Loss Of Intertidal Habitat Research Articles

A Small-scale Wave Tank For Living Shoreline Extension And Outreach

Hardened structures, such as bulkheads and seawalls, are currently the primary choice of shoreline protection for waterfront property owners. However, hardened shorelines are known to enhance erosion and often promote the loss of intertidal habitat. Living shorelines are a collection of environmentally friendly construction techniques that serve as an alternative to hardened shorelines through the incorporation of natural materials, such as native plants. To enhance extension and outreach efforts related to the promotion of living shorelines, we created a small-scale, hands-on wave tank that demonstrates the benefits of natural and living shorelines relative to hardened structures. This interactive tool allows the audience to view the differences between natural, living, and hardened shorelines for both aesthetics and wave energy reduction.

Estimating Effects of Sea Level Rise on Benthic Biodiversity and Ecosystem Functioning in a Large Meso-Tidal Coastal Lagoon.

Estuaries are among the world's most productive ecosystems, but due to their geographic location, they are at the forefront of anthropogenic pressures. Sea level rise (SLR) is one major consequence of climate change that poses a threat to estuaries with extensive intertidal habitats. The ecological implications of intertidal habitat loss have been largely overlooked despite their likely significance. We aimed to address this knowledge gap by investigating how benthic macroinvertebrate communities and their contributions to ecosystem function are likely to respond to SLR. Based on a spatially extensive dataset (119 sites) from a large coastal lagoon, depth, sediment chlorophyll concentrations, mud content, and average current speed were identified as the main drivers of community compositional turnover. Shifts in benthic community structure and associated functional implications were then evaluated using depth as a proxy for SLR. Three main macrofaunal groups representing intertidal, shallow subtidal, and deep subtidal habitats were identified. Functional trait analysis indicated low functional redundancy for a key intertidal suspension-feeding bivalve (Austrovenus stutchburyi) and the lack of a shallow subtidal functional replacement should intertidal habitats become inundated. These findings strongly suggest SLR and the associated environmental changes will alter estuarine macroinvertebrate communities, with implications for future ecosystem function and resilience.

Hindcasting Ecosystem Functioning Change in an Anthropogenized Estuary: Implications for an Era of Global Change

Understanding how altered hydrodynamics related to climate change and anthropogenic modifications affect ecosystem integrity of shallow coastal soft-sediment environments requires a sound integration of how species populations influence ecosystem functioning across heterogeneous spatial scales. Here, we hindcasted how intertidal habitat loss and altered hydrodynamic regimes between 1955 and 2010 associated with geomorphological change to accommodate expansion in anthropogenic activities in the Western Scheldt altered spatial patterns and basin-wide estimates of ecosystem functioning. To this end we combined an empirically derived metabolic model for the effect of the common ragworm Hediste diversicolor on sediment biogeochemistry (measured as sediment oxygen uptake) with a hydrodynamic and population biomass distribution model. Our integrative modeling approach predicted an overall decrease by 304 tons in ragworm biomass between 1955 and 2010, accounting for a reduction by 28% in stimulated sediment oxygen uptake at the landscape scale. Local gains or losses in habitat suitability and ecosystem functioning were primarily driven by changes in maximal current velocities and inundation regimes resulting from deepening, dredging and disposal practices. By looking into the past, we have demonstrated how hydro- and morphodynamic changes affect soft-sediment ecology and highlight the applicability of the integrative framework to upscale anticipated population effects on ecosystem functioning.

Full stomachs at empty tides: tidal cycle affects feeding activity and diet of the sandy beach gastropod Olivella minuta

