Is vegetation collapse on Borneo already in progress?

Abstract

Vegetation and tropical forests in particular have a central role in mitigating the effects of increasing levels of atmospheric CO2. Photosynthesis is the fundamental process during which CO2 is taken up by plants and fixed into carbohydrates. The effect of temperature on the rate of photosynthesis in different plant species is directly related to degree-days (D-D) as well as the leaf area index (LAI). Throughout the dry season, the reduced net primary productivity is tightly correlated with increasing D-D, while the reduction in soil moisture leads to progressive canopy thinning, indicated by decreasing LAI. Forest degradation exacerbated by soil erosion and depletion of nutrients in response to high rainfall intensities during the rainy season further disturbs the ecological balance of the entire ecosystem, destabilising it beyond its natural resilience. Given this fact, ground-based evidence and remote sensing-based findings, we propose a climatically induced cascade of events leading to a gradual alteration of the tropical forest ecosystems on Borneo with a diminishing ability to absorb CO2 and release O2. Such a feedback loop, which is primarily triggered by increases in temperature, has potentially dangerous outcome for tropical ecosystems and has already been observed in the north-western state of Brunei Darussalam. The island of Borneo as a whole seems to have reached a level of forest degradation that is beyond a point of no return. In the worst-case scenario, the next niche of stability may be a destruction of tropical forests and the loss of a major proportion of Earth’s biodiversity. Our aim is to stimulate further research on such occurrences and inspire the implementation of future preventative measures.