Coastal river deltas, home to approximately half a billion people, are facing significant threats not solely attributable to climate change. These regions have been vital since the last ice age, offering flat, fertile lands ideal for agriculture, and have evolved into major hubs for global shipping trade, fostering the growth of megacities like Dhaka, Cairo, and Shanghai.
Recent research involving 49 deltas worldwide, including the Nile, Mekong, and Mississippi, indicates that these areas are at increasing risk under all future climate change and development scenarios projected by the IPCC. Critical risks vary among deltas but generally include land subsidence, growing population density, intensive agriculture, ineffective governance, and limited capacity for adaptation.
A major concern is land subsidence, which in some deltas, occurs three times faster than sea level rise. This sinking is caused by the compaction of sediment piles under the weight of developments and the extraction of water, oil, and gas. It leads to relative sea level rise, causing issues like soil salinization, flooding, and in extreme cases, loss of coastal areas. For instance, about 25% of Jakarta, Indonesia, is projected to be submerged by 2050.
Densely populated deltas, such as the Nile, Ganges, and Pearl, are facing challenges from urban development, which impedes natural sediment delivery and exacerbates land sinking. Agriculture, particularly irrigation, is also a significant factor in subsidence. The impact on food production is notable, as seen in Vietnam’s Mekong delta, a major global rice supplier.
Adaptation capacity in delta regions varies, with many, like the Irrawaddy in Myanmar and African deltas including the Congo, Limpopo, and Zambezi, having low government effectiveness and readiness. International support is crucial, but the adaptation finance needs of developing countries are significantly higher than the current international public finance flows.
Solutions must address these multifaceted risks. Climate change mitigation remains critical, alongside managing groundwater and fossil fuel extraction. Urban and agricultural practices should be adapted to enhance flood resilience and accommodate delta processes. Engineered solutions like sea walls may be necessary, but they should not be the only strategy. Inclusive development of solutions involving local communities, experts, and proactive government action and financing is essential to address these complex challenges.