- Proposals by some of the world’s largest greenhouse gas emitters to transition their energy sectors away from fossil fuels and toward renewables have generally been welcomed by the scientific community as progress in the right direction.
- However, while acknowledging the energy transition as essential, energy experts caution policymakers to also consider the unintended social and ecological consequences of scaling up renewable infrastructure, such as large-scale hydropower dams and wind and solar farms.
- A new study finds that China’s plans to decarbonize its energy sector by 2060 could have inadvertent but severe impacts on local farmland and transboundary river basins, including the regionally significant Mekong and Salween.
- The authors say that strategies to reduce electricity demand combined with increased investment in emerging energy technologies could curb the need for further hydropower expansion in the upper stretches of the pivotal rivers, thereby reducing cascading downstream impacts.
The energy sector is the single largest source of human-caused greenhouse gas emissions, spurring plans the world over to transition the sector away from fossil fuels and toward renewables. While decarbonization plans by some of the world’s top emitters have generally been welcomed, energy experts say decision-makers must take care while designing decarbonization strategies to fully consider the unintended social and ecological consequences of rapidly scaling up renewable infrastructure.
“If we think of any major technological change, they always have costs and unintended consequences,” said Stefano Galelli, an associate professor of environmental engineering at Cornell University in the U.S. “The sooner we realize and address them, the more sustainable and equitable the energy transition will be. We have to do it right.”
In a new study published in Communications Earth & Environment, Galelli and his colleagues from China and the U.S. evaluate how China’s plans to decarbonize its energy sector by 2060 could have inadvertent but severe impacts on local farmland and transboundary river basins, including the regionally significant Mekong and Salween. The researchers also consider how alternative solutions and new technologies could help minimize the most egregious impacts.
“Decarbonizing is essential, we have to do it,” Galelli told Mongabay. “But we must think about trade-offs with the environment now, rather than afterwards. Getting an understanding of what could come in the next 40 years can give us an indication of the least-impactful pathways and give us an opportunity to steer the boat.”
Vital watercourses
Underpinning one of the world’s largest inland fisheries and sustaining unique ecosystems and freshwater species found nowhere else on the planet, the Mekong River charts a course from China through five Southeast Asian countries. However, booming hydropower development over the past two decades throughout the river basin has altered the river’s crucial seasonal flood pulse that drives regional fisheries and agricultural productivity.
As of mid-May 2024, there were 745 dams on the mainstream and tributaries of the Mekong Basin, according to the Mekong Dam Monitor run by the Washington, D.C.-based Stimson Center. Of these dams, 209 are for hydropower generation, with others used for irrigation, urban water supply, and flood control. Already beset by dam-driven geopolitical tensions, further large-scale damming of the Mekong’s upper reaches in China will inevitably compound problems along the already struggling river system.
Meanwhile, damming of China’s stretch of the Salween River, one of Southeast Asia’s last free-flowing river systems, could wreak similar havoc to life-sustaining processes in the river’s lower reaches that flow through Myanmar. Farmers in the conflict-torn country use traditional forms of agriculture along the river that rely on its natural flood cycle to bring sediment downstream, covering riparian land with nutrients that fertilize their crops. Communities in Myanmar have already repeatedly seen off state-led attempts to dam the Salween.
Radical changes to energy infrastructure
Focusing on the China Southern Power Grid (CSPG), China’s second-largest grid, where annual energy demand is projected to more than double by 2060, the researchers modeled various energy scenarios using estimates of hydropower availability at existing and planned dam locations, and geospatial data sets to identify potential wind and solar sites.
They found that roughly one-quarter of the CSPG’s power would need to be generated through hydropower to meet the increase in electricity demand and stay on target for full decarbonization by 2060. Under this scenario, hydropower would produce 172 gigawatts of power, 32 GW of which would have to come from 20 new dams.
While some of the new hydropower capacity is earmarked for China’s Pearl and Yangtze rivers, nearly 80% of the hydropower expansion would be within the transboundary Mekong and Salween river basins, according to the study.
The Yangtze and Mekong rivers “already carry the consequences of dam development, so one could easily foresee that the construction of new dams may exacerbate a variety of problems, such as the fragmentation of the river network, alteration of sediment and nutrient dynamics, obstruction of migratory routes of aquatic species, or hydrological alterations,” the study says.
Besides concerning downstream consequences of hydropower, experts have raised questions about whether large-scale hydropower is a valid pathway toward decarbonization. The effects of climate change could affect the long-term sustainability of hydropower, for instance. In the Mekong Basin, regional climate modeling data have led experts to question the viability of hydropower due to unpredictable seasonal water availability in the upper catchment linked to altered climate patterns. Also, studies have indicated that hydropower dams can be major greenhouse gas emitters, calling into question whether hydropower can credibly be considered green power.