ABSTRACTOlivella minuta is an abundant neogastropod on sandy beaches from Texas (USA) to southern Brazil. This study aimed to characterize and compare the feeding activity and diet of a Brazilian population of O. minuta in different tidal zones (intertidal and subtidal), and different tidal levels (high and low tides), with three combinations of tidal zone and level being studied (intertidal during low tide, intertidal during high tide and subtidal). The results showed that diet composition was generally similar among tidal conditions, with O. minuta being a generalist, feeding on 45 different food items. Feeding activity, however, was higher in the intertidal during low tide, whereas the richness and diversity of food items were higher in the intertidal during high tide. The higher feeding activity of O. minuta during low tide may be linked to a lower risk of predation; at low tide organisms may be able to feed for a longer time, and this may be particularly true on beaches with fine sand, where water retention is higher than that on beaches with coarse sand. The higher diversity of food items consumed in the intertidal during high tide is likely related to the increased prevalence of planktonic food during high tide. Our results indicate that tidal zone and level may strongly influence the feeding activity of coastal soft-bottom species and that species may show higher feeding activity during low tide. Given the current loss of intertidal habitats due to anthropogenic activity and climate-change associated factors, our study has important implications, highlighting the importance of intertidal areas for the ecology and conservation of sandy beach species.

Future sea-level rise drives rocky intertidal habitat loss and benthic community change.

The impacts of sea-level rise (SLR) are likely to be the greatest for ecosystems that exist at the land-sea interface, where small changes in sea-level could result in drastic changes in habitat availability. Rocky intertidal ecosystems possess a number of characteristics which make them highly vulnerable to changes in sea-level, yet our understanding of potential community-scale responses to future SLR scenarios is limited. Combining remote-sensing with in-situ large-area imaging, we quantified habitat extent and characterized the biological community at two rocky intertidal study locations in California, USA. We then used a model-based approach to estimate how a range of SLR scenarios would affect total habitat area, areal extent of dominant benthic space occupiers, and numerical abundance of invertebrates. Our results suggest that SLR will reduce total available rocky intertidal habitat area at our study locations, leading to an overall decrease in areal extent of dominant benthic space occupiers, and a reduction in invertebrate abundances. As large-scale environmental changes, such as SLR, accelerate in the next century, more extensive spatially explicit monitoring at ecologically relevant scales will be needed to visualize and quantify their impacts to biological systems.

The use of small-Unmanned Aerial Systems for high resolution analysis for intertidal wetland restoration schemes

Coastal and estuarine wetlands provide a range of important ecosystem services, but are currently being damaged and degraded due to human activities, reduced sediment supply and sea level rise. Managed realignment (MR) is one approach used to compensate for the loss of intertidal habitat, however saltmarshes in MR sites have been recognised to have lower biodiversity than natural environments. This has been associated with differences in the physical functioning including the sediment structure, reduced hydraulic connectivity, and lower topographic variability such as the abundance of intertidal creek networks. Intertidal morphology, including creek networks, play an important role in supporting and regulating saltmarsh environments through the supply of sediment, nutrients and water, and in draining intertidal marshes. However, there is a lack of empirical data on the formation and evolution of topographic features and variability in saltmarsh environments. This is likely to be due to creek networks in natural marshes already being in a state of quasi-equilibrium, making MR sites an ideal environment to investigate creek development. However, traditional remote sensing techniques (such as LiDAR) tend to be relatively expensive, infrequent and at a coarse resolution meaning small, but important (cm-scale), changes are often missed. This study advances the ability to detect these small scale changes by demonstrating the suitability and potential applications of using the emerging photogrammetric method Structure-from-Motion (SfM) on images taken using a small-Unmanned Aerial System (sUAS). Three surveys from a rapidly changing, near-breach site were taken at the Medmerry Managed Realignment Site in July 2016, September 2017 and July 2018. A suitable degree of confidence was found between the modelled surface and independent check points (vertical root-mean-square-errors of 0.0245, 0.0704 and 0.1571 for 2016, 2017 and 2018 respectively). DSMs of Difference (DoD) analysis was performed to evaluate elevation change, with areas experiencing up to 85 cm of accretion between 2016 and 2018. However, when considering the error associated with both surveys, between 2016 and 2017, only 34.39% of the survey area experienced change above the level of detection (LoD). In contrast, 76.97% experienced change greater than the LoD between 2017 and 2018. Stream order analysis classified the creek networks into five orders in 2016 and four orders in 2017 and 2018, with 2016 having a higher abundance (291 in 2016 compared to 117 (2017) and 112 (2018)) and density (0.44 m/m2 in 2016 compared to 0.27 m/m2 in both 2017 and 2018) of creek networks. These results provide an innovative high resolution insight into the evolution of restored intertidal wetlands, and suggest that SfM analysis of images taken using a sUAS can be a useful tool with the potential to be incorporated into studies of MR and natural saltmarsh sites. sUAS analysis can, therefore, advance the management of these environments to ensure the provision of ecosystem services and to protect against future anthropogenic activity, sea level rise and climate change.

