Improved land management and rainforest conservation in Sabah, Borneo
Long-term research by geographers led by Professor Rory Walsh and Dr Glen Reynolds in Sabah, Malaysian Borneo, has assessed the effects of selective logging and climatic change on erosion, forest ecosystems and forest regeneration in Sabah, and designed ways of reducing these negative impacts. The research was carried out as part of the multidisciplinary Royal Society South East Asia Rainforest Research Programme (SEARRP) based at Danum Valley in Sabah since 1985.
The research has had two foci. The hydrological research has included a >20-year monitoring record of slope and stream erosion in a river catchment that was selectively logged in 1989. This research revealed for the first time that 5-8 years after primary rainforest is logged a second peak in erosion can occur. This was linked to poorly-aligned mid-slope logging roads and the biological decay and collapse of logs in culverts and bridges leading to landslides in major rainfall events. These findings highlighted the need for improved logging-road alignment. Later research used sediment fingerprinting and dating techniques to analyse downstream sediment cores. Results were used to quantify changes in sources of sediment; and to relate the history of sedimentation to variations in logging intensity and practices. Downstream sedimentation rates and inferred erosion rates in the same steep terrain areas were six times higher with logging involving road construction in 1999-2001 than in the early 1980s when logs were floated down the river and logging intensities were light.
A second research focus was on recent climatic change and its impacts on rainforest dynamics and erosion. Archival climatic records were used to assess variations in extreme climatic events (droughts and heavy rainfall) over the past 100–150 years in Borneo and elsewhere in SE Asia. This demonstrated: (1) a sharp increase in drought magnitude and frequency since 1967 linked to El Niño events; (2) an E–W gradient in drought proneness across Sabah and Borneo; and (3) a natural resilience of primary forest to occasional drought, but an increased proneness to fire of logged and fragmented forest (and biodiversity loss and change). Pioneer research showing a progressive increase in water-use efficiency indicated by changes in carbon isotopes of wood in cross-sections of 210-700 year-old rainforest trees demonstrates their resilience so far in responding to increased atmospheric carbon dioxide.
Century-long daily rainfall records (unique for equatorial areas) at three stations in Sabah were used to demonstrate an upsurge in heavy rainstorm frequency to unprecedented levels since 1998, suggesting that Intergovernmental Panel on Climate Change (IPCC) predictions of increases in extreme rainfalls may already be occurring in Borneo. Consequences of the upsurge for increased river flows, sediment transport and slope erosion were demonstrated and the likelihood of a major landslide phase and downstream flooding if steep terrain is logged or converted to oil palm was highlighted.
Research findings from the Swansea team underpinned key land management and forest conservation decisions and policies adopted by the Sabah Government in 2008-13. On the hydrological side, the science demonstrating the benefits of carefully aligning logging roads and keeping steep (>25°) slopes under forest directly influenced modifications to logging protocols.
The climatic change and forest response research was accompanied by specific recommendations to the Sabah Government on the need to retain a large contiguous E–W unit of forest in eastern Sabah with buffer areas around primary forest conservation areas to (1) reduce fire risk and (2) increase the ability of forest ecosystems to adapt to climatic change. These recommendations lay behind a series of forest conservation decisions by the Sabah Government in 2008–2013 that together more than doubled the area of legally protected rainforest to form an east–west contiguous 5000 km2 rainforest area in eastern Sabah. The decisions represent a step-change in Government attitude and policy and followed invited participation of the Swansea scientists in a Sabah Government-organized workshop in September 2011 to develop Sabah’s REDD+ policy (the second phase of the United Nations ‘Reducing Emissions from Deforestation and forest Degradation’ initiative). The forest involved includes the largest remaining area of primary lowland rainforest in SE Asia and is key habitat for orang-utans – and many other endangered species of global importance.