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- Barbier, E.B., Hacker, Sally D., Kennedy, C., Koch, E.W., Stier, A.C., and Silliman, B.R. The value of estuarine and coastal ecosystem services. Ecological Monographs 81(2): 169-193, 2011.
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The global decline in estuarine and coastal ecosystems (ECEs) is affecting a number of critical benefits, or ecosystem services. We review the main ecological services across a variety of ECEs, including marshes, mangroves, nearshore coral reefs, seagrass beds, and sand beaches and dunes. Where possible, we indicate estimates of the key economic values arising from these services, and discuss how the natural variability of ECEs impacts their benefits, the synergistic relationships of ECEs across seascapes, and management implications. Although reliable valuation estimates are beginning to emerge for the key services of some ECEs, such as coral reefs, salt marshes, and mangroves, many of the important benefits of seagrass beds and sand dunes and beaches have not been assessed properly. Even for coral reefs, marshes, and mangroves, important ecological services have yet to be valued reliably, such as cross-ecosystem nutrient transfer (coral reefs), erosion control (marshes), and pollution control (mangroves). An important issue for valuing certain ECE services, such as coastal protection and habitat-fishery linkages, is that the ecological functions underlying these services vary spatially and temporally. Allowing for the connectivity between ECE habitats also may have important implications for assessing the ecological functions underlying key ecosystems services, such coastal protection, control of erosion, and habitat-fishery linkages. Finally, we conclude by suggesting an action plan for protecting and/or enhancing the immediate and longer-term values of ECE services. Because the connectivity of ECEs across land-sea gradients also influences the provision of certain ecosystem services, management of the entire seascape will be necessary to preserve such synergistic effects. Other key elements of an action plan include further ecological and economic collaborative research on valuing ECE services, improving institutional and legal frameworks for management, controlling and regulating destructive economic activities, and developing ecological restoration options.
- Gedan, K.B., Kirwan, M.L., Wolanski, E., Barbier, E.B., and Silliman, B.R. The present and future role of coastal wetland vegetation in protecting shorelines: answering recent challenges to the paradigm. Climatic Change 106(1): 7-29, 2011.
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For more than a century, coastal wetlands have been recognized for their ability to stabilize shorelines and protect coastal communities. However, this paradigm has recently been called into question by small-scale experimental evidence. Here, we conduct a literature review and a small meta-analysis of wave attenuation data, and we find overwhelming evidence in support of established theory. Our review suggests that mangrove and salt marsh vegetation afford context-dependent protection from erosion, storm surge, and potentially small tsunami waves. In biophysical models, field tests, and natural experiments, the presence of wetlands reduces wave heights, property damage, and human deaths. Meta-analysis of wave attenuation by vegetated and unvegetated wetland sites highlights the critical role of vegetation in attenuating waves. Although we find coastal wetland vegetation to be an effective shoreline buffer, wetlands cannot protect shorelines in all locations or scenarios; indeed large-scale regional erosion, river meandering, and large tsunami waves and storm surges can overwhelm the attenuation effect of vegetation. However, due to a nonlinear relationship between wave attenuation and wetland size, even small wetlands afford substantial protection from waves. Combining man-made structures with wetlands in ways that mimic nature is likely to increase coastal protection. Oyster domes, for example, can be used in combination with natural wetlands to protect shorelines and restore critical fishery habitat. Finally, coastal wetland vegetation modifies shorelines in ways (e.g. peat accretion) that increase shoreline integrity over long timescales and thus provides a lasting coastal adaptation measure that can protect shorelines against accelerated sea level rise and more frequent storm inundation. We conclude that the shoreline protection paradigm still stands, but that gaps remain in our knowledge about the mechanistic and context-dependent aspects of shoreline protection.
- Durr, H.H., Laruelle, G.G., van Kempen, C.M., Slomp, C.P., Meybeck, M., and Middelkoop, H. Worldwide typology of nearshore coastal systems: Defining the estuarine filter of river inputs to the oceans. Estuaries and Coasts 34(3): 441-458, 2011.
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We present a spatially explicit global overview of nearshore coastal types, based on hydrological, lithological and morphological criteria. A total of four main operational types act as active filters of both dissolved and suspended material entering the ocean from land: small deltas (type I), tidal systems (II), lagoons (III) and fjords (IV). Large rivers (V) largely bypass the nearshore filter, while karstic (VI) and arheic coasts (VII) act as inactive filters. This typology provides new insight into the spatial distribution and inherent heterogeneity of estuarine filters worldwide. The relative importance of each type at the global scale is calculated and types I, II, III and IV account for 32%, 22%, 8% and 26% of the global coastline, respectively, while 12% have a very limited nearshore coastal filter. As an application of this typology, the global estuarine surface area is re-estimated to 1.1 x 106 km2 instead of 1.4 x 106 km2 in earlier work.
- Clark, M.R., Watling, L., Rowden, A.A., Guinotte, J.M., and Smith, C.R. A global seamount classification to aid the scientific design of marine protected area networks. Ocean and Coastal Management 54(1): 19-36, 2011.
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Seamounts are prominent features of the world's seafloor, and are the target of deep-sea commercial fisheries, and of interest for minerals exploitation. They can host vulnerable benthic communities, which can be rapidly and severely impacted by human activities. There have been recent calls to establish networks of marine protected areas on the High Seas, including seamounts. However, there is little biological information on the benthic communities on seamounts, and this has limited the ability of scientists to inform managers about seamounts that should be protected as part of a network. In this paper we present a seamount classification based on "biologically meaningful" physical variables for which global-scale data are available. The approach involves the use of a general biogeographic classification for the bathyal depth zone (near-surface to 3500 m), and then uses four key environmental variables (overlying export production, summit depth, oxygen levels, and seamount proximity) to group seamounts with similar characteristics. This procedure is done in a simple hierarchical manner, which results in 194 seamount classes throughout the worlds oceans. The method was compared against a multivariate approach, and ground-truthed against octocoral data for the North Atlantic. We believe it gives biologically realistic groupings, in a transparent process that can be used to either directly select, or aid selection of, seamounts to be protected.
- Kirwan, M.L. and Blum, L.K. Enhanced decomposition offsets enhanced productivity and soil carbon accumulation in coastal wetlands responding to climate change. Biogeosciences 8(4): 987-993, 2011.
