The Rimba Raya Biodiversity Reserve REDD Project

Peat drainage. To be conservative, it is assumed that areasoutside the proposed plantation boundaries would be unaffectedby drainage under the baseline scenario. The analysis presentedhere also excludes the influence of tatahs (small canals used forillegal logging) on peat drainage. Fieldwork may show that tatahscause a background level of peat drainage in the area ofinfluence around each tatah; if these canals are shown tosignificantly affect drainage, baseline calculations will need to bemodified to take into account the background drainage impacts.For this analysis, it is assumed that all peat areas within theProject Area are undrained and that palm oil plantationsmaintain a constant drainage depth of 80 cm below the surface.This is based on data from Hooijer et al. (2006) who derived aminimum estimate of 0.80 m, a likely estimate of 0.95 m and amaximum estimate of 1.1 m.Drainage depth was linked to CO 2 emissions (in t CO 2 ha -­‐1 yr -­‐1 )using a regression relationship derived primarily from long-­termmonitoring of peat subsidence in drained peatlandscombined with peat carbon content and bulk density analysis.This method filters the contribution of peat compaction fromthe total subsidence rate, and the remainder is attributed toCO 2 emission (Wösten et al. 1997; Wösten and Ritzema2001). Long-­‐term monitoring of peat subsidence producesthe most accurate and reliable data, but yields only fewmeasurement points. For lack of a large enough populationof observations, a linear relation between drainage depth andCO 2 emission was fitted through the data whereas the actualrelation is known to be non-­‐linear. Therefore, Eq. 60 in theproposed methodology was applied as:where:MEB, dd , it 0.91DB,drain,itME B,dd,it = mean CO 2 emissions from drained peat instratum i, time t; t CO 2 /haD B,,drain,it = average depth of peat drainage oraverage depth to water table under thebaseline scenario in stratum i, time t; cmIn the drainage depth range most common in southeast Asianpeatlands, the relation is supported by results fromnumerous gas emission monitoring studies in peatlands. Therelation used in this analysis, derived on the basis of literaturereview, is considered conservative. Methane (CH 4 ) fluxesfrom peat were not accounted for because research to dateindicates that CH 4 fluxes in tropical peatlands are negligiblecompared to CO 2 fluxes (Furukawa et al. 2005; Hadi et al.2005; Jauhiainen et al. 2005).Baseline drainage emissions from the palm oil concessionsare estimated as 22.9 million t CO 2 e over the first ten years,with an average emission of close to 2.29M t CO 2 e yr-­‐1 forthe first ten years (Table 25).117