Habitats

Recreational and land use survey for Lac Bay Bonaire: A study towards mapping human activities in Lac Bay Bonaire and its catchment area and advising about the current management system.

Findings:

The main conclusion from this study is that at the moment tourists and locals use Lac Bay and its catchment area at levels and in ways that are not sustainable.

Recreational use:

  • Recreational use is concentrated on and around the Sorobon Peninsula. The major activities are beach and sports-related (sunbathing and windsurfing). The main water based activities are windsurfing and swimming/wading.
  • The social carrying capacity for the present kind of visitor and present kind of usage begins to become an issue around 250 beach visitors. Average visitor numbers on cruise days is 359 (highest is 760) and on weekends is 260.
  • There is a large difference in visitor numbers between cruise days and non- cruise days, with cruise days having the highest.
  • Awareness of Lac Bay’s regulations and zoning plan is low, resulting in certain activities taking place in sensitive zones.

Land use:

  • Fresh water surface-flow to the bay is affected by approximately 54 dams or more, and groundwater flow by many (uncounted) wells
  • 213 kunukus (farms on Bonaire) are present in Lac Bay and its catchment area.

Livestock densities within the natural areas surrounding Lac Bay are not sustainable. They exceed the ecological carrying capacity of the area.

Management Recommendations

- Develop and implement a set of measures that can be used to preserve and enhance the Lac visitor experience in accordance with social carrying capacity.

- Develop sunbathing and water sport possibilities elsewhere on Bonaire to distribute user densities from Lac Bay.

- Develop and implement a set of measures that can be used to preserve and enhance the natural values of Lac Bay.

  • Improve the implementation of the zoning plan.
  • Organize several facilities at Sorobon more properly.
  • Create a visitor centre at Sorobon.
  • Reduce livestock densities in the Lac Bay catchment area.

Key recommendations for further study:

  • Research on up to what extend tourists facilities are contributing to the eutrophication at Lac.
  • Research on the effect of sunscreen on coral bleaching at Lac.
  • Further research to obtain a clear overview of land use in Lac’s catchment area.
Date
2011
Data type
Research report
Theme
Research and monitoring
Geographic location
Bonaire

Marine Area Survey: an inventory of the natural and cultural marine resources of St. Eustatius, Netherlands Antilles

The purpose of this survey was to describe and map the natural and cultural resources of the marine environment with a view to sustainable development of these resources for tourism.The following main habitat types were identified: coral-encrusted rock, true coral reefs, sand with algal beds, and artificial habitat (wreck sites). The most important areas for recreational use and further tourism development are the reef complex south of the city pier, the reefs of Jenkins Bay and the archaeological sites in Oranjebaai.
In addition to describing and mapping the resources, an inventory of uses of the marine environment was made, being fisheries, diving and snorkeling, anchoring and ship's traffic. Individual uses were mapped and these maps were overlayed to show areas of conflict between uses. The overlays formed the basis for a zoning plan for the marine environment. This plan identifies certain zones for different uses, so as to avoid conflicts between users. The zoning plan proposes two marine park
zones, two archaeological zones, a large anchorage/harbor zone, traffic zones and a fisheries management zone. Since the institutional structure for managing the marine environment and enforcing the regulations of the zoning plan is not available at present, creation of a new non-governmental body is recommended for management. All interest groups should be represented in such a body. Once the Island Government approves the recommendations and the proposed zoning plan, a detailed
project proposal and budget need to be drafted and submitted for funding.