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Coastal wetlands are responsible for about half of all carbon burial in oceans, and their persistence as a valuable ecosystem depends largely on the ability to accumulate organic material at rates equivalent to relative sea level rise. Recent work suggests that elevated CO2 and temperature warming will increase organic matter productivity and the ability of marshes to survive sea level rise. However, we find in a series of preliminary experiments that organic decomposition rates increase by about 20% per degree of warming. Our measured temperature sensitivity is similar to studies from terrestrial systems, three times as high as the response of salt marsh productivity to temperature warming, and greater than the productivity response associated with elevated CO2 in C3 marsh plants. Although the experiments were simple and of short duration, they suggest that enhanced CO2 and warmer temperatures could actually make marshes less resilient to sea level rise, and tend to promote a release of soil carbon. Simple projections indicate that elevated temperatures will increase rates of sea level rise more than any acceleration in organic matter accumulation, suggesting the possibility of a positive feedback between climate, sea level rise, and carbon emissions in coastal environments.
- Andersen, T.J., Svinth, S., and Pejrup, M. Temporal variation of accumulation rates on a natural salt marsh in the 20th century — The impact of sea level rise and increased inundation frequency. Marine Geology 279(1-4): 178-187, 2011.
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Salt marshes are potentially threatened by sea level rise if sediment supply is unable to balance the rising sea. A rapid sea level rise is one of the pronounced effects of global warming and global sea level is at present rising at an elevated rate of about 3.4 mm y-1 on average. This increasing rate of sea level rise should make it possible to study the effect of rapidly rising sea level on salt marsh accumulation. However, such an understanding is generally hampered by lack of available data with sufficient precision. Here we present a high-precision dataset based on detailed radiometric measurements of 137Cs in 10 sediment cores retrieved at a natural and unmanaged micro tidal salt marsh. Two distinct 137Cs-peaks were found in all cores, one peak corresponding to the 1963-maximum caused by testing of nuclear weapons in the atmosphere and the other to the Chernobyl accident in 1986. Salt marsh accretion has generally kept pace with sea level rise since 1963 but comparison of the accumulation rates of minerogenic material in the period 1963-1986 and 1986-2003 revealed a slight decrease in accumulation with time in spite of an observed increase in inundation frequency. The observed decrease in sediment deposition is significant and gives reason for concern as it may be the first sign of a sedimentation deficiency which could be threatening this and other salt marshes in the case of a rapidly rising sea level. Our work demonstrates that the assumption of a constant relationship between salt marsh inundation and sediment deposition is not necessarily valid, even for a salt marsh that receives most of its allocthonous sediment from the adjacent sea. The apparent decrease in sediment deposition indicates that the basic assumption of sufficient sediment supply used in contemporary models dealing with salt marsh accretion is most probably not valid in the present case study and it may well be that this is also the case for many other salt marshes, especially if sea level continues to rise rapidly as indicated by some climate change scenarios.
- Kirwan, M.L., Murray, A.B., Donnelly, J.P., and Corbett, D.R. Rapid wetland expansion during European settlement and its implication for marsh survival under modern sediment delivery rates. Geology 39(5): 507-510, 2011.
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Fluctuations in sea-level rise rates are thought to dominate the formation and evolution of coastal wetlands. Here we demonstrate a contrasting scenario in which land-use-related changes in sediment delivery rates drive the formation of expansive marshland, and vegetation feedbacks maintain their morphology despite recent sediment supply reduction. Stratigraphic analysis and radiocarbon dating in the Plum Island Estuary (Massachusetts, United States) suggest that salt marshes expanded rapidly during the eighteenth and nineteenth centuries due to increased rates of sediment delivery following deforestation associated with European settlement. Numerical modeling coupled with the stratigraphic observations suggests that existing marshland could survive, but not form under the low suspended sediment concentrations observed in the estuary today. These results suggest that many of the expansive marshes that characterize the modern North American coast are metastable relicts of high nineteenth century sediment delivery rates, and that recent observations of degradation may represent a slow return to pre-settlement marsh extent. In contrast to ecosystem management practices in which restoring pre-anthropogenic conditions is seen as a way to increase ecosystem services, our results suggest that widespread efforts to restore valuable coastal wetlands actually prevent some systems from returning to a natural state.
- Bjerstedt, T.W. Impacting factors and cumulative impacts by midcentury on wetlands in the Louisiana coastal area. Journal of Coastal Research 27(6): 1029-1051, 2011.
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Natural and anthropogenic impacting factors simultaneously cause wetland loss in the Louisiana coastal area. Ongoing natural processes are integrated with anthropogenic impacting factors to rationalize the contribution of each impact type within a total system. From baseline conditions of today, two natural processes account for approximately 85% of the estimated cumulative land loss by 2050: (1) subsidence by sediment compaction and tectonism that is driven by the weight of the Mississippi Delta's sedimentary pile and (2) absolute sea-level rise. Hurricanes are sudden natural processes that act as impact accelerators. After the Mississippi River became hydrologically isolated from the delta it built, anthropogenic impacts coinciding with the ramp up to peak oil production in the Louisiana coastal area caused many direct impacts, such as the construction of access canals and pipelines, but indirect impacts are largely symptomatic of natural delta platform submergence. Formation extraction is the only significant anthropogenic activity influencing projected land losses: about 6%. Other anthropogenic activities, such as onshore development, maintenance dredging, and oil spills, are not significant impacting factors. Additive processes, such as delta outbuilding and coastal restoration, are also not significant. A growing body of Louisiana coastal area subsidence studies is proceeding in absence of insight as to how conclusions might be ordered by the subsurface structural fabric that has influenced coastal geomorphology and that continues to influence surface processes. Subsidence assessments have been heavily weighted with inputs based on surface and near-surface data sets that are easy to see and touch. Approaches using basin analysis techniques are a critical omission. Such outputs integrate subsurface geologic logs and seismic data sets into products able to inform decisions about locating coastal restoration or flood protection projects and avoid areas of geologically persistent subsidence.
- Kearney, M.S., Riter, J.C.A., and Turner, R.E. Freshwater river diversions for marsh restoration in Louisiana: Twenty-six years of changing vegetative cover and marsh area. Geophysical Research Letters 38(16): art. L16405, 2011.
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The restoration of Louisiana's coastal wetlands will be one of the largest, most costly and longest environmental remediation projects undertaken. We use Landsat data to show that freshwater diversions, a major restoration strategy, have not increased vegetation and marsh coverage in three freshwater diversions operating for ~19 years. Two analytic methods indicate no significant changes in either relative vegetation or overall marsh area from 1984 to 2005 in zones closest to diversion inlets. After Hurricanes Katrina and Rita, these zones sustained dramatic and enduring losses in vegetation and overall marsh area, whereas the changes in similar marshes of the adjacent reference sites were relatively moderate and short-lived. We suggest that this vulnerability to storm damage reflects the introduction of nutrients in the freshwater diversions (that add insignificant amounts of additional sediments), which promotes poor rhizome and root growth in marshes where below-ground biomass historically played the dominant role in vertical accretion.
