Sally D. Hacker

The value of estuarine and coastal ecosystem services

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.

Coastal Ecosystem-Based Management with Nonlinear Ecological Functions and Values

A common assumption is that ecosystem services respond linearly to changes in habitat size. This assumption leads frequently to an “all or none” choice of either preserving coastal habitats or converting them to human use. However, our survey of wave attenuation data from field studies of mangroves, salt marshes, seagrass beds, nearshore coral reefs, and sand dunes reveals that these relationships are rarely linear. By incorporating nonlinear wave attenuation in estimating coastal protection values of mangroves in Thailand, we show that the optimal land use option may instead be the integration of development and conservation consistent with ecosystem-based management goals. This result suggests that reconciling competing demands on coastal habitats should not always result in stark preservation-versus-conversion choices.

Non‐linearity in ecosystem services: temporal and spatial variability in coastal protection

Natural processes tend to vary over time and space, as well as between species. The ecosystem services these natural processes provide are therefore also highly variable. It is often assumed that ecosystem services are provided linearly (unvaryingly, at a steady rate), but natural processes are characterized by thresholds and limiting functions. In this paper, we describe the variability observed in wave attenuation provided by marshes, mangroves, seagrasses, and coral reefs and therefore also in coastal protection. We calculate the economic consequences of assuming coastal protection to be linear. We suggest that, in order to refine ecosystem-based management practices, it is essential that natural variability and cumulative effects be considered in the valuation of ecosystem services.

Ecosystem Services as a Common Language for Coastal Ecosystem‐Based Management

Ecosystem-based management is logistically and politically challenging because ecosystems are inherently complex and management decisions affect a multitude of groups. Coastal ecosystems, which lie at the interface between marine and terrestrial ecosystems and provide an array of ecosystem services to different groups, aptly illustrate these challenges. Successful ecosystem-based management of coastal ecosystems requires incorporating scientific information and the knowledge and views of interested parties into the decision-making process. Estimating the provision of ecosystem services under alternative management schemes offers a systematic way to incorporate biogeophysical and socioeconomic information and the views of individuals and groups in the policy and management process. Employing ecosystem services as a common language to improve the process of ecosystem-based management presents both benefits and difficulties. Benefits include a transparent method for assessing trade-offs associated with management alternatives, a common set of facts and common currency on which to base negotiations, and improved communication among groups with competing interests or differing worldviews. Yet challenges to this approach remain, including predicting how human interventions will affect ecosystems, how such changes will affect the provision of ecosystem services, and how changes in service provision will affect the welfare of different groups in society. In a case study from Puget Sound, Washington, we illustrate the potential of applying ecosystem services as a common language for ecosystem-based management.

Mechanisms of Competitive Dominance Between Crustose Coralline Algae: An Herbivore‐Mediated Competitive Reversal

Competitive superiority among encrusting species is established when the margin of one species consistently overgrows another. By measuring overgrowth patterns for the two most abundant tidepool species of crustose coralline algae (Lithophyllum im- pressum and Pseudolithophyllum whidbeyense) in the San Juan Islands of Washington State, we documented a reversal in competitive dominance that occurs at about the + 1 m level; L. impressum wins in upper zones and P. whidbeyense in lower zones. Regardless oftidepool elevation or species, thicker crusts overgrow thinner ones and crusts of equal thickness are competitively equal. Both crust species are grazed by limpets (primarily Lottia pelta and Tectura scutum), which are the dominant herbivores in tidepools. Laboratory experiments show that limpet grazing can reduce crust thickness. Laboratory and field analyses of limpet grazing indicate that corallines in tidepools in the upper intertidal zone are subject to high frequency (bite rate per unit area) and low intensity (penetration depth per bite) limpet grazing, whereas those in low tidepools are subjected to opposite grazing characteristics. L. impressum is a thick crust, which has a multicellular covering over its meristem. This covering protects the growing portion of the plant from the frequent, low-intensity herbivory that occurs in the higher tidepools. In contrast, P. whidbeyense lacks a multilayered epithallus and is more susceptible to injury in high tidepools. In low pools, meristems of both crusts are injured. L. impressum heals these deep wounds by regenerating vertically, but the net result is a thinner plant that is easily overgrown. P. whidbeyense dominates the low zone because it is capable of much more rapid lateral growth including over its own deep wounds; the crust overgrows itself, thereby developing a thicker thallus and improving its competitive success over L. impressum. We suggest that a continuum of defensive and regenerative characteristics exists among organisms; the adaptive nature of these depends on the levels of production and the frequency and intensity of disturbance in their environment. It is evident that herbivory is important in this system, not by the traditional mechanism of releasing limiting resources (e.g., primary space), but by mediating competitive abilities through the relative suscep- tibility to, and recovery from, herbivore-induced disturbance.

