Do Humans Make Southwestern Forests Less Vulnerable to Fire and Climate Changes?

Sunday, 16 February 2014
Columbus AB (Hyatt Regency Chicago)
Thomas W. Swetnam , University of Arizona, Tucson, AZ
Forests and communities are now extremely vulnerable to large, severe fires during droughts as a consequence of fire exclusion and other land use practices. The extent to which this vulnerability is influenced by climate and land-use remains unclear.  Multi-century case studies reveal that certain types of fire are critical for maintaining the health of forests in the Western U.S. In semi-arid pine forests of the Southwestern U.S., frequent surface fires clean out understory plants, maintain an open stand structure, and improve the resilience of these forests to severe droughts. The removal of these frequent, cool, surface fires during the 20th century by fire suppression has changed the fire-forest dynamic. Now, in the context of global warming, severe and extended droughts have turned Southwestern forests into tinderboxes that threaten homes, infrastructure, and the very forests that have attracted so many human communities to these landscapes. The expansion of the human built environment into these fire- and drought-prone forests has created a unique fire and forest management problem referred to as the Wildland Urban Interface or WUI.

Just as paleo-records have illuminated the dynamics of forest fire regimes and their relationship to climate, we look to the past through interdisciplinary socio-ecological research to understand the climate vulnerabilities of human and ecological communities at the WUI. Many of these landscapes were home to agricultural populations for centuries before Euroamerican colonization, seemingly without creating climate vulnerabilities that we are currently experiencing. In the southwestern Jemez Mountains in particular, more than 8,000 Ancestral Jemez villagers lived at population densities equivalent to the modern WUI for at least three centuries, through several severe droughts. We have brought together the insights of archaeology, dendrochronology, paleoecology, traditional ecological knowledge, and dynamic computer simulations to investigate the complex, long-term couplings of forest ecosystems, fire regimes, climate change, and human communities in the Ancestral Jemez landscape. This interdisciplinary research focuses on evaluating whether or not particular fire-forest-society relationships can enhance or erode the resilience of these fire-adapted forests. Our ongoing research addresses this question at multiple scales from the daily lived environment of the human communities, across their agricultural landscape, and beyond to encompass a mosaic of humanized, coupled human-natural, and natural landscape patches.