mangrove

Abstract
Mangroves are important intertidal forests that exist in tropical and subtropical areas around
the world. They are important coastal protectors, providing coastal stabilization and wave
mitigation. Besides their protective ability, they fulfill a number of ecosystem services like
nursery grounds for juvenile fish, carbon sequestration and pollutant filtering. However,
mangroves have been under heavy threat in many countries due to anthropogenic pressure,
causing major degradation rates. In Lac bay, Bonaire, a big lagoon consisting of mangroves
and seagrass for example, high sedimentation due to erosion has caused channels to close,
creating hypersaline conditions in ponds together with high temperatures. The forest around
Lac bay therefore experienced high mortality rates and a strong decline in the systems’
health. Another bay, Lagun, showed similar degradation in the back pond, but due to lack of
documentation the actual cause is still uncertain. It is important to find out whether siltation,
hypersalinity and high temperatures are also an issue at Lagun in order to create a
successful restoration plan.

Vegetation, soil composition, conductivity and temperature were analyzed for several plots at
different location types around Lagun, including the degraded part in the pond. Results
showed that the silt layer in the pond was significantly higher than the other location types,
which indicates root burial caused by high sedimentation rates. Conductivity (as a measure
for salinity) and temperature were, contrary to the hypothesis, not higher in the pond
compared to other locations, and showed no significant relationship to mangrove abundance.
This could be explained by fresh water input due to heavy rainfall during the rainy season
that had just ended. For now, restoration measures should focus on mitigating external
pressures through habitat regeneration. Sediment trapping in and around watersheds and
runoff areas connected to Lagun could decrease the sedimentation rate and prevent burial
and floor elevation. Channel connection to Lagun could increase water circulation and might
help to prevent a larger part of the pond from drying out during the dry season. Active
planting can be combined with habitat restoration measures to increase survivability of
mangrove seedlings. Besides restoration efforts, more research needs to be done on the
existing pressures at Lagun, including Sargassum and trash inflow from the ocean, erosion
rates, pond water and soil quality and the effect of the nearby landfill on mangroves.
Documentation and monitoring of Lagun should be continued in order to obtain more
information about the processes at hand. With sea levels rising due to climate change, it is
crucial for Bonaire to have stable coastlines that can mitigate effects of storm surges, in
which mangrove forests play an important role.

This presentation gives an overview of the thesis work conducted to map the hydrological connectivity within the mangrove channels of Lac Bay, Bonaire,

Goal of research:

•Insight into Lac Bay

•Hydrodynamic behaviour

•Effect of creeks

Research Questions:

To what extent do existing creeks contribute to the tidal exchange in the mangrove forest of Lac Bay and how does creek restoration affect this tidal exchange?

•What physical characteristics affect the tidal dynamics of the Lac Bay mangroves?

•What are the hydrodynamic spatial and temporal effects of the tidal wave on the mangrove forest in Lac Bay?

•To what extent do creeks contribute to the tidal exchange in the Lac Bay mangroves and can the tidal exchange be increased by creek restoration?

Between October 25th and 28th, Bonaire’s Mangrove Maniacs hosted their first Mangrove Restoration Workshop .  The goal was to provide a platform for researchers, conservationists, park authorities or anyone passionate about nature restoration to share ideas and knowledge on mangrove restoration techniques.  With representatives from over 12 countries, including 20 in person and 40 virtual participants, this workshop strengthens the mangrove conservation network across the Caribbean.

Mangrove Restoration Workshop Presentations. Photo credit: Mangrove Maniacs

International Collaboration

Representatives from around the world including Aruba, Bonaire, Curaçao, the Bahamas, Jamaica, St. Lucia, Martinique, the Netherlands, Mexico, Belize, Costa Rica and the United States tuned in to share ideas for mangrove restoration practices.  Throughout this four-day event, participants engaged in meaningful dialogue, swapping ideas and tips on ways to maximize conservation efforts.  In addition, the last two days provided hands on experience in mangrove restoration, building and maintaining mangrove nurseries, as well as outplanting both along the coast and within degraded areas.

Funding and support was provided by the Regional Activity Centre for the Specially Protected Areas and Wildlife (CAR SPAW), Mangrove Maniacs, STINAPA Bonaire and the Dutch Caribbean Nature Alliance.  Presentations throughout the workshop spanned from expert University partners to representatives from NGOs to enthusiastic citizens.  In total, over 20 people were able to attend the workshop in person and over 40 participants logged in to attend the workshop virtually.

Lessons Learned

Participants in mangrove channel. Photo credit: Jessica Johnson

In addition to creating new networks and collaborative partnership opportunities, this workshop provided firsthand experience in the field of mangrove restoration.  Mangroves are continuing to gain recognition not only for their ability to provide critical habitats and coastal protection but also as a significant tool for building resilience against climate change.  This workshop provided key insight into the importance of maintaining environments to serve as carbon sinks as well as the ability to leverage Blue Carbon in future reporting and financing prospects.

