Coastal river deltas face major threats beyond climate change 

Coastal river deltas are under an enormous amount of strain and the dangers they face extend beyond climate change, according to a new study from Lund University and Utrecht University. 

The researchers have identified the pressures that pose the biggest threats by analyzing possible future development across 49 coastal river deltas worldwide. 

Ineffective governance 

The results suggest that poor environmental governance is the biggest threat to the sustainability of deltas. This is particularly the case in Africa and Asia.

Study lead author Murray Scown is an associate senior lecturer at the Lund University Centre for Sustainability Studies.

“We can clearly show that many risks are not linked to climate,” said Scown. “While climate change is a global problem, other important risk factors like land subsidence, population density and ineffective governance are local problems.” 

“Risks to deltas will only increase over time, so now is the time for governments to take action.”

Global sustainable development

Home to more than half a billion people, coastal river deltas support agriculture, fisheries, cities, and unique ecosystems. 

“Deltas play a critical role in the ambition to achieve global sustainable development given their relatively large shares in population and productive croplands, as well as their precarious low-lying position between upstream river basin development and rising seas,” wrote the researchers.

Sea-level rise 

The experts noted that the low elevation of deltas means that they are highly exposed to risks from relative sea-level rise, flooding, and salinization. 

“As a result of these risks and further urbanization, ecosystems in deltas are increasingly degraded or lost,” wrote the researchers.

Uncertain future

The loss of delta environments could have major consequences. Despite the importance of deltas for sustainable development, the future of deltas around the globe remain highly uncertain and unexplored, the researchers noted. 

Focus of the study 

The team analyzed five different IPCC scenarios for global development in deltas all over the world to predict possible risks throughout the rest of the century. The study was focused on 13 primary risk factors. 

The experts studied famous deltas such as the Nile and the Mississippi, but also included deltas that are less well-known such as the Volta and Zambezi deltas. 

“The 49 deltas analyzed for this research include the most populated and largest coastal deltas in the world, as well as a range of smaller and less populated deltas to provide a representative sample of the world’s deltas across climates, biomes, and socio-economic development states,” wrote the study authors.

Critical insights

The analysis revealed that, under all five scenarios, the biggest threats to coastal river deltas are population density, land subsidence, sea-level rise, crop land use, and ineffective governance.

Land subsidence was found to be the greatest risk factor for the Mekong delta in Vietnam, while extreme sea levels are among the most concerning risk factors for deltas in China and several other parts of the world. 

Under certain scenarios, population density was the biggest future threat for the Nile, Niger, and the Ganges deltas.

Potentially devastating consequences 

“Analyzed all together, we can see that the Asian mega-deltas are at greatest risk, with potentially devastating consequences for millions of people, and for the environment,” said Scown. 

“They are under pressure from population growth, intense agricultural land use, relative sea-level rise, and lagging adaptation readiness.”

Urgent action is needed

Study co-author Philip Minderhoud, assistant professor at Wageningen University and Research, said that instead of sitting back, governments need to think long-term, and put plans in place to reduce or mitigate risks. 

“In the Mekong delta, for example, the Vietnamese government are making strong efforts to restrict future groundwater extraction in the delta to reduce land subsidence and salinization,” said Minderhoud.

The study is published in the journal Global Environmental Change.

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