- Kolker, A.S., Allison, M.A., and Hameed, S. An evaluation of subsidence rates and sea-level variability in the northern Gulf of Mexico. Geophysical Research Letters 38(21): art. L21404, 2011.
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While subsidence is widely recognized as a driver of geomorphic change in the northern Gulf of Mexico (GOM), there is considerable disagreement over the rates of subsidence and the interpreted variability in these rates, which leads to controversies over the impacts of subsidence on surface land area change. Here we present a new method to calculate subsidence rates from the tide gauge record that is based on an understanding of the meteorological drivers of inter-annual sea-level change. In Grand Isle, LA and Galveston, TX, we explicitly show that temporal patterns of subsidence are closely linked to subsurface fluid withdrawal and coastal land loss, and suggest changes in withdrawal rates can both increase and decrease rates of subsidence and wetland loss. Our results also imply that the volume of sediment needed to rebuild GOM wetlands may currently fall within the low end of some restoration scenarios.
- Turner, R.E. Beneath the salt marsh canopy: Loss of soil strength with increasing nutrient loads. Estuaries and Coasts 34(5): 1084-1093, 2011.
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Although the broadly observed increase in nutrient loading rates to coastal waters in the last 100 years may increase aboveground biomass, it also tends to increase soil metabolism and lower root and rhizome biomass-responses that can compromise soil strength. Fourteen different multiyear field combinations of nutrient amendments to salt marshes were made to determine the relationship between soil strength and various nitrogen, phosphorus, and nitrogen+phosphorus loadings. There was a proportional decline in soil strength that reached 35% in the 60- to 100-cm soil layer at the highest loadings and did not level off. These loading rates are equivalent to those in the flow path of the Caernarvon river diversion, a major wetland restoration project near New Orleans; 12% of the wetlands in the flow path were converted to open water in 2005. The increased nutrient loading from the Mississippi River watershed this century has also driven the formation of the low oxygen zone (the "Dead Zone") that forms off the Louisiana-Texas shelf each summer. These results suggest that improving water quality in the watershed will aid the restoration of both offshore waters and coastal wetland ecosystems.
- Zhong, B. and Xu, Y.J. Risk of inundation to coastal wetlands and soil organic carbon and organic nitrogen accounting in Louisiana, USA. Environmental Science and Technology 45(19): 8241-8246, 2011.
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Exceeding 1.2 million acres (4856 km2) since the 1930s, coastal wetland loss has been the most threatening environmental problem in Louisiana, United States. This study utilized high-resolution LiDAR (Light Detection and Ranging) and DEM (Digital Elevation Model) data sets to assess the risk of potential wetland loss due to future sea level rises, their spatial distribution, and the associated loss of soil organic carbon (SOC) and organic nitrogen (SON) estimated from the State Soil Geographic (STATSGO) Database and National Wetlands Inventory (NWI) digital data. Potential inundation areas were divided into five elevation scales: <0 cm, 0-50 cm, 50-100 cm, 100-150 cm, and 150-200 cm above mean sea level. The study found that southeastern Louisiana on the Mississippi River Delta, specifically the Pontchartrain and Barataria Basins, are most vulnerable to sea-level rise induced inundation. Accordingly, approximately 42,264,600 t of SOC and 2,817,640 t of SON would be inundated by 2050 using an average wetland SOC density (203 t per hectare) for the inundation areas between 0 and 50 cm. The estimated annual SOC and SON loss from Louisiana's coast is 17% of annual organic carbon and 6-8% of annual organic nitrogen inputs from the Mississippi River.
- Gedan, K.B., Altieri, A.H., and Bertness, M.D. Uncertain future of New England salt marshes. Marine Ecology Progress Series 434: 229-237, 2011.
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Salt marsh plant communities have long been envisioned as dynamic, resilient systems that quickly recover from human impacts and natural disturbances. But are salt marshes sufficiently resilient to withstand the escalating intensity and scale of human impacts in coastal environments? In this study we examined the independent and interactive effects of emerging threats to New England salt marshes (temperature increase, accelerating eutrophication, consumer-driven salt marsh die-off, and sea level rise) to understand the future trajectory of these ecologically valuable ecosystems. While marsh plant communities remain resilient to many disturbances, loss of critical foundation species and changing tidal inundation regimes may short circuit marsh resilience in the future. Accelerating sea level rise and salt marsh die-off in particular may interact to overwhelm the compensatory mechanisms of marshes and increase their vulnerability to drowning. Management of marshes will require difficult decisions to balance ecosystem service tradeoffs and conservation goals, which, in light of the immediate threat of salt marsh loss, should focus on maintaining ecosystem resilience.
- Giri, C., Ochieng, E., Tieszen, L.L., Zhu, Z., Singh, A., Loveland, T., Masek, J., and Duke, N. Status and distribution of mangrove forests of the world using earth observation satellite data. Global Ecology and Biogeography 20(1): 154-159, 2011.
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Aim Our scientific understanding of the extent and distribution of mangrove forests of the world is inadequate. The available global mangrove databases, compiled using disparate geospatial data sources and national statistics, need to be improved. Here, we mapped the status and distributions of global mangroves using recently available Global Land Survey (GLS) data and the Landsat archive. Methods We interpreted approximately 1000 Landsat scenes using hybrid supervised and unsupervised digital image classification techniques. Each image was normalized for variation in solar angle and earth-sun distance by converting the digital number values to the top-of-the-atmosphere reflectance. Ground truth data and existing maps and databases were used to select training samples and also for iterative labelling. Results were validated using existing GIS data and the published literature to map 'true mangroves'. Results The total area of mangroves in the year 2000 was 137,760 km2 in 118 countries and territories in the tropical and subtropical regions of the world. Approximately 75% of world's mangroves are found in just 15 countries, and only 6.9% are protected under the existing protected areas network (IUCN I-IV). Our study confirms earlier findings that the biogeographic distribution of mangroves is generally confined to the tropical and subtropical regions and the largest percentage of mangroves is found between 5° N and 5° S latitude. Main conclusions We report that the remaining area of mangrove forest in the world is less than previously thought. Our estimate is 12.3% smaller than the most recent estimate by the Food and Agriculture Organization (FAO) of the United Nations. We present the most comprehensive, globally consistent and highest resolution (30 m) global mangrove database ever created. We developed and used better mapping techniques and data sources and mapped mangroves with better spatial and thematic details than previous studies.
