A study from Sabah, Malaysian Borneo, has highlighted the severe impact of tropical forest loss on biodiversity, forest structure, and ecosystem functioning. Conducted as part of the Stability of Altered Forest Ecosystems (SAFE) Project, the research compared old-growth forests, moderately and heavily logged forests, and oil palm plantations. The findings revealed significant harm to biodiversity and ecological functions by deforestation and logging.
Launched in 2011, the SAFE Project aims to understand the ecological consequences of forest fragmentation. This study collated data from 82 datasets, collected across various forest plots over five years, using advanced sampling techniques.
Researchers analysed critical ecological factors, including canopy height, soil nutrients, carbon storage, species diversity, and ecosystem functions, employing linear mixed-effects models to assess the impact of different levels of disturbance.
Selective logging and the conversion of forests to oil palm plantations were linked to severe biodiversity loss. Old-growth forests were found to host the richest biodiversity, supporting a wide range of soil microbes, insects, birds, and bats. In contrast, logged forests exhibited reduced species richness, while oil palm plantations experienced drastic declines in biodiversity.
Sensitive species, particularly soil fungi and ectomycorrhizal communities essential for forest health, were heavily affected. Disturbance-tolerant species, such as certain bacteria and generalist insects, became more dominant in degraded habitats, while mature forest-dependent species disappeared.
Populations of birds, bats, and beetles also declined significantly, especially in oil palm plantations, where canopy-dependent and soil-associated species were most at risk.
Biodiversity’s response of to disturbances was nuanced. Some bat species adapted to moderately logged forests, showing slight population increases. However, this trend reversed in highly degraded habitats.
Soil microbial communities showed mixed responses. While bacterial richness improved in some disturbed areas, fungi, particularly those supporting dipterocarp trees, were highly sensitive to logging and land-use changes.
Structural changes were evident in logged forests, with lower canopy heights and fewer large trees. Oil palm plantations, meanwhile, exhibited a simplified canopy structure.
Indicators of carbon storage and soil health declined significantly in logged and converted forests. Above-ground carbon storage and soil health markers were particularly affected. While some ecosystem functions, like litter decomposition, remained resilient, crucial processes such as nutrient cycling were severely impacted in oil palm plantations.
The findings underscored the importance of preserving old-growth forests and recognising the ecological value of moderately logged forests. Maintaining riparian reserves and high-carbon stock areas within agricultural regions, as recommended by the Roundtable on Sustainable Palm Oil, could help mitigate biodiversity loss.
Lead researcher Charles J Marsh, from Yale University’s Department of Ecology and Evolution, emphasised the sensitivity of forest structure to even low-intensity logging. He called for global efforts to minimise disturbances in healthy forests, restore degraded lands, and promote sustainable land-use practices.
Although focused on lowland tropical forests in Sabah, the study provided a framework for similar ecosystem-wide research in other tropical regions. Future studies could investigate whether these findings hold true across varied landscapes and broader land-use contexts.