| dc.description.abstract | Borneo is one of the most species rich regions in the world, but it also has some of the highest rates of deforestation. Much of the remaining unprotected forest is within Indonesian Borneo, but the country’s high rate of deforestation and expansion of industrial concessions threatens those few intact regions. While we know Indonesia has some of the highest national rates of deforestation, this rate is averaged across regions with varying levels of forestry activity. As such, more regional conservation effort would benefit from focused assessment, particularly in areas under active exploitation, so that the consequences of deforestation in the landscape of interest can be addressed.
Borneo’s mammals constitute a rich and varied group of species, many of which are endemic. However, due primarily to anthropogenic impacts, many are now threatened and endangered. Although Bornean mammals have been extensively studied for decades, there are still regions and forest types for which we have limited understanding of the mammal communities. Even within the forests themselves, our knowledge is biased towards terrestrial mammal communities due to our methods of observation. However, tropical forests are vertically complex habitats, supporting numerous arboreal and semi-arboreal species. The expansion of typically terrestrial camera trap survey methods into the canopy is beginning to highlight how our neglect for arboreal observations has biased our understanding of mammal communities in the tropics.
The Rungan Forest Landscape (Rungan) in Indonesian Borneo is a place in need of both localized assessments of deforestation and research into its ecology and mammal community. The Rungan has a large, contiguous forest with regions that are unprotected and regions under active concession development. However, the Rungan’s ecology is poorly understood as little research has been done in the landscape. It also contains Kerangas, a rare and poorly studied type of dry lowland forest for which we have no understanding of the mammal community composition. Peat swamp is the other dominant forest type in the landscape, which is known to support high mammal richness and whose preservation is crucial for climate change mitigation due to their immense peat deposits. Given the rarity of large areas of intact forest in Borneo, the presence of ecologically important species and habitats, and the lack of research there to-date, the Rungan represents an important conservation and research opportunity.
In this thesis I assess the Rungan landscape in two distinct ways: I evaluate the patterns of deforestation and then assess the mammal community in both terrestrial and arboreal space across the habitat types.
I first classify the Rungan’s landcover for 2015 and 2018 to evaluate the change in forest cover. Using these outputs and data on the allocation on industrial concessions in the landscape, I evaluate the patterns of deforestation and the resulting forest spatial attributes across land-uses and forest types. I calculate forest fragmentation and forest cover in 2015 and 2018, and I combine these metrics into ‘forest-continuity’. Species perceive and respond to the same landscape at different spatial scales, so will be variably impacted by deforestation and fragmentation of a landscape. To account for this, I evaluate the landscape’s spatial attributes – fragmentation and forest cover – at three different spatial resolutions. To identify areas of relatively intact forest, I designate a threshold for the degree of fragmentation and amount of forest cover, above which I term ‘high-continuity’.
I assess the mammal community at a study site in the Rungan which is located where two well defined forest types meet – Kerangas and Low Pole (a sub-habitat of peat swamp) – creating a third Transition habitat between them. I use terrestrial and arboreal camera traps to determine the mammal community across habitat types and strata. Using arboreal camera trap surveys is still an emerging method, so here I evaluate the contribution of arboreal cameras to the species richness detected. A common source of sampling error for camera trap data is imperfect detection – when an individual or species is present in the area being sampled but is not detected. Occupancy modelling was developed to account for imperfect detection, enabling more robust comparisons of mammal communities. As such, I use hierarchical multi-species occupancy models to evaluate the mammal metacommunity structure and species-specific occupancy in each habitat type.
From my landcover assessment, I found that the Rungan had a substantially higher rate of deforestation (-7.8%/year) than the Indonesian average (-0.78%/year). Most of the forest loss was in industrial concessions (-8.8%/year) but the rate of deforestation outside of concession areas was also high (-5.3%/year). Although small-scale forestry activity does occur outside of concessions, the disparity between the national rate and that outside of concessions is alarming. Additionally, most deforestation occurred in the Dry lowland forest (containing Kerangas), with minimal losses in Peat swamp. This difference was largely due to concessions being predominantly distributed in Dry lowland while some of the Peat swamp forest has been put under a moratorium on development. From the assessment of fragmentation and forest cover, I found a reduction in amount of high-continuity forest area and a widening of the gaps between adjacent high-continuity regions. The region that has conservation potential is the high-continuity forest outside of concessions. In 2018, this represented 522 – 628 km2, depending on the spatial resolution of analysis. However, Peat swamp is disproportionately represented in that high-continuity forest outside of concessions, and that which does occur in Dry lowland is itself divided around the landscape.
I found high mammal species richness in the study site (47 species), with 43 species detected in Kerangas and 29 species detected in Low Pole. Including arboreal camera traps significantly increased the number of species detected, more than expected by doubling the terrestrial effort alone. The arboreal camera traps provided valuable information beyond just the number of species, such as detections of threatened species, increased understanding of habitat use, and the detection of two species whose current known geographic distributions exclude Central Kalimantan. The outputs from the occupancy models showed that mammal richness and species-specific occupancy probability tended to be higher in Kerangas and Transition compared to Low Pole. This was true for both terrestrial and arboreal communities. I also found that some species detected by both terrestrial and arboreal surveys differed in their mean occupancy values between strata in the same habitat.
My research highlights the importance of regional-scale analysis of deforestation patterns and the importance of comprehensive surveys of both terrestrial and arboreal space when studying mammal communities. I illustrate that national averages are not necessarily representative of the patterns of forest loss in unprotected and actively exploited landscapes. Regional-scale analysis should be done to better understand patterns and drivers of deforestation, and to identify areas of conservation priority. The impacts of deforestation are species-specific though, so it is also important to account for variability in species’ perceptions of the landscape. My research also shows that combing arboreal and terrestrial camera trap surveys produces a more accurate representation of the mammal community than terrestrial surveys alone. This leads to more accurate community- and species- level assessments, which is essential for conservation and impact assessments. As the first assessment of the mammal community in Kerangas, I have also shown that it supports a rich mammal community and is of high ecological and conservation value. | en_GB |
