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Sandy Shores Estuaries Delta Lakes Tropical Shelf Seas and Shores Coastal Seas

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    General

    Nearshore estuarine and marine ecosystems, such as seagrass meadows, marshes, mangrove forests and coral reefs serve many important functions in tropical coastal waters. These ecosystems have a high primary and secondary productivity and support a great abundance and diversity of fish and invertebrates (Blaber et al., 2000, Beck et al., 2001).

    The seabed of tropical coastal waters can be rocky, sandy, muddy or a mixture of these. Depending on the bed composition, mangrove forests, seagrass meadows and coral reef ecosystems can be found. These fragile, biologically diverse ecosystems thrive in the warm, wet tropics. Upwelling of nutrient-rich waters supports large populations of microscopic plants and animals, resp. called phytoplankton and zooplankton. Plankton, in turn, feeds many species of fish and other marine life. People in turn depend on harvesting this flora and fauna.

    In this part we describe tropical shelf seas and shores. For information on temperate coastal seas see here and for temperate sandy shores see here.

    Within the Building with Nature sub-program on tropical coastal shelf seas and shores we focus on the coast of Singapore and its neighbouring countries Malaysia, Thailand and Indonesia. These waters are confronted with increased turbidity levels and coastal erosion, due to river inputs and anthropogenic activities. This may affect coastal ecosystems and habitats.

    System description

    Although the tropics are formally defined by their latitude (between Cancer and Capricorn), it is more convenient from a physical point of view to define tropical seas by their physical characteristics (temperature and precipitation) and ecological properties (reflected in the occurrence of e.g. corals, mangroves and seagrasses). This means that some coastal seas and shorelines partly located in the subtropics can be regarded as tropical systems.

    Ecological system

    Three types of ecological communities are specifically found in tropical shelf seas and shores, viz. seagrasses, mangroves and coral reefs.

    Seagrasses comprise a functional group of about 60 to 70 species of underwater marine flowering plants worldwide. They grow primarily on soft substrates from the intertidal area down to maximum depths of around 70 m. In shallow (coastal) waters, they can form dense meadows that constitute valuable and often overlooked habitats that provide important ecological (and economical) functions and services, for example breeding habitats of fish and turtles, shelter for hundreds of marine fish species against their predators and food for mega-herbivores such as green sea turtles, dugongs and manatees. Seagrasses often occur in proximity to coral reefs, mangroves, shellfish reefs and other marine ecosystems, with which there can be significant ecological interactions.

    Mangroves are forests growing in tropical and sub-tropical tidal areas. The forest consists of tree species that can tolerate regular flooding by saline seawater. This tolerance is due to one of the most distinct characteristics of the mangrove trees: aerial roots which are exposed to air part of the day. These enable them to survive in anoxic sediments.

    Coral reefs a are well-recognized feature of tropical oceans. The seas surrounding tropical islands and low-latitude continental shelves away from major river deltas are ideal for coral reef formation. Over millennia, very large reefs have formed in the Caribbean Sea, and especially in the southwest Pacific Ocean. Coral reefs are impressive three-dimensional structures built up over many centuries by small, coral polyps that live in symbiosis (mutual beneficiary relationship) with microscopic algae, called zooxanthellae. These algae require light to grow, so coral reefs only occur in areas that receive enough light. The depth to which coral reefs can occur therefore depends on the interplay of depth and the transparency of the water. The coral polyps protect the algae against predators; the algae provide the coral with excessive sugars. Together they can extract calcium carbonate from seawater to build their limestone skeleton as the coral polyps bud and grow. Over time massive coral reefs structures are formed by these reef builders which create habitat for many other species.

    Physical drivers

    Important physical drivers of the tropical coastal system differ from their temperate counterparts in a number of aspects:

    1. The weather system is monsoon-dominated, which results in a seasonally varying precipitation and wind climate. This seasonal variation is more pronounced than in temperate zones. Precipitation variation is reflected in fluvial water and sediment supply, wind climate variation yields varying residual currents.
    2. Diurnal tides tend to be more pronounced in tropical than in temperate coastal seas (Hoitink et al., 2003). This yields relatively variable tides, often displaying a pronounced seasonal variation and low-frequency currents (van Maren & Gerritsen, 2012).
    3. Solar irradiation, and therefore sea surface temperature, is higher and more constant than in temperate regions. This promotes ecosystems that are typical for the tropics, with little or no seasonal variation in vegetation.
    4. The sediment yield in the tropics is larger than in temperate regions (Milliman & Meade, 1983). This is the result of strong weathering, in Asia also combined with a relative abundance of mountainous islands and the Himalayas.

