Mangroves

The role of creeks for tidal exchange in the mangrove forest of Lac Bay, Bonaire

Nederlands below.

The mangrove forest of Lac Bay, Bonaire, is experiencing a die-off of trees in its northern area. Increasing the tidal exchange by creek restoration likely increases the living conditions for the mangrove trees. In the first months of 2022, a collaboration between the Mangrove Maniacs and the University of Twente was set up to investigate the hydrodynamic properties of the area and looked into the effects of creek restoration.

 

Creek in Lac Bay opened by the Mangrove Maniacs. Photo source: Rob van Zee

Lac Bay

Mangrove systems worldwide promote ecological diversity while also being economically valuable for humanity. If a mangrove forest experiences die-back, it loses the services it provides. One such case is the mangrove forest of Lac Bay, Bonaire. The northern side of Lac Bay, also known as Awa di Lodo, is experiencing a die-back of mangroves. Unsustainable overgrazing by livestock on Bonaire has depleted the area of ground cover vegetation resulting in the wind, vehicle traffic, and rainwater mobilizing and transporting sediment into Awa di Lodo. The excess sediment in combination with growing mangrove roots clogs lagoons and creeks, eventually closing off these creeks, reducing the hydrological connectivity between the front and back of the forest. High evaporation rates and a low influx of freshwater create hypersaline conditions in Awa di Lodo. The Mangrove Maniacs are trying to open the mangrove creeks so the tidal exchange (the tide-induced volume of water reaching Awa di Lodo) increases, lowering the salinity values in the area. However, it is yet unclear to what extent the existing creeks contribute to the tidal exchange in Lac Bay and to what extent creek restoration can improve the tidal exchange in Lac Bay.

 

Research

At the start of the year 2022, a group of researchers from the University of Twente monitored water levels and velocities and mapped topographic characteristics of Lac Bay. One of the goals was to create insight into the hydrodynamics of the mangrove system through in-depth analysis of this data. The propagation of the tidal wave, relations between the water levels and velocities and the tidal asymmetry were investigated. Next, a numerical model was developed to quantify the influence of creeks on the tidal exchange and to investigate the effect of creek restoration on the tidal exchange. To quantify the tidal exchange, the residence time of the water in Awa di Lodo was computed, which is the time it takes (in days) for the tidal exchange to completely replace the total water volume of Awa di Lodo.

 

Results

The obtained data shows that the diurnal tidal wave has a negligible delay in the open water of Lac Bay. In Awa di Lodo, high water is reached on average more than four hours later than in the open bay. During spring tides, the tidal range in the open water is sufficiently large to create an increasing trend in the water level in Awa di Lodo. The water level in Awa di Lodo lowers again when the tidal range decreases during consecutive neap tides. Flow velocities in the creeks mainly depended on the water level difference between the open water and Awa di Lodo. Both ebb- and flood-dominant peak velocity asymmetries are observed in the creeks. The observed flood-dominant tidal duration asymmetry in Awa di Lodo indicates that sheet flow during high tides is responsible for the fast increase of the water level in Awa di Lodo while during low tides the creeks are responsible for the outflow.

The hydrodynamic model showed that creeks significantly influence the tidal exchange from the open water in Lac Bay to Awa di Lodo (Table 1). A new creek connection to Awa di Lodo, preferably by extension of the creek through the center of the mangrove system, is found to be the most efficient to increase the tidal exchange. It was also concluded that the widening of the creeks, deepening of the creeks or the extension of the eastern creek system would have a limited effect on the tidal exchange. Hence creek restoration is shown to be an effective measure to increase the tidal exchange in the mangrove forest of Lac Bay.

 

Table 1: Tidal exchange, residence time and the ratio of the residence time of any of the scenarios compared to the reference scenario. Red coloured rows indicate a decrease in tidal exchange and blue coloured rows indicate an increase in tidal exchange. A darker shade implies a greater decrease/increase

 

Impacts on the future

The data analysis and the developed hydrodynamic model will be important tools for the Mangrove Maniacs to make decisions on where to open new creeks and to study the impact of their work. By having more insight into the hydrodynamics of Lac Bay, the mangrove restoration will become more effective and thus increase the ecological value of the area.

For more information, you can read the full report using the DCBD link below.

