Human impacts

In augustus 2011 is er op Bonaire onderzoek gedaan naar de manier waarop de exploitatie van een rioolstelsel en een rioolwaterzuiveringsinstallatie op een verantwoorde manier kan plaatsvinden. Dit onderzoek is door de Stichting ABC Advies uitgevoerd op verzoek van USONA, die ter plaatse dit project begeleidt en de financiering ervan bewaakt namens de EU. Het onderzoek is uitgevoerd door lezing van een groot aantal publicaties van verschillende aard. Voor zover deze van belang zijn, zijn deze genoemd in dit rapport. Naast lezing van documenten is het bezoek ter plaatse en de diverse gesprekken met direct verantwoordelijken zoals bestuurders, medewerkers van USONA en anderen betrokkenen van grote waarde voor de beeldvorming van de onderzoeker geweest. In de bijlagen bij dit rapport is een lijst van gevoerde gesprekken opgenomen1 . De kern van de onderzoeksuitkomst is dat het hebben van een rioolstelsel en een zuivering voor Bonaire van onschatbare waarde is, maar dat door het Openbaar Lichaam Bonaire nog veel keuzes moeten worden gemaakt alvorens een heffingenstelsel operationeel is. In het rapport worden daarvoor enkele richtinggevende mogelijkheden geschetst. De bijkomende problematiek van een tijdelijke afvalwaterzuivering die een nogal permanent karakter heeft gekregen is complicerend, ook voor de dekking van de exploitatielasten, maar maakt geen onderdeel uit van de onderzoeksvraag. Dit geldt eveneens voor het vraagstuk van het beheer van de zuivering. Ook dat onderwerp, hoewel het zeker raakvlakken heeft met de exploitatiekosten en dus ook het tarief, kan –vanwege de onzekerheid over de uitkomst van dit vraagstuk- geen onderdeel uitmaken van dit rapport. Bij dit rapport is een opzet gemaakt voor een kostenoverzicht van de jaarlijkse exploitatielasten van het ‘Bonaire Sewerage and Sanitation Project’. De onderzoeksperiode van ruim 1 week is niet voldoende om deze cijfers ook zonder nader onderzoek en overleg met (technisch en financieel) ter plaatse deskundigen over te nemen. De opzet biedt naar de mening van onderzoeker wel een aanzienlijk beter inzicht dan tot nu voorhanden was. Vanaf het moment dat het Bestuurscollege en de Eilandraad enkele, in deze rapportage genoemde, keuzes hebben gemaakt is het (nog) verder uitwerken van de exploitatiebegroting en het tarievenstelsel aan de orde. Ook kan dan de benodigde regelgeving worden opgesteld. Het zou, vanwege het grote belang dat met het slagen van dit project is gemoeid, naar de mening van onderzoeker een goede vervolgstap zijn dat de uitkomsten van deze rapportage met direct betrokkenen op het Bonaire worden besproken. Daarbij wordt gedacht aan de DROB, het hoofd financiën en andere betrokkenen. Indien nodig kan dan verfijning plaatsvinden.

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.

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.

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. 

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.

Abstract:

Marine reserves, in which exploitation of marine organisms and other human activities are restricted or prohibited, can be valuable tools for marine conservation and fisheries management. No-take marine reserves support greater density, size, and diversity of fishes than exploited areas, with most benefits accruing to heavily exploited species. Protected areas can also export biomass to sustain or increase the overall yield of adjacent fisheries. These effects can be especially significant for organisms with small home ranges, such as coral reef fish. Although there are many benefits to creating marine reserves they are also costly to manage and can infringe on people’s recreation and livelihoods. For marine reserves to be used as management tools, a comprehensive knowledge of the ecosystems is needed and reserve impacts should be regularly monitored.

St. Eustatius Marine Park and two no-take marine reserves were established by the Statian government in 1996 to promote dive tourism and sustainable fisheries. No fisheries study was carried out prior to reserve implementation to determine the status of fish stocks. In the summer of 2008, surveys were undertaken inside and outside the marine reserves to census reef fish and habitat to establish a current baseline and to evaluate the effects of the marine reserves on reef fish populations. The data that was collected was used to answer three questions about the current state of the Marine Park: 1) are there habitat related differences between reserve areas and non-reserve areas or between reef types? 2) do fish density, diversity, or biomass differ between protected and unprotected sites or between reef types? and 3) do habitat characteristics, reserve status, or reef type influence fish density, diversity, and biomass?

