Site icon Conservation news

A Brazilian city restores its mangroves to protect against climate change

  • A broad coalition of organizations is working to conserve and restore mangroves in the Greater Florianópolis area on Brazil’s southern Atlantic coast.
  • Mangroves are critical tropical ecosystems that dampen coastal erosion, serve as nurseries for aquatic species, and store more carbon per hectare than terrestrial forests.
  • These properties make mangroves a key part of coastal cities’ strategies to mitigate climate change and adapt to its consequences, such as rising sea levels.

Red, white and black mangroves are tropical ecosystem trees that exist between sea and river, in a unique condition of brackish water — the halfway point between freshwater and saltwater. In this transition zone that’s subject to tides, the plants have adapted by developing their own structures to breathe underwater and better cling to the muddy soil by using prop roots. Mangrove forests can be found along almost the entire Brazilian coast.

Considered nurseries for marine life, species that eventually migrate out to sea, mangroves are key to the fishing supply chain, both small-scale and industrial.

Just like any other ecosystem, mangroves provide natural services that people benefit, from such as carbon sequestration — up to 15 times more than forests on a hectare-for-hectare basis — and protection against the impact of sea waves, which can cause erosion in places where the native vegetation has been stripped away. However, these biodiverse areas are increasingly threatened by urbanization, invasive exotic species, sewage disposal, fires, and climate change.

Due to the inevitable rise in sea levels and the increase in the frequency and intensity of storms, coastal cities need investments and adaptation measures focused on reducing risks and minimizing the impacts caused by extreme weather events.

According to projections by the United Nations’ Intergovernmental Panel on Climate Change (IPCC), sea levels are expected to rise by 20 centimeters (8 inches) by 2050 if the increase in the global average temperature remains below 2° Celsius (3.6° Fahrenheit) above pre-industrial levels.

It may seem a small increase, but it will cause greater coastal erosion problems and indicates that future flooding will reach higher places that historically have never flooded, affecting more people and causing more damage. Rising sea levels are associated with ocean warming, which in turn interferes with rainfall, causing stronger weather events.

The relief at top shows the Greater Florianópolis area as it is today, compared to a projected 2-meter (6-foot) rise in sea level. Image courtesy of Roots of Cooperation.

The island of Santa Catarina on Brazil’s southern Atlantic coast is part of the state of the same name and home to the state capital, Florianópolis. It also hosts mangrove forests, which a network of public institutions, civil society organizations, conservation units and community members are working together to conserve. Known as the Roots of Cooperation project (Raízes da Cooperação), the coalition focuses on mitigation of and adaptation to climate change.

The project comprises three pillars: restoration, environmental education, and scientific research. This makes it a pioneering initiative for a work of this magnitude in the state. Throughout Brazil, there are only a handful of initiatives working with mangroves.

“The project is based on this triad, a socioeconomic concern that answers some questions related to current climate change, such as, for example, how coastal ecosystems and coastal cities will be impacted by rising sea levels,” says project head Dilton de Castro from the NGO ANAMA, which promotes sustainable socioenvironmental development initiatives.

The project’s permanent staff includes 15 people from five institutions: ANAMA, the Federal University of Santa Catarina (UFSC), the Santa Catarina state environmental institute (IMA), the Environmental Management and Education Agency (AGEA) and the Çarakura Institute.

Researchers collecting mangrove soil samples in Florianópolis to study. Image courtesy of Dilton de Castro.

Mangroves instead of pine trees

The mangroves targeted for restoration are located in the river basin with the highest population density in Santa Catarina, which also includes the main water sources that supply the Greater Florianópolis area. The project extends across protected areas in the municipalities of Palhoça, São José and Florianópolis itself, which are home to Guarani Mbyá Indigenous communities and small-scale fishers, among other social groups.

Now in the final third of its duration — the project began in February 2023 and runs until February 2025 — it works with state-owned oil and gas giant Petrobras’s CSR program to carry out ecological restoration activities in mangroves and salt marshes. There’s a focus on replanting native species and removing invasive ones; environmental education and social mobilization through seminars, courses, workshops, meetings and collective actions; and two scientific studies on carbon sequestration and sea level rise.

Activities under the project have been carried out in conservation units and surrounding areas of Serra do Tabuleiro State Park (in Palhoça municipality), Carijós Ecological Station and Pirajubaé Extractive Reserve (Florianópolis), and Morro dos Cavalos Indigenous Land (Palhoça).

The conservation and restoration activities in Palhoça cover a total area 10 hectares (nearly 25 acres), comprising 7 hectares (17 acres) of mangroves on two islands in the Madre River and the Maciambu River, 3 hectares (7 acres) of salt marshes surrounding the visitor center at Serra do Tabuleiro State Park.

Pines cut down on an island in the Madre River. Image courtesy of Adrio Ceteno/IMA.

The direct benefits of restoration create indirect benefits that can promote the protection and resilience of 55 hectares (136 acres) of mangroves, salt marshes, wetlands and forests in the area.