The team also calculated that decarbonization by 2060 would require the conversion of roughly 40,000 square kilometers (15,400 square miles) of cropland for solar and wind projects. A significant proportion of the land the researchers identified as available for such expansion is confined to one province, Guangxi. “This might be a heavy burden for the province,” the study says, “and result in significant ecological, social and financial costs to local communities.”
Planning overlooks dam impacts
Mathias Kondolf, a professor of environmental planning at the University of California Berkeley, said energy planning has typically overlooked the very real impacts of hydropower dams in the Mekong region. He said analyses like the CSPG study are vital to help planners prioritize the placement of dams and other renewables and the phasing of construction.
“In many cases we can develop a portfolio of dams that provides comparable levels of energy generation, but with much lower environmental impact than the default of letting developers propose sites based strictly on criteria such a short-term economic return, proximity to electric grids, etc.,” Kondolf told Mongabay in an email.
In addition to better planning of new dams, it might also be possible to reduce the impact of the existing dams along the Mekong. A 2022 study by several of the same authors, for instance, indicated that coordinating the operation of all hydropower dams in the basin, by phasing water releases and restrictions, could maintain power supplies while improving the quality of the river’s vital floodpulse.
Curb the need for more dams
The researchers’ models indicate, however, that other pathways that avoid the worst transboundary river impacts of decarbonizing the CSPG exist. Strategies to reduce electricity demand combined with increased investment in emerging energy technologies could curb the need for further hydropower expansion in the upper stretches of the pivotal rivers, they say, thereby reducing cascading downstream impacts.
Central to the feasibility of this alternative scenario are nascent technologies, such as coal carbon capture and storage (CCS), whereby coal-fired power plants are retrofitted to harness and storing the carbon they would otherwise emit. But coal CCS still has some way to go before it can be deployed at the scale and efficiency necessary to offset the loss of hydropower, and questions remain about whether it can be developed within the time frame required.
“There are various challenges that may impede the widespread adoption of CCS technologies, such as uncertainty in future costs, technology immaturity risk, environmental concerns, and potential policy restrictions. Investments and research in CCS are therefore necessary,” the study says.
Besides coal CCS, there are other promising energy technologies that could broaden the options for decarbonization, not just in China, but around the globe, Galelli said. He cited agrivoltaics (where solar panels share land with crops), more efficient batteries, and positioning solar arrays on water bodies such as hydropower reservoirs, as high-potential solutions. Solar in particular will have to feature prominently in any scenario of decarbonization of the CSPG, Galelli added, therefore finding ways to minimize the land use requirements will be key.
Ultimately, however, decarbonization will always be challenging unless electricity demand can be reduced. “We always think that we have to decarbonize in order to meet demand. But demand is not written in stone,” Galelli said. “There is a lot that can be done; from educating people, to continuing to develop new technologies that allow electricity to be stored better.”
Galelli said he hopes the analysis will help China identify equitable and environmentally sound pathways toward decarbonization. “Unfortunately, we cannot really solve all environmental trade-offs — that’s just in the nature of building infrastructure. But trying to minimize them and working with all parties involved, that is something that we can do.”
Carolyn Cowan is a staff writer for Mongabay. Follow her on 𝕏, @CarolynCowan11.
Banner image: Farmers in downstream countries use traditional forms of agriculture that rely on nutrients from the Salween and Mekong’s natural flood cycles. Image by Demelza Stokes.
Citations:
Jin, X., Chowdhury, A. K., Liu, B., Cheng, C., & Galelli, S. (2024). China Southern Power Grid’s decarbonization likely to impact cropland and transboundary rivers. Communications Earth & Environment, 5(1). doi:10.1038/s43247-024-01363-1
Galelli, S., Dang, T. D., Ng, J. Y., Chowdhury, A. K., & Arias, M. E. (2022). Opportunities to curb hydrological alterations via dam re-operation in the Mekong. Nature Sustainability, 5(12), 1058-1069. doi:10.1038/s41893-022-00971-z
Deemer, B. R., Harrison, J. A., Li, S., Beaulieu, J. J., DelSontro, T., Barros, N., … Vonk, J. A. (2016). Greenhouse gas emissions from reservoir water surfaces: A new global synthesis. BioScience, 66(11), 949-964. doi:10.1093/biosci/biw117
See related story:
Hydropower in doubt as climate impacts Mekong Basin water availability
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