Expanding wildland-urban interface alters forest structure and landscape context in the northern United States

Abstract

The wildland-urban interface (WUI), where housing intermingles with wildland vegetation, is the fastest-growing land use type in the United States. Given the ecological and social benefits of forest ecosystems, there is a growing need to more fully understand how such development alters the landscape context and structure of these WUI forests. In a space-for-time analysis we utilized land cover data, forest inventory plots, and housing density data over time to examine differences in forest characteristics of the northern US across three WUI change classes: (1) forest that has been in WUI housing density levels since at least 1990 (old-WUI), (2) forest where development crossed the WUI housing density threshold after 1990 (new-WUI), and (3) forest with little to no housing development (non-WUI). Of the 184 million acres of forest in the study area, 34 million acres (19%) were in old-WUI, 12 million acres (7%) were new-WUI, and 136 million acres (74%) were non-WUI. In general, as areas transitioned from non-WUI to newer WUI to older more established WUI, the forest was associated with decreased spatial integrity, increased forest-developed edges, and lower proportions of forest in the surrounding landscape. Forest in the WUI had greater carbon storage, with greater aboveground biomass, relative stand density, and more live trees per hectare than non-WUI forest, suggesting greater capacity to sequester carbon compared to non-WUI forest. At the same time, WUI forest also had significantly reduced structural diversity compared to non-WUI forest, with fewer saplings, seedlings, and dead trees per hectare. Forest that more recently crossed the WUI housing density threshold appeared to be on a trajectory towards that of old-WUI forest. These differences in forest structure across the northern US suggest reduced capacity for forest regeneration in the WUI and the potential for changes in other ecological functions.

Review of Remote Sensing-Based Methods for Forest Aboveground Biomass Estimation: Progress, Challenges, and Prospects

“…In addition, the forest AGB estimates for some specific areas are also of interest, such as the wildland-urban interface (WUI) [225]. WUI, where built-up intermingles with wildland vegetation, is the fastest-growing land use type in the United States [226]. Some studies have shown that forest in the WUI had greater carbon storage, with greater aboveground biomass, relative stand density, and more live trees per hectare than non-WUI forest, suggesting a greater capacity to sequester carbon compared to non-WUI forest [226].…”

Cap. 7. Bosques. En: La Quinta Evaluación Nacional del Clima.

“…En el Este, los bosques de la WUI conservan árboles más grandes y biomasa sobre el suelo que los bosques menos desarrollados, pero con menos diversidad estructural (es decir, los bosques de la WUI tienen menos árboles jóvenes, plántulas y árboles muertos). Esto suscita preocupación por la disminución de la función ecológica, la reducción de la diversidad del hábitat de la vida silvestre y la vulnerabilidad al calentamiento 55 . En el Oeste, la exclusión de los incendios forestales en bosques secos históricamente adaptados a incendios frecuentes ha alterado la estructura y composición de los bosques, lo que ocasiona una mayor carga de combustible en la superficie y en el dosel y aumentando la vulnerabilidad a los incendios forestales de alta severidad 56,57 .…”

Evaluation of Biodiversity Maintenance Capacity in Forest Landscapes: A Case Study in Beijing, China

“…FRAGSTATS software has found extensive application in calculating diverse landscape indices, including fragmentation [30] and diversity [31], enabling analysis and monitoring of the temporal and spatial variations in landscape patterns. Previous studies have demonstrated the effect of patch-level landscape structure on multiple ecosystem services of forests [32,33], which contribute to improving habitat protection and biodiversity [34]. However, the current understanding of the most important drivers behind the BMC of forests at the landscape level has not yet been developed [35,36].…”