Date
1993
Data type
Research report
Theme
Research and monitoring
Geographic location
St. Eustatius

Assessment of Ramsar site Lac Bonaire – June 2010

Findings

The main issues that Lac Bay faces were identified as follows:

  1. Filling-in of Lac and reduced water circulation. Over-grazing by extensive livestock husbandry as well as non-sustainable land-use practices (e.g. barren fields) has resulted in an accelerated infilling of the bay with sediment, which hampers water circulation and causes mangrove die-off. This has lead to a gradual reduction of the effective nursery and habitat surface of the bay over the last decades.
  2. Increase in uncontrolled recreational pressure. The Lac ecosystem has been modified or altered by construction of roads, the building of hotels, subterraneous nutrient enrichment by untreated sewage and more. Trampling is causing an important decrease in sea grass bed coverage in the bay. Endangered species such as turtles and nesting birds are vulnerable to human disturbance (Lac is intensively used for various kinds of recreation).
  3. Litter contamination. Marine litter washed in from the open ocean and abandoned fishing lines in the deeper parts of Lac are big issues.
  4. Algal blooms. While the outer reef is in very good health, many of the inner reef’s corals, gorgonians and sponges are being overgrown by the crustose calcareous alga Ramicrusta sp. This may cause a serious decline in living corals inside the bay.

Management Recommendations:

The highest priority is to start habitat restoration.

Direct enforcement of existing and new legislation is crucial as well as a permanent presence of one or more officials.

Filling-in of Lac and reduced water circulation

  • Tackle the livestock overgrazing problem in the whole watershed.
  • Regularly open up the former channels to the rear areas of the mangroves and re-establish circulation and water quality.
  • Remove filled-in sediments and reforest with red mangroves in the rear stagnant areas of Lac so as to re-establish mangrove and fish nursery habitat.

Address increase in uncontrolled recreational pressure

  • Set upper limits for the various users.
  • Strictly limit public access to seagrass areas using a combination of zoning, demarcation and enforcement.
  • Upgrade the visitor facilities designed to limit or steer user impact towards low sensitivity areas.
  • Monitor the human use of the bay.
  • Assess Lac’s current bird use and their vulnerability to disturbance.

Litter contamination

  • Conduct regular cleanups with volunteers and monitor litter densities.
  • Limit and regulate fishing inside of Lac.
  • Conduct PAH  (polyaromatic hydrocarbon) studies of the water in Lac.

Algal blooms

  • Periodic annual monitoring of enteric bacterial presence at high risk locations.
  • Install a monitoring program to assess the nutrient situation in Lac at several locations.
  • Continue monitoring of coral overgrowth by Ramicrusta sp. 
Date
2010
Data type
Research report
Theme
Research and monitoring
Report number
C066/10
Geographic location
Bonaire

Lac Bonaire - Restoration Action Spear Points, September 2010

Lac Bay, Bonaire is the most important mangrove and seagrass area of Bonaire and has been undergoing steady ecological decline in the last decades. Based on an initial assessment of conservation management issue and potential solutions, as, conducted by IMARES in June 2010, the Dutch Ministry of Agriculture, Nature and Food Quality (LNV) asked IMARES to return to Bonaire to work with Stinapa Bonaire to choose narrower priorities and jointly make a short-list of topics as a working document for cooperation and action. In the beginning of September, site visits and discussions were held in Bonaire with the manager of Lac Bay and various stakeholders to identify and agree on priority issues for action. This working report gives the results of that visit.

Four action spear point projects were identified, based on urgency and feasibility based on local Bonaire and Dutch IMARES expertise. The projects are as follows:

1. Mangrove restoration demonstration pilot study
The basic objective is to reestablish water depth and tidal connection in high marsh salt areas that have resulted from infilling with sediment, and restore them as effective mangrove and low marsh fish nursery habitats. By collecting baseline data before the restoration activities take place, it will be possible to monitor and compare and assess changes in fauna and flora at the restoration sites and hence evaluate the effectiveness of the measures implemented.

2. Baseline ecological study of the zonation of aquatic communities
The goal is to complete a scientific description of Lac’s aquatic community zonation as it exists at landscape level today. This will provide the framework against which large-scale community change and effectiveness of mitigation measures can be monitored and evaluated.