Recent changes in the number of spoon-billed sandpipers Calidris pygmaea wintering on the Upper Gulf of Mottama in Myanmar

AbstractThe spoon-billed sandpiper Calidris pygmaea, a migratory Arctic-breeding shorebird, is one of the rarest birds and its population has declined since the 1970s. We surveyed its most important known wintering area in the Upper Gulf of Mottama in Myanmar to estimate recent (2009–2016) changes in its numbers there. The total number of small shorebirds present in the Upper Gulf was counted and the proportion of them that were spoon-billed sandpipers was estimated from sample scans. These two quantities were multiplied together to give the estimated number of spoon-billed sandpipers in each of 4 years. Total numbers of combined small shorebird species tripled from 21,000 to 63,000 between 2009 and 2016, coincident with efforts to reduce hunting pressure on waterbirds. However, the proportion of small shorebirds that were spoon-billed sandpipers declined and their estimated absolute numbers fell by about half, from 244 to 112 individuals. It is probable that loss of intertidal habitat and shorebird hunting elsewhere on the migration route of the spoon-billed sandpipers wintering at Mottama is causing a continued decline, although this is occurring at a less rapid rate than that recorded from Arctic Russia before 2010. The number of spoon-billed sandpipers wintering on the Upper Gulf of Mottama remains the highest single-site total for this species from any known wintering site. Preventing resurgence of illegal shorebird hunting and ensuring long-term protection of the intertidal feeding habitats and roost sites in the Gulf are high priorities if extinction of this species is to be averted.

Loss of habitat leads to loss of birds: reflections on the Jiangsu, China, coastal development plans

Prompted by the realization that parts of the coast of southern Jiangsu Province, China, are under threat of reclamation, we here summarize evidence that loss of intertidal habitats around the Yellow Sea and at other parts along the Chinese and Korean coasts has already led to severe population declines of migratory shorebirds, including multiple endangered species. All the evidence currently at hand suggest that the plans to reclaim (develop) additional intertidal habitat in this region poses a substantial threat to the remaining shorebird populations. We recommend that new Environmental Impact Assessments are warranted before further reductions in the extent of mudflats take place.

Attributes of the earthquake-uplifted intertidal habitats and their implications to the Maribojoc and Loon coastal fisheries

Other than the devastating impact on infrastructures and human lives, the 7.2 Mw earthquake that shook Bohol and its vicinity in October 2013 also apparently caused massive damage on the coastal habitats: (1) collapse of many coral reefs/domes compromised by underwater cracks, mostly > 1 m wide, traversing the numerous reef formations; (2) substantial ground subsidence (i.e., >1 m in Tubigon and vicinity) with sea-level-rise implications to the existing mangroves and seagrass beds, and; (3) massive loss of intertidal habitats due significant ground uplift, drying up extensive areas of mangroves, seagrass beds, sandflats, and rocky shores particularly in the municipalities of Maribojoc and Loon. This paper provides quantification of the attributes of the uplifted area, determining the pre-quake extent of the intertidal habitats, and attempting to reconstruct some intertidal community assemblages based on post-quake artefacts. We determined the total extent of the intertidal area severely affected by the ground uplift amounting to >400 ha, comprised of mangroves (42 ha; 10%), seagrass beds (135 ha; 32%), reef slope corals (148; 35%), and intertidal sandflats, mudflats and rocky habitats (altogether, 94 ha; 22%). This impact may be grossly translated to a US$ 4.4 million of economic loss annually. Our ground elevation- and transect truthing surveys of habitat artefacts generally validated our areal approximations. Also, across these transects, we confirmed speciose pre-quake assemblage of important invertebrates and other taxa occurring in these intertidal areas. In strong contrast to the exposed seagrass beds and coral areas, which were already all dried-up and died, most mangroves were still surviving after 8 months post uplift (i.e., practically no more tidal inundation since Oct 2013), albeit now in strong competition against the aggressive colonization of terrestrial plants. We recommend the close monitoring of the fate of the surviving mangroves and the likely transformation of such into completely terrestrial ecosystems. We likewise recommend the close monitoring of the coastal fisheries as may be linked to such post-quake loss of intertidal habitats, and carefully design management measures to mitigate such impact.

