Strategising for climate change mitigation

In 2017, with the collective efforts of the climate change research community, researchers established five Shared Socioeconomic Pathways (SSP) to facilitate climate change research and policy analysis. The SSPs can be combined with a range of climate outcomes to depict future scenarios of alternative socioeconomic and policy developments and its implications on energy, land use, and emissions throughout the 21st century. Multiple scenarios point toward a common goal in helping countries across the world better mitigate global warming.

To achieve such an ambitious goal, appropriate land-based mitigation strategies need to be in place in order to have a significant impact on reducing greenhouse gases. Adopting cutting-edge modelling technologies, a research team led by Assistant Professor He Xiaogang from the Department of Civil and Environmental Engineering under the NUS College of Design and Engineering has identified key areas across the globe to effectively employ two land-based mitigation strategies, namely bioenergy expansion and forestation, to potentially achieve this goal.

The results of their environmental simulations and climate projections extracted from their model framework were published in PNAS on 5 February 2024.

Striking a balance: More trees or more bioenergy

Despite being an alternative energy source to fossil fuels, cultivating bioenergy could come with some undesirable environmental consequences, such as carbon and greenhouse gas emissions, as well as exacerbating water stress. This was examined in another study led by Asst Prof He which was published in Science Advances in 2022.These consequences could negate the potential benefits of increasing the adoption of bioenergy. Another mitigation strategy is forestation, however having more trees might not be a right fit for all regions across the world.

To investigate the impact of these two mitigation strategies, the NUS team made use of their modelling framework to make projections on future climates, carbon sequestration and global temperatures.

From their analysis, the researchers discovered that forestation - to establish new forests or restore damaged forests - has a greater positive impact on capturing carbon from the atmosphere compared to bioenergy usage. However, with technological advancements, the researchers foresee bioenergy usage might surpass forestation in its role in carbon capture.

When examined regionally, the researchers discovered that the forestation strategy is most effective in removing carbon if employed in regions that support forest growth, such as Southeast Asia, Central Africa and South America. From their model projections, the researchers showed that forestation in the Central United States and Europe resulted in negligible carbon absorption due to poor tree growth.

When comparing the impact of both mitigation strategies on planetary climate, the researchers found that while bioenergy use results in cooler planetary climate, this cooling effect is not uniform across all regions around the world. In particular, Southeast Asia and Central Africa are more vulnerable to warmer temperatures if the bioenergy usage strategy is adopted, unlike the Central United States and European regions which may experience a relatively cooler climate.

The researchers noted that based on their model projections of future climate scenarios resulting from forestation and increased bioenergy usage, it is important to consider the regional environmental conditions when developing policies and strategies to mitigate climate change.

“Our study provides valuable insights for future land use and evaluates the implications of two alternative land-based climate mitigation strategies, highlighting that climate mitigation strategies are not one-size-fits-all. To achieve the desired greenhouse and carbon emission goals, emphasis has to be placed on effective allocation of resources for appropriate mitigation strategies,” said Asst Prof He.

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