3. Recreational and land use survey for Lac Bay and its catchment area
The goal is to identify user problems and potential solutions by mapping and assessing user density and pressures in Lac

4. Study of avifaunal habitat use of Lac Bay
The goal is to identify bird habitat use problems and potential solutions by assessing habitat use of Lac by birds during the migratory season.

(A fifth project for implementation by Stinapa and Dienst LVV was identified)
5. Lac mangrove channel clearing project
Re-establish water flow from the Bakuna dam to Lac using a pipe system.

The Lac mangrove channel clearing project of Stinapa was reviewed and judged to be valuable and important. The baseline study of zonation of aquatic communities (project 2) is urgently needed in this respect to allow short and long-term evaluation of this project which need to become a structural part of Lac Bay management. Routine mangrove channel maintenance was identified as ideal work for involvement of Bonaire youths and volunteers, to rekindle public involvement in caring for Lac and its rich natural and cultural-historical heritage. 

Management Recommendations:

A project plan is presented by which all four projects can be delivered by December 2012. These projects can count on government and broad community support. In this all, Stinapa indicated to be willing to provide basic free lodging to interns and scientists at their science accommodations at the entrance of Washington-Slagbaai National Park. The ability and willingness of IMARES to recruit and guide students and interns for these projects was an important selection criterion to help restrain total project costs. The action spear points will, nevertheless, require funding as well as permits from the Island Government of Bonaire. With LNV various funding options were reviewed and discussed, and the need for permits was discussed with DROB (Dienst Ruimtelijke Ontwikkeling en Beheer) Bonaire. DROB envisioned few problems with the required permits. The visit was concluded by the joint resolve to work out ways to maintain momentum and proceed towards the implementation phase.

Date
2010
Data type
Research report
Theme
Governance
Education and outreach
Research and monitoring
Report number
C131/10
Geographic location
Bonaire

Community Change within a Caribbean Coral Reef Marine Protected Area following Two Decades of Local Management

Structural change in both the habitat and reef-associated fish assemblages within spatially managed coral reefs can provide key insights into the benefits and limitations of Marine Protected Areas (MPAs). While MPA zoning effects on particular target species are well reported, we are yet to fully resolve the various affects of spatial management on the structure of coral reef communities over decadal time scales. Here, we document mixed affects of MPA zoning on fish density, biomass and species richness over the 21 years since establishment of the Saba Marine Park (SMP). Although we found significantly greater biomass and species richness of reef-associated fishes within shallow habitats (5 meters depth) closed to fishing, this did not hold for deeper (15 m) habitats, and there was a widespread decline (38% decrease) in live hard coral cover and a 68% loss of carnivorous reef fishes across all zones of the SMP from the 1990s to 2008. Given the importance of live coral for the maintenance and replenishment of reef fishes, and the likely role of chronic disturbance in driving coral decline across the region, we explore how local spatial management can help protect coral reef ecosystems within the context of large- scale environmental pressures and disturbances outside the purview of local MPA management. 

Date
2012
Data type
Scientific article
Theme
Governance
Research and monitoring
Journal

A landscape ecological vegetation map of Sint Eustatius (Lesser Antilles)

Abstract:

A semi-detailed landscape-based vegetation map (scale: 1: 37,500) based on field data from 1999 has been available as an update of Stoffers’ 1956 map of the Lesser Antillean island of St. Eustatius, Netherlands Caribbean, but up to now was never finalized or published. In this report we complete the documentation of that map to provide new insights into vegetation change over a period of more than 40 years, and a quantitative reference point for future studies on landscape-level vegetation development for the island.

The principal lower sections of the 21 km2 island of St. Eustatius possess a tropical savannah climate according to the Köppen (1931) classification system, and the documented flora of the island amounts to 505 species. Color aerial photographs (1: 8,000) taken in 1991 and field data from 1999 were used to produce the map. A total of 84 vegetation sample plots were analysed using a stratified random sampling design and TWINSPAN cluster analysis.