Climate Change Adaptation: Putting Principles into Practice

Carrying out wildlife conservation in a changing climate requires planning on long timescales at both a site and network level, while also having the flexibility to adapt actions at sites over short timescales in response to changing conditions and new information. The Royal Society for the Protection of Birds (RSPB), a land-owning wildlife conservation charity in the UK, achieves this on its nature reserves through its system of management planning. This involves setting network-wide objectives which inform the 25-year vision and 5-year conservation objectives for each site. Progress toward achieving each site's conservation objectives is reviewed annually, to identify any adjustments which might be needed to the site's management. The conservation objectives and 25-year vision of each site are reviewed every 5 years.Significant predicted [corrected] long-term impacts of climate change most frequently identified at RSPB reserves are: loss of intertidal habitat through coastal squeeze, loss of low-lying islands due to higher sea levels and coastal erosion, loss of coastal freshwater and brackish wetlands due to increased coastal flooding, and changes in the hydrology of wetlands. The main types of adaptation measures in place on RSPB reserves to address climate change-related impacts are: re-creation of intertidal habitat, re-creation and restoration of freshwater wetlands away from vulnerable coastal areas, blocking artificial drainage on peatlands, and addressing pressures on freshwater supply for lowland wet grasslands in eastern and southeastern England. Developing partnerships between organizations has been crucial in delivering large-scale adaptation projects.

Refinements to the EFDC model for predicting the hydro-environmental impacts of a barrage across the Severn Estuary

This paper presents an investigation of the impacts of a Severn Barrage on the hydro-environment of the Bristol Channel and Severn Estuary using the Environmental Fluid Dynamics Code (EFDC) model with a recently developed Barrage module (EFDC_B). Details are given of a barrage module being implemented into the EFDC model to represent the various hydraulic structures, such as turbines and sluice gates, as deployed along the barrage line. Several cases, both with and without the barrage, have been simulated to investigate the potential changes on the peak water levels, minimum water depths and peak tidal currents arising from a barrage. The impacts of a barrage on the salinity concentration distribution have also been simulated in both 2D and 3D modes. The predicted results showed that the maximum water levels could be significantly reduced, especially downstream of the barrage and for much of the region in the Severn Estuary and that the minimum water depths would be changed so much that there would be 80.5 km2 loss of intertidal habitats due to the sitting of a barrage across the estuary. Likewise, the peak tidal currents would be considerably reduced, and by as much as a half in the middle of the main channel. The predicted salinity concentrations results indicated that at high water, the salinity concentrations would be reduced by 1–2 ppt downstream and upstream of the barrage and salinity concentrations in the region near Beachley would be reduced by up to 5 ppt, and that at low water, salinity concentrations would be reduced by 0.5–1 ppt in the middle of the Bristol Channel and by typically 0.5 ppt and 1 ppt downstream and upstream of the barrage, respectively. The predicted results also indicated that salinity concentrations downstream and upstream of the barrage would be under a stable state with slight oscillations all the time due to the effects of the barrage. A comparison between the salinity concentration distributions predicted by the 2D and 3D models indicated that the two models produced similar salinity distributions, especially in the Severn Estuary and in the region between the middle of the Bristol Channel and the seaward open boundary.