    As a combined result, tropical coastal seas show a strong seasonality in water levels, current patterns, discharge and sediment load, whereas water temperature and vegetation exhibit a weak or even zero seasonal variation.

    Governance system

    Besides coastal protection important issues in the environment of tropical shelf seas and shores are often the provision of food or earnings by tourism from the sensitive ecosystems such as coral reefs. Local communities are key stakeholders as they heavily depend on the services that these ecosystems provide. Also many different (worldwide) organizations and NGO’s such as the WWF are important actors, as they put their focus on the protection of the tropical environment.

    Results of the efforts of the NGO’s and organizations that act on an international level are the presence of Marine Protected Areas and the enforcement of international guidelines. In case of the development of marine infrastructure projects these guidelines can for example dictate the relocation of ecosystems or the compensation of their loss. The Worldbank has its own guidelines regarding the environment and if a development is undertaken with a loan, it imposes its rules and regulations. Local regulation however, if any, usually overrules the Worldbank regulation.

    For more information on governance processes see Governance.

    Ecosystem services

    Natural ecosystems in general provide a multitude of resources and services to mankind. Collectively, these benefits are known as ecosystem services. The issue of ecosystem services has been discussed for decades. In 2004, the United Nations Millennium Ecosystem Assessment (MEA), and more recently 'The Economics of Ecosystems and Biodiversity' (TEEB) studies, divided the ecosystem services into four categories:

    • provision, such as the production of food and water, or the availability of mineable resources;
    • regulation, such as the control of climate and disease;
    • cultural, such as spiritual and recreational benefits; and
    • support, such as nutrient cycles and crop pollination.

    Provision services

    The ecosystem services provided by tropical coastal ecosystems are described below.

    This category concerns the products to be obtained from ecosystems. Examples of products provided by tropical coastal ecosystems are listed below.

    • Food i.e. fish, shellfish, invertebrates. Mangrove forests, seagrass meadows and coral reefs provide habitat for a diverse flora and fauna, which constitute an important food source.
    • Biodiversity and genetic resources. Mangrove forests, seagrass meadows and coral reefs support a great abundance and diversity of fish and invertebrates.
    • Materials i.e. charcoal, coral mining. Mangrove forests are source of wood (e.g. for fuel), while coral reefs have been mined to extract lime for building construction. Seagrass may be used for preserving (moistening) fisheries products such as crabs.

    Regulation services

    Benefits that arise from how a system regulates processes, resources and its own properties are called regulation services. Benefits obtained from regulation by tropical coastal ecosystems are the following.

    • Erosion control/stabilization of sediment. Mangrove forests and seagrass meadows retain soil between their root structures and provide sediment stabilization, thus preventing or mitigating the loss of soil (erosion) by erosive processes caused by wind, river run-off or wave energy.
    • Coastal protection. Mangrove forests, seagrass meadows and coral reefs dissipate hydrodynamic energy, such as wave energy, and thereby protect their hinterland.
    • Disruption of fresh water discharge. Mangrove forest slows down the fresh water flow to sea, therewith increasing the fresh water availability in inland areas.
    • Nutrient filter. Mangrove forests and seagrass meadows act as nutrient filters for terrestrial waters flowing through them. Nutrients are absorbed in the system, thus preventing them to fertilize the sea.
    • Nitrogen fixation. Coral reefs can fixate nitrogen in nutrient-starved environments, where nitrogen may be of major importance to primary production.
    • Pollution fixation. Mangrove forests and seagrass meadows fixate pollutants.
    • Re-mineralization of in-organic and organic materials.
    • Supply of organic material to surrounding ecosystems.
    • Oxygen production. Mangrove forests and seagrass meadows convert CO2 into O2.
    • Carbon sequestration. Mangrove forests, seagrass meadows and coral reefs act as a carbon dioxide sink and capture carbon dioxide through biogeochemical activity, sedimentation and biological activity.
    • Water catchment and groundwater re-charge by mangrove forests.

    Cultural services

    These are non-material benefits people obtain from ecosystems.