- Lewis, M., Pryor, R., and Wilking, L. Fate and effects of anthropogenic chemicals in mangrove ecosystems: A review. Environmental Pollution 159(10): 2328-2346, 2011.
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The scientific literature for fate and effects of non-nutrient contaminant concentrations is skewed for reports describing sediment contamination and bioaccumulation for trace metals. Concentrations for at least 22 trace metals have been reported in mangrove sediments. Some concentrations exceed sediment quality guidelines suggesting adverse effects. Bioaccumulation results are available for at least 11 trace metals, 12 mangrove tissues, 33 mangrove species and 53 species of mangrove-habitat biota. Results are specific to species, tissues, life stage, and season and accumulated concentrations and bioconcentration factors are usually low. Toxicity tests have been conducted with 12 mangrove species and 8 species of mangrove-related fauna. As many as 39 effect parameters, most sublethal, have been monitored during the usual 3 to 6 month test durations. Generalizations and extrapolations for toxicity between species and chemicals are restricted by data scarcity and lack of experimental consistency. This hinders chemical risk assessments and validation of effects-based criteria.
- Santos, H.F., Carmo, F.L., Paes, J.E.S., Rosado, A.S., and Peixoto, R.S. Bioremediation of mangroves impacted by petroleum. Water Air and Soil Pollution 216(1-4): 329-350, 2011.
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The majority of oil from oceanic oil spills (e.g. the recent accident in the Gulf of Mexico) converges on coastal ecosystems such as mangroves. Microorganisms are directly involved in biogeochemical cycles as key drivers of the degradation of many carbon sources, including petroleum hydrocarbons. When properly understood and managed, microorganisms provide a wide range of ecosystem services, such as bioremediation, and are a promising alternative for the recovery of impacted environments. Previous studies have been conducted with emphasis on developing and selecting strategies for bioremediation of mangroves, mostly in vitro, with few field applications described in the literature. Many factors can affect the success of bioremediation of oil in mangroves, including the presence and activity of the oil-degrading microorganisms in the sediment, availability and concentration of oil and nutrients, salinity, temperature and oil toxicity. More studies are needed to provide efficient bioremediation strategies to be applicable in large areas of mangroves impacted with oil. A major challenge to mangrove bioremediation is defining pollution levels and measuring recuperation of a mangrove. Typically, chemical parameters of pollution levels, such as polycyclic aromatic hydrocarbons (PAHs), are used but are extremely variable in field measurements. Therefore, meaningful mangrove monitoring strategies must be developed. This review will present the state of the art of bioremediation in oil-contaminated mangroves, new data about the use of different mangrove microcosms with and without tide simulation, the main factors that influence the success of bioremediation in mangroves and new prospects for the use of molecular tools to monitor the bioremediation process. We believe that in some environments, such as mangroves, bioremediation may be the most appropriate approach for cleanup. Because of the peculiarities and heterogeneity of these environments, which hinder the use of other physical and chemical analyses, we suggest that measuring plant recuperation should be considered with reduction in polycyclic aromatic hydrocarbons (PAHs). This is a crucial discussion because these key marine environments are threatened with worldwide disappearance. We highlight the need for and suggest new ways to conserve, protect and restore these environments.
- Donato, D.C., Kauffman, J.B., Murdiyarso, D., Kurnianto, S., Stidham, M., and Kanninen, M. Mangroves among the most carbon-rich forests in the tropics. Nature Geoscience 4(5): 293-297, 2011.
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Mangrove forests occur along ocean coastlines throughout the tropics, and support numerous ecosystem services, including fisheries production and nutrient cycling. However, the areal extent of mangrove forests has declined by 30-50% over the past half century as a result of coastal development, aquaculture expansion and over-harvesting. Carbon emissions resulting from mangrove loss are uncertain, owing in part to a lack of broad-scale data on the amount of carbon stored in these ecosystems, particularly below ground. Here, we quantified whole-ecosystem carbon storage by measuring tree and dead wood biomass, soil carbon content, and soil depth in 25 mangrove forests across a broad area of the Indo-Pacific region – spanning 30° of latitude and 73° of longitude – where mangrove area and diversity are greatest. These data indicate that mangroves are among the most carbon-rich forests in the tropics, containing on average 1,023 Mg carbon per hectare. Organic-rich soils ranged from 0.5 m to more than 3 m in depth and accounted for 49-98% of carbon storage in these systems. Combining our data with other published information, we estimate that mangrove deforestation generates emissions of 0.02–0.12 Pg carbon per year – as much as around 10% of emissions from deforestation globally, despite accounting for just 0.7% of tropical forest area.
- Bhattarai, B. and Giri, C. Assessment of mangrove forests in the Pacific region using Landsat imagery. Journal of Applied Remote Sensing 5: art. 053509, 2011.
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The information on the mangrove forests for the Pacific region is scarce or outdated. A regional assessment based on a consistent methodology and data sources was needed to understand their true extent. Our investigation offers a regionally consistent, high resolution (30 m), and the most comprehensive mapping of mangrove forests on the islands of American Samoa, Fiji, French Polynesia, Guam, Hawaii, Kiribati, Marshall Islands, Micronesia, Nauru, New Caledonia, Northern Mariana Islands, Palau, Papua New Guinea, Samoa, Solomon Islands, Tonga, Tuvalu, Vanuatu, and Wallis and Futuna Islands for the year 2000. We employed a hybrid supervised and unsupervised image classification technique on a total of 128 Landsat scenes gathered between 1999 and 2004, and validated the results using existing geographic information science (GIS) datasets, high resolution imagery, and published literature. We also draw a comparative analysis with the mangrove forests inventory published by the Food and Agriculture Association (FAO) of the United Nations. Our estimate shows a total of 623755 hectares of mangrove forests in the Pacific region; an increase of 18% from FAO's estimates. Although mangrove forests are disproportionately distributed toward a few larger islands on the western Pacific, they are also significant in many smaller islands.
- McNally, C.G., Uchida, E., and Gold, A.J. The effect of a protected area on the tradeoffs between short-run and long-run benefits from mangrove ecosystems. Proceedings of the National Academy of Sciences [USA] 108(34): 13945-13950, 2011.
