The impacts of recent drought on fire, forest loss, and regional smoke emissions in lowland Bolivia

Joshua P Heyer,Mitchell J Power,Margreet J E Van Marle,Robert D Field

doi:10.5194/bg-15-4317-2018

Abstract

Abstract. In the southern Amazon relationships have been established among drought, human activities that cause forest loss, fire, and smoke emissions. We explore the impacts of recent drought on fire, forest loss, and atmospheric visibility in lowland Bolivia. To assess human influence on fire, we consider climate, fire, and vegetation dynamics in an area largely excluded from human activities since 1979, Noel Kempff Mercado National Park (NK) in northeastern Bolivia. We use data from five sources: the Moderate Resolution Imaging Spectroradiometer Collection 6 active fire product (2001–2015) (MODIS C6), Global Fire WEather Database (GFWED) data (1982–2015), MODIS land cover data (2001–2010), MODIS forest loss data (2000–2012), and the regional extinction coefficient for the southwestern Amazon (i.e., Bext), which is derived from horizontal visibility data from surface stations at the World Meteorological Organization (WMO) level (1973–2015). The Bext is affected by smoke and acts as a proxy for visibility and regional fire emissions. In lowland Bolivia from 2001 to 2015, interannual Drought Code (DC) variability was linked to fire activity, while from 1982 to 2015, interannual DC variability was linked to Bext. From 2001 to 2015, the Bext and MODIS C6 active fire data for lowland Bolivia captured fire seasonality, and covaried between low- and high-fire years. Consistent with previous studies, our results suggest Bext can be used as a longer-term proxy of regional fire emissions in southwestern Amazonia. Overall, our study found drought conditions were the dominant control on interannual fire variability in lowland Bolivia, and fires within NK were limited to the Cerrado and seasonally inundated wetland biomes. Our results suggest lowland Bolivian tropical forests were susceptible to human activities that may have amplified fire during drought. Human activities and drought need to be considered in future projections of southern Amazonian fire, in regard to carbon emissions and global climate.

Highlights

Observations from the southern Amazon reveal fire emissions increased from 1987 through the early 2000s (van Marle et al, 2017)
For lowland Bolivia from 2001 to 2015, a significant relationship was found between mean monthly MODIS C6 fire data and Bext data, with a 95 % correlation confidence interval of 0.76–0.86
Relationships among Bolivia monthly MODIS C6 fire data and mean monthly Global Fire WEather Database (GFWED) precipitation (Fig. 3b) and temperature (Fig. 3d) variables were weaker than relationships among Bolivia monthly MODIS C6 fire data and mean www.biogeosciences.net/15/4317/2018/

Summary

Introduction

Observations from the southern Amazon reveal fire emissions increased from 1987 through the early 2000s (van Marle et al, 2017). To minimize the impacts of deforestation and fire on deforestation in the Amazon, and in turn on carbon emissions and global climate, restrictions on land expansion and policies regulating beef and soy production in the Brazilian Amazon were implemented during the early 2000s (Nepstad et al, 2014). While these restrictions and policy changes helped reduce deforestation from 2004 to 2013 (Nepstad et al, 2014), others suggest a decrease in demand for Amazon resources. Amplifying the effects of deforestation and fire on forest loss in the southern Amazon were drought conditions during the early 2000s (Brown et al, 2006; Aragão et al, 2007; Marengo et al, 2008), raising the question of what the relationships among recent drought, fire, and forest loss in lowland Bolivia are

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