More info in the Dutch Caribbean Biodiversity Database

 

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De invloed van kreken op de getijdenuitwisseling in het mangrovebos van Lac Bay, Bonaire

Het mangrovebos van Lac Bay, Bonaire, ervaart het afsterven van bomen in het noordelijke gebied. Er is een goede kans dat het verhogen van de getijdenuitwisseling door het herstellen van mangrove kreken de leefomstandigheden van de bomen verbeterd. In de eerste maanden van 2022 is een samenwerking opgezet tussen de Mangrove Maniacs en de Universiteit Twente om de hydrodynamische eigenschappen van het gebied en de effecten van kreekherstel te onderzoeken.

Kreek in Lac Bay die geopend is door de Mangrove Maniacs. Photo source: Rob van Zee

Lac Bay

Wereldwijd bevorderen mangrovesystemen ecologische diversiteit terwijl ze ook van economische waarde zijn voor de mensheid. Als een mangrovebos sterft, verliest het een voor een groot deel de waarde die het kan toevoegen aan de wereld. Een voorbeeld hiervan is het mangrovebos van Lac Bay, Bonaire. Het gebied aan de noordkant van Lac Bay, ook wel bekend als Awa di Lodo, ervaart het afsterven van mangroven. Niet-duurzame overbegrazing door vee op Bonaire heeft het gebied ontdaan van bodem bedekkende vegetatie, waardoor wind, autoverkeer en regenwater de kans hebben om sediment naar Awa di Lodo te transporteren. Overtollig sediment in combinatie met de groeiende mangrovewortels verstoppen de lagunes en kreken waardoor deze uiteindelijk dicht komen te zitten. Hierdoor wordt de hydrologische connectiviteit tussen de voor- en achterkant van het bos wordt verminderd. Hoge verdampingswaarden en een lage instroom van zoet water creëren extreem zoute omstandigheden in Awa di Lodo. De Mangrove Maniacs proberen de  mangrove kreken te openen zodat de getijdenuitwisseling (het volume water dat door het getij Awa di Lodo bereikt) toeneemt, waardoor het zoutgehalte in het gebied daalt. Het is echter nog onduidelijk in hoeverre de bestaande kreken bijdragen aan de getijdenuitwisseling in Lac Bay en in hoeverre kreekherstel de getijdenuitwisseling in Lac Bay kan verbeteren.

 

Onderzoek

Begin 2022 heeft een groep onderzoekers van de Universiteit Twente de waterstanden en snelheden gemeten en topografische kenmerken van Lac Bay in kaart gebracht. Een van de doelen een diepgaande data-analyse om inzicht te krijgen in de hydrodynamica van het mangrovesysteem. Er is gekeken naar de voortplanting van de vloedgolf, relaties tussen de waterstanden en watersnelheden en naar de getijdenasymmetrie. Vervolgens werd een numeriek model ontwikkeld om de invloed van kreken op de getijdenuitwisseling te kwantificeren en om het effect van kreekherstel op de getijdenuitwisseling te onderzoeken. Om de getijwisseling te kwantificeren is de verblijftijd van het water in Awa di Lodo berekend, dat de tijd die nodig is (in dagen) voordat de getijwisseling het totale watervolume van Awa di Lodo volledig heeft vervangen.

 

 

Resultaten

Uit de verkregen data blijkt dat de dagelijkse vloedgolf een verwaarloosbare vertraging heeft in het open water van Lac Bay. In Awa di Lodo wordt het hoogwater gemiddeld meer dan vier uur later bereikt dan in de open baai. Tijdens springtij is het getijverschil in het open water groot genoeg om een ​​stijgende trend in het waterpeil in Awa di Lodo te creëren. Het waterpeil in Awa di Lodo daalt weer wanneer het getijverschil afneemt bij opeenvolgende doodtij. Stroomsnelheden in de kreken zijn vooral afhankelijk van het waterpeilverschil tussen het open water en Awa di Lodo. In de kreken worden zowel eb- als vloed-dominante pieksnelheidsasymmetrieën waargenomen. De waargenomen vloed-dominante asymmetrie in de getijdenduur in Awa di Lodo geeft aan dat de stroming tussen de mangrovebomen door tijdens hoogwater verantwoordelijk is voor de snelle stijging van het waterpeil in Awa di Lodo. Tijdens eb zijn juist de kreken verantwoordelijk voor de uitstroom en de daling van het waterpeil in Awa di Lodo.