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Protected areas are used to sustain biodiversity and ecosystem services. However, protected areas can create tradeoffs spatially and temporally among ecosystem services, which can affect the welfare of dependent local communities. This study examines the effect of a protected area on the tradeoff between two extractive ecosystem services from mangrove forests: cutting mangroves (fuelwood) and harvesting the shrimp and fish that thrive if mangroves are not cut. We demonstrate the effect in the context of Saadani National Park (SANAPA) in Tanzania, where enforcement of prohibition of mangrove harvesting was strengthened to preserve biodiversity. Remote sensing data of mangrove cover over time are integrated with georeferenced household survey data in an econometric framework to identify the causal effect of mangrove protection on income components directly linked to mangrove ecosystem services. Our findings suggest that many households experienced an immediate loss in the consumption of mangrove firewood, with the loss most prevalent in richer households. However, all wealth classes appear to benefit from long-term sustainability gains in shrimping and fishing that result from mangrove protection. On average, we find that a 10% increase in the mangrove cover within SANAPA boundaries in a 5-km2 radius of the subvillage increases shrimping income by approximately twofold. The creation of SANAPA shifted the future trajectory of the area from one in which mangroves were experiencing uncontrolled cutting to one in which mangrove conservation is providing gains in income for the local villages as a result of the preservation of nursery habitat and biodiversity.
- Scyphers, S.B., Powers, S.P., Heck, K., and Byron, D. Oyster reefs as natural breakwaters mitigate shoreline loss and facilitate fisheries. PLoS ONE 6(8): art. e22396, 2011.
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Shorelines at the interface of marine, estuarine and terrestrial biomes are among the most degraded and threatened habitats in the coastal zone because of their sensitivity to sea level rise, storms and increased human utilization. Previous efforts to protect shorelines have largely involved constructing bulkheads and seawalls which can detrimentally affect nearshore habitats. Recently, efforts have shifted towards "living shoreline" approaches that include biogenic breakwater reefs. Our study experimentally tested the efficacy of breakwater reefs constructed of oyster shell for protecting eroding coastal shorelines and their effect on nearshore fish and shellfish communities. Along two different stretches of eroding shoreline, we created replicated pairs of subtidal breakwater reefs and established unaltered reference areas as controls. At both sites we measured shoreline and bathymetric change and quantified oyster recruitment, fish and mobile macro-invertebrate abundances. Breakwater reef treatments mitigated shoreline retreat by more than 40% at one site, but overall vegetation retreat and erosion rates were high across all treatments and at both sites. Oyster settlement and subsequent survival were observed at both sites, with mean adult densities reaching more than eighty oysters m-2 at one site. We found the corridor between intertidal marsh and oyster reef breakwaters supported higher abundances and different communities of fishes than control plots without oyster reef habitat. Among the fishes and mobile invertebrates that appeared to be strongly enhanced were several economically-important species. Blue crabs (Callinectes sapidus) were the most clearly enhanced (+297%) by the presence of breakwater reefs, while red drum (Sciaenops ocellatus) (+108%), spotted seatrout (Cynoscion nebulosus) (+88%) and flounder (Paralichthys sp.) (+79%) also benefited. Although the vertical relief of the breakwater reefs was reduced over the course of our study and this compromised the shoreline protection capacity, the observed habitat value demonstrates ecological justification for future, more robust shoreline protection projects.
- Beck, M.W. et al. Oyster reefs at risk and recommendations for conservation, restoration, and management. BioScience 61(2): 107-116, 2011.
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Native oyster reefs once dominated many estuaries, ecologically and economically. Centuries of resource extraction exacerbated by coastal degradation have pushed oyster reefs to the brink of functional extinction worldwide. We examined the condition of oyster reefs across 144 bays and 44 ecoregions; our comparisons of past with present abundances indicate that more than 90% of them have been lost in bays (70%) and eco regions (63%). In many bays, more than 99% of oyster reefs have been lost and are functionally extinct. Overall, we estimate that 85% of oyster reefs have been lost globally. Most of the world's remaining wild capture of native oysters (>75%) comes from just five ecoregions in North America, yet the condition of reefs in these ecoregions is poor at best, except in the Gulf of Mexico. We identify many cost-effective solutions for conservation, restoration, and the management of fisheries and nonnative species that could reverse these oyster losses and restore reef ecosystem services.
- Provoost, S., Jones, M.L.M., and Edmondson, S.E. Changes in landscape and vegetation of coastal dunes in northwest Europe: a review. Journal of Coastal Conservation 15(1): 207-226, 2011.
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In coastal dunes, landscape changes are a rule, rather than an exception. This paper gives an overview of changes in landscape and vegetation with a focus on the past century. The history of dunes is characterised by phases of sand drift, alternated with geomorphological stability. The historical development of dune woodland during these stable phases has been documented for sites all over Europe. Vegetation reconstructions of historical open dune habitats however is very difficult due to limited preservation of fossil remains. People have drastically altered coastal dune landscapes through centuries of exploitation and more recently development of the coast. Historical land use has generally pushed vegetation back into a semi-natural state. During roughly the past century a tendency of increasing fixation and succession is observed on coastal dunes throughout northwest Europe. Six causes of change are discussed. 1) Changes in land use, mainly abandonment of agricultural practices, have led to the development of late successional stages such as scrub and woodland. 2) Crashing rabbit populations due to myxomatosis in the 1950s caused vigorous grass growth and probably stimulated scrub development. 3) A general tendency of landscape fixation is observed due to both natural and anthropogenic factors. 4) Eutrophication, mainly due to atmospheric nitrogen deposition is clearly linked to grass encroachment on acidic but also on some calcareous dunes. 5) The impact of climate change on vegetation is still unclear but probably lengthening of growing season and maybe enhanced CO2 concentrations have led to an acceleration of succession. 6) A general anthropogenisation of the landscape occurs with rapid spread of non-native species as an important consequence. The reconstruction of a natural reference landscape is considered largely unattainable because of irreversible changes and the long tradition of human impact, in many cases since the development of the dunes. Two contradictory elements need reconciliation. First, the general acceleration of succession and scrub and woodland development in particular is partly caused by a decreased anthropogenic interference in the landscape and deserves more appreciation. Second, most biodiversity values are largely linked to open, early succession dune habitats and are threatened by the same tendency. Apart from internal nature management, in which grazing plays an important part, re-mobilisation of stable, senescent dunes is an important challenge for dune management.
- Schierding, M., Vahder, S., Dau, L., and Irmler, U. Impacts on biodiversity at Baltic Sea beaches. Biodiversity and Conservation 20(9): 1973-1985, 2011.