DCNA’s director, Tadzio Bervoets, took the opportunity to stress the importance of supporting and growing research and education opportunities for students within the Caribbean region.  Caribbean islands have the unique ability to showcase a wide variety of natural habitats, perfect for conducting research and staying on the cutting edge of habitat restoration and conservation techniques.  Fostering this thirst for knowledge and educational growth within local Caribbean populations will be key to pushing the Caribbean to the forefront of environmental research.  Knowledge sharing opportunities, such as these, provide unique opportunities to bring together a wide range of people to maximize communal understanding of mangrove forests.  As climate change and human-driven pressures continue to increase, interventions from all levels will be required.

Members from Bonaire’s STINAPA and Aruba’s FPNA working together to plant buttonwood tree. Photo credit: Mangrove Maniacs

More Information

To learn more about the workshop, please visit the Mangrove Maniacs’ webpage (www.mangrovemaniacs.org/workshop2021).  From here you will find links to most of the presentations as well as contact information for presenting participants.  For more information on how you can get involved, contact your local park authority or join the Mangrove Maniacs mailing list by using this link.

Article published in BioNews 49

Healthy mangroves act as carbon sinks, storing a variety of greenhouse gases.  As mangroves degrade this ability is lost, but to what extend is still unknown. A 2019 study of Bonaire’s mangroves worked to analyze the differences between intact and degraded mangroves’ ability to store carbon. This work proved that preserving healthy wetlands is crucial in the fight against climate change.

Greenhouse gases, such as carbon dioxide (CO2) and methane (CH4), play an important role in accelerating global warming, worsening the conditions of climate change. When in balance, there are environmental systems in place which can trap greenhouse gases and allow an equilibrium to be reached.  Wetlands serve as a prime example of areas where productive plant communities are capable of storing and using large amounts of carbon through decomposition and photosynthesis.

Blue Carbon

Carbon which is stored within coastal environments has become known as “blue carbon” and could become key in building resilience against climate change moving forward. Of these blue carbon areas, mangroves are some of the most carbon-rich ecosystems on earth.  Through their dense leaf canopies and complex root systems, it is estimated that they are able to store carbon at a rate of 50 times higher thantropical rainforests.

Unfortunately, these areas are under threat.  Recent estimates have found that nearly one-third of these forests have been removed due to coastal development and land conversion.  In the Caribbean alone, nearly 24% of mangrove area was lost between 1980 and 2005.  When these areas are destroyed, not only do we lose the benefits of future carbon storage, but we begin adding carbon to the atmosphere that had been previously trapped in the sediment.

Scientists are just beginning to understand the importance of these ecosystems.  New policies are being drafted to advocate for these areas as important carbon sinks and policymakers are working to imbed these concepts into future climate change mitigation strategies.  Although the differences between healthy and clear-cut mangrove forests have already been studied, there is still a lack of information concerning forests which slowly degrade.  This slow degradation is generally the result of deteriorating environmental conditions, which causes trees to gradually die off.  As climate conditions continue to harshen, it can be expected that the remaining mangrove forests could see an increase in gradual die off, so understanding how this impacts their ability to function as a carbon sink will become critical.

Lac Bay

This is the case on Bonaire, where the mangrove forests around Lac Bay have been in gradual decline for decades.  A recent study conducted by the University of Bremen and the Leibniz Center for Marine Tropical Research and STINAPA Bonaire worked to understand these differences by quantifying the carbon sink capabilities of healthy and gradually degrading mangrove areas.

The area which was studied experience high sediment run off, as overgrazing and urban development have removed ground vegetation which would normally minimized erosion.  This high sediment run off has caused infilling within the mangrove forest, minimizing water circulation and creating areas of stagnant and hypersaline waters.  These conditions have led to the gradual die back of mangroves.  The presence of healthy and degraded mangroves within the same forest made Bonaire the perfect location to study the differences in these environments to better understand the carbon dynamics of these areas.

The Study

Measurements were taken between January and March of 2019.  17 plots of intact mangroves and 15 plots of degraded mangroves were selected.  In the end, a striking difference was found between these two areas.  Healthy, intact mangroves were seen to have larger amounts of both above ground (leaves, branches, trunks) and below ground (roots, sediment) biomass than those in degraded areas.  Degraded areas had very little aboveground biomass, resulting in less photosynthesis, less sedimentation and more erosion, chemical weathering and higher rates of decomposition within the sediment.  This complete loss of aboveground carbon capture and erosion of sediment meant that these areas could no longer be considered a carbon sink, but in fact act more as a carbon source, allowing previously trapped carbon to reenter the atmosphere or neighboring waters.