Het hydrodynamische model toonde aan dat kreken een significante invloed hebben op de getijdenuitwisseling van het open water in Lac Bay naar Awa di Lodo (Tabel 1). Een nieuwe kreekverbinding met Awa di Lodo, ​​bij voorkeur door verlenging van de kreek door het midden van het mangrovesysteem, blijkt het meest efficiënt te zijn om de getijdenuitwisseling te vergroten. Ook werd geconcludeerd dat de verbreding van de kreken, de verdieping van de kreken of de uitbreiding van het oostelijke krekenstelsel een beperkt effect op de getijdenuitwisseling zou hebben. Daarom is aangetoond dat kreekherstel een effectieve maatregel is om de getijdenuitwisseling in het mangrovebos van Lac Bay te vergroten.

 

Tabel 1: Getijdenuitwisseling, verblijftijd en de verhouding van de verblijftijd van elk van de scenario’s ten opzichte van het referentiescenario. Roodgekleurde rijen duiden op een afname van de getijwisseling en blauwgekleurde rijen duiden op een toename van de getijwisseling. Een donkerdere tint impliceert een grotere afname/toename

 

Impact op de toekomst

De data-analyse en het ontwikkelde hydrodynamische model zullen belangrijke instrumenten zijn voor de Mangrove Maniacs om beslissingen te nemen over waar nieuwe kreken te openen en om de impact van hun werk te bestuderen. Door meer inzicht te krijgen in de hydrodynamica van Lac Bay zal het herstel van het mangrovebos effectiever worden en zal daarmee de ecologische waarde van het gebied vergroten.

More info in the Dutch Caribbean Biodiversity Database

 

 

Published in BioNews 57.

 

Date
2022
Data type
Media
Theme
Research and monitoring
Geographic location
Bonaire
Author

New Research on Mangrove Restoration for Bonaire

Nederlands below.

 

Since 2020, the Mangrove Maniacs have planted over 1500 mangroves along the southwest coast of Bonaire. A new collaborative project with Van Hall Larenstein University of Applied Sciences monitored and mapped these newly planted mangroves. A healthy fringing mangrove forest will provide new habitat, nursery, and foraging grounds as well as a vital line of coastal defense for the southern wetlands.

 

Red mangrove. Photo credit: Jasper Raijmakers

IMPORTANCE OF MANGROVES

Worldwide, mangroves become more important each day due to the threats of climate change and sea level rising. Unfortunately, Bonaire is no exception to these threats. Mangroves provide multiple ecosystem goods and services (EGS). One of the main EGS is coastal protection due to their ability to attenuate waves, prevent erosion and increase sedimentation. Furthermore, they are important for their ability to store blue carbon, which is carbon stored in coastal and marine ecosystems. Mangroves sequestrate and store more carbon per unit area than tropical rainforests due to their woody prop roots and dense above and belowground biomass. Also, they have a high biodiversity, serve as a fish and bird nursery, and provide opportunities for ecotourism.

 

RESEARCH

Recently, Jasper Raijmakers, an undergraduate from the International Forest and Nature Management program of Van Hall Larenstein University of Applied Sciences, worked with the Mangrove Maniacs to map and monitor the planting sites along the southwest coast, as well as compare and evaluate two mangrove restoration techniques. For all large planting sites, the numbers of alive, dead and tagged red and black mangrove outplants were counted in a grid and presented in a heat map (an example can be seen below).

To compliment the maps, the success rate of the standard outplanting mangrove restoration technique was compared against the thesis work of student Shamyi Lanjouw, a WUR MSc Forest and Nature Conservation student, who was conducting her thesis on mangrove restoration with the use of BESE-elements®. BESE-elements® are biodegradable 3D structures that offer structural stability for intertidal vegetation. Interestingly, using both techniques found high survival rates and statistically speaking there was no significant difference between the relative growth rates between the two methods. The implications of this show that, in this particular case, investing in additional restoration material is not more effective than using traditional methods.

 

IMPACT ON FUTURE

These maps will be a vital management tool for mangrove restoration in the future. Using these maps, land area managers can quickly access an overview of the large planting sites, as well as have information needed to support monitoring of the outplants, track the project’s progress, as well as aid in identifying future planting sites. In addition, these maps will provide helpful visuals for publications and social media of the Mangrove Maniacs. A healthy fringing mangrove forest will provide the first line of coastal defense along the southern wetlands. Buffering against rising sea levels, worsening storms and erosion, these mangroves will protect the fragile salt pans and lakes located throughout the south. Furthermore, by providing a physical buffer between land and sea, this will also help mitigate human pressure along the south, also serving to protect the iconic nearshore coral reefs within this area.

