Wrong measures aggravate coastal erosion

Maldives island

Maldives island. (Image: SimonSkafar / iStock)

Small island states like the Maldives are severely affected by climate change and the resulting rise in sea levels. But man-made interventions in coastal structures also contribute to coastal erosion, as a study has now shown. On some islands in the Maldives, structures such as ports, but also improperly planned protective measures have damaged the coasts even more than the rise in sea levels.

The rise in sea level particularly affects flat coasts and islands. Because they have little to counter the rising tides. Most of the atolls in the Pacific and Indian Oceans are only around one meter above sea level and are already being flooded with increasing frequency. Climate forecasts predict a global mean rise in sea level of more than one meter by the end of this century. Adaptation to this development is therefore particularly important for small island states.

But in order to find out which adaptation strategies best protect the coasts of the island states, the exact causes of the damage must first be determined. Above all, the erosion of beaches and coasts is mostly based on an interplay of climate, sea and the properties of the coast itself. Using the example of the Maldives, Gabriel David from the Technical University of Braunschweig and his colleagues have therefore examined more closely which natural or anthropogenic processes are reinforce coastal erosion there. The aim was to be able to counter undesirable developments in the adaptation to the climate-related rise in sea levels more effectively.

Building inhibits natural growth

The team actually found what they were looking for: “Among other things, we found that coastal structures that were built can actually contribute to coastal erosion to a similar extent as the consequences of climate change itself,” reports David. This is the case on the Maldives island of Fuvahmulah, among others. As the scientists found out, a port built around 20 years ago prevents the natural transport of sediment. These sand shifts usually help keep atoll shorelines intact. “A reef island actually has very good opportunities for natural adaptation to rising sea levels if the offshore coral reefs are intact and the transport or distribution of sediments is naturally made possible,” explains David.

But the dike built on Fuvahmulah hinders this natural process and thus the “growing” of the coast with the sea level. It undermines the supply of sand and thus prevents the transport and thus the natural protective functions of the island. According to the research team, this illustrates that adaptation to climate change in sensitive island states must always be undertaken with a view to the natural conditions. Incorrect development measures and adaptation strategies, on the other hand, could lead to considerable negative impacts, which are superimposed on small island states with the effects of climate change that are already taking place and which will intensify in the future.

The problem of politics

The researchers also see the socio-political conditions in many island states as a cause of such undesirable developments: the best solution is not always chosen in order to receive international funding and advance the economy. “The results show the partially impaired adaptive capacities of small island states in their perception and handling of climate-related changes,” explains Torsten Schlurmann from Leibniz University in Hanover. “Top-down political processes with centralized government models are often major structural challenges in these countries.”

Many local actors and politicians are well aware of the causes and consequences and are questioning some of the adjustments made at the central level. “The government of the Maldives, however, is planning to set up classic coastal protection infrastructures as a countermeasure – among other things, a tried and tested means of obtaining external funding with international help,” says Schlurmann.

Source: Leibniz University Hannover; Technical article: Nature Communications, doi: 10.1038 / s41467-021-26082-5)

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