Connecting Global Climate Change Mitigation Policies to Local Dynamics in Africa

Andrea Castelletti
Department of Electronics, Information and Bioengineering, Politecnico di Milano, Milano, Italy

Matteo Giuliani
Department of Electronics, Information and Bioengineering, Politecnico di Milano, Milano, Italy

Winning article: Unintended consequences of climate change mitigation for African river basins (Nature Climate Change, 2022)

“This study is foundational in the exploration of side effects for African river basins of global policies safeguarding our climate within planetary boundaries”

The Water-Energy-Food (WEF) Nexus is a major global focus as the world seeks to address climate change and meet sustainable development goals because it allows a better understanding of the interdependencies and interactions between water, energy, and food systems. These three elements are essential for human well-being and are deeply interconnected, with changes or disruptions in one component that can have ripple effects across the entire system. Addressing the challenges within the WEF Nexus requires an integrated and interdisciplinary approach that considers the trade-offs, synergies, and potential co-benefits across sectors.

Emerging climate change mitigation policies focus on the implementation of global measures relying on carbon prices to attain rapid emissions reductions, with less attention paid to the quantification of local-scale impacts of abatement options for diverse groups of stakeholders with potentially conflicting needs or preferences. To help guide future policy decisions, there is a growing need for tools allowing the integration of socio-economic, climate, hydrologic, irrigation, and power systems to explore alternative future and their local effects.

Our research addresses this gap by investigating how multisector dynamics across interconnected WEF systems at the local scale are impacted by global climate change mitigation policies. Our analysis uses a river basin-scale model of the Zambezi Watercourse in southern Africa that enables exploration of synergies, trade-offs and vulnerabilities for the WEF systems, including hydropower production, irrigation supply and ecosystem services in one of the largest transboundary river basins in Africa as well as in the world. Specifically, we explore the interactions of climate change with global socioeconomic development by considering a large ensemble of global scenarios simulated by the Global Change Analysis Model (GCAM), a model widely used in major integrated climate–energy–economic assessments.

The main finding   of our research is a warning about the potential unintended harmful local impacts to African river basins if global leaders fail to coordinate climate change mitigation. For example, our projections suggest the Zambezi Watercourse will be exposed to severe risks of performance degradation across all the components of the WEF systems mostly due to alternative land-use change policies. In particular, policy fragmentation between developed and developing countries in their approach to addressing carbon emissions from land-use changes could encourage proliferation of large-scale agricultural projects in Africa if land-use emissions are priced lower there. This rapid increase in agricultural land use could generate irrigation demands that are two times higher than under globally coordinated approaches to emissions reduction. Higher irrigation demands constrain the availability of water resources for hydropower production or the provision of ecosystem services, which could add stress to African economies and natural ecosystems. Analogous vulnerabilities are found across most basins in southern and western Africa, raising concerns about the equity of these global climate change mitigation policies for African countries.

Photo 1. Sugar cane fields in Zambia with pivot irrigation using sprinklers that rotate around a central water pump, generating gigantic circles (credits ATEC-3D).

Our study sheds light on the importance of connecting global climate change mitigation policies to their potential impacts on local multisector dynamics. While only a few years ago we did not have modeling tools and computing resources to run these simulation experiments, we can now use similar tools for better understanding the impacts of global policies at the local scale and for supporting the adoption of evidence-based policies that foster a more sustainable and equitable transition to a decarbonized future. As the world moves towards implementing mitigation and adaptation strategies to climate change, these studies will become increasingly important in navigating synergies, tradeoffs, and vulnerabilities within interconnected food, energy, and water systems across scales.

We plan to adopt this approach for investigating the role of hydropower in the African energy transition, where many countries are striving to meet increasing energy demands driven by population growth and improving living standards. To reduce emissions, many national capacity expansion plans are attempting to use low-carbon electricity sources and exploit the untapped continental hydropower potential with 300 new hydropower projects planned in Africa for a total of around 100 GW of new installed capacity. However, climate, socio-economic, and technological changes are making these investments in new dams more risky and less economically efficient. As the cost of other renewables continues to decline, solar and wind power are projected to becoming more competitive and potentially cheaper alternatives that could substitute planned hydroelectric dams. This strategy reduces the variability of the energy output, reducing the exposure to long-term hydrological changes. Harmonizing global policies with local needs and strategies is key to understand how global planetary boundaries map into local multisector impacts and correct potentially unintended discrepancies.

Photo 2. Leading author of the winning article, Matteo Giuliani.