    • Education and scientific resources. Mangrove forests, seagrass meadows and coral reefs are important subjects of scientific research and education.
    • Climate change record. Coral reefs are slowly growing structures, taking many years to gain large proportions. Therefore, their internal structure can serve as a proxy for climate changes in the past.
    • Possibilities for recreation such as fishing, scuba-diving, etc. Especially seagrass meadows and coral reefs provide many opportunities for recreational activities.
    • Cultural, spiritual and artisan values. Mangrove forests and coral reefs are of importance as spiritual locations and as inspiration for artistic activities.
    • Aesthetic values. Mangrove forests, seagrass meadows and coral reefs provide scenery that is often appreciated for its beauty.

    Supporting services

    Some services are necessary for the production of all other ecosystem services, without yielding direct benefits to humans. Examples from tropical coastal ecosystems are:

    • Nursery habitat; mangrove forests, seagrass meadows and coral reefs provide feeding and breeding grounds to a large number of species, including many of economic importance.
    • Resilience to human impact and natural hazards: mangrove forests, seagrass meadows and coral reefs may assist in recovery after natural or human-induced disasters.
    • Top soil formation: Mangroves aid soil formation by trapping sediment and debris. Also their roots and pneumatophores accumulate sediments.
    • Refuge area: mangrove forests, seagrass meadows and coral reefs provide multiple species with shelter.
    • Cross-ecosystem nutrient transfer by coral reefs.

    Ecosystem values

    The table below (Modified after Barbier et al., 2011) gives an impression of the monetary value of some of these ecosystem services. The original valuation estimates are not expressed in standardized units because of possible misinterpretation.

    Ecosystem

    Service

    Ecosystem service value examples

    Location

    Coral reef

    Coastal protection

    US$1,74.ha-1.yr-1

    for Indian Ocean based on impacts from 1998 bleaching event on property values

     

    Fisheries

    US$15-45.000.km-2.yr-1 in sustainable fishing for local consumption and
    US$5-10.000 for live-fish export

    The Philippines

     

    Tourism

    US$88.000 total consumer surplus for 40.000 tourists to marine parks

    Seychelles

    Seagrass beds

    Maintenance of Fisheries

    loss of 12.700ha of seagrasses; associated with lost fishery production of AU$235.000

    Australia

    Mangrove forest

    Raw materials and food

    US$484-585.ha-1.yr-1 capitalized value of collected products

    Thailand

     

    Coastal protection

    US$8.966-10.821 ha-1 capaitalized value for storm protection

    Thailand

     

    Erosion control

    US$3.679.ha-1.yr-1 annualized replacement costs

    Thailand

     

    Maintenance of Fisheries

    US$708-987.ha-1 capitalized value of increased offshore fishery production

    Thailand

     

    Carbon Sequestration

    US$30.50.ha-1.yr-1

    World wide

    BwN opportunities

    In tropical environments, the livelihoods of communities often depend strongly on ecosystem services. Understandably the focus in less developed areas is on socio-economic developments, but these are not always realised in a sustainable manner.

    The Building with Nature approach aims at realising socio-economic developments paying full attention to environmental processes in order to achieve sustainability. Additionally, the Building with Nature approach looks for opportunities to optimize natural processes and enhance ecosystem services.

    Large-scale civil engineering infrastructure developments are essential for economic growth and safety in deltas and coastal areas. Extensive land reclamations continue to provide new  land needed to sustain the anticipated growth of population and economy in the region. It is a major challenge to develop of an area and at the same time increase or maintain the ecosystem services of the environment. The Building with Nature sub-program for tropical shelf seas and shores focuses on two themes:

    1. Ecosystem-based management of dredging operations; and
    2. Eco-dynamic design of  coastal protection systems.

    Ecosystem based management of dredging operations

    Traditional approach

    Marine infrastructure development projects (involving dredging, reclamation and construction works) are crucial for coastal protection and economic development of delta and coastal regions, including harbours and industrial activities. In tropical regions, these infrastructure development activities often take place in the vicinity of valuable and vulnerable marine nature. Dredging activities, for instance, may cause sediment stress that affects sensitive marine ecosystems such as coral reefs and seagrass meadows.

    Current environmental legislation typically focuses on the potential adverse impacts of such development projects. Dredging operations often have to observe rigid limits on dredging-induced turbidity to protect the marine ecosystems, limits that have been copied from elsewhere or presume long-term exposure. It is quite possible, however, that exceeding such limits temporarily is not harmful to the ecosystem, as long as it does not continue for too long. On the other hand, if the ecosystem is exposed to sediment concentrations below the limit for an extended period of time, this can have disproportionate effects and may even alter the system’s sensitivity to short-term ‘storm-like’ pulses.

