Climate change is widely accepted as one of the greatest challenges faced by countries today. Policymakers are increasingly questioning the sustainability of the global economy, citing widespread market failures as contributing factors; however, various constraints have hindered the design and implementation of coordinated mitigation policies. The predicted global impacts of climate change are thus discouraging, .
Understanding the impact of climate change on developing economies is a high priority. Given their insufficient economic, institutional, and technological capacity to fight climate change, these regions are the focus of the policy debate on climate vulnerability. How will these societies adapt during the next decades? What could be the mechanisms behind these adjustments? How could policymakers moderate associated welfare losses? This article hints at answers to these questions from the perspective of climate migration.
Why study climate migration in sub-Saharan Africa?
There are many reasons to focus on climate-induced migration. Most that still rely on rudimental, climate-vulnerable technologies (Wollburg et al. 2024). Demographically, they feature the highest population growth rates in the world (UN 2019). Declining farm yields could inevitably displace this growing population from their homelands (Kala et al. 2023), potentially leading to a process known as the Great Climate Migration (Lustgarten 2020).
In , I investigate this by looking at future climate migration in sub-Saharan Africa (SSA). In addition to being low-income rural economies, SSA countries also lack market integration, which becomes an additional obstacle to adaptation (Nath 2024, Porteous 2024, Cruz and Rossi-Hansberg 2024). I incorporate these features in a quantitative framework that projects how migration flows will react to future climate damages within and across countries in SSA. I also use it for policy experiments that highlight the benefits and trade-offs of market integration policies.
How will climate change affect Sub-Saharan Africa?
Climate change will have a significant impact on agriculture in SSA, especially since the region grows several differently vulnerable crops. While some regions, such as SSA, will be damaged by a warming planet, others are expected to benefit from it. This means that climate adaptation could take place locally through crop diversification. While many highly suitable locations are not expected to adapt, less suitable locations are. Figure 1 illustrates this pattern for cassava in SSA.
Figure 1. Climate change effects on potential cassava yields for 2000 (left) and 2080 (right)
Intuitively, affected individuals could react to these changes by moving away. The reality, however, may not be so simple due to high mobility barriers. Moreover, if yield changes allow affected regions to produce goods from other sectors (e.g. another crop or urban goods), individuals may not need to move away from their home regions. In other words, climate change could structurally change affected regions, moving people away from regions (and/or sectors) that are today extremely poor and unproductive (Lagakos et al. 2023, Conte 2023, Conte et al. 2021, Nath 2024). However, in the high frictional context of SSA, such an adaptation process may not occur, making welfare losses more significant.
Developing a quantitative framework for future climate migration in SSA
To quantitatively assess the SSA responses to the above dimensions, I develop a spatial general equilibrium model, following Costinot et al. (2016) and Desmet and Rossi-Hansberg (2024), combined with FAO-GAEZ data, that predicts future population displacement, sectoral reallocation of production, and the welfare consequences of climate change.
One important assumption is that agricultural crops are necessity goods, which agents cannot fully substitute with non-agricultural goods. This limits the capacity for structural change in response to climate change, a feature referred to as the 'food problem' (Gollin et al. 2014, Nath 2024). Importantly, the model calibration carefully quantifies the extent of spatial frictions in SSA with a novel, granular spatial dataset on bilateral intra/international migration flows and prices. The magnitude of the estimated trade and migration barriers within and across SSA countries are substantially larger compared to equivalent numbers for developed economies.
The main exercise simulates the SSA economy as climate change unfolds as per the RCP 8.5 (business-as-usual) scenario throughout this century. On aggregate, climate migration flows consist of about 20 million individuals, with associated welfare losses (measured as GDP pc) in the order of -1.8%. Non-agricultural employment changes (a measure of structural change) decrease slightly. The underlying mechanism is the food problem mentioned above: affected locations, unable to adapt through migration or sectoral specialization, employ more people in agriculture to produce enough food, i.e. they are caught in a climate-induced poverty trap.
Figure 2 documents how these aggregate results are distributed across space. Many locations experience severe outmigration (Panel A) and welfare losses (Panel B). Hence, the modest aggregate numbers in Panel A mask the many losers and few beneficiaries of climate migration. Table 1 Panel B corroborates this, as countries in the bottom percentiles of the welfare losses' distribution experience losses of about -15%.
Figure 2. Aggregate and distributional climate change effects across SSA
Panel A. Climate migration across SSA Panel B. Welfare losses across SSA
What if Africa adopts EU migration and trade policies?
A key takeaway of this research is the link between spatial frictions and the magnitude of climate change effects. By hindering adaptation margins such as migration or sectoral switching, trade and mobility barriers prevent the efficient reallocation of factors and magnify welfare losses. Therefore, reducing such barriers would permit SSA to better adapt. I test this hypothesis using a policy experiment that simulates a scenario in which SSA integrates the EU's national migration and trade policies.
I find that reduced migration barriers increase climate migration but reduce aggregate welfare losses by around half. Lower mobility barriers boost the push aspect of climate change, reallocating labour out of unproductive rural regions. However, these aggregate gains hide an underlying cost. While the policy makes individuals that migrate better off, those left behind remain as worse off as before; the distribution of welfare changes across countries thus remains wide and skewed. This experiment uncovers a trade-off associated with climate change mitigation and migration policy: it can reduce aggregate losses at the expense of more climate migration and high regional inequality.
Combining both policies demonstrates that trade openness mitigates this trade-off. Although these policies reduce aggregate losses, climate migration and welfare inequalities also decrease. This increases the allocation efficiency of factors across sectors and space, fostering a climate-driven process of structural change (i.e. a relative increase in non-agricultural employment). This has important policy implications: by combining both tools, SSA policymakers can leverage climate change to drive structural transformation, enabling a more equitable shift through trade and migration.
Policy implications for climate change and structural transformation in developing countries
Climate change need not result in negative outcomes if rural economies can successfully adapt. With sufficiently low mobility barriers, climate change could encourage a population shift out of poor, low-productivity rural locations, triggering a process of structural transformation. Openness to trade will shape the aggregate and distributional welfare effects of this process by enabling affected economies to shift production to less affected sectors. Future policies should focus on these factors to help vulnerable economies adapt more seamlessly to change climate.