The value of wader foraging behaviour study to assess the success of restored intertidal areas

The loss of intertidal habitat in estuaries has resulted in the need to create new habitats in order to protect waterbird populations. In order to examine the waterbird colonisation of restored intertidal areas created in 2003 through the realignment of the flood defence in the Humber Estuary (UK), the feeding behaviour of Redshank (Tringa totanus) was observed in April 2008. Numbers of pecks, probes and paces (numbers of steps) and the prey intake events were compared between Redshank foraging on the restored mudflat and on the adjacent established mudflat. Redshank prey intake and success rate (prey intake divided by the total numbers of pecks and probes) were significantly lower on the restored mudflat compared to the adjacent established mudflat. Conversely, the number of steps taken while foraging and the number of paces per successful feeding event were significantly greater on the restored mudflat. This shows that focal behaviour in restored intertidal areas can be directly compared with that in natural established mudflat in order to examine differences in foraging behaviour. The findings emphasise that a study of foraging behaviour should be incorporated into the assessment of restoration success of intertidal areas as an indication of habitat quality.

Settlement of RedshankTringa totanusFollowing Winter Habitat Loss: Effects of Prior Knowledge and Age

The ability of animals to survive habitat loss is likely to be dependent not only on the proximity of alternative habitat but also on the ability of individuals to relocate. Here, we examine influences on the settlement behaviour of Redshank Tringa totanus following winter intertidal habitat loss resulting from the construction of a barrage at Cardiff Bay, on the Severn Estuary, UK. Results supported previous studies showing that the species is highly faithful to its wintering sites. Redshank were reluctant to leave Cardiff Bay in the first winter following habitat loss: birds used the site at all tidal stages for eight days after barrage-closure and thereafter continued to roost there. Birds moved at most 19 km, the distances that individuals moved being inversely related to their age, indicating that young birds were less attached to the bay and so more plastic in their response to change. Settlement also appeared to be influenced by prior knowledge — notably, one site previously only used nocturnally b...

Opportunities of, and constraints to, the use of intertidal agri-environment schemes for sustainable coastal defence: A case study of the Blackwater Estuary, southeast England

The factors affecting the uptake of intertidal creation options of UK government agri-environment schemes were examined through interviews with coastal landowners and local organisational representatives in the Blackwater Estuary, Essex. Responses were analysed to examine the perceptions of previous and new schemes, and the extenuating factors hindering uptake. Participation decisions initially appeared to be driven by financial constraints, cultural attitudes and a history of organisational distrust. Further analysis, in the context of a participation spectrum, suggested that decisions were based upon the conservation ethos of the landowner and the public perception of managed realignment. This information was used to develop new promotional strategies which could be utilised by Defra and Natural England (formerly English Nature) to improve uptake, and thereby meet Government targets to tackle intertidal habitat loss.

Assessing the development of newly created habitat for wintering estuarine birds

The term coastal squeeze has been used to describe the process whereby hard flood defences in areas subjected to relative sea level rise constrain the ability of an estuarine system to respond naturally, thus leading to a loss of intertidal habitat, with an associated potential reduction in the carrying capacity of the estuarine system for fish and bird populations. The process of coastal squeeze, coupled with the long-term effects of climate change, has generated the need to create or restore intertidal habitats in estuaries. In Humber Estuary (UK) it is estimated that over 700 hectares of intertidal habitat will be lost due to coastal squeeze and rising sea levels over the next 50 years. In order to address this net loss, a process known as ‘managed realignment’ has been employed as an estuarine habitat management tool, whereby sections of flood defences are moved inland to create or restore intertidal habitat and offset potential losses in carrying capacity. On the Humber, the Paull Holme Strays site, to the east of Hull, has been the first managed realignment site on the estuary to become operational. The site at Paull Holme Strays was breached in September 2003 creating approximately 80 hectares of intertidal habitat. In order to assess the development of the waterbird assemblage at the Paull Holme Strays site, and ultimately the success of the habitat creation technique, monthly ornithological surveys were undertaken in the newly created habitat and on the mudflat fronting the managed realignment site. The analysis of avifaunal usage data at Paull Holme Strays has demonstrated that within 3 years of creation, the new intertidal habitat is capable of supporting at low water, a functional waterbird assemblage of similar composition to that of adjacent existing intertidal areas. At Paull Holme Strays, this has been achieved with little ongoing management of new habitats.

