Philip Shearman

Extreme Differences in Forest Degradation in Borneo: Comparing Practices in Sarawak, Sabah, and Brunei

The Malaysian states of Sabah and Sarawak are global hotspots of forest loss and degradation due to timber and oil palm industries; however, the rates and patterns of change have remained poorly measured by conventional field or satellite approaches. Using 30 m resolution optical imagery acquired since 1990, forest cover and logging roads were mapped throughout Malaysian Borneo and Brunei using the Carnegie Landsat Analysis System. We uncovered ∼364,000 km of roads constructed through the forests of this region. We estimated that in 2009 there were at most 45,400 km2 of intact forest ecosystems in Malaysian Borneo and Brunei. Critically, we found that nearly 80% of the land surface of Sabah and Sarawak was impacted by previously undocumented, high-impact logging or clearing operations from 1990 to 2009. This contrasted strongly with neighbouring Brunei, where 54% of the land area remained covered by unlogged forest. Overall, only 8% and 3% of land area in Sabah and Sarawak, respectively, was covered by intact forests under designated protected areas. Our assessment shows that very few forest ecosystems remain intact in Sabah or Sarawak, but that Brunei, by largely excluding industrial logging from its borders, has been comparatively successful in protecting its forests.

Estimating rainforest biomass stocks and carbon loss from deforestation and degradation in Papua New Guinea 1972-2002: Best estimates, uncertainties and research needs.

Reduction of carbon emissions from tropical deforestation and forest degradation is being considered a cost-effective way of mitigating the impacts of global warming. If such reductions are to be implemented, accurate and repeatable measurements of forest cover change and biomass will be required. In Papua New Guinea (PNG), which has one of the worlds largest remaining areas of tropical forest, we used the best available data to estimate rainforest carbon stocks, and emissions from deforestation and degradation. We collated all available PNG field measurements which could be used to estimate carbon stocks in logged and unlogged forest. We extrapolated these plot-level estimates across the forested landscape using high-resolution forest mapping. We found the best estimate of forest carbon stocks contained in logged and unlogged forest in 2002 to be 4770 Mt (+/-13%). Our best estimate of gross forest carbon released through deforestation and degradation between 1972 and 2002 was 1178 Mt (+/-18%). By applying a long-term forest change model, we estimated that the carbon loss resulting from deforestation and degradation in 2001 was 53 Mt (+/-18%), rising from 24 Mt (+/-15%) in 1972. Forty-one percent of 2001 emissions resulted from logging, rising from 21% in 1972. Reducing emissions from logging is therefore a priority for PNG. The large uncertainty in our estimates of carbon stocks and fluxes is primarily due to the dearth of field measurements in both logged and unlogged forest, and the lack of PNG logging damage studies. Research priorities for PNG to increase the accuracy of forest carbon stock assessments are the collection of field measurements in unlogged forest and more spatially explicit logging damage studies.

Trends in Deltaic Change over Three Decades in the Asia-Pacific Region

ABSTRACT Shearman, P.; Bryan, J., and Walsh, J.P., 2013. Trends in deltaic change over three decades in the Asia-Pacific region Over the past decades, studies have shown considerable change in mangrove and deltaic systems around the world. Arguments for the controlling processes encompass natural and anthropogenic phenomena, including sea level rise, storms, sediment supply changes and enhanced subsidence. To evaluate whether similar gross trends are apparent across several larger systems, this research employed a consistent methodology to conduct region-wide change analyses of five major mangrove deltaic systems in the Asia-Pacific region that are reported to be under varying degrees of risk (“no risk,” Fly and Kikori-Purari; “in peril,” Ganges-Brahmaputra, Irrawaddy, Mekong). With the use of a full-scale semiautomated classification, the extent of mangroves was mapped and compared for two Landsat satellite image series at least 20 years apart. Overall, we found a net contraction in mangrove area of 76 km2, or −0.28%, but trends in mangrove change varied across the five systems. We document net contractions in the Ganges-Brahmaputra, Fly, and Kikori-Purari and a net expansion in the Irrawaddy and Mekong. The biggest relative decline in mangrove area occurred in the Fly delta, which experienced a decline of 3.9% over 36 years. The largest relative increase of 2.7% over 20 years occurred in the Irrawaddy, whereas the Mekong was relatively stable with only a modest 0.14% decline over 20 years. System-wide patterns and rates of change were variable and complex. Generally, erosion is occurring at the mouths of rivers, where exposure to ocean processes (e.g. waves) is greatest, despite the large sediment supply by these great rivers (albeit reduced in some cases). The observed losses in the Ganges-Brahmaputra are not surprising considering the known anthropogenic effects, but given that similar change trends are occurring in the Fly and Kikori-Purari delta systems despite potentially increased sediment loading (e.g. from deforestation and mining) and without other anthropogenic effects (subsurface withdrawals or river rerouting), some of this morphological change might be attributed to an enhanced eustatic sea level rise. However, change in climate, marine processes (e.g. wave conditions), effective sea level rise (e.g. a local oceanographic or tectonically controlled response), or autogenic geomorphodynamics cannot be ruled out. Alarmingly, deltas that have the greatest and most intact mangrove systems (the Fly and Kikori-Purari systems) or those parts of deltas that are still forested, such as in the western Sundarbans, are being eroded the fastest of the studied systems. A more concerted effort to monitor large-scale delta changes is recommended.