    Insights into the site-specific responses and thresholds of corals and seagrass in relation to sediment stress, including the effects of earlier sensitization and the ability to recover, offer opportunities to shift from the current emission-based norms towards impact-based norms.  An impact-based approach will result in lower costs for mitigation as system knowledge increases and 'worst-case' assumptions can be avoided.

    Building with Nature approach

    As mentioned before, increased turbidity and sedimentation as a result of anthropogenic activities can be a significant threat to tropical marine ecosystems such as coral reefs and seagrass meadows. In some regions with a high background turbidity and sedimentation however, these ecosystems show a certain degree of tolerance and resilience to such stress events. This leads to the hypothesis that coral and seagrass ecosystems will be able to tolerate anthropogenic sediment stress to an extent that falls within the range and frequency of the natural variability of these parameters.

    In order to realise the shift from an emission-based to an impact-based approach, it is important:

    • to generate knowledge on the critical thresholds of these marine ecosystems and the factors that contribute to their recovery potential. Such knowledge is essential to better predict the effects of dredging and marine infrastructure development, to set realistic and ecologically meaningful indicators and norms for marine construction operations and for a sustainable management of these sensitive ecosystems.
    • to integrate knowledge and models into a generic rapid assessment tool that quantifies the cause-effect chain, in support of the ecodynamic design process, the sustainable execution of marine construction operations and the communication thereof. This rapid assessment tool can also serve as a tool for adaptive management of dredging operations.

    Eco-dynamic design for coastal protection

    Traditional approach

    The traditional design of coastal protection primarily focuses on protection of the land against flooding and retention of beach sediments for recreation purposes. Besides these primary goals, limited attention is paid to accompanying coastal aspects, such as the preservation or development of ecological value. This often results in hard, steep (often vertical) structures on the interface between water and land, leaving hardly any space for natural processes to play a role in local habitat development. Under natural circumstances, the transition between land and water is a bio-diverse area providing a suite of ecosystem services. This transition zone would require a wider stretch of coast than the traditional hard structures, which is not always plainly ideal to the coastal managers because of the space requirement. Coastal land is extremely valuable, thus the traditional train of thought is that it is more ideal to implement a coastal protection solution which utilizes the least amount of space, thus maximizing the remaining coastal space for community use. 

    Building with Nature approach

    Many coastal ecosystems in the tropics (mangroves, sea grass meadows and reefs) are known to contribute significantly to coastal protection and to provide many valuable ecosystem services. For example, some experiments in Singapore have showed that it is possible to improve biodiversity on hard coastal infrastructural works while maintaining the primary functionality. Hence, coastal ecosystems could benefit greatly from infrastructural works that enhance local biodiversity. Alternatively, soft solutions can also be employed to address coastal protection needs, such as have been implemented along the dutch coast (Case - Sand Engine Delfland). In this transitioning time period from traditional solutions to eco-dynamic solutions, hybrid solutions are likely the most common way forward. A good example of a hybrid solution in a tropical environment is that which has been proposed for East Coast Park, on the southwestern shores of Singapore (Case - East Coast Park (ECP) Design Pilot). In this proposed conceptual design (Tutorial - Building with Nature Design), a suite of Eco-Dynamic Design (a.k.a. Building with Nature Design) components have been integrated to obtain a possible solution which addresses the structural erosion in combination with enhancing both the recreation and ecological value of this highly utilized public park. 

    An eco-friendly design requires integrating ecosystem requirements from the start of the design process. This creates opportunities to ‘improve’ (i.e. to enhance functionality and/or diversity) and extend coastal ecosystems while realizing engineering objectives. As many of these ecosystems offer valuable ecosystem services (e.g. wave attenuation, food production, etc.), such a design may be economically more attractive than a traditional design.

    To seize the opportunities for ecodynamic designs for coastal protection:

    • Use existing and newly developed knowledge on the habitat requirements of the  ecosystems involved.
    • Gain insight into how the relative physical, ecological and socio-economic systems  behave; why are certain ecosystem characteristics absent / present and how can the system be stimulated to provide the necessary services?