The Future of Mangroves

Interestingly, this study found that carbon left the slowly degrading areas slower than in forests where mangroves were intentionally cleared.  This could be important for future climate change mitigation plans as scientists believe that climate change will increase aridity in parts of the Caribbean, Central and South America and South Asia altering hydrology and causing seasonal hypersalinity which will lead to the gradual die off of large amounts of remaining forests. Understanding these differences will be key in forecasting the ability for natural areas to serve as carbon sinks in the future. This study proved that slowly degrading mangroves are no longer functioning as carbon sinks and efforts must be made to keep the remaining forests intact and healthy if we hope to find more natural solutions to minimizing our carbon footprint.

https://www.dcbd.nl/document/impacts-wetland-dieback-carbon-dynamics-com...

Article publish in Bionews 41

Abstract

Human development, extreme weather events and rising sea levels are driving the loss anddegradation of many of the world’s mangrove ecosystems. Mangrove forests are natural coastalbarriers that provide protection from erosion and storms while also supplying material andbiodiversity services tohuman andnon-humancommunities worldwide. In recent years innovativeand novel products of ecological engineering have emerged to safeguard and restore coastalecosystems. Biodegradable Ecosystem EngineeringElements(BESE) are one such innovation thathave been shown to stabilize sediment, attenuate waves, and mimic dense root mats to facilitatethe establishment of coastal vegetation. This studyinvestigatesthe effect of a built BESE structureon abiotic factors andRhizophora mangletransplant responsesalong a high-wave energy coastlineon the island of Bonaire, Dutch Caribbean. Results reveal that BESEelementsdo not significantlyalter wave-energy and sediment mobility, or increase transplant survival, shoot growth rate andbiomass allocation. Survival rate of transplants was significantly higher when secured by rockscompared to BESE structures and bare sediment, highlighting simple, local, and low-cost methodsfor restoration. Despite not being significant, there were indications of the potential for BESEstructures toattenuate a minimal amount of waves and stabilize propagules for greater investmentin above-ground biomass during establishment. Yet, longer monitoring is needed to validate this.Limitations ofthe BESE structuressuggest thattheymay be more optimally used below-ground onsediment substrate, in larger clustered structures, or within interconnected foreshore ecosystemsfor landscape-level coastal protection and resilience.

Presentation from the Mangrove Restoration Workshop.  

Presentation from the Mangrove Restoration Workshop.  

Presentation from the Mangrove Restoration Workshop.  

Presented in 2021 Mangrove Restoration Workshop

After news was received that the Netherlands Antilles' largest and as yet
almost unspoiled lagoon would be involved in development plans, a
scientific survey was organised for obtaining new data on the present
condition of Lac, Bonaire.
The field work took place between i and 28 August, 1967, by Dr. P. J.
Roos, Amsterdam - who had already studied the coral fauna of Lac
in 1965 - and between 7 August and 23 September by Dr. P. WAGENAAR
HUMMELINCK, Utrecht, who first visited the lagoon in 1930. Roos did
most of the underwater work whereas HUMMELINCK collected biological
specimens from about 60 localities. The survey was initiated by the
Foundation for Scientific Research in Surinam and the Netherlands
Antilles (STUDIEKRING) and was financed by the Netherlands Foundation
for the Advancement of Tropical Research (WOTRO). The material is
being studied in the Zoological Laboratory of the State University at
Utrecht, in cooperation with specialists; most of the results will be
published in the Foundation's "Studies on the Fauna of Curacao and
other Caribbean Islands".
The Lac covers about 8 km^; of this one third is mangrove and shallow
mud flats (Figs. 3-5, 12). The transparency of the water is striking,
compared with that of other inland bays in the Lesser Antilles. Dearth of
nutrients may cause the absence of mangrove-oysters and other mollusks
known to occur in abundance in other mangrove lagoons, and also the
scarcity of balanids and other animal species which are common in
similar Caribbean environments.
Lac is separated from the sea by a barrier of coral debris; a shallow
flat of white sand occurs inshore (Figs. 3-4, 5, 12). The basin has vast
7"Aa/assj'a flats, whose shallower parts may be very muddy, often with
abundant Ha/twerfa. Syrtngorfjum grows near the entrance of Lac and
in other sandy areas. .4uraiwwV/ea is common in several inlets, where it
may grow in profusion. i?w/>£ia is found in creeks and ponds of high
salinity. .Di/j/an/Wa has been collected only once (Figs. 7, 12, 52).
More data on the fauna and flora are shown in Figs. 8-11. The distribution
of the small form of Afe/ongena we/ongena appears to have been
much larger some 30 years ago. CAfowe cawee/Za/a was not found in Lac
recently but it was abundant a few thousands years ago when the lagoon
extended further inland (Figs. 11, 51). It is likely that the fauna of Lac
has become poorer in recent times. The big heaps of S/tt>m6«s £tgas have
not visibly increased in size during the last thirty years (Figs. 8, 35-36).
During the last century the landscape has changed considerably.
Formerly the broad sandy barrier which separates the basin from the
mangrove-flat in the north (Figs. 12, 17-18, 24, 26, 46-47) had several
large openings through which the water could circulate. Afterwards part