasing severity with greater fuel loads until a decline in severity in the tallest and most voluminous forest canopies. Critically, indicators of canopy fuel volumes (like biomass and height) became decoupled from severity patterns in extreme topographic and weather conditions (slopes >20°; winds > 9.3 m/s). On the other hand, vertical continuity metrics like layering and ladder fuels more consistently predicted severity in extreme conditions - especially ladder fuels, where sparse understories were uniformly associated with lower severity levels. These results confirm that GEDI-derived fuel estimates can overcome limitations of optical imagery and airborne lidar for quantifying the interactive drivers of wildfire severity. Furthermore, these findings have direct implications for designing treatment interventions that target ladder fuels versus entire canopies and for delineating wildfire risk across topographic and weather conditions.
Authors: Christopher R. Hakkenberg, Matthew L. Clark, Tim Bailey, Patrick Burns, Scott J. Goetz
Institutions: Northern Arizona University, Sonoma State University
Language: English
Topic: Fire effects on ecosystems
Subfield: Global and Planetary Change
Field: Environmental Science
Domain: Physical Sciences
SDGs: Life on land, Climate action
Open Access status: gold
Estimated APC paid: $3,290
Awards: G5567820535, MORE COMPREHENSIVE MAPPING OF EARTH S BIODIVERSITY IS A PRIORITY TO HELP PREVENT FURTHER BIOTIC IMPOVERISHMENT AND MAINTAIN ECOSYSTEM FUNCTIONS AND SERVICES. INTERGOVERNMENTAL ORGANIZATIONS NATIONAL GOVERNMENTS AND NON-GOVERNMENTAL ORGANIZATIONS HAVE DEVELOPED NUMEROUS APPROACHES TO MAP AND MONITOR BIODIVERSITY PRIORITIES AND TO REPORT ON STATUS AND TRENDS IN BIODIVERSITY. THE GROUP ON EARTH OBSERVATIONS BIODIVERSITY OBSERVATION NETWORK (GEO BON) A FLAGSHIP GEO PROGRAM HAS BEEN AT THE FOREFRONT OF EFFORTS TO COORDINATE AND DELIVER THIS BIODIVERSITY INFORMATION TO NATIONAL GOVERNMENTS RESEARCHERS AND OTHER GROUPS WITH AN INTEREST IN CONSERVING BIODIVERSITY. THE ESSENTIAL BIODIVERSITY VARIABLE FRAMEWORK (EBV) AND THE BON IN A BOX TOOL ARE TWO OF GEO BON S PRIMARY VEHICLES FOR ORGANIZING AND DELIVERING TECHNICAL INFORMATION TO ITS PARTICIPANTS. IN ADDITION TO GLOBAL EFFORTS GEO BON FACILITATES NATIONAL AND REGIONAL BONS. COLOMBIA WITH OVERSIGHT FROM THE COLOMBIAN MINISTRY OF ENVIRONMENT AND ASSISTANCE FROM GEO BON IS CURRENTLY DEVELOPING ITS NATIONAL FRAMEWORK FOR BIODIVERSITY OBSERVATIONS. COLOMBIA S INSTITUTO DE INVESTIGACI N DE RECURSOS BIOL GICOS ALEXANDER VON HUMBOLDT (IAVH) A NON-REGULATORY GOVERNMENT RESEARCH INSTITUTE IS PRIMARILY RESPONSIBLE FOR DEVELOPING THE FRAMEWORK. IAVH IS MAKING PROGRESS ON MULTIPLE FRONTS INCLUDING DEVELOPMENT OF THE BIOMODELOS APPLICATION WHICH INFORMS THE SPECIES POPULATIONS EBV. HOWEVER DEVELOPMENT OF A HABITAT STRUCTURE EBV IS STILL NEEDED AND WOULD MAKE A VALUABLE ADDITION TO COLOMBIA S NATIONAL BIODIVERSITY OBSERVATION FRAMEWORK. HABITAT STRUCTURE IS ONE OF SIX EBV CLASSES DEFINED IN THE EBV FRAMEWORK AND HAS BEEN HIGHLIGHTED AS A PRIORITY FOR MAPPING FROM SPACE. ALTHOUGH EARTH OBSERVATIONS HAVE GREATLY INCREASED OUR UNDERSTANDING OF EARTH S ECOSYSTEMS OVER THE PAST SEVERAL DECADES ESPECIALLY THE HORIZONTAL DISTRIBUTION OF FORESTS AND OTHER MAJOR VEGETATION TYPES WE STILL LACK PRECISE MEASUREMENTS OF VERTICAL HABITAT STRUCTURE AND ITS DISTRIBUTION FOR LARGE AREAS. LIDAR DATA FROM NASA S GLOBAL ECOSYSTEM DYNAMICS INVESTIGATION (GEDI) WHICH IS CURRENTLY UNDERWAY WILL SIGNIFICANTLY ENHANCE HABITAT STRUCTURE INFORMATION AVAILABLE FOR LARGE FRACTIONS OF THE EARTH S FORESTS. BECAUSE OF ITS SAMPLING DENSITY (~15 BILLION SAMPLES OVER ITS TWO YEAR LIFESPAN) AND FOOTPRINT SIZE (~25 M DIAMETER) IT WILL DO SO WITH HIGH PRECISION AND AT SCALES COMMENSURATE WITH IN-SITU BIODIVERSITY OBSERVATIONS AND MODERATE RESOLUTION OPTICAL SENSORS SUCH AS LANDSAT AND SENTINEL. THUS GEDI CAN SERVE AS A FOUNDATION FOR GLOBAL AND NATIONAL LEVEL HABITAT STRUCTURE EBVS. TO BUILD ON COLOMBIA S ACTIVE INVOLVEMENT IN GEO BON AND LEVERAGE NEW HABITAT STRUCTURE INFORMATION PROVIDED BY GEDI WE PROPOSE TO DEVELOP A CUTTING EDGE LIDAR BASED HABITAT STRUCTURE METRIC AS A GEO BON ESSENTIAL BIODIVERSITY VARIABLE (EBV) APPLICATION. OUR PRIMARY OBJECTIVES ARE TO: 1) DEVELOP A CONSISTENT AND SCALABLE WORKFLOW THAT USES SPACEBORNE LIDAR MEASUREMENTS TO PROVIDE HIGH PRECISION ESTIMATES OF THE EXTENT AND DISTRIBUTION OF FOREST STRUCTURAL TYPES ESTABLISHING BASELINES FOR SUBNATIONAL NATIONAL AND INTERNATIONAL BIODIVERSITY TARGETS AND REPORTING REQUIREMENTS. 2) WORK WITH IAVH TO INCORPORATE EBV DATA AND WORKFLOWS INTO COLOMBIA S BIODIVERSITY OBSERVATION FRAMEWORK. THE PROPOSED WORK WILL CONTRIBUTE TO THE GEO WORK PLAN BY SUPPORTING THE EFFORTS OF GEO BON TO LEVERAGE EARTH OBSERVATIONS FOR DEVELOPMENT AND IMPLEMENTATION OF A FOREST STRUCTURE EBV THAT DESCRIBES AND QUANTIFIES FOREST VERTICAL STRUCTURE ACROSS ECOSYSTEMS., G7656097817
OpenAlex ID: W4404538815