Work

Short‐Interval Fire and Climatic Drying Drive Shrubland‐to‐Herbaceous Conversion Across California

Year: 2026

Type: article

Abstract: ABSTRACT One of the most profound ecological consequences of rapid global change is abrupt vegetation type conversion (VTC) from one life form to another. Using fractional vegetation cover from 1986 and 2024, we quantified statewide change in non‐forested vegetation across California regions and modeled drivers of shrubland to herbaceous conversion with stepwise logistic regression and gradient‐boosted trees. Across most regions, we found a clear trajectory toward increased herbaceous cover and reduced shrub dominance, and despite different assumptions, both modeling approaches converged on the same hierarchy of predictors. Short‐interval fire was the strongest and most consistent driver of VTC, with additional influence from warm‐season aridity and temperature, proximity to the wildland‐urban interface (WUI), and nitrogen deposition. These results extend decades of plot‐ and landscape‐scale work from southern California to a statewide context, confirming that conversion risk is highest where recurrent fire, climatic drying, and human interface co‐occur, and lowest in cooler, wetter regions with longer fire‐return intervals. Management that avoids short‐interval reburns in shrublands, reduces human ignitions near development, and pairs fuels work with invasive grass control could help to slow or prevent further shrubland loss.

Source: Global Change Biology Communications

DOI: 10.1002/gcb4.70020

Authors: Alexandra D. Syphard, Heather Rustigian‐Romsos, Charlie Schrader‐Patton, Emma C. Underwood

Institutions: Conservation Biology Institute, RedCastle Resources (United States), Western Wildland Environmental Threat Assessment Center, Institute of the Environment, University of California, Davis

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: diamond

Funders: California Department of Forestry and Fire Protection, Western Wildland Environmental Threat Assessment Center