Example heat map for Red Slave outplanting site.

 

For more information you can find the full reports of Jasper Raijmakers and Shamyi Lanjouw using the links below.

Lanjouw, S. 2022. Testing a biodegradable engineering product for mangrove restoration along a high wave-energy coastline. Wageningen University and Research. Thesis Report.

Raijmakers, J.R. 2022. Map mangrove planting sites and compare and evaluate mangrove restoration techniques. Van Hall Larenstein, University of Applied Sciences. Thesis Report.

 

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Nieuw onderzoek naar mangroverestauratie voor Bonaire

Sinds 2020 hebben de Mangrove Maniacs meer dan 1500 mangroven geplant langs de zuidwestkust van Bonaire. In een nieuw samenwerkingsproject met Hogeschool Van Hall Larenstein zijn deze nieuw aangeplante mangroven gemonitord en in kaart gebracht. Een gezond mangrovebos aan de zuidwestkust zal nieuwe leefgebieden, kraamkamers en foerageergebieden creëren. Net zoals een vitale kustverdedigingslinie voor de zuidelijke wetlands.

BELANG VAN MANGROVEN

Wereldwijd worden mangroven elke dag belangrijker door de dreigingen veroorzaakt door klimaatverandering en zeespiegelstijging. Helaas is Bonaire geen uitzondering op deze bedreigingen. Mangroven leveren meerdere diensten. Een van de belangrijkste dienst is kustbescherming doordat ze golven dempen, erosie voorkomen en sedimentatie vergroten. Bovendien zijn ze belangrijk voor het vastleggen van CO2. Mangroven leggen meer CO2 vast dan tropische regenwouden vanwege hun houtachtige luchtwortels en dichte boven- en ondergrondse biomassa. Ze hebben een hoge biodiversiteit, dienen als broedplaats voor vogels en habitat voor juveniele vissen. Ook bieden ze kansen voor ecotoerisme.

 

ONDERZOEK

Onlangs heeft Jasper Raijmakers, een student van de opleiding Internationaal Bos- en Natuurbeheer van Hogeschool Van Hall Larenstein, samen met de Mangrove Maniacs gewerkt aan het in kaart brengen en monitoren van de mangroven langs de zuidwestkust, en het vergelijken en evalueren van twee mangroverestauratie technieken. Voor alle grote aanplantgebieden werden de aantallen levende, dode en gemonitorde rode en zwarte mangroven geteld in een raster en weergegeven in een hittekaart.

Als aanvulling op de kaarten werd het succespercentage van de standaard uitplantingstechniek voor mangroveherstel vergeleken met de scriptie van student Shamyi Lanjouw, een WUR MSc-student Bos- en natuurbescherming, die haar scriptie uitvoerde over mangroveherstel met behulp van BESE-elementen®. BESE-elementen® zijn biologisch afbreekbare 3D-structuren die structurele stabiliteit bieden voor inter-getijdenvegetatie. Bij beide technieken werden hoge overlevingspercentages gevonden. Statistisch gezien was er geen significant verschil tussen de relatieve groeisnelheden tussen de twee methoden. Dus in dit specifieke geval investeren in aanvullend restauratiemateriaal is niet effectiever dan het gebruik van traditionele methoden.

 

IMPACT OP DE TOEKOMST

Deze kaarten zullen in de toekomst een essentieel beheersinstrument zijn voor het herstel van mangroven. Met behulp van deze kaarten hebben beheerders snel toegang tot een overzicht van de grote aanplantgebieden, evenals informatie die nodig is om het monitoren van de mangroven te ondersteunen, de voortgang van het project te volgen en te helpen bij het identificeren van toekomstige aanplantgebieden. Bovendien zullen deze kaarten nuttige beelden bieden voor publicaties en sociale media van de Mangrove Maniacs. Een gezond mangrovebos langs de zuidwestkust zal de eerste kustverdedigingslinie vormen langs de zuidelijke wetlands. Deze mangroven bufferen tegen stijgende zeespiegels, extremere stormen en erosie. Hierdoor zullen de kwetsbare zoutpannen en meren in het zuiden worden beschermd. Deze fysieke buffer zal ook dienen als bescherming van de iconische koraalriffen in dit gebied.