Four main and 16 sub-landscape types were distinguished based on geology, geomorphology and different mixes and expressions of the component vegetation types. The five principal landscape types are in descending order of importance: H1, H2, M4, M9 and C, and covered some 67 % of the seminatural habitat of the island. H1 and H2 are the Pisonia-Justicia hills and Pisonia-Bothriochloa hills and are limited to The Mountains area. Analysis of the sampling data resulted in the distinction of 13 (semi)natural vegetation types. The three principal vegetation types were, the Pisonia-Justicia type, Pisonia-Ayenia type and Bothriochloa-Bouteloua type which together accounted for 38 % of total (semi)natural vegetation cover. The following well-developed vegetation types of St. Eustatius represent primary climax communities: Types 1, 2, 3, 5 and 7, all found in and around the Quill in the southwestern part of the island. A comparison of the vegetation types in the present study with those of Stoffers (1956) showed that only one vegetation type closely resembles one in Stoffers’ study. Major changes have taken place in certain types of the natural vegetation of the island in the intervening five decades.

The majority of the central sections of the island around Oranjestad the so-named “Cultuurvlakte”, amounting to approximately 25 % of the surface of the island, have suffered intensive disturbance due to past agriculture, livestock husbandry and invasive species and were not mapped. Only a small remnant portion of the semi-natural lowlands vegetation (L1 and L2) was left in the coastal reaches of Billy’s Gut. Nevertheless, this area is heavily affected by grazing and the invasive vine Antigonon leptopus.

A comparison with the 1950s vegetation map by Stoffers shows that the rarest and most valuable elfin woodland vegetation of the rim of the Quill crater had been largely lost and that the areas he described as “Montane thickets” (Type 2) had declined and been degraded. We speculate that these losses may be most directly attributable to the impact of recent hurricanes and/or grazing by introduced livestock. On the lower slopes of the Quill, several areas mapped by Stoffers as farmland had been abandoned and have evidently regenerated into mixed deciduous and evergreen thorny woodlands.

The vegetation of the Mountains area showed some recovery since the 1950s. There were more evergreen bushes, and less Acacia and Leucaena than Stoffers described. The vegetation Stoffers described for the lowlands had more Acacia than we found but the invasive Antigonon has since dramatically increased as a ubiquitous and often dominant species. The former importance of Opuntia prickly pear cacti in disturbed vegetations has dramatically declined since the 1950s. We ascribe this to the likely effect of the invasive parasitic insect Cactoblastis cactorum. In the 1980s and 1990s many Opuntia cacti were seen affected by this insect (G. Lopes, pers. comm.).

Our field data show that all wilderness areas of St. Eustatius remained heavily affected by grazers. This reduces the resilience of natural vegetations and interferes with natural succession by imparting heavy losses to hardwood seedlings and saplings (see e.g. Melendez-Ackerman et al. 2008), by reducing plant biomass (which increases exposure to wind and sun), and by favoring hardy invasive plant species. In Curaçao, large scale reduction in densities of feral grazers in the Christoffelpark since 1993 has led to rapid recovery of several rare plant species and vegetation types. The problem of feral livestock remains severe. Therefore the number one priority for terrestrial conservation in St. Eustatius will be to reduce feral grazer densities and impacts in key wilderness areas.

Management Recommendations:

Parts of the natural areas of both The Mountains and the Quill are protected by law, but goats and other roaming livestock are omnipresent in all habitats and continue to have evident impacts on the vegetation. Aside from generally reducing the resilience of the vegetation to major disturbance, intensive impact in the herbaceous layers likely affects regeneration of rare hardwood species directly through selective predation and indirectly by overall desiccation and increased exposure to the elements. Goats have a broad diet in the region and species eaten include canopy, mid-canopy and understory species (Melendez-Ackerman et al. 2008). Vegetation degradation further also affects the competitive balance towards (unpalatable) invasive species such as Antigonon leptopus, Pedilanthus tithymaloides, and Leucaena leucocephala, which have expanded massively into natural habitat in the last 50 years. Not only is general vegetation degradation suggested as a problem to endangered breeding seabirds, but goats likely also directly trample nesting burrows of seabirds (Collier & Brown 2009).