    Herewith, eco-designs for soft and hard coastlines in tropical environments can be developed that enhance the ecological potential of the system while realising the functionality required for the area (i.e. recreation, shipping, industry, safety, etc.). More a practical example of how this works, please refer to the East Coast Park Design Pilot (East Coast Park (ECP) Design Pilot)

    Case examples

    Within the Building with Nature research program, the regional coastal waters around Singapore were the focus of one of the case studies. The tropical coastal waters around Singapore are turbid, thus providing an ideal environment for a specific component of these studies, viz. the ecosystem’s potential to deal with turbidity. For comparison, also clearer tropical shelf seas and shorelines were investigated in the region (e.g. Indonesia, Malaysia and Thailand).

    Ecological System of Singapore Marine Waters

    Like elsewhere, seagrass meadows in Singapore play a vital role in supporting coastal and marine communities and in maintaining a diverse flora and fauna. They are important to fish productivity and play an important role in maintaining coastal water quality and clarity. The seagrasses of Singapore are also important food for marine green turtles and dugongs. To date, a total of 12 different seagrass species have been recorded in Singapore (Yaakub, 2008; McKenzie et al., 2009).

    The foundation tree species (i.e. the most abundant species building the system) in the mangroves around Singapore typically follow a clear zonation along the elevation gradient, going from the sea-side towards the higher and less inundated areas. Mangroves around Singapore contain several flagship species (i.e. species appealing to the broad public and/or of particular interest to conservation). The most appealing is probably the long-tailed macaque monkeys ( Macaca fascicularis ) that live by digging up mud crabs. Another of the most characteristic species is the mudskipper, which is an early evolutionary species reflecting the transition from sea to land. Mudlobsters ( Thallasia anomala ) are remarkable because of the large mounds they can create. Male fiddler crabs ( Uca spp.) can not be missed on the mudflats, waving their one large claw to court females. The spitting archerfish (Toxotes jaculatrix) is remarkable in that it ‘hunts’ insect by shooting them using a jet of water. Bats living in the mangroves (e.g. lesser dog-faced fruit bat,  Cynopterus brachyotis  and long-tongued nectar bat ( Macroglossus minimus ) are highly important for pollination of some of the mangrove tree species like sonneratia.

    Despite major losses in the last half century, the coral reefs of Singapore still have high species richness: more than 250 species of hard or "stony" corals from 55 genera, providing habitat for more than 120 reef fish species from 30 families.Within Case Singapore, a coral breeding workshop was carried out at the Tropical Marine Science Institute, on Saint John's Island (off the southern coast of Singapore). The workshop was led by SECORE, where over the course of one week the participants were taught essential hands-on techniques, such as the collection of coral gametes during spawning events, fertilization techniques in the lab, rearing of embryos, maintenance of larval cultures, and about the settlement and transport of larvae.

    For additional information on the Singapore ecological system, please refer to Singapore QuickScan

    Physical System of Singapore Marine Waters

    The physical dynamics of the coastal waters around Singapore are dominated by the tidal regime and the wind patterns of the South China Sea, as well as by the local river discharges The wave climate is relatively mild (wave heights < 1m). The large-scale currents in the South China Sea are generated by the annual variation of the monsoon winds and by tides with a pronounced spatially varying dominance of semi-diurnal and diurnal tidal constituents. This may lead to very strong current anomalies in Singapore Strait.

    Several small rivers drain into the coastal waters around Singapore. The largest of these is the Johor River, flowing into the Johor Estuary, a drowned river valley. Several smaller river systems flow into the Johor Strait from Malaysia. From Singapore, the Punggol, the Sungei Buloh, the Sungei Kranji, the Sungei Seletar, the Sungei Serangoon flow into the Johor Strait while the Sungei Kallang drains into Singapore Strait. The discharges of the smaller rivers are poorly known, but the discharge of the Johor River has a long-term mean value of 37.5 m3/s and varies between 70 m3/s in December to around 30 m3/s from February to October. The sediment load of these rivers is hardly known, though one study gave an average sediment concentration for the Johor River of 79.8 mg/l, with minimum and maximum values of 35 mg/l and 164 mg/l, respectively.

    The seafloor in most of Singapore's coastal waters is covered with unconsolidated sand and mud. Mudflats and mangrove forests border the estuaries draining into Singapore's coastal waters from Malaysia, especially along the Johor Estuary. Measurements show that sedimentation rates in the Strait of Johor and the Johor estuary vary from around 20 (Johor estuary and parts of the Straits) to several thousands of mg/cm2/year (Johor Strait). Around Singapore, turbidity was not measured until recently, and therefore its apparent increase is mainly based on qualitative or semi-quantitative observations. The maximum water depth at which coral reefs and seagrass meadows occur, for instance, has decreased over the last few decades (i.e. since 1965). The present-day suspended sediment concentration along the west coast of the southern islands of Singapore is typically between 5 and 20 mg/l.

