# Satellite-Based Estimation of Carbon Dioxide Budget in Tropical Peatland Ecosystems
## 1 Introduction  
Carbon dioxide (CO\({}_{2}\)) is one of the gases causing global warming [1]. Peatland ecosystems are expected to play an essential role in global warming mitigation as carbon reservoirs [2]. The impacts of peatlands on greenhouse gas emissions have been examined [3, 4]. Despite covering only 3% of the global land area, peatlands contain about one-third of global soil organic carbon [5]. Peat soils contain a high carbon density and consist of undecomposed carbon that is induced by a large amount of biomass under shallow groundwater table (_GWT_) conditions [6]. Recent disturbances in the ecosystem due to deforestation, wildfires, and groundwater drainages have significantly altered their CO\({}_{2}\) budget [3]. Therefore, estimating their carbon budget and proposing methods to suppress CO\({}_{2}\) emission acrosspeatland regions have become main issues in environmental research [7]. Additionally, according to the United Nations Framework Convention on Climate Change (UNFCCC) and the Kyoto Protocol, a country-based assessment of carbon emissions is politically required for full carbon accounting (FCA) and carbon offset as a measure of the reduction of carbon emissions [8]. The Paris Agreement has been accelerating intergovernmental climate actions [9]. The Intergovernmental Panel on Climate Change (IPCC) published the Guidelines for National Greenhouse Gas Inventories and included calculations for carbon emission in their greenhouse gas model algorithm in 2006 [10]. The organic matter content in tropical peat forest is estimated at up to 70 Pg C, which accounts for 20% of the global peat soil carbon and 2% of the global soil carbon [11; 12]. Lowland peatlands in Southeast Asia cover 27.1 Mha, of which more than 22.5 Mha are in Indonesia, where peatlands account for 12% of the land area and over 50% of the lowland area [13]. In Indonesia, CO\({}_{2}\) is increasingly being released into the atmosphere due to drainage and fires associated with the expansion of plantations and illegal logging due to the Mega Rice Project of 1999 [14; 15; 16]. The fires and drainages are associated with changes in groundwater levels represented by the \(GWT\). The \(GWT\) is an essential factor influencing the fluctuation of CO\({}_{2}\) emissions from peatlands, because if the \(GWT\) declines, the peat decomposition is promoted and fires can occur, which could then result in more CO\({}_{2}\) being released [12; 17; 18]. [PERSON] et al. [19] investigated the distribution of groundwater by using a hydrological model, showing that fire risk is higher in dry areas within peatlands. Remote sensing techniques are suitable for generating maps of the spatial distribution of moisture conditions by using meteorological information. The Keetch-Byram drought index (KBDI) is a typical index for estimating the possibility of fire occurrence and is derived by the empirical relationship between surface dryness and vegetation types [20]. A previous study successfully modeled the long-term dynamics of the \(GWT\) in tropical peatlands in Indonesia on a daily basis by using satellite-based land surface temperature (LST) and precipitation (P) data [21]. The spatial distributions of the \(GWT\) found in [21] can be used to upscale point-based ecosystem respiration (\(R_{e}\)) observations to whole tropical peatland areas in Indonesia since the estimation relies on satellite data. CO\({}_{2}\) fluxes observed at site scales when using the eddy covariance technique and the accumulated data shared via a global network of flux observations (e.g., a global network of flux measurement sites (FLUXNET)) [22] are useful to model CO\({}_{2}\) fluxes and to upscale these fluxes to large scales [23; 24]. [PERSON] et al. [25] measured net ecosystem CO\({}_{2}\) exchange (NEE) and estimated \(R_{e}\) and gross primary production (GPP) in tropical peatlands in Indonesia from 2004 to 2008.