Mangroves are located in wetlands, along the shores or deltas of rivers (in tropical and subtropical salt waters areas). They consist of both woody vegetation (for which an extensive root system is characteristic) and shrubs. They are an important space for many types of habitats used by diverse species of plants and animals.
Mangroves are the most effective coastal protection against hurricanes, coastal erosion, tsunamis, storms, floods and cyclones. (They absorb the wave energy from 13 to 66% in a 100m wide belt and reduce the height of the storm wave (from 50 to 100%) in a 500m wide belt). A 1000 m wide mangrove strip reduces the flood height by 5 to 50 cm / km. Reduces the height of the tsunami by 5 – 30%. The wave reduction increases with the root density of mangrove forests (the density and height of the tree crowns are important). Mixed mangroves with different tree age structures are the most effective.
Dense roots of mangroves also retain sediment and participate in soil construction – its height increases by 10 mm per year, so they can be an component of coastal protection against the effects of rising sea and ocean levels.
They purify water (retain pollutants, including large ones), and reduce the amount of carbon dioxide. They purify rainwater. They have a great influence on the development and proper functioning of sea meadows and coral reefs, salt marshes and dunes.
The condition of mangrove forests is influenced by climatic changes (both sea level and water temperature rise). They support the development of aquaculture and fisheries.
References and additional resources
https://www.nature.org/media/oceansandcoasts/mangroves-for-coastal-defence.pdf
http://nrcsolutions.org/mangroves/
Example:
Sanya Mangrove Park
The project is an example of how to create mangrove forests in urban spaces, serving both environmental and social roles. This project was created in China in the city of Sanya. It assumes the restoration of mangrove forests damaged as a result of the island’s urbanization. They were created in place of concrete breakwaters protecting the city from sea waves. 10 hectares of shores along the Sanya River were used for the implementation of the project (here salt water from the sea and fresh water from the land meet), additionally the area was heavily degraded and cut off by a highway.
Material from the demolition of concrete structures was used for the design and construction of the park. Meandering waterways were modeled, thus increasing the coastline from 700 m to 4,000 m, which plays an important ecological role (creating more habitats). On the whole area, from the side of the highway, terraces were built on which plants were planted. They purify rainwater from sidewalks and streets. Infrastructure in the form of footbridges, platforms, sidewalks, and observation towers was also built, encouraging tourists and residents of the city to use the new park space.
Source: https://www.asla.org/2020awards/178.html