Wildfire dynamics and impacts on a tropical Andean oak forest

Abstract

Wildfires have increasingly damaged Andean tropical forests. However, both a poor understanding of wildfire dynamics and ecosystem response limits awareness about the magnitude of the problem and design management strategies. We estimate the impacts and significant drivers of wildfires by dating and mapping recent wildfires in an Andean tropical forest area, the Iguaque mountains. A large part of Iguaque hosts a population of the only Quercus species in South America, Quercus humboldtii. We used remote-sensing, official reports and social mapping to reconstruct the recent history of wildfires and change in oak forest patches in Iguaque. Between 1990 and 2017, 25 wildfires were recorded, with fire intervals between 4 and 21 years. These events burned 28.4% of the Iguaque mountains and showed a significant increasing trend in extent. Wildfires mostly occurred in the south, during the driest months, and their number and extent showed substantial interannual variations related to El Niño–Southern Oscillation cycles. Wildfires contributed to a 45% reduction in oak forests along with the fragmentation of existing populations. Our study presents evidence of the extent and impact of wildfires in Iguaque and provides new insights on fire dynamics in Andean tropical forests.

Disrupted montane forest recovery hinders biodiversity conservation in the tropical Andes

“…At a continental level, forest recovery trajectories might be driven by extreme climate events, such as droughts and heatwaves, which can cause tree mortality during forest succession (Hartmann et al, 2022) and might lead to continental‐scale trends of “disrupted recovery”. El Niño Southern Oscillation cycles have been shown to impact forest recovery (Wigneron et al, 2020), as observed in our case study landscape in the Colombian Iguaque National park during the 2014 El Niño period (Aguilar‐Garavito et al, 2021), which was a period that coincided with a low point of NDWI values in our time series.…”

“…El Niño period (Aguilar-Garavito et al, 2021), which was a period that coincided with a low point of NDWI values in our time series.…”

“…We found mostly “arrested” or “no recovery” areas, with early or mid‐succession tree cover stages by the end of the study period. Interacting natural disturbance could be reducing forest recovery, such as El Niño episodes causing wildfires in 2010 and 2012, leading to reduced biomass and eventually causing tree mortality of some species (Aguilar‐Garavito et al, 2021; Salazar et al, 2020), leading to years of stagnation or partial reversal of forest recovery. Moreover, several disturbances probably inhibit forest recovery: invasive pasture grasses, such as those in the genera Melinis and Andropogon , dominate highly disturbed and burnt areas, and increasing visitor pressure leads to trampling and disturbance of young vegetation and destabilization of soils near hiking trails (D. Armenteras, personal observation).…”

“…These sites have distinct histories of degradation and land abandonment, such as a combination of agricultural, pastoral or fire legacies. They span various subtypes of ATMF (Supporting Information Supplementary S1) and have all been studied previously (Aguilar‐Garavito et al, 2021; Oliveras et al, 2018; Wilson & Coomes, 2019; Wilson & Rhemtulla, 2016). We consulted local ecologists, conservation managers and the authors of previous studies to evaluate whether our recovery trajectory method provide an accurate represention of the forest recovery patterns in these landscapes.…”

“…ATMFs provide a suite of ecosystem services to both uplands and lowlands and are a major ecosystem in the Tropical Andes Biodiversity Hotspot (Myers et al, 2000). However, deforestation for land conversion (Zador et al, 2015), wildfires (Aguilar‐Garavito et al, 2021; Oliveras et al, 2018) and climate change (Fadrique et al, 2018) have caused widespread ecosystem changes over the last decades. Between 2001 and 2014, 50,000 km 2 of woody vegetation in the tropical and subtropical Andes was cleared (Aide et al, 2019).…”