Biophysical feedback mediates effects of invasive grasses on coastal dune shape

Vegetation at the aquatic-terrestrial interface can alter landscape features through its growth and interactions with sediment and fluids. Even similar species may impart different effects due to variation in their interactions and feedbacks with the environment. Consequently, replacement of one engineering species by another can cause significant change in the physical environment. Here we investigate the species-specific ecological mechanisms influencing the geomorphology of U.S. Pacific Northwest coastal dunes. Over the last century, this system changed from open, shifting sand dunes with sparse vegetation (including native beach grass, Elymus mollis), to densely vegetated continuous foredune ridges resulting from the introduction and subsequent invasions of two nonnative grass species (Ammophila arenaria and Ammophila breviligulata), each of which is associated with different dune shapes and sediment supply rates along the coast. Here we propose a biophysical feedback responsible for differences in dune shape, and we investigate two, non-mutually exclusive ecological mechanisms for these differences: (1) species differ in their ability to capture sand and (2) species differ in their growth habit in response to sand deposition. To investigate sand capture, we used a moveable bed wind tunnel experiment and found that increasing tiller density increased sand capture efficiency and that, under different experimental densities, the native grass had higher sand capture efficiency compared to the Ammophila congeners. However, the greater densities of nonnative grasses under field conditions suggest that they have greater potential to capture more sand overall. We used a mesocosm experiment to look at plant growth responses to sand deposition and found that, in response to increasing sand supply rates, A. arenaria produced higher-density vertical tillers (characteristic of higher sand capture efficiency), while A. breviligulata and E. mollis responded with lower-density lateral tiller growth (characteristic of lower sand capture efficiency). Combined, these experiments provide evidence for a species-specific effect on coastal dune shape. Understanding how dominant ecosystem engineers, especially nonnative ones, differ in their interactions with abiotic factors is necessary to better parameterize coastal vulnerability models and inform management practices related to both coastal protection ecosystem services and ecosystem restoration.

PHYSICAL FACTORS VS. BIOTIC RESISTANCE IN CONTROLLING THE INVASION OF AN ESTUARINE MARSH GRASS

We examined the relative roles of biotic resistance and abiotic factors in controlling the establishment and early survival of an invasive marine grass, Spartina anglica, in the Pacific Northwest. S. anglica can invade diverse estuarine habitats, including established salt marshes, mudflats, and cobble beaches; these vary in native species assemblages and in abiotic conditions, especially sediment salinity, water content, and composition. In four habitat types in northern Puget Sound, we conducted a seed addition experiment to quantify germination and early growth. In vegetated habitats we also manipulated plant neighbors. Seed germination and early growth varied with habitat and zone, but physical factors played a more important role than species interactions. Seedlings in low-salinity marshes and mudflats grew almost 10 times larger than those in coarse-grained or high-salinity habitats. Patterns of seedling persistence among habitats matched those of natural seedling abundances and mirrored the degree ...

A Marine Plant (Spartina Anglica) Invades Widely Varying Habitats: Potential Mechanisms of Invasion and Control

We report on the habitat dependent invasion and control pattern of the English cordgrass, Spartina anglica C. E. Hubbard, in Puget Sound, Washington. In 36 years, the plant has successfully invaded 73 sites, affecting 3311 ha of marine intertidal habitat, which if allowed to solidly fill, would equal ∼ 400 ha. Invasion and control both depend on habitat type. Mudflats and low salinity marshes have significantly more solid area of S. anglica than do high salinity marshes and cobble beaches. Control efforts since 1997 have resulted in a 13% decline of the grass. We find that high salinity marshes have the greatest decline (∼ 70%), low salinity marshes have the lowest decline (∼ 10%), and mudflat (∼ 29%) and cobble beaches (∼ 21%) have intermediate losses. We hypothesize that invasion success and control are dependent on a relatively complex interplay between habitat physical conditions and species interactions.

Current status of marine protected areas in latin america and the Caribbean.

Marine protected areas (MPAs), including no-take marine reserves (MRs), play an important role in the conservation of marine biodiversity. We document the status of MPAs and MRs in Latin America and the Caribbean, where little has been reported on the scope of such protection. Our survey of protected area databases, published and unpublished literature, and Internet searches yielded information from 30 countries and 12 overseas territories. At present more than 700 MPAs have been established, covering more than 300,000 km(2) or 1.5% of the coastal and shelf waters. We report on the status of 3 categories of protection: MPAs (limited take throughout the area), MRs (no-take throughout the area), and mixed-use (a limited-take MPA that contains an MR). The majority of protected areas in Latin America and the Caribbean are MPAs, which allow some or extensive extractive activities throughout the designated area. These 571 sites cover 51,505 km(2) or 0.3% of coastal and shelf waters. There are 98 MRs covering 16,862 km(2) or 0.1% of the coastal and shelf waters. Mixed-use MPAs are the fewest in number (87), but cover the largest area (236,853 km(2), 1.2%). Across Latin America and the Caribbean, many biogeographic provinces are underrepresented in these protected areas. Large coastal regions remain unprotected, in particular, the southern Pacific and southern Atlantic coasts of South America. Our analysis reveals multiple opportunities to strengthen marine conservation in Latin America and the Caribbean by improving implementation, management, and enforcement of existing MPAs; adding new MPAs and MRs strategically to enhance connectivity and sustainability of existing protection; and establishing new networks of MPAs and MRs or combinations thereof to enhance protection where little currently exists.

Invasive grasses, climate change, and exposure to storm-wave overtopping in coastal dune ecosystems.

The worlds coastal habitats are critical to human well-being, but are also highly sensitive to human habitat alterations and climate change. In particular, global climate is increasing sea levels and potentially altering storm intensities, which may result in increased risk of flooding in coastal areas. In the Pacific Northwest (USA), coastal dunes that protect the coast from flooding are largely the product of a grass introduced from Europe over a century ago (Ammophila arenaria). An introduced congener (A. breviligulata) is displacing A. arenaria and reducing dune height. Here we quantify the relative exposure to storm-wave induced dune overtopping posed by the A. breviligulata invasion in the face of projected multi-decadal changes in sea level and storm intensity. In our models, altered storm intensity was the largest driver of overtopping extent, however the invasion by A. breviligulata tripled the number of areas vulnerable to overtopping and posed a fourfold larger exposure than sea-level rise over multi-decadal time scales. Our work demonstrates the importance of a transdisciplinary approach that draws on insights from ecology, geomorphology, and civil engineering to assess the vulnerability of ecosystem services in light of global change.