Consequently, priorities for nature conservation are to:

  • Reduce grazer densities in all areas,
  • Protect the most sensitive vegetations using total grazer exclusion, and
  • Experiment with methods to spur vegetation recovery, including erosion control, propagation of rare and endangered species and reforestation with indigenous species
  • Establish permanent plots in areas with the most sensitive vegetations in order to better understand causal factors of short- and longer term changes. 

This report is part of the Wageningen University BO research program (BO-11-011.05-004) and has been financed by the Ministry of Economic Affairs, Agriculture and Innovation (EL&I) under project number 4308202004.

Date
2012
Data type
Research report
Theme
Research and monitoring
Report number
C053/12
Geographic location
St. Eustatius

Land Cover and Forest Formation Distributions for St. Kitts, Nevis, St. Eustatius, Grenada and Barbados from Decision Tree Classification of Cloud-Cleared Satellite Imagery

Satellite image-based mapping of tropical forests is vital to conservation planning. Standard methods for automated image classification, however, limit classification detail in complex tropical landscapes. In this study, we test an approach to Landsat image interpretation on four islands of the Lesser Antilles, including Grenada and St. Kitts, Nevis and St. Eustatius, testing a more detailed classification than earlier work in the latter three islands. Secondly, we estimate the extents of land cover and protected forest by formation for five islands and ask how land cover has changed over the second half of the 20th century. The image interpretation approach combines image mosaics and ancillary geographic data, classifying the resulting set of raster data with decision tree software. Cloud-free image mosaics for one or two seasons were created by applying regression tree normalization to scene dates that could fill cloudy areas in a base scene. Such mosaics are also known as cloud-filled, cloud-minimized or cloud-cleared imagery, mosaics, or composites. The approach accurately distinguished several classes that more standard methods would confuse; the seamless mosaics aided reference data collection; and the multiseason imagery allowed us to separate drought deciduous forests and woodlands from semi-deciduous ones. Cultivated land areas declined 60 to 100 percent from about 1945 to 2000 on several islands. Meanwhile, forest cover has increased 50 to 950%. This trend will likely continue where sugar cane cultivation has dominated. Like the island of Puerto Rico, most higher-elevation forest formations are protected in formal or informal reserves. Also similarly, lowland forests, which are drier forest types on these islands, are not well represented in reserves. Former cultivated lands in lowland areas could provide lands for new reserves of drier forest types. The land-use history of these islands may provide insight for planners in countries currently considering lowland forest clearing for agriculture. 

Date
2008
Data type
Scientific article
Theme
Research and monitoring
Geographic location
St. Eustatius

Attraction of settlement-stage coral reef fishes to reef noise

We compared catches of settlement-stage reef fishes in light traps attached to underwater speakers playing reef sounds with those of silent traps during a summer recruitment season at Lizard Island, Great Barrier Reef, Australia. Of the total 40191 reef fishes we collected, significantly more (67%; Wilcoxon and Binomial tests: p< 0.001) appeared in the traps with broadcast reef noise. Traps deployed with speakers consistently caught a greater diversity of species (Wilcoxon test: p< 0.001, total 81 vs 68) than did silent traps. This study provides a clear demonstration that the settlement-stages of a broad range of families of coral reef fishes are attracted to reef sounds

Date
2004
Data type
Scientific article
Theme
Research and monitoring

Generic ecological assessment framework for coastal ecosystems in the Caribbean Netherlands

Abstract:

The aim of this study was to draft a generic ecological assessment framework for coastal systems in Caribbean Netherlands (CN) that offers guidance in the process of license-applications of planned activities that could impact coastal systems, as well as a general guidance towards environmental and ecological monitoring related to proposed projects and existing activities. The study was limited to the review of (inter)national ecological assessment frameworks and monitoring initiatives; peer-reviewed academic literature was not consulted. Though this draft framework provides guidance, it limits itself to standard practice and general regulations. Further fine-tuning of the framework is required to be applicable to the specific situation in CN. Furthermore, it is the responsibility of the individual initiators to customize an adequate and comprehensive ecological impact assessment and monitoring-plan adjusted to the spatial and temporal scale relevant of the type of activities and possible impact resulting from the project.

