title: Community assessment of tropical tree biomass: challenges and opportunities for REDD.
abstract: BACKGROUND
  REDD+ programs rely on accurate forest carbon monitoring. Several REDD+ projects have recently shown that local communities can monitor above ground biomass as well as external professionals, but at lower costs. However, the precision and accuracy of carbon monitoring conducted by local communities have rarely been assessed in the tropics. The aim of this study was to investigate different sources of error in tree biomass measurements conducted by community monitors and determine the effect on biomass estimates. Furthermore, we explored the potential of local ecological knowledge to assess wood density and botanical identification of trees.
  
  
  RESULTS
  Community monitors were able to measure tree DBH accurately, but some large errors were found in girth measurements of large and odd-shaped trees. Monitors with experience from the logging industry performed better than monitors without previous experience. Indeed, only experienced monitors were able to discriminate trees with low wood densities. Local ecological knowledge did not allow consistent tree identification across monitors.
  
  
  CONCLUSIONS
  Future REDD+ programmes may benefit from the systematic training of local monitors in tree DBH measurement, with special attention given to large and odd-shaped trees. A better understanding of traditional classification systems and concepts is required for local tree identifications and wood density estimates to become useful in monitoring of biomass and tree diversity.
authors.affiliation: Faculty of Science, Institute of Food and Resource Economics, University of Copenhagen, Rolighedsvej 25, 1958 Frederiksberg C, Denmark.
authors.forename: Ida
authors.initials: I
authors.lastname: Theilade
authors.affiliation: CarboForExpert, 1248 Hermance, Switzerland.
authors.forename: Ervan
authors.identifier: 0000-0003-1182-4032
authors.initials: E
authors.lastname: Rutishauser
authors.affiliation: Nordic Agency for Development and Ecology (NORDECO), Skindergade 23, 1159 Copenhagen K, Denmark.
authors.forename: Michael K
authors.initials: MK
authors.lastname: Poulsen
keywords: Community monitoring; Indonesia; MRV; REDD+; Species identification; Tree biomass; Wood density