Voor meer informatie kunt u de volledige scripties van Jasper Raijmakers en Shamyi Lanjouw vinden via onderstaande links.

Lanjouw, S. 2022. Testing a biodegradable engineering product for mangrove restoration along a high wave-energy coastline. Wageningen University and Research. Thesis Report.

Raijmakers, J.R. 2022. Map mangrove planting sites and compare and evaluate mangrove restoration techniques. Van Hall Larenstein, University of Applied Sciences. Thesis Report.

 

 

Published in BioNews 55.

 

Date
2022
Data type
Media
Theme
Research and monitoring
Geographic location
Bonaire

Protecting Bonaire against Coastal Flooding A participatory multi-criteria analysis of coastal adaptation options

Part of the larger The impacts of climate change on Bonaire (2022-present) report available here.
 

Summary

Coastal hazards pose a significant threat to small islands, especially in combination with Sea Level Rise (SLR). Currently, the small Caribbean island of Bonaire is poorly protected against coastal flooding and there is a lack of local knowledge on potential adaptation options and their benefits and trade-offs. This study aims to fill this gap by evaluating how different coastal adaptation options to protect Bonaire are valued, considering economic, social, environmental, and technical criteria. This is evaluated using a participatory Multi-Criteria Analysis (MCA) that includes key stakeholders through semistructured interviews and the use of an online questionnaire. A wide variety of coastal adaptation options, ranging from grey infrastructure to softer Nature-based Solutions (NbS), is assessed based on an interdisciplinary set of 10 different criteria, providing a holistic view of the consequences of each option. The results show that NbS, especially mangrove restoration, and spatial zoning measures are overall perceived to be most beneficial. The least favourable adaptation strategies include the construction of any type of seawall and doing nothing. While an MCA does not lead to a final perfect solution, it does provide valuable comparative information about potential future adaptation strategies for Bonaire, which can be used to aid policy makers in the decision-making process. Moving forward, it is important to further strengthen the results of this study by conducting additional quantified analyses, including an evaluation of the spatial suitability of specific measures or combinations of measures. Moreover, to ensure public support for any final policy decisions, regardless of the specific measures that a

Date
2022
Data type
Research report
Theme
Education and outreach
Research and monitoring
Geographic location
Bonaire

Bonaire's Southern Wetlands Management Plan

EXECUTIVE SUMMARY

The southern wetlands of Bonaire represent a unique environment for the island. Consisting of a wide variety of habitat types including caves, karsts, dry tropical forests, coastal areas, salt pans and mangroves. The Ramsar site Pekelmeer lies completely in this area, as well as a small portion of the buffer zone of the Ramsar site Lac Bay.

Culturally, a number of Bonaire’s historic monuments and tributes to its past can be found as you drive around the perimeter, from ruins of old salt pans to the remains of slave huts and gravestones. Maintaining and respecting these sober reminders of Bonaire’s history is vital to ensuring the sacrifices of the enslaved populations are not forgotten. It would be impossible to separate the historic and cultural identity of Bonaire from this area.

Economically the southern wetlands represent commercial opportunities for salt extraction by Cargill Salt Works as well as a significant driver of tourism, whether it is history enthusiasts, cyclists, kiteboarders, recreational fishers, scuba divers or bird watchers.

The cultural and economic value of this area is only surpassed by its environmental value. The southern wetlands are recognized internationally as an Important Bird Area (IBA), as a site of regional importance by the Western Hemisphere Shorebird Reserve Network, as an area important for sea turtle nesting and as a Ramsar site. The Ramsar site Pekelmeer, which encompasses most of the southern portion of the wetlands, is critical to a number of threatened, endangered or keystone species. Pekelmeer offers a much-needed rest stop for a number of migratory bird species while also serving as an important breeding ground for the Caribbean Flamingo and five different tern species. Furthermore, the southern wetlands constitute most of the natural habitat of the rare and endemic Bonaire Sabal Palm.