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Sandy and shingle beaches were investigated in 2009 and 2010 along the coast of the Baltic Sea in northern Germany with the purpose of assessing biodiversity gradients from shingle to sandy beaches, from beach to primary dunes, and the impacts of tourism on biodiversity. On nine beach sites, ranging between 100% shingle and 99% sand without shingle, Carabidae, Staphylinidae, and Araneae were studied. Two of the six sandy beaches were open and four were closed to tourists. Additionally, trampling effects from tourists, species richness of plants, and plant cover were investigated on sixteen beaches. According to results, primary dunes showed higher species richness in carabids and spiders, but not in staphylinds. Shingle beaches exhibited lower species richness in Staphylinidae and Araneae, but not in Carabidae. As estimated by the Jackknife II method, shingle beaches were the lowest in total species richness. Trampling intensity ranged from 0 footprints m-2 day-1 on closed beaches, up to a maximum of 30 footprints m-2 day-1. On "intensively" used beaches (12 footprints m-2 day-1, on average), reduction of plant cover was more pronounced than on "extensively" used beaches (7 footprints m-2 day-1, on average). Both plant cover and plant species richness were lower on intensively and extensively used beaches than on closed beaches. In arthropods, only staphylind and spider species richness was significantly lower on open beaches than on closed beaches, but no differences were found in carabids. Referring to our results, trampling effects from tourists have high impact on species richness of sandy beaches, on both intensively and extensively used sites.
- Nordstrom, K.F., Jackson, N.L., Kraus, N.C., Kana, T.W., Bearce, R., Bocamazo, L.M., Young, D.R., and De Butts, H.A. Enhancing geomorphic and biologic functions and values on backshores and dunes of developed shores: a review of opportunities and constraints. Environmental Conservation 38(3): 288-302, 2011.
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This article identifies ways to overcome impediments to restoring natural features on developed shores where human-use functions are the dominant driving forces. Suggestions are made for (1) incorporating natural features and natural dynamism into beach nourishment projects; (2) addressing constraints in size and space; (3) reducing the impact of human actions and elements in the landscape; (4) integrating endangered species programmes; (5) overcoming impediments to implementing restoration projects; (6) conducting post-construction evaluations and actions; (7) obtaining public support; and (8) addressing regulatory issues. Beach nourishment projects can better mimic natural landforms, while protecting infrastructure and habitat, creating space for dunes, and providing sediment for dune building. Dunes can have more value as habitat if sub-environments representative of natural gradients are accommodated. Greater human effort will be required to maintain both dynamic and stable zones for habitat, and these zones may be restricted to smaller scales. Controls can be placed on human actions, such as raking the beach, driving on the beach, walking through the dune, emplacing more structures than necessary and introducing exotic vegetation for landscaping. Regulatory restrictions that now prevent environmentally friendly actions can be eased, and adaptive management and education programmes can be implemented.
- Feagin, R.A., Smith, W.K., Psuty, N.P., Young, D.R., Martinez, M.L., Carter, G.A., Lucas, K.L., Gibeaut, J.C., Gemma, J.N., and Koske, R.E. Barrier islands: Coupling anthropogenic stability with ecological sustainability. Journal of Coastal Research 26(6): 987-992, 2010.
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Barrier islands provide a host of critical ecosystem services to heavily populated coastal regions of the world yet they are quite vulnerable to ongoing sea level rise and a potential increase in the frequency and intensity of oceanic storms. These islands are being degraded at an alarming rate in part because of anthropogenic attempts at stabilization. In this article we outline a possible sustainability strategy that incorporates the natural degree of substrate instability on these sedimentary landscapes. We recommend placing the focus for managing barrier islands on maintaining ecosystem function and process development rather than emphasizing barrier islands as structural impediments to wave and storm energy.
- Stutz, M.L. and Pilkey, O.H. Open-ocean barrier islands: Global influence of climatic, oceanographic, and depositional settings. Journal of Coastal Research 27(2): 207-222, 2011.
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A satellite-based inventory of barrier islands was used to study the influence of depositional setting, climate, and tide regime on island distribution and morphology. The survey reveals 20,783 km of shoreline occupied by 2149 barrier islands worldwide. Their distribution is strongly related to sea level history in addition to the influence of tectonic setting. Rising sea level in the late Holocene (5000 YBP present) is associated with greatest island abundance, especially on North Atlantic and Arctic coastal plains. Stable or falling sea level in the same time frame, a pattern typical of the Southern Hemisphere, is associated with a lower abundance of islands and a higher percentage of islands along deltas rather than coastal plains. Both coastal plain and deltaic island morphology are sensitive to the wave tide regime; however, island length is 40% greater along coastal plains whereas inlet width is 40% greater on deltas. Island morphology is also fundamentally affected by climate. Island lengths in the Arctic are on average (5 km) only half the global average (10 km) because of the effect of sea ice on fetch and thus wave energy. Storm frequency in the high and middle latitudes is suggested to result in shorter and narrower islands relative to those on swell-dominated low-latitude coasts. The ratio of storm wave height to annual mean wave height is a good indicator of the degree of storm influence on island evolution. The potential for significant climate and sea level change this century underscores the need to improve understanding of the fundamental roles that these two factors have played historically in island evolution in order to predict their future impacts on the islands.
- Zhang, K.Q. and Leatherman, S. Barrier island population along the U.S. Atlantic and Gulf Coasts. Journal of Coastal Research 27(2): 356-363, 2011.
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Barrier islands, the dominant geomorphic features along the U.S. Atlantic and Gulf Coasts, are a favorite place for living and visiting. Unfortunately, barrier islands are vulnerable to storm-surge flooding and erosion because of low elevations and the movement of sand by waves and tides. In order to estimate the impacts of surge flooding, sea-level rise, and erosion on barrier islands, the lengths and areas of barrier islands and population living there were quantified using high-resolution satellite imagery from Google Earth and 1990-2000 census block data. The total length and area of barrier islands spanning 18 states along the U.S. Atlantic and Gulf Coasts are about 3700 km and 6800 km2, respectively. There are approximately 1.4 million people living on barrier islands, half of which are in Florida according to 2000 census data. The population densities of barrier islands are three times those of coastal states on average, and the population increased 14% from 1990 to 2000. The collision course of population increases and development in the face of accelerated sea-level rise due to global climate change makes barrier islands more vulnerable.
- Van Dover, C.L. Mining seafloor massive sulphides and biodiversity: what is at risk? ICES Journal of Marine Science 68(2): 341-348, 2011.
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Scientific exploration of the deep sea in the late 1970s led to the discovery of seafloor massive sulphides at hydrothermal vents. More recently, sulphide deposits containing high grades of ore have been discovered in the southwest Pacific. In addition to metal-rich ores, hydrothermal vents host ecosystems based on microbial chemoautotrophic primary production, with endemic invertebrate species adapted in special ways to the vent environment. Although there has been considerable effort to study the biology and ecology of vent systems in the decades since these systems were first discovered, there has been limited attention paid to conservation issues. Three priority recommendations for conservation science at hydrothermal vent settings are identified here: (i) determine the natural conservation units for key species with differing life histories; (ii) identify a set of first principles for the design of preservation reference areas and conservation areas; (iii) develop and test methods for effective mitigation and restoration to enhance the recovery of biodiversity in sulphide systems that may be subject to open-cut mining.