A cost–benefit appraisal of coastal managed realignment policy

European coasts are coming under increasing threat as a result of climate change from erosion and flooding. While coastal defences such as sea walls have been constructed since Roman times to protect human settlements from the sea, it is now increasingly recognised that these defences are unsustainable. The security provided by ‘hard’ engineered defences has encouraged development on the coast, and the defences themselves have led to the loss of intertidal habitat and the natural protection it provides. An alternative to maintaining ‘hard’ defences (hold-the-line) to protect land from increasing sea levels is managed realignment, where the engineered defences are deliberately breached. By allowing the coastline to recede to a new line of defence further inland, intertidal habitat is created providing natural protection from flooding and erosion. The study evaluates the economic efficiency—using cost–benefit analysis—of various managed realignment scenarios compared to a strategy of holding-the-line within the Humber estuary in North-east England. The results of this analysis show that managed realignment can be more economically efficient than holding-the-line over a sufficiently long time period—generally greater than 25 years. Sensitivity analysis demonstrates that results are more sensitive to the amount and value of intertidal habitat generated than they are to the amount and value of carbon stored by this habitat. Cost–benefit analysis is viewed as one component of a wider policy appraisal process within integrated coastal management.

Global Climate Change and Sea Level Rise: Potential Losses of Intertidal Habitat for Shorebirds

Abstract Global warming is expected to result in an acceleration in current rates of sea level rise, inundating many low-lying coastal and intertidal areas. This could have important implications for organisms that depend on these sites, including shorebirds that rely on them for feeding habitat during their migrations and in winter. We modeled the potential changes in the extent of intertidal foraging habitat for shorebirds at five sites in the United States that currently support internationally important numbers of migrating and wintering birds. Even assuming a conservative global warming scenario of 2°C within the next century (the most recent projections range between 1.4°C and 5.8°C), we project major intertidal habitat loss at four of the sites (Willapa Bay, Humboldt Bay, San Francisco Bay, and Delaware Bay). Projected losses range between 20% and 70% of current intertidal habitat. Such losses might jeopardize the ability of these sites to continue to support their current shorebird numbers. The mo...

Intertidal habitat loss and wildfowl numbers: applications of a spatial depletion model

1. A spatial depletion model of the responses of grazing wildfowl to the availability of intertidal vegetation at Lindisfarne National Nature reserve, north‐east England, was used to investigate the capacity of the site’s beds of Zostera and other intertidal vegetation to support brent geese Branta bernicla hrota and wigeon Anas penelope. 2. Recent total winter counts of brent geese and wigeon were both only 40% of the maximum that the food supply at the site could theoretically support. Other factors must have been restricting their numbers. Earlier arrival of brent geese at the site could increase the number of brent goose‐days which could be supported, but would have only a slight negative effect on the wigeon‐days. 3. The model was used to examine three conservation issues: encroachment of Spartina anglica, sea level rise and loss of food plants from the whole site (which could result from increased autumn storms or plant disease). Loss from the top of the shore through encroachment by Spartina anglica had the greatest effect on the site’s capacity to sustain geese and wigeon. Loss from the bottom of the shore, as would occur through sea level rise, had less impact. Increased loss of vegetation over the whole site would have an intermediate effect. 4. This work has important implications for the management of the site. Factors such as hunting, that may be restricting current numbers below those that could be supported by the food supply, require urgent investigation. Model predictions indicate that encroachment of Spartina is likely to depress local populations of brent geese and wigeon under current conditions only if it results in the complete loss of Zostera from the top 500 m of the shore.

The effect of estuarine engineering schemes on birds

This paper reviews research into aspects of the ecology of estuarine birds which have special relevance to the effect of reclamation. The principal points arising are: 1. Birds do not use intertidal flats uniformly. 2. The distribution of birds is correlated with the density of food, with preferred areas being filled first. 3. Increasing density of birds increases aggressive encounters, may decrease feeding success and decrease available food. 4. At times in winter birds find food difficult to obtain and mortality increases by about ten times. 5. A relatively small additional increase in winter mortality could result in a lowering of total population size by approximately 50%. 6. Reclamation would reduce feeding areas and probably exacerbate the problems which are already occurring. 7. International census data provide objective measures for assessing the importance of the potential impact of a scheme of birds. 8. Habitat gain due to reservoirs or polder areas in Britain would involve, in international numbers, very few birds. There would be internationally important numbers affected by the loss of intertidal habitat.