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Highlights • In Ghana's forest zone, 2016 was the driest year during the period 2003–2017. • In 2016, forest reserves had more active fire detections than in any other year. • Most fires inside forest reserves occurred in the moist semi-deciduous type. • The percent area burned was highest in the most degraded forest reserves. • Drought led to more fire in 2016 and degradation influenced the locations of fires. Abstract Forest reserves in Ghana are the only significant refugia of natural tropical forests, but they are threatened by land use pressures that have led to widespread forest degradation. Additional stress from climate perturbations, such as droughts, can reduce fuel moisture and lead to fires that render the reserves more vulnerable to further degradation. Here, we explore recent drought-associated wildfires in the forest zone of Ghana to better understand the combined effects of forest degradation and drought stress on fire in the forest reserves. We used remotely sensed Earth observations from MODIS and Landsat 8 along with Climate Hazards Group Infrared Precipitation with Stations (CHIRPS) precipitation data, to study fires that occurred during drought conditions in 2016. Fires were widespread in 2016, with an estimated 2137 km2 of forest reserve area burned. During the period 2003–2017, forest reserves experienced the most active fire detections in 2016. The majority of these fires were located in the moist semi-deciduous forests, the largest and most economically valuable forest type, accounting for more than 50% of all active fires and burned area. Forest reserves within the moist semi-deciduous forest type also had the highest standardized fire anomalies in 2016. There was a higher percentage of burned area in degraded forest reserves than in more intact reserves. These results underscore the vulnerability of Ghana's forest reserves, particularly in the moist semi-deciduous type, to fires during severe droughts. Although drought predisposes moist tropical forests to fire, forest degradation also influences the spatial pattern and extent of burned forests. Fire-induced forest degradation presents a major challenge for conservation of humid tropical forests in the region. Within the context of REDD+ and other climate change mitigation and adaptation programs in West Africa, it will be imperative to incorporate effective fire management strategies into ongoing efforts to reduce forest degradation and sustain forest resilience. [ABSTRACT FROM AUTHOR]

Abstract: Forest edges in the Amazon are very dynamic with ongoing deforestation adding new edges as older edges are eroded. Rates of edge erosion and the composition of edge ages, together with distance from edges, are very important factors in determining the magnitude of forest degradation such as biomass collapse and carbon flux. However, we lack an understanding of how these factors change through time and over the different stages of deforestation. In this study, we quantify the spatial and temporal structures of forest edge in Rondônia, southwestern Amazon, by analyses of 22 years of annual satellite imagery, and discuss the implications for biomass dynamics and forest degradation caused by edges. Our results from three different stages of deforestation (early, intermediate and advanced) reveal that more than 50% of forest edges were eliminated in the first four years after edge creation and only 20% of edges survived more than 10 years. High edge erosion rates in the first year imply that many edges disappear before going through the process of edge-induced biomass collapse. At the early stage of deforestation, young forest edges are predominant, while at the advanced deforestation stage more than 50% of total edges are >10 years old. Rapid erosion is more prevalent in early stages, when young forest edges dominate the landscape. Edge-related biomass collapse is substantially more advanced in heavily deforested regions where forests are mostly surrounded mostly by older edges, but relatively few edges remain at this point. [Copyright &y& Elsevier]

• Forest fires in Acre in 2005 and 2010 formed 120,000 ha of bamboo-dominated forest. • After fire, tree damage caused by the growth of bamboo culms can double or triple. • The bamboo-dominated forest has less trees and species diversity than other forests. • Besides the fire, human-climate interactions increase the risk of bamboo expansion. Since the late 1980s the Amazon rainforest has been affected by major forest fires every 3–5 years, mainly in the southwestern portion of the region. Besides the reduction of forest biomass and changes in structure and floristic composition, these forest fires favor the expansion of bamboo in forests in the southwestern Amazon. However, we know little about the impact of fire on bamboo expansion and changes in forest structure. The goal of this study is to quantify forest degradation by fire in areas with bamboo in the eastern portion of the state of Acre, Brazil, based upon a combination of forest-inventory and satellite remote-sensing data. The forest fires were defined by remote sensing as those in which the crowns of the trees were directly or indirectly affected by fire to the point that they cause a detectable impact on the optical satellite images in the 1984–2016 period. We measured trees and bamboo in 6 ha distributed in twelve 0.5-ha plots (100 m × 50 m) in unburned forest, forest burned in 2005, burned forest in 2010 and forest burned in both 2005 and 2010. Our results show change in the structure of the forest with a reduction in the number of live trees as the number of bamboo culms increases after the forest fires. The amount of breakage and damage to the trees by the bamboo culms can double or triple with the expansion of the bamboo after fire impact. Bamboo expansion was identified based on an increase of the proportion of pixels with near-infrared channel reflectance values > 3500. The impact of forest fires resulted in incursion and dominance of bamboo culms over an area of 120,000 ha, changing the forest type of this area to "bamboo-dominated forest." Our results clearly show that drought-induced forest fires with anthropogenic sources are capable of shifting the structure of forest in southwestern Amazonia towards bamboo-dominated forest. With future climate scenarios indicating more frequent and extensive droughts due to global warming, which, together with the use of fire for new deforestation and for managing pasture and agricultural fields, can be expected to cause more forests in southwestern Amazonia to be exposed to extensive fires and potential increase in bamboo density. [ABSTRACT FROM AUTHOR]