    For additional information on the Singapore physical system, please refer to Singapore QuickScan

    Case Study Singapore

    The high population density and rapid socio-economic development of Singapore in the last decades has led to extensive land reclamation works. New beaches, industrial parks, commercial and housing development, port and airport facilities, and other important infrastructures have increased the surface area with nearly 20%. These reclamation works strongly influence the hydrodynamics and sediment dynamics around Singapore, by modifying residual currents and maximum flow velocities, and by creating low-energy sheltered areas. The construction phase, with extensive dredging activities, has had a temporary environmental effect. Forest clearance enhancing upland erosion and catchment urbanisation enhancing flash floods have both increased the sediment input into the sea.

    The Singapore sub-program focuses on two themes, viz.:

    1. prediction and monitoring of species response to sedimentation and turbidity;
    2. guidelines, knowledge and designs for bio-diverse coastal protection.

    Prediction and monitoring of species response to sedimentation and turbidity

    Impact assessment studies typically focus on the prevention of adverse impacts of Marine Infrastructure Development (MID) projects, including the construction and operation phase. Often this is done by limiting measurable physical parameters such as turbidity, overflow volume or sedimentation. Unfortunately, the criteria and the associated restrictive measures often lack local ecological meaning and are scientifically poorly underpinned. The Singapore sub-program aims at filling up this knowledge gap as much as possible.

    The main objectives of the sub-program are:

    (1) to develop so-called species response curves for coral and seagrass in Singaporean waters;

    (2) to develop a prototype numerical tool for rapid assessment of species response to the effects of dredging operations;

    (3) to identify early warning indicators for negative species response during these activities.

    The program involves the following activities:

    • Mesocosm experiments in which corals and seagrass are subjected to variable levels of shading- and sedimentation. In the experiments, not only the magnitude, but also the duration of the stress factor is manipulated, and the responses of tolerant and sensitive species are compared. Post-stress recovery and the effect of repetitive stress events on sea grass are also examined by monitoring recovery in experimental (man-made) gaps and artificially buried plots in the field.
    • Monitoring at three coral reefs in Singapore to assess the natural variability in Suspended Particulate Matter (SPM) concentrations, light exposure, sedimentation and coral response. These data are used to develop species and community response curves, to be included in the relevant modules of the interactive dredging design tool.
    • Development of an Interactive Dredge Planning Tool, a rapid assessment tool to determine dredging-induced stressor intensity levels in an area and to generate maps of the predicted ecological effect. This tool can also be used to generate dredging suitability maps, which indicate where and when dredging is possible without unacceptable environmental effects. The setup of the Interactive Dredge Planning Tool and an illustrative showcase are presented here.

    Eco-dynamic design for coastal protection

    Many coastal ecosystems are known to contribute significantly to coastal protection and to provide many valuable ecosystem services. Yet, the design of most present-day coastal protection structures ignores this ability of ecosystems or has not been optimized to facilitate ecological functions. Both these structures and the ecosystem in which they are embedded can greatly profit from applying ecodynamic design principles.

    In the Singapore case, we assess how large-scale marine infrastructure projects, existing as well as envisaged, may be used to extend and strengthen local ecosystems. This represents a paradigm shift from a technical functionality-based approach with ecosystem impact reduction towards an ecosystem-based approach. Integrating the ecosystem functioning and its potential from the start into the design may offer opportunities to strengthen (i.e. enhance functionality and/or diversity) Opportunities by using ecosystem connectivity or diversity) and extend coastal ecosystems while at the same time achieving the infrastructural functionality targets. Moreover, as many ecosystems offer valuable ecosystem services the economical benefits of such an approach may well exceed the extra costs.

    Within the Building with Nature program, the following aspects are studied in relation to eco-dynamic design for coastal protection in tropical environments.