Fundamental to the draft framework is a network approach in which the impact chain between the activity and ecosystem components is specified by a suit of pressures. The broad strategy of the ecological assessment framework consists of three major phases:

  1. Establishing the context in which the project will take place.
  2. Scoping of the project activities, their pressures and the environmental descriptors relevant to the projected area.
  3. Assessment and evaluation of the pressures on the environmental descriptors.

For each phase practical guidance is provided in the form of questions. While answering these questions an overview is established of all relevant activities, pressures, and environmental descriptors. Each phase is further elaborated upon in the report. An adaptive and interactive management approach is required for the processes of the three phases. Informative environmental descriptors groups were identified based on international monitoring initiatives (Benthic diversity, Coral health, Species requiring special attention, Fish diversity, Chemical water quality, Physical structure) and for each descriptor indicators are proposed. Further study is required into which indicators are most appropriate for CN.

Threshold levels are not commonly available for each of the environmental descriptors. Significance testing in the absence of threshold levels is discussed in de report. A practical guidance is proposed to evaluate and categorize the significance of an impact by listing questions related to the nature, magnitude and intensity of the (expected) impacts. Reference is made to relevant (inter) national treaties or ordinances in which qualitative goals are reported.

This report provides practical guidance and considerations on how to establish appropriate reference situations in a changing environment. The reference situations must be chosen using best available information about the physical and biological characteristics of the environment to ensure that they represent suitable reference conditions. Important factors to consider are summed up in this report. A well set-up monitoring design should include multiple reference sites (spread across space and time) to allow the authorities and the initiator to tease apart natural variability and general trends in decline (e.g. due to climate change) from changes caused by the initiated project.

The proposed framework has not yet been tested with pilot situations or cross-referenced with the legal framework in CN, nor has it been evaluated with stakeholders. It is highly recommended to evaluate this framework by applying it to pilot or actual cases, and to adapt were necessary. 

Date
2012
Data type
Research report
Theme
Legislation
Research and monitoring
Report number
C122/12
Geographic location
Bonaire
Saba
St. Eustatius

Protection of High Seas biodiversity in the Antilles, West Africa and Antarctica: inventory of EBSAs and VMEs

Abstract:

To protect deep-sea biodiversity, the United Nations have adopted a number of resolutions that should protect vulnerable marine ecosystems (VMEs), such as cold water corals and sponges, by the regulation of deep-sea fisheries on the high seas. In a parallel process, the Convention on Biological Diversity (CBD) calls upon states to identify Ecological and Biological Significant Areas (EBSAs) that serve as focal areas, without any special legal status, and establish a network of marine protected areas by 2012. In addition, at the tenth meeting of the Conference to the Parties of the CBD in Nagoya, in 2010, it was agreed that by 2020, 10% of coastal and marine areas should be protected.

The Netherlands is involved in both processes since our country has ratified the CBD and therefore is bound to contribute to the protection of biodiversity, both in its national waters and in the high seas. In this report we provide a worldwide overview on the protection of VMEs and of the status of the EBSA selection processes as per March 2012. Next, we zoom in on three areas that are of interest to the Dutch government (Caribbean, West Africa, Antarctica) and we summarize the spatial protection measures, list the closed VME areas and EBSA selection processes and we provide information on the regional seas conventions and their mandates.

Date
2012
Data type
Other resources
Theme
Research and monitoring
Geographic location
Aruba
Bonaire
Curacao
Saba
St. Eustatius
St. Maarten
Author