This study determined that habitat differences among the survey sites affected reef fish populations more than reserve status. However, the no-take reserves may still be important for protecting reef fish populations. The two reserves have been in place for more than 10 years and it is unknown what happened to fish populations during that time. Future research, employing the methods of this study, can be used to monitor reef fish populations and habitat over time to better determine if the reserves are having beneficial effects. 

Abstract:

There are about 25 fishermen on the island of St. Eustatius. Considering the small scale island economy this is a significant social economical factor that can not be overseen by the local Island Government. The money that is generated by the fishery sector, directly and indirectly, is invested back into the St. Eustatius economy, since all the fishermen are locals. In addition indirect taxes are generated from fuel, two stroke oil, fishing gear, spare parts and engines. The aggregated value of the fishery sector is also an important factor to the island economy. The spiny lobster (Panulirus argus) fishery is without doubt the most important fishery on the island. The total lobster catch for 2003 is estimated to be approximately 4 tons, which represents a gross value of 100,000 NAf.

The St. Eustatius fishermen primarily fish on the narrow shelf surrounding the island. In 1996 the Island Council of St. Eustatius approved the Marine Park Ordinance 1996, creating a marine park and setting out regulations (diving, fishing etc.) for this marine park. Subsequently the St. Eustatius National Park Foundation (STENAPA) was requested to manage the park and active management started in 1997. STENAPA therefore has the effective control over the island shelf from the high water mark to the 30 meter (100 ft) depth contour. In addition, 2 marine park reserves were put in place to be managed by the STENAPA foundation, where fishing is restricted to hand line fishing. Furthermore the fishermen were restricted to catching a maximum of 20 queen conch (Strombus gigas) per year in the marine park area, without any base line study had taken place. The St.Eustatius fishermen find that the best fishing grounds were designated to be marine reserves, and after several quite severe incidents that took place over the years between them and STENAPA fishers have become distrustful of the local Island Government’s actions and STENAPA. In addition, it is the fishermen’s experience that catches have gone down significantly since STENAPA took over management of the park area. An other factor that has even worsened the situation is that tankers, coming and going to the St. Eustatius oil terminal, are anchoring in the marine park area (within the 30 meter depth contour), and are destroying the fishing grounds with their anchor and anchor chain, and cutting away the traps. The fishermen find that the habitat destruction by the oil tankers is much more severe than their “relatively small” violations of the marine park ordinance. Since the management of the marine park and thus the fishing grounds is a STENAPA matter, a critical success factor for sustainable management of the park area, and consequently the fishing grounds, is improving the communication and cooperation between the STENAPA foundation, the fishermen and local island Government, and finding a solution for the anchoring problem. 

Findings:

The main conclusion from this study is that the combined levels of anthropogenic impact on the bay currently exceed sustainable levels. Lac Bay is experiencing a long-term decline in productive habitat area all the while non-sustainable grazing of vegetation, eutrophication, seagrass trampling and high levels of litter contamination have been documented.

Lac catchment area

• The Lac catchment area was mapped using satellite imagery combined with field verification and gave a preliminary estimated size of about 22.6 km2 of surrounding lands. This area consists of a mix of semi- natural deciduous and dry-evergreen vegetation types and at least 213 small part-time farms.
• There are at least 52 dams that obstruct or retard water flow and many wells from which groundwater can be or is being extracted.
• Extensive livestock husbandry (goat and sheep) occurs at densities higher than 1 animal per hectare. Such densities well exceed densities that permit ecological recovery (0.1 animal per hectare).

Recreational use

• The Lac lagoon is intensively used for recreation. From 9 in the morning to 4:30 pm practically every day anywhere from 100 - 400 people are present on or along the shorelines of the bay at any given moment. Highest numbers occur during cruise ship days.
• The majority of recreational use of Lac is concentrated on and around the Sorobon Peninsula.
• The major recreational activities at Lac are sunbathing, windsurfing and swimming or wading. Little current use is directed towards nature activities
• Usage patterns and awareness differ importantly between the four different user-categories of cruise tourists, stay-over tourists, foreign residents and inhabitants born on Bonaire.

Anthropogenic impacts

• The inner borders of the seagrass exclosures display much bare space due to trampling.
• As there is no sewage treatment and as the available toilets and cesspits are generally defunct, beach visitation definitely result in nutrient enrichment in the waters of the bay
• Beach litter contamination is a matter of concern along mangrove shores at entrance of the bay and the lagoon-bottom immediately off the public beach of Sorobon.
• High levels of uses pose issues of disturbance for birds and sea turtles.
• Additional problems are the rapid invasion of the exotic seagrass, Halophila stipulacea and a bloom of an encrusting (possibly invasive) calcareous alga (Ramicrusta sp.) that is smothering live corals at the seaward side of the bay.

