Peat and vegetation fires in Equatorial Asia: Emissions, impacts and prevention

Vegetation and peat fires occur regularly in Indonesia following a history of land-use change, deforestation, and peatland drainage, which has resulted in an environment prone to fire. Fires occur in the dry season (August – October), and are greatest during periods of drought, resulting in strong inter-annual variability in emissions. Fires destroy agricultural crops and forest, and emit considerable amounts of carbon dioxide, particulate matter (PM) and other trace gases. These emissions have local, regional and international impacts, affecting human health, and resulting in economic losses. Emissions from peat fires are uncertain, however, due to uncertainties in the burn dynamics. Policy efforts to prevent fire in Indonesia include recently announced plans for restoration of degraded peatlands. The effect of peatland restoration on fire is not well known.

This thesis gives the first consistent estimate of emissions and the public health and economic impacts of Indonesian fires during 2004-2015, and is also the first to estimate the potential economic benefits of peatland restoration. The largest dry season fire emissions were in 2015, with 9.4 Tg of PM2.5 emitted, over three times the average for the period. Peat fires contributed 68% of PM emissions in this year. In total for 2004-2015, dry season fires emitted 32 Tg of PM2.5¬, around half of which came from peat burning. It has been shown that a better representation of peat fire emissions improves model simulations of PM concentrations. In particular, soil moisture has been shown to be an important controlling factor of burn depth.

The Weather Research and Forecasting model with chemistry has been used to simulate dry season PM concentrations for the 6 largest fire events during 2004-2015, showing that Indonesian fires regularly expose millions of people to poor air quality for long periods. Estimating the health impacts of long-term exposure to PM, it has been shown that fire emissions from dry season fires resulted in an estimated 131 700 excess deaths during the 2004-2015 period. Fires result in substantial economic losses, with the largest six Indonesian fire events costing US$93.7 billion through damages to land cover, long term health impacts, and CO2 emissions. It has been shown that the cost of fires outweighs the financial benefit.

The benefit of peatland restoration has been evaluated, and it has been found that restoring 2.49 Mha of peatland could have resulted in CO2 and PM2.5 fire emissions being reduced by 18% and 24% respectively, the latter preventing 12,000 premature mortalities across the 6 fire events. Restoration would have prevented US$8.6 billion of fire costs over the 6 events, and has been shown to be a cost effective policy for reducing the impacts of fires.

The emissions inventory created during this work will enable a better upstanding of Indonesian peat fires, continuing beyond the work presented in this thesis. The findings of this thesis will contribute to the ongoing discussion of Indonesian fires, with relevance for both research and policy.