Deforestation and degradation in Papua New Guinea: a response to Filer and colleagues, 2009

Papua New Guinea’s (PNG) forests are a vital natural resource for the human population that they sustain, the wide biological diversity they contain, the ecological services they provide and their global role in maintaining climatic processes (Hunt, 2006; Bryan et al., in press). The population of PNG is expanding by approximately 2–3% annually, requiring forest clearance for subsistence cultivation, and over recent decades the log export industry has expanded greatly. Though these and other drivers of forest change are well known, there has been considerable debate regarding the extent and rate at which forests are being degraded or converted to other forms of land use. This debate has been fuelled by an absence of recent accurate data, and coloured by the politics associated with industrial rainforest exploitation and more recently, carbon-related REDD projects1. To address this deficiency we undertook a 6-year research project that involved mapping the entire PNG forest estate at high resolution, and compared this with maps from the early 1970s. Our results provide detailed, accurate measurement of the area and condition of forest in PNG, how much forest has been cleared or degraded over the past three decades, and what caused these changes. Our research was initially published as a detailed report (Shearman et al., 2008) that has also been published, in abbreviated form, in the peerreviewed journal Biotropica (Shearman et al., 2009). Our most controversial finding was that overall rates of forest clearance and degradation were much higher than those estimated in the early 1990s (Hammermaster and Saunders, 1995; McAlpine and Quigley, 1998; McAlpine and Freyne, 2001). This is partly because the rates are accelerating but it is mostly due to technical differences in measuring forest cover and forest cover change. Our research has been widely cited and accepted, however Filer et al. (2009) question some of the findings in Shearman et al. (2008), and we take this opportunity to address these issues. Many of the comments in Filer et al. (2009) suggest that the authors have placed undue reliance on older studies of PNG forests (notably Hammermaster and Saunders, 1995: Forest Inventory Mapping System, FIMS) and are unfamiliar with the strengths and limitations of the various techniques that have been used for monitoring vegetation cover and change. It is important to appreciate that FIMS was intended to assess the stocks of various forest types at a broad scale, including areas that had been commercially logged; it

Kinetic energy generation in heat engines and heat pumps: the relationship between surface pressure, temperature and circulation cell size