- Van Dover, C.L. Tighten regulations on deep-sea mining. Nature 470(7332): 31-33, 2011.
- Ramirez-Llodra, E., Tyler, P.A., Baker, M.C., Bergstad, O.A., Clark, M.R., Escobar, E., Levin, L.A., Menot, L., Rowden, A.A., Smith, C.R., and Van Dover, C.L. Man and the last great wilderness: Human impact on the deep sea. PLoS ONE 6(8): art. e22588, 2011.
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The deep sea, the largest ecosystem on Earth and one of the least studied, harbours high biodiversity and provides a wealth of resources. Although humans have used the oceans for millennia, technological developments now allow exploitation of fisheries resources, hydrocarbons and minerals below 2000 m depth. The remoteness of the deep seafloor has promoted the disposal of residues and litter. Ocean acidification and climate change now bring a new dimension of global effects. Thus the challenges facing the deep sea are large and accelerating, providing a new imperative for the science community, industry and national and international organizations to work together to develop successful exploitation management and conservation of the deep-sea ecosystem. This paper provides scientific expert judgement and a semi-quantitative analysis of past, present and future impacts of human-related activities on global deep-sea habitats within three categories: disposal, exploitation and climate change. The analysis is the result of a Census of Marine Life – SYNDEEP workshop (September 2008). A detailed review of known impacts and their effects is provided. The analysis shows how, in recent decades, the most significant anthropogenic activities that affect the deep sea have evolved from mainly disposal (past) to exploitation (present). We predict that from now and into the future, increases in atmospheric CO2 and facets and consequences of climate change will have the most impact on deep-sea habitats and their fauna. Synergies between different anthropogenic pressures and associated effects are discussed, indicating that most synergies are related to increased atmospheric CO2 and climate change effects. We identify deep-sea ecosystems we believe are at higher risk from human impacts in the near future: benthic communities on sedimentary upper slopes, cold-water corals, canyon benthic communities and seamount pelagic and benthic communities. We finalise this review with a short discussion on protection and management methods.
- Macreadie, P.I., Fowler, A.M., and Booth, D.J. Rigs-to-reefs: will the deep sea benefit from artificial habitat? Frontiers in Ecology and the Environment 9(8): 455-461, 2011.
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As a peak in the global number of offshore oil rigs requiring decommissioning approaches, there is growing pressure for the implementation of a "rigs-to-reefs" program in the deep sea, whereby obsolete rigs are converted into artificial reefs. Such decommissioned rigs could enhance biological productivity, improve ecological connectivity, and facilitate conservation/restoration of deep-sea benthos (eg cold-water corals) by restricting access to fishing trawlers. Preliminary evidence indicates that decommissioned rigs in shallower waters can also help rebuild declining fish stocks. Conversely, potential negative impacts include physical damage to existing benthic habitats within the "drop zone", undesired changes in marine food webs, facilitation of the spread of invasive species, and release of contaminants as rigs corrode. We discuss key areas for future research and suggest alternatives to offset or minimize negative impacts. Overall, a rigs-to-reefs program may be a valid option for deep-sea benthic conservation.
- Rogers, A.D. et al. The discovery of new deep-sea hydrothermal vent communities in the Southern Ocean and implications for biogeography. PLoS Biology 10(1): art. e1001234, 2012.
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Since the first discovery of deep-sea hydrothermal vents along the Galápagos Rift in 1977, numerous vent sites and endemic faunal assemblages have been found along mid-ocean ridges and back-arc basins at low to mid latitudes. These discoveries have suggested the existence of separate biogeographic provinces in the Atlantic and the North West Pacific, the existence of a province including the South West Pacific and Indian Ocean, and a separation of the North East Pacific, North East Pacific Rise, and South East Pacific Rise. The Southern Ocean is known to be a region of high deep-sea species diversity and centre of origin for the global deep-sea fauna. It has also been proposed as a gateway connecting hydrothermal vents in different oceans but is little explored because of extreme conditions. Since 2009 we have explored two segments of the East Scotia Ridge (ESR) in the Southern Ocean using a remotely operated vehicle. In each segment we located deep-sea hydrothermal vents hosting high-temperature black smokers up to 382.8°C and diffuse venting. The chemosynthetic ecosystems hosted by these vents are dominated by a new yeti crab (Kiwa n. sp.), stalked barnacles, limpets, peltospiroid gastropods, anemones, and a predatory sea star. Taxa abundant in vent ecosystems in other oceans, including polychaete worms (Siboglinidae), bathymodiolid mussels, and alvinocaridid shrimps, are absent from the ESR vents. These groups, except the Siboglinidae, possess planktotrophic larvae, rare in Antarctic marine invertebrates, suggesting that the environmental conditions of the Southern Ocean may act as a dispersal filter for vent taxa. Evidence from the distinctive fauna, the unique community structure, and multivariate analyses suggest that the Antarctic vent ecosystems represent a new vent biogeographic province. However, multivariate analyses of species present at the ESR and at other deep-sea hydrothermal vents globally indicate that vent biogeography is more complex than previously recognised.
- Nordstrom, K.F., Jackson, N.L., Kraus, N.C., Kana, T.W., Bearce, R., Bocamazo, L.M., Young, D.R., and De Butts, H.A.. 2011. Mitigating Climate Change through Restoration and Management of Coastal Wetlands and Near-shore Marine Ecosystems: Challenges and Opportunities. Environment Department Paper 121, World Bank, Washington, DC. 59pp.
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There is overwhelming consensus amongst climate scientists that the Earth's warming in recent decades has been caused primarily by human activities that have increased the amount of greenhouse gases (GHGs) in the atmosphere. To mitigate the most serious impacts of climate change a range of different strategies to lower carbon dioxide (CO2) concentrations in the atmosphere are required. Building on outcomes and recommendations from various coastal carbon activities, this report explains the GHG dynamics of coastal wetlands and marine ecosystems. The importance of coastal wetland and near-shore marine ecosystem carbon pools for climate change mitigation are described, with a brief overview of the status of these systems, including drivers of change and implications of degradation of carbon pools. An overview is given of policy opportunities under ongoing United Nation Framework Convention on Climate Change (UNFCCC) negotiations and through revision of Intergovernmental Panel on Climate Change (IPCC) carbon accounting methodologies and eligible mitigation activities for developing as well as developed countries. The main recommendations for action are provided.