This management plan offers a description of the southern wetlands (chapter 1), a legal and legislative overview (chapter 2), a description of resources and utilities (chapter 3), an explanation of the spatial development plan (chapter 4), an overview of conservation target habitats (chapter 5), an analysis of threats and issues (chapter 6), an outline of management actions and strategies (chapter 7), and provides recommendations for the management plan evaluation and review (chapter 8). Conserving this unique wetland will be a major challenge. A critical first step is to designate Pekelmeer as a protected area under island and national legislation, and appoint a management authority.

Date
2022
Data type
Research report
Theme
Governance
Education and outreach
Legislation
Research and monitoring
Geographic location
Bonaire

The role of creeks for tidal exchange in the mangrove forest of Lac Bay, Bonaire

Abstract

The mangrove forest in Lac Bay, Bonaire, experiences a die-off of trees in its northern area (Awa di Lodo). This die-off is caused by a combination of hypersaline conditions, long inundation periods and excess sedimentation. It is expected that an increase in the tidal exchange between Lac Bay and Awa di Lodo will decrease the mangrove stressors in Awa di Lodo creating improved environmental conditions for mangroves to grow. The tidal exchange consists of flow through the vegetated forest (sheet flow) and through the creeks (creek flow). Awa di Lodo has two main creeks connections to the forest fringe, the eastern and the western creek system. Due to mangrove roots growing into the creeks in combination with sedimentation, the creeks eventually close off and thereby reduce the creek flow. The Mangrove Maniacs are restoring the creeks in Lac Bay to improve environmental conditions for mangroves and they want a better understanding of the impacts of their work. This study aims to create more insight into the tidal-induced hydrodynamic processes in Lac Bay and the contribution of creeks in the mangrove forest to the tidal exchange.

During a field campaign from January to March 2022 field data were collected on flow velocities, water levels and topographic characteristics of Lac Bay. The field campaign spanned three spring-neap tidal cycles. The analysis of the gathered data was combined with a literature study to investigate the hydrodynamic characteristics in the area. Based on the data from the field campaign, a hydrodynamic model (Delft3D) was built to analyse the effects of tidal creeks restoration on flow velocities, tidal exchange and water levels of Awa di Lodo.

The field measurements show that the tidal wave is diurnal and has a negligible delay propagating through the open water of Lac Bay. In Awa di Lodo, high water is reached on average more than four hours later than in the open bay. During spring tide, the tidal range in the open water is sufficiently large to create an increasing trend in the water level in Awa di Lodo. The water level lowers again when the tidal range decreases during neap tide. Flow velocities in the creeks mainly depend on the water level difference between the open water and Awa di Lodo, meaning that larger water level differences induce larger flow velocities. In addition, the western creek connecting the bay with Awa di Lodo shows a strong flood dominant peak velocity asymmetry, while the eastern creek varies from marginally flood dominant during spring tides, to strongly ebb dominant during neap tide. A flood dominant tidal duration asymmetry in Awa di Lodo indicates that sheet flow during high tides is responsible for the fast increase of the water level in Awa di Lodo while during low tides the creeks are responsible for the outflow.

The hydrodynamic model simulations of the tidal dynamics in Lac Bay replicate the magnitude of the measured flow velocities in the creeks of Lac Bay. The model does not show the measured ebb flow in the western and centre creek. Water levels in Awa di Lodo are modelled well, except for an overestimation of low water levels and an overestimation of the water level increase. It was found that creeks have a significant influence on the tidal exchange between the open water and Lac Bay. The model showed that the creation of a new creek connection to Awa di Lodo, either by extending the centre creek or by creating a new creek, is found to be the most efficient to increase the tidal exchange. It was concluded that the widening of the creeks, deepening of the creeks or extension of the eastern creek system would have a limited effect on the tidal exchange. Creek restoration is shown to be an effective measure to increase the tidal exchange in the mangrove forest of Lac Bay.

Date
2022
Data type
Research report
Theme
Research and monitoring
Report number
University of Twente
Geographic location
Bonaire
Author

State of the World’s Mangroves 2021

The Global Mangrove Alliance’s recent report on the State of the World’s mangroves served as a call to action for mangrove conservation and restoration projects.  Although many of the trends centered around mangroves have looked bleak, new research shows that these areas are highly restorable meaning quick action can have significant, positive effects.

Global Mangroves

Mangroves are vital ecosystems providing coastal defense against sea level rise and worsening storms, creating critical habitats including nursery and breeding grounds, and can serve as carbon sinks making them a vital link in achieving net-zero carbon emissions by 2050.  It is estimated that nearly 15% of the world’s mangroves can be found between North and South America, mostly within the Caribbean. Unfortunately, many of the world’s mangroves have been lost or are severely degraded due to coastal development, the expansion of shrimp farming and human pollution.