The kinetic energy budget of the atmosphere’s meridional circulation cells is analytically assessed. In the upper atmosphere kinetic energy generation grows with increasing surface temperature difference ∆Ts between the cold and warm ends of a circulation cell; in the lower atmosphere it declines. A requirement that kinetic energy generation is positive in the lower atmosphere limits the poleward cell extension L of Hadley cells via a relationship between ∆Ts and surface pressure difference ∆ps: an upper limit exists when ∆ps does not grow with increasing ∆Ts. This pattern is demonstrated here using monthly data from MERRA re-analysis. Kinetic energy generation along air streamlines in the boundary layer does not exceed 40 J mol−1; it declines with growing L and reaches zero for the largest observed L at 2 km height. The limited meridional cell size necessitates the appearance of heat pumps – circulation cells with negative work output where the low-level air moves towards colder areas. These cells consume the positive work output of the heat engines – cells where the low-level air moves towards the warmer areas – and can in theory drive the global efficiency of atmospheric circulation down to zero. Relative contributions of ∆ps and ∆Ts to kinetic energy generation are evaluated: ∆Ts dominates in the upper atmosphere, while ∆ps dominates in the lower. Analysis and empirical evidence indicate that the net kinetic power output on Earth is dominated by surface pressure gradients, with minor net kinetic energy generation in the upper atmosphere. The role of condensation in generating surface pressure gradients is discussed.ABSTRACT The pattern and size of the Earth’s atmospheric circulation cells determine regional climates and challenge theorists. Here the authors present a theoretical framework that relates the size of meridional cells to the kinetic energy generation within them. Circulation cells are considered as heat engines (or heat pumps) driven by surface gradients of pressure and temperature. This approach allows an analytical assessment of kinetic energy generation in the meridional cells from the known values of surface pressure and temperature differences across the cell, and . Two major patterns emerge. First, the authors find that kinetic energy generation in the upper and lower atmosphere respond in contrasting ways to surface temperature: with growing , kinetic energy generation increases in the upper atmosphere but declines in the lower. A requirement that kinetic energy generation must be positive in the lower atmosphere can limit the poleward cell extension of the Hadley cells via a relationship between and . The limited extent of the Hadley cells necessitates the appearance of heat pumps (Ferrel cells) – circulation cells with negative work output. These cells consume the positive work output of the Hadley cells (heat engines) and can in theory drive the global efficiency of an axisymmetric atmospheric circulation down to zero. Second, the authors show that, within a cell, kinetic energy generation is largely determined by in the upper atmosphere, and by in the lower. By absolute magnitude, the temperature contribution is about 10 times larger. However, since the heat pumps act as sinks of kinetic energy in the upper atmosphere, the net kinetic energy generation in the upper atmosphere, as well as the net impact of surface temperature, is reduced. The authors use NCAR/NCEP and MERRA data to verify the obtained theoretical relationships. These observations confirm considerable cancellation between the temperature-related sources and sinks of kinetic energy in the upper atmosphere. Both the theoretical approach and observations highlight a major contribution from surface pressure gradients, rather than temperature, in the kinetic energy budget of meridional circulation. The findings urge increased attention to surface pressure gradients as determinants of the meridional circulation patterns.

On estimating tropical forest carbon dynamics in Papua New Guinea

One of the few initiatives to address ongoing global warming that did not completely stall at the UNFCCC climate change negotiations was the reduction emissions from deforestation and forest degradation (REDD). REDD has a focus on the forests of the tropics. Unfortunately forest mensuration in most tropical countries has been inadequate to accurately determine forest carbon stocks, much less the effects of land use and changes in land use on them (Houghton et al. 2009; Bryan et al. 2010a). Whilst tropical logging is known to be widespread, the exact areas of tropical forest subject to logging have not been accurately mapped (Asner et al. 2009) or mapped with sufficient regularity to provide adequate data on the areas subject to this activity. Biomass losses due to logging have usually been derived from limited plot data, or derived via various models from estimates of regional biomass and timber extraction volumes (Houghton et al. 2009) and thus encapsulate considerable uncertainty. For these reasons the carbon impact of tropical logging remains an open question, and one that needs to be closed before any international institutional arrangement considers promoting forms of timber extraction as a tool for controlling carbon emissions. Here, we examine the current state of forest carbon research in Papua New Guinea (PNG) to illustrate the problems that can arise by developing forest management policy prematurely from incomplete forest research. The question of the effects of logging on carbon stocks in Papua New Guinea has been addressed by Shearman et al. (2008, 2010) and Bryan et al. (2010a), who concluded that the available data were inadequate to derive accurate conclusions on the quanta involved. It has been most recently addressed by Fox et al. (2010) who are confident that their analysis of permanent sampling plots (PSPs) ‘provides a sound basis for estimating C dynamics associated with LULUCF’ (p. 7), LULUCF being land use, land use change and forestry. In the present paper, we examine the attributes of data that would provide such a sound basis, examine the data of Fox et al. (2010) in this context, and comment on the possible political implications of accepting the type of data used by Fox et al. (2010) as valid in the context of REDD. To understand the effects of changing the manner in which forests are used or managed on carbon balances, data are needed on stocks and flows. The starting point is to understand the carbon stocks in forests that have not been subject to human modification within a timeframe relevant to rates of regeneration. As Bryan et al. (2010a) and Fox et al. (2010) emphasise, confidence in this outcome requires adequate unbiased sampling of forests undisturbed by humans and extrapolation of the results of this sampling using accurate spatial data layers representing the different types of undisturbed forest.