“It’s like the human body,” Castro says. “If you have a knee problem, you stop doing several activities and that affects the system as a whole. But once you cure the problem, you have a healthy body.” The same concept of resilience, he says, boosts the positive effects of on-site conservation.

The team says it hopes to expand and strengthen protection of the mangroves and salt marshes with the participation of community members; 600 people were involved in the first year, and 2,000 are expected to have participated by the end of the project.

On the environmental education front, the project kicked off with a seminar at its launch in the state legislature, followed by eight ecological restoration workshops, other workshops on how to fight forest fires, and a theoretical and practical training course on citizen science development for managers and teachers. These in turn have resulted in the development of further initiatives in the communities surrounding Carijós Ecological Station, Pirajubaé Extractive Reserve and Serra do Tabuleiro State Park.

The training series will include two more phases this year and will culminate in a seminar to present the outcome of the project. Ongoing training on honey production using stingless bees is also underway for four villages in Morro dos Cavalos Indigenous Territory.

Mangrove area with pine trees in the background leading up to Mount Cambirela. This landscape is part of Serra do Tabuleiro State Park in Palhoça. Image courtesy of Dilton de Castro.

Responses to tackle the climate crisis

With support from UFSC’s graduate studies program in oceanography, two studies are being carried out under the project to better understand the contribution of mangrove conservation and restoration to the mitigation of and adaptation to climate change. In addition to threatening mangroves with rising sea levels, the increase in the global temperature is expanding tropical areas, causing mangroves to advance toward the south of the state.

Master’s students are currently comparing the potential for carbon sequestration and storage in natural mangroves and those growing in the landfills of the Greater Florianópolis area. To do this, they’ve collected soil samples from four mangrove areas: two natural ones and two from the artificially created landfills.

The study aims to find out whether mangroves in the latter, human-generated ecosystem have the same carbon-absorbing capacity as natural ones. “Mangrove soil has a high carbon storage capacity, which is why we chose to focus our main analysis on soil rather than roots and leaves,” says Aline Zanetti, a master’s student working on the project.

Mangroves accumulate 50-90% of their carbon in the soil. The waterlogged soil gives rise to a low-oxygen environment, which means that the organic matter that piles up here — leaves, branches, dead animals — don’t decompose as quickly as they would in the open air, thus keeping the carbon they hold in the soil for longer. It’s this waterlogged property that makes coastal ecosystems much more effective carbon sinks than terrestrial forests. For their study, the researchers will also collect samples of mangrove roots to see if there’s a difference in the carbon stock potential of created and natural mangrove roots.

Participants carry out an exercise during a workshop on fighting forest fires. Image courtesy of Gisele Elis.

The other study being carried out under the project is at the doctoral level, and aims to quantify changes in coastal flooding patterns in the Greater Florianópolis area based on projections of future climate change impacts. The research effort is developing a geographic database of the area that will also contribute to the project’s assessment, monitoring and ecological restoration. The mapping is also expected to help support studies on vulnerability and future occupation in the area. The researchers plan to publish their results in a scientific journal and also in a book about the mangroves of southern Brazil.

“Based on spatial analyses conducted through remote sensing and geoprocessing, we compared this information with public policies: basin plans, sanitation plans, urban masterplans, management plans, and coastal management,” says Luiz Pimenta, a geographer and doctoral candidate working on the project.

Pimenta and his team’s analysis of city master plans show that urban expansion zones are located precisely in flood-prone areas. “The more the sea rises, which is related to an increase in the planet’s temperature, the more these extreme events such as rain, tornadoes and coastal erosion will intensify, and public policy is creating future scenarios that are disaster scenarios,” Pimenta says. “The projections for occupation of areas are scary.”

In Santa Catarina’s hydrographic region 08, which covers 22 municipalities centered around the Greater Florianópolis area, 60% of urban zones already suffer from flooding as a result of rainfall.

“The risk for coastal cities is the increase in these heavy rainfall events, which are linked to the planet as a whole, with the curves of extreme events going from 300 mm to 700 mm [12 in to 28 in] of rainfall, as well as rising sea levels,” Pimenta says. “Thinking that cities are growing and that there will be more people living in flood zones, the tendency is to increase the vulnerability of communities unless effective public prevention policies are created to change that.”

Climate adaptation and mitigation measures include nature-based solutions, rehabilitation and restoration of ecosystems vulnerable to extreme events, the possibility of relocating people, and the creation of mechanisms and means for communities to face these types of event. The latter include so-called non-structuring actions such as environmental education, and structuring ones such as building seawalls and embankments.

Project proponents say investment is needed in research, such as that being conducted under this project. Knowledge of the carbon stock potential and rehabilitation and restoration of mangroves is key for developing strategies for coastal cities like Florianópolis to mitigate against and adapt to the worst impacts of climate change, in addition to protecting the biodiversity of a unique ecosystem and contributing to the sustainability of the ways of life of traditional communities.

Banner image: Mangrove forest in Ponta da Daniela, a peninsula at the north of Santa Catarina Island that may disappear with rising sea levels. Image courtesy of Roots of Cooperation.

This story was reported by Mongabay’s Brazil team and first published here on our Brazil site on May 17, 2024.

Exit mobile version