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Restoring Mangroves & Managing the Mangrove Fern

Blogpost written by Luis Carlos Solis, Technical Assistant


The mangrove fern, an opportunist in disturbed environments

Mangroves are one of the most threatened ecosystems in the world. Unfortunately, mangroves in Costa Rica are no exception –  every day, mangroves around the country are devastated due to human activity, despite being declared protected areas . There are more than 80 protected mangroves identified in Costa Rica, representing approximately 41,002 hectares (101 318 acres), of which 99% are located in the Pacific. Just north of the Osa,  Térraba Sierpe National Wetland stands out as the most extensive mangrove in the country, with an area greater than 16,000 hectares (39 537 acres) – representing almost 40% of the mangroves reported for the entire country!

Terraba- Sierpe Wetland

Terraba- Sierpe Wetland from above by Frank Uhlig

 

The Térraba Sierpe National Wetland was declared internationally important  in 1995 by the International Convention on Ramsar Wetlands and through the Costa Rican Forestry Law. Through this designation, it became prohibited to cut or exploit the timber resources of this ecosystem. Prior to this in the 1970’s, timber was legally extracted in this area for the production of coal, firewood and construction materials, as well as bark for tannins and molluscs. This, combined with a large illegal extraction decimated much of this valuable mangrove forest.

In the 1980’s, the extraction and use of wood products from Térraba Sierpe Wetland led to a massive establishment of the mangrove fern Acrostichum aureum –  a native species that has a tendency to become overabundant with lots of light. In a healthy mangrove ecosystem, this mangrove fern coexists and is regulated by the shade of the large mangrove trees.  However, once mangrove trees are cut, the fern takes advantage of the light and space and becomes difficult to eradicate. High densities of this fern then prevent smaller mangrove saplings to grow and to establish healthy mangrove trees. Thus, in order to restore the mangrove ecosystem back to a more natural state, active restoration strategies must include removal of this aggressive fern.

 

mangrove fern

Mangrove fern is regulated by mangrove trees. In a healthy ecosystem, the fern is more easily managed and lives in balance.

 

mangrove fern

Without the presence of mangrove trees, the mangrove fern takes over. As an opportunistic species, this fern becomes overly abundant and grows very tall.

 

As Osa Conservation has been committed to protecting and restoring the Térraba Sierpe National Wetland, we plan to restore 50 hectares (20 acres) of mangroves that are currently occupied by the Acrostichum fern. As part of our new project called “Effective Strengthening of Mangrove Ecosystems in Costa Rica (Terraba Sierpe) and Improvement of the Quality of Life of the Local Coastal Population,” we aim to restore the structure and functions of this important mangrove ecosystem and help empower local communities  to responsibly manage the non-timber resources offered by the mangrove.

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We had a wonderful time recently celebrating this project. Working a with a wonderful group of partners, we are grateful to all of the participants who came out to support the project and we look forward to continuing to collaborate on this important effort to protect and restore this vital ecosystem.

 

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