How Do Saltmarshes Protect Coastlines?

Rising seas and fiercer storms threaten coastal communities globally. With 15% of the world’s population living on coastlines, effective planning is critical. Saltmarsh restoration is a resilient, cost-effective alternative to traditional storm defences.

What are saltmarshes?

Saltmarshes are the interface between land and sea. These coastal wetlands form along shorelines in areas where sediment accumulates. Saltmarshes are dynamic: they evolve with tidal rhythms, being periodically submerged and exposed. Specialised salt-tolerant plants and biodiversity thrive in these ever-changing landscapes. Saltmarshes serve as critical nursery grounds for fish, habitats for amphibians, and resting stops for migratory birds. Saltmarshes are found across temperate coastlines globally. Their tropical counterpart are mangroves, where salt-tolerant trees grow in place of saltmarshes.

How do saltmarshes protect coastlines? 

When a storm arrives, saltmarshes act as a buffer, dissipating wave energy and sheltering inland areas from the full force of the surge. Unlike typical sea defences, known as “grey infrastructure” (such as concrete seawalls) which simply resist water until they potentially fail, saltmarshes are a “nature-based solutions” that buffer storms while offering multiple benefits. They act as natural water filters, trapping pollutants and sediments, while simultaneously sequestering vast amounts of “blue carbon”. For local communities, coastal wetlands like saltmarshes and mangroves are a rich resource, supporting sustainable fisheries as well as offering recreational spaces.

How do saltmarshes form? 

Saltmarshes take centuries to develop naturally:

1. Sediments collect on shallow sandy or muddy coastlines in area of low current and wave height. This creates areas along the coast that are flooded less frequently with the tide.
2. Pioneer plants like glass wort (salicornia) spread, with the young shoots and plant matter creating a filter that retains more and more sediment at low tide.
3. Over time land is higher than the regular tidelines and other plants colonise the area, further stablishing the saltmarsh through root formation. It’s a positive feedback loop which expands the saltmarsh.
4. Areas emerge with varying flooding frequency in which three typical vegetation zones become established (pioneer zone, low saltmarsh, and high saltmarsh).
5. Eventually tidal creeks and channels form through which the saltmarsh is drained.

Why do we need to protect and restore saltmarshes? 

Coastlines are multiple-use areas and many saltmarshes have been drained or filled to make way for urban development and agriculture. Some regions of Europe have lost as much as 80% of coastal wetlands and seagrasses. In doing so, we have dismantled the natural infrastructure and inherent resilience of our coastlines. As climate change makes storms more frequent and sea levels rise, restoring saltmarshes is key to protecting our coastlines and coastal communities. Even restoring saltmarshes with less than ten metres in width can significantly buffer waves.

Evidence: The protective power of saltmarshes is backed by robust scientific data:

Wave reduction: According to a meta-analysis of 69 scientific studies, saltmarshes can reduce wave heights by an average of 72%.

Disaster mitigation: When Hurricane Sandy struck the North-Eastern US coast in 2012, impacting heavily urbanised areas like New York and New Jersey, it was estimated that temperate coastal wetlands reduced property damages by more than 10% on average. In some areas, the damage reduction benefit reached as high as 29%.

Economic value: The value of saltmarshes for buffering against storm impacts is immense. In the U.K, where 85% saltmarshes have been lost since the 19th century due to land reclamation, the protective service of saltmarshes has been estimated at up to £786 million per year.

Creating resilient coastlines 

Regions4Climate unites 12 European regions to accelerate the transition toward climate resilience. In the Basque Country, local partners are focusing on Txingudi Bay, a zone critically exposed to rising sea levels, to restore its original marshland ecosystem.

This involves:

• Restoring 5.5 hectares of saltmarsh
• Evaluating the ecological and social impacts of restoration
• Strengthening adaptive governance and planning

By translating these on-the-ground lessons into actionable policy, the project aims to establish saltmarsh restoration as a scalable, nature-based solution for protecting coastlines across Europe and beyond.