    • Habitat requirements of the tropical ecosystems, coral reefs, seagrass meadows and mangrove forests. To stimulate the development or to rehabilitate these ecosystems requires insight into the conditions under which they can develop and thrive. In this wiki, the Building Block - Development of Mangroves as ecosystem engineer gives a concise overview of these requirements for mangroves. Similar building blocks provide an overview for coral and seagrass. The knowledge page of opportunities offered by ecosystem connectivity summarizes results of related scientific research on the establishment of mangroves and ecosystem services they provide, and on integrated perspectives on tropical coastal ecosystems and ecosystem resilience.
    • Design pilot East Coast Park: Development of four conceptual designs and one detailed design, following the BwN steps and tutorials: Conceptual eco-dynamic design tutorial and Detailed Building with Nature design tutorial. The Building Block - Perched beaches is elaborated as part of the detailed design. The Tool - Visual Thinking resulted from an eco-engineering course organized in Singapore. Visualization is the process of transferring a concept or design to an image on paper. This tool can be utilized particularly during concept development, brainstorming sessions and work sessions focusing on the generation of conceptual designs.
    • The Building Block - Biodiverse Hard substrates: Increasing urbanisation has resulted in extensive replacement of natural habitats by man-made protective structures, for example an artificial seawall. Being vertically steep and structurally quite simple, this compressed intertidal region typically does not represent a shoreline habitat that can support the kind of biodiversity expected in this otherwise unique-,- land-sea environment. This building block shows how the limited small-scale habitat structure of seawalls around Singapore may be engineered to enhance their biodiversity without bringing back diseases such as malaria. Understanding how to improve the value of seawalls as surrogates of natural habitats is important for intertidal biodiversity conservation on modified shorelines.

    Lessons learned

    This section gives an overview of generic lessons learned so far from the Singapore sub-program. Project specific lessons learned can be found in the various wiki-deliverables from this sub-program (also see the links above).

    Physical processes

    • When planning to develop a prototype eco-dynamic design for coastal protection works, about 80% of the time is needed to obtain the necessary insight into the functioning of the local environmental en administrative systems. The remaining time needs to be reserved for the first design detailing phase.
    • When sufficient data on the physical system (e.g. water levels, bathymetric maps) are not readily available, a literature survey combined with sensitivity analyses using numerical models may prove to be a useful approach to gaining insight into the local physical system behaviour.
    • Spatial patterns in the occurrence of seagrass meadows, coral reefs and mangrove forest provide qualitative information on the physical system’s state.
    • Any dredge plume dispersal study needs to take due account of residual current patterns at the relevant spatial and temporal scales as they largely determine the fate and transport of suspended sediments.

    Ecological processes

    • It is difficult, if not impossible, to translate ecological thresholds derived from monitoring and manipulative lab and field experiments to universally applicable criteria, standards and restrictions for dredging operations, as the results of the experiments are species- and location- specific.
    • For this reason it is also not possible to derive these threshold and criteria from literature or other projects.
    • Guidelines can be given on how site-specific ecological thresholds and criteria can be determined using manipulative laboratory experiments, field experiments and/or monitoring campaigns.

    Governance processes

    • Different countries have different habits and different procedures. What might work in one area, might not work in another setting.
    • Presenting courses, seminars on opportunities, if not readily perceived, can work positively in spreading the philosophy behind BwN.
    • Be aware that other countries might have other interests and priorities than sustainability.  

    References

    Literature

    • Cockcroft, A.C. and A. McLachlan. 1993. Nitrogen budget for a high-energy ecosystem. Marine Ecology Progress Series 100: pp. 287-299
    • Milliman & Meade, 1983. World-wide delivery of river sediment to the oceans. Jour. Geology 91: pp. 1-21.
    • Wilkinson, C., O. Linden, H. Cesar, G. Hodgson, J. Rubens & A.E. Strong., 1999. Ecological and socioeconomic impacts of 1998 coral mortality in the Indian Ocean: an ENSO impact and a warning of future change? Ambio 28: pp.188-196.
    • White, A.T., H.P. Vogt, and T. Arin. 2000. Philippine coral reefs under threat: the economic losses caused by reef destruction. Marine Pollution Bulletin 40: pp. 598-605.

    Images

    • Tropical waters
    • Seagrass meadows
    • Corals
    • Seagrass
    • Mangroves
    • Corals
    • Global sea surface temperature. From aquarius.nasa.gov.
    • Global distributions of mangrove, seagrass beds and coral reefs: Gillis, L.G. (in prep.), doctoral thesis.
    • Annual discharge of suspended sediment (in million tons) and sediment yield (t/km 2): Milliman and Meade (1983) World-wide delivery of river sediment to the oceans: Jour. Geology: v. 91, p. 1-21.
    • 150 types of coral in Singapore
    • Dredging plume
    • Opportunities

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