Distant neighbors: recent wildfire patterns of the Madrean Sky Islands of southwestern United States and northwestern Mexico

Abstract

Background: Information about contemporary fire regimes across the Sky Island mountain ranges of the Madrean Archipelago Ecoregion in the southwestern United States and northern Mexico can provide insight into how historical fire management and land use have influenced fire regimes, and can be used to guide fuels management, ecological restoration, and habitat conservation. To contribute to a better understanding of spatial and temporal patterns of fires in the region relative to environmental and anthropogenic influences, we augmented existing fire perimeter data for the US by mapping wildfires that occurred in the Mexican Sky Islands from 1985 to 2011. Results: A total of 254 fires were identified across the region: 99 fires in Mexico (μ = 3901 ha, σ = 5066 ha) and 155 in the US (μ = 3808 ha, σ = 8368 ha). The Animas, Chiricahua, Huachuca-Patagonia, and Santa Catalina mountains in the US, and El Pinito in Mexico had the highest proportion of total area burned (>50%) relative to Sky Island size. Sky Islands adjacent to the border had the greatest number of fires, and many of these fires were large with complex shapes. Wildfire occurred more often in remote biomes, characterized by evergreen woodlands and conifer forests with cooler, wetter conditions. The five largest fires (>25 000 ha) all occurred during twenty-first century droughts (2002 to 2003 and 2011); four of these were in the US and one in Mexico. Overall, high variation in fire shape and size were observed in both wetter and drier years, contributing to landscape heterogeneity across the region. Conclusions: Future research on regional fire patterns, including fire severity, will enhance opportunities for collaborative efforts between countries, improve knowledge about ecological patterns and processes in the borderlands, and support long-term planning and restoration efforts.

Contemporary Fire Regimes Provide a Critical Perspective on Restoration Needs in the Mexico-United States Borderlands

“…Our analyses across this vast, culturally and ecologically diverse region illuminates important contemporary patterns of fire occurrence and fire effects and how they have varied from those experienced historically. Results of this study, in combination with recent work on traits and spatiotemporal distribution of recent fires in this large region of high conservation value 18,19 are especially significant in Mexico, where past studies in the Sky Islands region were limited to only a few small areas. 25,27,72 Understanding fire regimes across climate gradients that underpin plant community composition and structure can aid in evaluating the potential impacts of human activities on fire.…”

“…Like other parts of western North America where fire suppression was prevalent, this region has seen a general trend toward more and larger fires over the past 3 decades, particularly in the United States. 19,20 Understanding the natural variability of fire activity in relation to both climate and human activities is critical to evaluating shifts in fire regimes. 21 Historically, an abundance of ignition sources from both lightning and humans, and a consistent period of dry weather during late spring and early summer fostered wildfire in the Madrean Sky Island region, except at lower elevations in Desertscrub and subtropical Thornscrub, which lacked fuel continuity.…”

“…Satellite data from the past 32 years shows that large fires were common during this period in both the United States and Mexico, with the largest fires (>25 000 ha) observed primarily in the United States during recent droughts. 19 Identifying climate conditions where recent fires burned, the severity and frequency of fire, and the influence of land management can provide information that is critical and complementary to historical perspectives, and inform fuels treatments and restoration planning, given the uncertainty around how fires and vegetation communities will respond to future climate change. 28 The goal of this study is to describe and analyze patterns of recent wildfires to help guide long-term restoration and fire management in the Sky Islands region of the United States and Mexico.…”

Wildfire Risk and Hazardous Fuel Reduction Treatments Along the US-Mexico Border: A Review of the Science (1986-2019)

“…68,[70][71][72] Historical fire regimes along the border interact with land-use and associated characteristicsincluding livestock grazing, [73][74][75] land ownership, 76 and the degree of remoteness and historical management practices. 2 Larger fires were found to historically occur within the United States compared with Mexico, likely due to higher levels of fire exclusion and resulting fuel buildup. 2 Much of the research on the topic of remote sensing and modeling was conducted across different plant communities including desert scrub, woodland, and forest of the Madrean Archipelago.…”

“…2 Larger fires were found to historically occur within the United States compared with Mexico, likely due to higher levels of fire exclusion and resulting fuel buildup. 2 Much of the research on the topic of remote sensing and modeling was conducted across different plant communities including desert scrub, woodland, and forest of the Madrean Archipelago. Many studies focused on fuel types and biomass to assess wildfire risk [77][78][79][80][81][82][83][84] or used spectral vegetation indices to measure impacts of previous fires.…”