We combined two existing datasets of vegetation aboveground biomass (AGB) (Saatchi et al., 2011; Baccini et al., 2012) into a pan-tropical AGB map at 1-km resolution using an independent reference dataset of field observations and locally-calibrated high-resolution biomass maps, harmonized and upscaled to 14,477 1-km AGB estimates. Our data fusion approach uses bias removal and weighted linear averaging that incorporates and spatializes the biomass patterns indicated by the reference data. The method was applied independently in areas (strata) with homogeneous error patterns of the input (Saatchi and Baccini) maps, which were estimated from the reference data and additional covariates. Based on the fused map, we estimated AGB stock for the tropics (23.4 N – 23.4 S) of 375 Pg dry mass, 9% – 18% lower than the Saatchi and Baccini estimates. The fused map also showed differing spatial patterns of AGB over large areas, with higher AGB density in the dense forest areas in the Congo basin, Eastern Amazon and South-East Asia, and lower values in Central America and in most dry vegetation areas of Africa than either of the input maps. The validation exercise, based on 2,118 estimates from the reference dataset not used in the fusion process, showed that the fused map had a RMSE 15 – 21% lower than that of the input maps and, most importantly, nearly unbiased estimates (mean bias 5 Mg dry mass ha-1 vs. 21 and 28 Mg ha-1 for the input maps). The fusion method can be applied at any scale including the policy-relevant national level, where it can provide improved biomass estimates by integrating existing regional biomass maps as input maps and additional, country-specific reference datasets.
Tag: forest inventories
Balancing supply and demand: A case study of rattan in the Danau Sentarum national park, West Kalimantan, Indonesia
The Danau Sentarum National Park (DSNP), Kalimantan, Indonesia, covers 30 000 ha of lake and 81 000 ha of lowland, seasonally flooded forest. It is the largest network of inland lakes in Borneo. The park is inhabited by over 5500 Malay fishermen. Most of the fishing implements used by the local population are made from rattan, and large quantities of rattan are also harvested and sold to timber companies for lashing together rafts of logs. The 3 most commonly used species at DSNP are duri antu (Calamus schistoacanthus), duri tapah (Calamus tapa) and duri pelanduk (Ceratolobus hallierianus). Inventories indicate that the 3 rattans differ greatly in the number of harvestable clumps/ha (>4.0 m tall). The duri antu populations average over 900 clumps/ha, duri pelanduk grows at densities of 400-500 clumps/ha, and duri tapah averages only 50 clumps/ha. Based on the observed relationship between clump height and the number of canes/clump, it is estimated that there are over 34 000 duri antu canes/ha growing in the flooded forest of DSNP. An analysis of local demand, productivity and current harvest intensities reveals that local rattan resources are being gradually overexploited. Several fishing communities have started to manage their rattan resources by controlling harvests and rehabilitating and enriching natural stands.
The impact of forest management plans on trees and carbon: Modeling a decade of harvesting data in Cameroon
By 2010, about 25% (180 million ha) of The International Tropical Timber Organization (ITTO) producer countries’ permanent forest estate was being managed using an approved forest management plan (FMP). While the existence of a FMP is often used as evidence of sustainable forest management (SFM), State officials mandated to monitor and verify FMPs’ implementation often lack the technical knowledge and political incentives to assess the changes that have been introduced, notably in terms of harvested volumes and species. Among tropical timber producers, Cameroon is considered to be exemplary for its progressive forest regulatory framework. Here we aim to estimate for the first time in sub-Saharan Africa the causal impact of the implementation of FMPs on harvested volumes, species and carbon stocks. We do so by using a 12-year (1998-2009) unbalanced longitudinal data set of a detailed, official harvesting inventory of 81 concessions in Cameroon. Results provide evidence to the theoretical expectations that for many years many practitioners have had on the implementation of SFM, i.e. that FMPs show a substantial opportunity to reduce carbon emissions from forest while presenting logging companies with acceptable financial trade-offs. We explore the technical and political reasons for our findings and conclude that these analyses are important for countries that are underwriting carbon-related schemes in which they propose to reduce their emissions through the effective implementation of SFM. We also demonstrate that producer countries do record useful information that, when effectively used, can help them to inform their policies and improve their sustainable development strategies.