- Irving, A.D., Connell, S.D., and Russell, B.D. Restoring coastal plants to improve global carbon storage: Reaping what we sow. PLoS ONE 6(3): art. e18311, 2011.
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Long-term carbon capture and storage (CCS) is currently considered a viable strategy for mitigating rising levels of atmospheric CO2 and associated impacts of global climate change. Until recently, the significant below-ground CCS capacity of coastal vegetation such as seagrasses, salt marshes, and mangroves has largely gone unrecognized in models of global carbon transfer. However, this reservoir of natural, free, and sustainable carbon storage potential is increasingly jeopardized by alarming trends in coastal habitat loss, totalling 30-50% of global abundance over the last century alone. Human intervention to restore lost habitats is a potentially powerful solution to improve natural rates of global CCS, but data suggest this approach is unlikely to substantially improve long-term CCS unless current restoration efforts are increased to an industrial scale. Failure to do so raises the question of whether resources currently used for expensive and time-consuming restoration projects would be more wisely invested in arresting further habitat loss and encouraging natural recovery.
- Mcleod, E., Chmura, G.L., Bouillon, S., Salm, R., Björk, M., Duarte, C. M., Lovelock, C.E., Schlesinger, W.H., and Silliman, B.R. A blueprint for blue carbon: toward an improved understanding of the role of vegetated coastal habitats in sequestering CO2. Frontiers in Ecology and the Environment 9(10): 552-560, 2011.
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Recent research has highlighted the valuable role that coastal and marine ecosystems play in sequestering carbon dioxide (CO2). The carbon (C) sequestered in vegetated coastal ecosystems, specifically mangrove forests, seagrass beds, and salt marshes, has been termed "blue carbon". Although their global area is one to two orders of magnitude smaller than that of terrestrial forests, the contribution of vegetated coastal habitats per unit area to long-term C sequestration is much greater, in part because of their efficiency in trapping suspended matter and associated organic C during tidal inundation. Despite the value of mangrove forests, seagrass beds, and salt marshes in sequestering C, and the other goods and services they provide, these systems are being lost at critical rates and action is urgently needed to prevent further degradation and loss. Recognition of the C sequestration value of vegetated coastal ecosystems provides a strong argument for their protection and restoration; however, it is necessary to improve scientific understanding of the underlying mechanisms that control C sequestration in these ecosystems. Here, we identify key areas of uncertainty and specific actions needed to address them.
- Borsje, B.W., van Wesenbeeck, B.K., Dekker, F., Paalvast, P., Bouma, T.J., van Katwijk, M.M., and de Vries, M.B. How ecological engineering can serve in coastal protection. Ecological Engineering 37(2): 113-122, 2011.
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Traditionally, protection of the coastal area from flooding is approached from an engineering perspective. This approach has often resulted in negative or unforeseen impacts on local ecology and is even known to impact surrounding ecosystems on larger scales. In this paper, the utilization of ecosystem engineering species for achieving civil-engineering objectives or the facilitation of multiple use of limited space in coastal protection is focused upon, either by using ecosystem engineering species that trap sediment and damp waves (oyster beds, mussel beds, willow floodplains and marram grass), or by adjusting hard substrates to enhance ecological functioning. Translating desired coastal protection functionality into designs that make use of the capability of appropriate ecosystem engineering species is, however, hampered by lack of a generic framework to decide which ecosystem engineering species or what type of hard-substrate adaptations may be used where and when. In this paper we review successful implementation of ecosystem engineering species in coastal protection for a sandy shore and propose a framework to select the appropriate measures based on the spatial and temporal scale of coastal protection, resulting in a dynamic interaction between engineering and ecology. Modeling and monitoring the bio-physical interactions is needed, as it allows to upscale successful implementations and predict otherwise unforeseen impacts.
- Browne, M.A. and Chapman, M.G. Ecologically informed engineering reduces loss of intertidal biodiversity on artificial shorelines. Environmental Science and Technology 45(19): 8204-8207, 2011.
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Worldwide responses to urbanization, expanding populations and climatic change mean biodiverse habitats are replaced with expensive, but necessary infrastructure. Coastal cities support vast expanses of buildings and roads along the coast or on 'reclaimed' land, leading to 'armouring' of shorelines with walls, revetments and offshore structures to reduce erosion and flooding. Currently infrastructure is designed to meet engineering and financial criteria, without considering its value as habitat, despite artificial shorelines causing loss of intertidal species and altering ecological natural processes that sustain natural biodiversity. Most research on ameliorating these impacts focus on soft-sediment habitats and larger flora (e.g., restoring marshes, encouraging plants to grow on walls). In response to needs for greater collaboration between ecologists and engineers to create infrastructure to better support biodiversity, we show how such collaborations lead to small-scale and inexpensive ecologically informed engineering which reduces loss of species of algae and animals from rocky shores replaced by walls. Adding experimental novel habitats to walls mimicking rock-pools (e.g., cavities, attaching flowerpots) increased numbers of species by 110% within months, in particular mobile animals most affected by replacing natural shores with walls. These advances provide new insights about melding engineering and ecological knowledge to sustain biodiversity in cities.
- Chapman, M.G. and Underwood, A.J. Evaluation of ecological engineering of "armoured" shorelines to improve their value as habitat. Journal of Experimental Marine Biology and Ecology 400(1-2): 302-313, 2011.
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People have caused major impacts on nearshore and intertidal habitats by building infrastructure associated with shipping, recreation, residential and commercial developments. Together with the desire or need to control erosion, these have led to increased "armouring" of intertidal shorelines, with seawalls, revetments, onshore and offshore groynes and other defence systems, piers and docks replacing natural habitats. Despite the long history of such changes, until relatively recently there had been limited research on the impacts of such alterations to shorelines, especially when compared to research into effects of urbanisation on terrestrial habitats. In addition, most research to date has focussed on the impacts of such changes on the ecological structure of assemblages, i.e. the numbers and types of organisms affected, rather than on ecological processes. With the realisation that most coastal infrastructure cannot be removed, there is now an increasing research effort into ways that infrastructure can be built to meet engineering requirements, but to also increase its value as habitat – ecological engineering. In this review, we discuss the major impacts and the experimental research that has been and is being done to build coastal infrastructure in a more biodiversity-friendly manner. Much of the review has focussed on seawalls, which is where most of the experimental work has been done to date. Finally, we raise some concerns about the types of research effort that are still needed and caution against wholesale implementation of what seem like simple remedies, without evidence that they will have the desired effect in the long term.
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