Assessing Spatio-Temporal Variability of Wildfires and their Impact on Sub-Saharan Ecosystems and Air Quality Using Multisource Remotely Sensed Data and Trend Analysis

Kganyago Kganyago,Shikwambana Shikwambana

doi:10.3390/su11236811

Abstract

Globally, wildfires are considered the most commonly occurring disasters, resulting from natural and anthropogenic ignition sources. Wildfires consist of burning standing biomass at erratic degrees of intensity, severity, and frequency. Consequently, wildfires generate large amounts of smoke and other toxic pollutants that have devastating impacts on ambient air quality and human health. There is, therefore, a need for a comprehensive study that characterizes land–atmosphere interactions with regard to wildfires, critical for understanding the interrelated and multidimensional impacts of wildfires. Current studies have a limited scope and a narrow focus, usually only focusing on one aspect of wildfire impacts, such as air quality without simultaneously considering the impacts on land surface changes and vice versa. In this study, we use several multisource data to determine the spatial distribution, frequency, disturbance characteristics of and variability and distribution of pollutants emitted by wildfires. The specific objectives were to (1) study the sources of wildfires and the period they are prevalent in sub-Saharan Africa over a 9 year period, i.e., 2007–2016, (2) estimate the seasonal disturbance of wildfires on various vegetation types, (3) determine the spatial distribution of black carbon (BC), carbon monoxide (CO) and smoke, and (4) determine the vertical height distribution of smoke. The results show largest burned areas in December–January–February (DJF), June–July–August (JJA) and September–October–November (SON) seasons, and reciprocal high emissions of BC, CO, and smoke, as observed by Modern-Era Retrospective Analysis for Research and Applications version 2 (MERRA-2) and Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO). In addition, the results reveal an increasing trend in the magnitude of BC, and CO concentration driven by meteorological conditions such as low precipitation, low relative humidity, and low latent heat flux. Overall, this study demonstrates the value of multisource remotely sensed data in characterising long-term wildfire patterns and associated emissions. The results in this study are critical for informing better regional fire management and air quality control strategies to preserve endangered species and habitats, promote sustainable land management, and reduce greenhouse gases (GHG) emissions.

Highlights

Wildfires are common in many parts of the world, igniting either naturally by lightning or intentionally by anthropogenic activities such as grassland management, deforestation and “slash and burn” agricultural practices
Using GLOBCOVER, the Vegetation Continuous Field (VCF), Moderate Resolution Imaging Spectroradiometer (MODIS) Fire Radiative Power (FRP) and the Tropical Rainfall Measuring Mission (TRMM) datasets, Cardozo, Shimabukuro, Pereira and Silva [12] found that biomass of broadleaved evergreen or semi-deciduous forest were mostly burned, attributed to grassland management practices, agricultural land clearing and the deforestation of the Amazon tropical rainforest
In order to characterise the ecological impacts of wildfires, this study employed multisource remotely sensed data from MODIS, MERIS, SPOT, and Proba-V

Summary

Introduction

Wildfires are common in many parts of the world, igniting either naturally by lightning or intentionally by anthropogenic activities such as grassland management, deforestation and “slash and burn” agricultural practices. Studies at a global scale show that wildfires led to approximately 400 million hectares (ha) of burned land area, causing destruction of property, biodiversity, ecosystems and associated services in their path [1,2]. Information on fire frequency, intensity and burned area (BA) is critical for understanding and alleviating the environmental, atmospheric and socio-economic impacts of wildfires [3]. The availability of operational satellite-based products, such as land cover, temperature, rainfall, tree cover, etc., provide prospects for assessing and quantifying the impact of wildfires on the ecosystems and biodiversity. Using GLOBCOVER, the Vegetation Continuous Field (VCF), Moderate Resolution Imaging Spectroradiometer (MODIS) Fire Radiative Power (FRP) and the Tropical Rainfall Measuring Mission (TRMM) datasets, Cardozo, Shimabukuro, Pereira and Silva [12] found that biomass of broadleaved evergreen or semi-deciduous forest were mostly burned, attributed to grassland management practices, agricultural land clearing and the deforestation of the Amazon tropical rainforest

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