Management Recommendations:

• Develop sunbathing and water sport possibilities elsewhere on Bonaire to distribute user densities away from Lac.
• Upgrade user facilities and infrastructure at Lac. These include toilets and septic system, garbage disposal, organized parking, shade, signage and markers for the various management zones.
• Implement a Visitor Centre to provide visitor service (products and added value-information) and enforcement.
• Reduce grazer densities in the watershed and/or around the bay.
• Discourage/prohibit the use of throw-away food and beverage packaging at Lac and participate actively in the regional Marine Litter Action Plan developed by UNEP.
• Design a boom system to herd and trap contaminants entering Lac before they penetrate the mangrove fringes.
• Organize regular beach clean-ups in Lac.

Research to address knowledge gaps

• Further map and quantify anthropogenic effects in the watershed area (pollution, water diversion and extraction, forestation, grazing, farming, erosion) and their effects on Lac (in terms of sedimentation, reduced freshwater influx, nutrient loading).
• Document traffic levels on Kaminda di Sorobon and its effects in terms of disturbance, road-kills and littering.
• Study the concentration and effects of litter-derived contaminants on the environment and biota of the bay.
• Study the distribution and habitat selection of sea turtles in the bay as related to diet, food availability, water temperature, disturbance and other factors.
• Study the use of more and/or larger exclosures to improve seagrass coverage in the Sorobon area.

Abstract:

The endangered Lesser Antillean Iguana, Iguana delicatissima, is an emblematic species for the island of St. Eustatius and in Caribbean Netherlands it is only found on St. Eustatius. In this study we conducted an extensive population survey for the iguana and compared densities in different areas to densities documented most recently in 2004. We conducted 39 field surveys and spent a total of 80 hours and 21 minutes searching for iguanas. We covered 63,672 m of trails and tracks and found only 22 iguanas. An overall average of 3.70 hours were searched for each iguana found. Due to the low encounter rates, detailed estimation and comparison of population densities remain problematic. Overall population density was 0.35 iguanas per hectare which represents 0.5-1% of densities documented elsewhere in healthy populations. Current population densities have declined across all habitats since the 2004 survey. Iguana encounter rates and densities in natural habitat were highest for the region where the northern hills abut onto the central plain. Island-wide, those areas provide the best combination of sun, shelter, food and potential for nesting sites. The population of the Lower Town sector, indicated in 2004 as the most dense and promising subpopulation, has all but disappeared. Island-wide, the residential estate subdivisions remains the second-most important area for the iguana.

We conclude that even though several valuable conservation measures are in place (e.g. establishment of legally protected parks, designation as a legally protected species and a successfully-run awareness campaign), the status of the iguana has not improved significantly in the last 8 years. Our results show that compared to 2004 when the population was estimated to number 425 (275-650) animals, current population size certainly lies on the low side of this range. This is far below the required minimum viable population size of 5000 animals and means that the iguana is critically endangered on St. Eustatius. It is readily vulnerable to extirpation on the island. Human hunting is likely a minor problem, shelter and food availability on the island are abundant, and invasive predator densities in the wild are relatively low. Of the 28 documented instances of death or endangerment of iguanas during the study period, most were attributable to anthropogenic causes. Suitable nesting sites for the iguana appear very limited, especially due to a combination of geology and vegetation. Therefore, lack of nesting sites and high iguana mortalities due to anthropogenic causes are suggested as the two core factors limiting recovery of the iguana on St. Eustatius .

Management Recommendations:

The following management measures are proposed:

1. Protect current populations by:

• Prevention of introduction of invasive species
  (Train and equip border officials to prevent potential entry of the mongoose and the Green Iguana from neighbouring islands),
• Enforcement and upgrading of legal protection 
  (Implement enforcement and upgrade protective legislation),
• Development and protection of additional nesting sites 
  (Develop and maintain new additional nesting habitat, a measure that is both easy and inexpensive),
• Establishment of an “iguana-friendly yard” programme
  (Establish a programme to promote “iguana-friendly” gardens, as the main means of reducing cumulative mortality).

2. Increase the biological knowledge about the iguana by conducting studies for a better knowledge of the critical biological parameters,

3. Create public awareness for the plight of the species,

4. Establish a small, local husbandry project.
(Development of an in situ husbandry and breeding project could serve a pivotal role in bolstering the other core program themes and especially offers a relaxed setting in which islanders can experience the iguana as the gentle and beautiful animal that it is).

This report is part of the Wageningen University BO research program (BO-11-011.05-004) and was financed by the Ministry of Economic Affairs, Agriculture and Innovation (EL&I) under project number 4308701004.