Cloud to coast: assessing, monitoring and managing forest carbon in Papua New Guinea

Considerable investment into tropical forest management for carbon sequestration is now demanding an improved understanding of the state of these forests. This includes management options for forest protection or restoration, as well as addressing the needs of forest dependent communities that forego forest exploitation. These needs are particularly acute in the Papua New Guinea, which houses large tracks of relatively intact tropical forests. This thesis aims to address these need by 1) reviewing global carbon stocks and fluxes in tropical forests and providing an assessment of seven forest carbon management practices, 2) examining the relationship between above ground biomass (AGB) and environmental factors through an extensive field campaign in the Morobe province of Papua New Guinea (PNG) along a 3,100m elevation gradient, 3) assessing the potential for engaging local people to monitor forest carbon stocks by evaluating the robustness of data collected by locally-based monitoring programs and 4) exploring mechanisms to incorporate the needs of forest-dependent people into land-use planning for lowered carbon emissions by testing an approach that integrates socioeconomic datasets into a more traditional biophysical land-use planning model. The seven carbon management or 'recarbonization' practices reviewed in Chapter 2 exhibit a large variation in carbon sequestration potential. These potential to sequester carbon was positively associated with levels of land degradation and resource input. Given the distinct co-benefits, risks and costs associated with each practice, the review outlines the potential for government, community, conservation and industry initiatives to profit from recarbonization strategies. The review summarizes the benefits of incentivizing a variety of recarbonization actions and moving beyond the current focus on forest protection. Research conducted along a forested elevation gradient in Papua New Guinea, presented in Chapter 3 of this thesis; found that climatic and edaphic variables were poor predictors of AGB. Instead, natural disturbance was the most significant predictor of AGB. From sampling AGB on very steep forest slopes, up to 80° slope, this research demonstrates for the first time that slope angle can be used to predict the occurrence of natural disturbance and in turn, forest biomass. This finding can be used to further improve models that estimate AGB at the landscape scale, especially in montane areas. Chapter 3 presents the first field assessment of forest carbon stores in the three main forest types in PNG (Lowland, Montane and Upper-montane) along with secondary grasslands; revealing the highest carbon stocks yet recorded in high altitude forests anywhere in the world. High forest-carbon stocks were best explained by the distribution of a large number of tree species found above 2,200 m asl, which grew to exceptional girth and height. The presence of large trees in high altitude tropical cloud forests is generally uncommon; the large trees in the study coincided with a set of optimal climatic conditions similar to those found in temperate maritime areas which contain the largest trees on Earth. This research challenges the common belief that high altitude tropical forests are stunted and low, with low carbon stocks, and highlights the value of conducting fieldwork in difficult-to-access montane areas. Involving local people in monitoring forest-carbon stocks could potentially increase monitoring capacity in developing countries, which currently falls short of the requirements by the Intergovernmental Panel on Climate Change (IPCC). Chapter 4 of this thesis assessed the robustness of locally-based monitoring programs by designing a training program that aimed to teach forest-biomass inventory protocols to people with little or no formal education but with remarkable 'traditional' ecological knowledge about their forests. Three communities were involved in the study, and a total of 4,481 'expert' and 'non-expert' measurement pairs of tree diameter, tree height, numbers of trees and plot surface area were compared from 41 sites. The results demonstrate that biomass estimates by experts and non-experts were not statistically different and thus community-based monitoring could be used overcome barriers to reducing forest-carbon emissions in developing countries. The study takes a hierarchical approach to track the types of error in the field that lead to the largest discrepancy in biomass at the landscape scale, and demonstrates that the most common errors are not the most significant errors. In particular the research highlights the importance of accurate recording of measurements on large trees, especially height, and underscores the disproportionate effect on AGB estimates when single large trees are missed from an inventoried plot. This research demonstrates that targeting those errors that cause the large discrepancies could serve to improve forest biomass inventories and training protocols for experts and non-experts alike. Ensuring the viability of forest carbon projects not only requires a sound knowledge of their carbon stock and an ability to monitor changes in carbon stocks over time, it also requires the implementation of management interventions that are locally relevant and considers the needs of people affected by any interventions. However, integrating societal needs within forest management strategies remains difficult because of the lack of tools for linking socio-economic data to land-use planning models. Chapter 5 explores protection and restoration actions in a landscape where people depend on forests for their livelihood. The study integrates socio-economic data from Poverty Environment Network (PEN) surveys into a more traditional biophysical framework that includes land-cover change analysis along with soil and vegetation carbon stocks associated with different land-use types. Including socioeconomic variables significantly altered the scope for emissions reduction, partly because the land-use types not only varied in carbon stocks but also because of the essential environmental products and services they provided to communities. Moreover, the research highlights the importance of local threats to carbon stores in the study area, with per capita fuelwood extraction exceeding emissions from fossil fuel, cement and anthropogenic fires as the main source of emissions in the region, in the absence of industrial logging. These results suggest that the inclusion of fire management in Upper-montane forest should be a priority for emissions reduction in the study region and potentially in PNG as whole. Moreover, the results demonstrate the additional carbon benefits of establishing coffee plantations that use the native Casuarina, a common shade tree used in PNG. These shade trees store three times more carbon per volume than the most commonly used shade tree species in coffee plantations worldwide. By using some of the societal-environmental synergies identified in this research, PNG could become an important contributor to the global fight to curb anthropogenic carbon emissions, while also improving the livelihoods of the PNG population that depends on, owns, or manage these forests, as they have for millennia