Red Mangrove. Photo credit: Christian König

Luckily the Global Mangrove Alliance has been tracking the state of the world’s mangroves since it’s creation in 2018.  Through influencing local policies and public awareness on the importance of these habitats, there has already been some improvements in trends.  Overall, they found that the rate of mangrove loss has slowed worldwide since 2016. Furthermore, nearly 42% of all remaining mangroves are within protected areas. A number of recent projects have also demonstrated that mangrove area loss is highly restorable, meaning it’s not too late to save these critical ecosystems.

Dutch Caribbean Mangroves

Within the Dutch Caribbean, four of the islands have mangrove forests: St. Maarten, Aruba, Curacao, and Bonaire.  Of these, Bonaire has the largest of the mangrove forests, of which, nearly all fall within the designated National Marine Park. STINAPA along with other local NGOs have been diligently working to restore these mangrove areas. In fact, one of these restoration projects recently received international recognition with an IUCN BEST 2.0+ grant which funds restoration, reforestation, and scientific monitoring efforts on Bonaire through February 2023.  Additionally, groups such as the Mangrove Maniacs dedicate countless volunteer hours maintaining important water circulation channels to ensure the mangroves of Lac Bay stay healthy and thriving.

Call to Action

Red Mangrove. Photo credit: Marjolijn Lopes Cardozo

There is an urgent need to understand the extent of local mangrove areas and preserve and restore where possible. Governments need to include mangrove management into policy and planning. The private sector can benefit by recognizing mangroves as an investment opportunity, through options such as carbon markets, blue bonds and insurance-based investments. NGO’s and local groups can work to increase awareness and spearhead projects.  Academia and research communities can prioritize projects which help improve available data and modeling tools. Lastly, you, the individual can be involved by advocating for mangroves by spreading knowledge and looking for opportunities to get involved.

Want to get involved?

This Sunday, October 3rd, the Mangrove Maniacs of Bonaire will be hosting a mangrove outplanting event.  Volunteers will be planting mangroves along the southern coast to increase the natural mangrove fringing forest of this area.  These fringing forests are vital for minimizing coastal erosion and serving to protect this area from increased storm activity. Learn more by following along on the Mangrove Maniacs’ Facebook page.

You can find a link to the full State of the World’s Mangroves using the DCBD button below.

https://www.dcbd.nl/document/state-worlds-mangroves-2021

 

Article published in BioNews 47

 

Date
2021
Data type
Media
Theme
Education and outreach
Research and monitoring
Geographic location
Aruba
Bonaire
Curacao
St. Maarten
Author

Hydraulic circulation of the tides in Lac Bay, Bonaire.

In Lac Bay, Bonaire, a part of the mangrove forest is dying partly because of reduced water circulation through the forest. Tidal waves are the main drivers of the water circulation in the forest. In this study, the tidal behaviour is analysed based on water depth measurements from earlier studies in 2012 in Lac Bay. Time series are used to determine the tidal range (difference between minimum and maximum water depth), the dominant tidal constituent (harmonic analysis) and the water circulation through the forest (difference between the timing of highest water depth). The results show that locations close to open water in the bay have on average a large tidal range (27.8-28.1 cm) than locations in the forest (3.4-8.1 cm), with limited to no seasonal fluctuations. The dominant tide in Lac Bay is the lunisolar diurnal constituent (K1). Water depth changes from stations close to open water could be explained reasonably but in other locations they were distorted by the forest and could not be fully explained. It was found that the water moves slowly through the forest in a circular manner, moving around the islands and through the forest, thereby creating a delay in high water depths up to five-and-a-half hours.

 

Key words: Mangroves; Lac Bay; Water depths; Tidal range; Dominant tide; Tidal constituents

Date
2022
Data type
Scientific article
Theme
Research and monitoring
Geographic location
Bonaire
Author

Ma Kote Mangroves

Overview of St. Lucia's Mangroves

Used to draw comparisons with the mangroves of Aruba, Bonaire, Curacao and St. Maarten

Presented in 2021 Mangrove Restoration Workshop

Date
2021
Data type
Media
Theme
Education and outreach
Research and monitoring