Since the early 2000s, Africa's urban population has more than doubled, to over 600 million in 2020. If current growth continues, the urban population is expected to double again by 2050. In Africa, the annual rate of urban expansion is outpacing the growth rate of the urban population. Globally, future urban expansion is expected to result in significant losses of food production, reductions in biodiversity, and increased emissions from land-use change, putting livelihoods and the natural environment at risk.
Recent studies on the environmental impacts of urban expansion typically treat it as the conversion of different land covers into urban land and focus only on direct impacts. In a new study published in Nature Sustainability, IIASA researchers and their colleagues demonstrate the complexity of expected urbanization and its various environmental impacts.
“Africa is urbanizing most rapidly and therefore its food systems are also changing rapidly. This puts enormous pressure on food security in what is already one of the most food-insecure regions in the world,” said study author Coen de Vos, visiting research assistant in the Integrated Biosphere Futures Research Group at IIASA's Biodiversity and Natural Resources Program. “Our study takes into account both direct land-use changes and indirect effects of urbanization on agricultural shifts and dietary changes, particularly with regard to rice consumption.”
The researchers developed a way to synthesize all this information using the GLOBIOM model, producing an elaborate, complex, and multidimensional study unprecedented in its scope. The results show that, contrary to common belief, the impact of urban expansion on food production losses is limited, as agricultural land simply expands elsewhere. At the same time, the impact on natural land is more significant, including not only the direct impact of urban expansion but also the subsequent displacement of agricultural land.
The most significant environmental ramifications will come from dietary changes, especially rice consumption. Rice consumption will increase in African cities, so more rice will need to be produced, increasing reliance on imports and local production. This will result in increased methane emissions, further loss of natural areas, changes in water use and biodiversity loss.
“These results add to the evidence that our diet is one of the major drivers of the health of the planet,” explains study co-author Marta Kojka, a researcher in IIASA's Integrated Future Biosphere Research Group.
The researchers emphasize that policymakers should adopt a holistic approach in their decision-making processes: incorporating indirect impacts of land use and dietary changes into land-use planning and policymaking is essential to address future sustainability challenges.
reference
De Vos, K., Janssens, C., Jacobs, L., Campforts, B., Boere, E., Kozicka, M., Leclère, D., HavlÃk, P., Hemerijckx, LM, Van Rompaey, A., Maertens, M., Govers, G. (2024) Food systems and biodiversity in Africa are affected by urbanization through dietary changes, not area expansion. Nature Sustainability DOI: 10.1038/s41893-024-01362-2
