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Deforestation – Climate –Atmospheric composition – Fire interactions and feedbacks

Periodic Reporting for period 2 - DECAF (Deforestation – Climate –Atmospheric composition – Fire interactions and feedbacks)

Reporting period: 2019-09-01 to 2021-02-28

Tropical deforestation and forest degradation have important environmental impacts. Extensive air pollution from deforestation fires is a serious health issue across the tropics, but large uncertainties remain in its quantification. Deforestation alters rainfall, both through changes to the land surface and through the impacts of smoke from deforestation fires. However, the magnitude and sign of the rainfall response to deforestation is not clear because underlying land-atmosphere interactions are poorly understood and because the net response is a result of multiple, complex interactions that have not been fully assessed. The impacts of deforestation on atmospheric composition and climate causes a complex set of biosphere interactions resulting in potential Earth system feedbacks. These feedbacks have not yet been quantified and so their importance is not known. Despite recent progress, many of these key interactions between deforestation, fire, atmospheric composition and climate remain poorly understood. In particular, previous studies focused on individual interactions; the combined impacts of land surface change and smoke from fires on air quality and climate have not been quantified. Action to mitigate the air quality and climate impacts of deforestation and associated fires is hindered by these substantial gaps in understanding. The overarching hypothesis of DECAF is that the impact of deforestation on air quality, climate and the Earth System is underestimated because there have been no integrated studies of the combined interactions and feedbacks between deforestation and the Earth system. DECAF will address this important challenge, delivering improved process-level knowledge of the impacts of deforestation on atmospheric composition and climate and a step change in our understanding of the impact of deforestation on the Earth system.

Aim and objectives The primary aim of DECAF is to make a step change in our understanding of the impacts of deforestation on the Earth system through the interactions and feedbacks between tropical deforestation, fires, atmospheric composition and climate. DECAF is the first integrated study of the combined interactions and feedbacks between tropical deforestation, fire, atmospheric composition and climate. DECAF has the following objectives:

Objective 1) To understand the interactions between tropical land-use change and fire.

Objective 2) To quantify particulate emissions from tropical fires and make the first robust estimate of the impact of deforestation fires on air pollution.

Objective 3) To quantify the impacts of tropical deforestation on rainfall, accounting for both changes in land surface and atmospheric aerosol.

Objective 4) To explore the Earth System interactions associated with deforestation and deforestation fire.

To address this important challenge, DECAF will exploit new information from laboratory experiments, in-situ and satellite observations in combination with state-of-the-art numerical models.
Through Activity 1 (Deforestation – Fire Interactions) we have worked to understand the drivers of deforestation and fire (Doggart et al., 2020a), the drivers of impacts of selective logging (Ngo et al., 2020) and the drivers of changing biofuel use (Doggart et al., 2020b). Our work demonstrates that agriculture, not charcoal, is the main driver of deforestation in Tanzania. Beyond protected areas, there is no clear policy limiting the conversion of forests to agricultural land. Reducing deforestation in Tanzania requires greater inter-sectoral coordination between the agriculture, livestock, land, energy and forest sectors. To understand the drivers and impacts of logging in Vietnam, we combined information from livelihood surveys, remote sensing and forest inventories around a protected natural forest area in North Central Vietnam. Our analysis suggests activities to reduce forest degradation in protected areas are likely to be financially viable through Vietnam's REDD+ program. Using the city of Dar es Salaam, in Tanzania, as a case study, we looked at how national energy policy has influenced household cooking energy use. Our work shows energy policy needs to acknowledge the continued dominance of charcoal in urban energy use. Greater inter-sectoral coordination is needed to improve the sustainability of urban residential energy supplies.

Through Activity 2 Particulate emissions from tropical fires and impacts on air quality we have worked to constrain fire emissions and assess impacts on air quality (Butt et al., 2020) and the impacts of interventions to reduce fire and air quality impacts (Conibear et al., 2020). We estimate that the prevention of vegetation fires would have averted 16 800 (95UI: 16 300–17 400) premature deaths across South America. The health benefits of fire prevention in the Amazon are comparable to those found in Equatorial Asia. We quantified the impacts of a transition of household energy from solid fuel use to liquefied petroleum gas (LPG) on public health in India from ambient and household PM2.5 exposure. We estimate that the transition to LPG would reduce ambient PM2.5 concentrations by 25%. Reduced exposure to total PM2.5 results in a 29% reduction in the loss of healthy life, preventing 348 000 premature mortalities every year. Our work shows that a transition to clean household energy can substantially improve public health in India, however, these large public health benefits are dependent on the complete transition to clean fuels for all.

Through Activity 3 Impacts of deforestation on rainfall we have started to use remote sensing and models to assess the impacts of land-use change on rainfall and local and regional climate.
Through Activity 1 (Deforestation – Fire Interactions) we have developed new methodologies to assess the drivers of deforestation and fire in tropical countries. In Doggart et al. (2020) we combined satellite remote sensing with field surveys and interviews to better assess the drivers. Through ground surveys and stakeholder interviews we assessed the proximate deforestation drivers at each point.

Through Activity 2 Particulate emissions from tropical fires and impacts on air quality we have combined remote sensing and atmospheric models to constrain fire emissions and assess impacts on air quality (Butt et al., 2020). This work has so far focused on the Amazon. We estimate that the prevention of vegetation fires would have averted 16 800 premature deaths across South America. The health benefits of fire prevention in the Amazon are comparable to those found in Equatorial Asia.

Through Activity 1 (Deforestation – Fire Interactions) we have developed new interdisciplinary approaches to assess the role of the selective logging on forest biomass in tropical forests. Our analysis combines field data, satellite remote sensing and participatory interviews (Ngo et al., 2020). Analysis of Landsat images over the period 1990 to 2014 combined with forest inventory data, demonstrates selective logging was leading to ongoing degradation of natural forests resulting in loss of 3.3 ± 0.8 Mg biomass ha−1 yr−1 across the protected area. We estimate that preventing illegal logging would incur local opportunity costs of USD $4.10 ± 0.90 per Mg CO2, similar to previous estimates for tropical forest protected areas and substantially less than the opportunity costs in timber or agricultural concessions.
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