Coastal protection and conservation on sandy beaches and dunes : Context-dependent tradeoffs in ecosystem service supply

Managing multiple ecosystem services (ESs) across landscapes presents a central challenge for ecosystem-based management, because services often exhibit spatiotemporal variation and weak associations with co-occurring ESs. Further focus on the mechanistic relationships among ESs and their underlying biophysical processes provides greater insight into the causes of variation and covariation among ESs, thus serving as a guide to enhance their supply while preventing adverse outcomes. Here, we used the U.S. Pacific Northwest coastal dune ecosystem to examine how invasive beachgrass management affects three ESs: coastal protection, western snowy plover conservation, and endemic foredune plant conservation. At seven coastal dune habitat restoration areas, we observed spatial variation in the supply of each ES and further identified a tradeoff between western snowy plover conservation and coastal protection. While the ESs were collectively influenced by the invasive beachgrasses and the foredunes they create, the magnitude of the synergies and tradeoffs were influenced by numerous non-shared drivers, including nearshore geomorphology, changes in foredune shape as a result of restoration, and other management actions irrespective of restoration. Incorporation of these shared and non-shared drivers into future coastal management planning may reduce tradeoffs among Pacific Northwest dune ESs. With better understanding of ES relationships, it becomes possible to identify management actions that may enhance synergies and mitigate tradeoffs, leading to better decisions for nature and people. Key words: coastal protection; conservation; ecosystem management; ecosystem services; natural capital; restoration

Contour plot of (A) native cover and (B) species richness shows differences in distribution across across chronosequence ages and dune gradient in dunes of different <i>Ammophila</i> dominance.

<p>Contours show areas of increasing cover or richness across both gradients. Quadrats from sites dominated by <i>A</i>. <i>arenaria</i> are shown in red, those from <i>A</i>. <i>breviligulata</i> sites shown in blue. See main text and <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0117283#pone.0117283.g002" target="_blank">Fig. 2</a> caption for additional details.</p

Invasive Congeners Differ in Successional Impacts across Space and Time

<div><p>Invasive species can alter the succession of ecological communities because they are often adapted to the disturbed conditions that initiate succession. The extent to which this occurs may depend on how widely they are distributed across environmental gradients and how long they persist over the course of succession. We focus on plant communities of the USA Pacific Northwest coastal dunes, where disturbance is characterized by changes in sediment supply, and the plant community is dominated by two introduced grasses – the long-established <i>Ammophila arenaria</i> and the currently invading <i>A. breviligulata</i>. Previous studies showed that <i>A. breviligulata</i> has replaced <i>A. arenaria</i> and reduced community diversity. We hypothesize that this is largely due to <i>A. breviligulata</i> occupying a wider distribution across spatial environmental gradients and persisting in later-successional habitat than <i>A. arenaria</i>. We used multi-decadal chronosequences and a resurvey study spanning 2 decades to characterize distributions of both species across space and time, and investigated how these distributions were associated with changes in the plant community. The invading <i>A. breviligulata</i> persisted longer and occupied a wider spatial distribution across the dune, and this corresponded with a reduction in plant species richness and native cover. Furthermore, backdunes previously dominated by <i>A. arenaria</i> switched to being dominated by <i>A. breviligulata</i>, forest, or developed land over a 23-yr period. <i>Ammophila breviligulata</i> likely invades by displacing <i>A. arenaria</i>, and reduces plant diversity by maintaining its dominance into later successional backdunes. Our results suggest distinct roles in succession, with <i>A. arenaria</i> playing a more classically facilitative role and <i>A. breviligulata</i> a more inhibitory role. Differential abilities of closely-related invasive species to persist through time and occupy heterogeneous environments allows for distinct impacts on communities during succession.</p></div

Changes in <i>Ammophila</i> cover and plant richness over a 21-year period from 1988 to 2009.

<p>‘Switch’ refers to transects that had substantial <i>A</i>. <i>arenaria</i> in 1988 and were dominated by <i>A</i>. <i>breviligulata</i> in 2009. “Estab.’ refers to transects that were dominated by <i>A</i>. <i>breviligulata</i> in both 1988 and 2009. (A) Mean relative <i>Ammophila</i> cover ± S.E.; (B) Relative <i>Ammophila</i> cover across the dune gradient; (C) Mean plant richness ± S.E.; (D) Plant richness across the dune gradient. Light red denotes switched transects in 1988; light blue denotes established transects in 1988; dark red denotes switched transects in 2009; dark blue denotes established transects in 2009. Three separate linear contrasts shown at different heights in (A) and (C), stars signify significance (p < 0.05), NS signifies not significant. For (B), there was a significant difference in <i>Ammophila</i> cover between switched and established transects in 1988 but not in 2009. For (D), there were no significant differences in richness along the dune gradient within either 1988 or 2009. See <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0117283#pone.0117283.t001" target="_blank">Table 1</a> for full models.</p

Foredune cross-section schematics.

<p>(A) Foredunes contain both spatial and temporal gradients along their cross-sections. Foredune consists of toe, crest, and heel moving from left to right. For the spatial dune gradient, quadrats were assigned values between-1 and 1 for their placement along the dune cross-section. Chronosequence age increased from the dune toe to heel (see main text for details). Shoreline and backdune are shown for orientation. (B) Historical dune consisting of only <i>Ammophila arenaria</i> (gray). (C) Invasion of historical dune by <i>A</i>. <i>breviligulata</i> (black) through preemptive colonization of a new dune. <i>Ammophila arenaria</i> retains its original population, and a backdune invasion boundary delineates the two species’ distributions along the dune. (D) Invasion of historical dune by <i>A</i>. <i>breviligulata</i> through displacement of <i>A</i>. <i>arenaria</i>. Note that there is no longer a backdune invasion boundary because the <i>A</i>. <i>arenaria</i> has been locally extirpated.</p

Contour plot of <i>Ammophila</i> cover shows distinct species distributions across chronosequence ages and dune gradient.

<p>Contours show areas of increasing cover across both gradients. Contours were created using predicted values of generalized linear models (see main text for details). Chronosequence ages were calculated for each quadrat using aerial photos and shoreline change rates (see main text for details). Dune gradient was calculated for each quadrat based on its standardized location along dune cross sections with the toe, crest, and heel at-1, 0, and 1, respectively. Each point on figure refers to the chronosequence age and dune gradient for an individual quadrat. Sites dominated by <i>A</i>. <i>arenaria</i> are shown in red, and those from <i>A</i>. <i>breviligulata</i> sites shown in blue.</p

Results from the decadal study using linear mixed models with independent linear contrasts.

<p>Results from the decadal study using linear mixed models with independent linear contrasts.</p

Literature-based latitudinal distribution and possible range shifts of two US east coast dune grass species (Uniola paniculata and Ammophila breviligulata)

Previous work on the US Atlantic coast has generally shown that coastal foredunes are dominated by two dune grass species, Ammophila breviligulata (American beachgrass) and Uniola paniculata (sea oats). From Virginia northward, A. breviligulata dominates, while U. paniculata is the dominant grass south of Virginia. Previous work suggests that these grasses influence the shape of coastal foredunes in species-specific ways, and that they respond differently to environmental stressors; thus, it is important to know which species dominates a given dune system. The range boundaries of these two species remains unclear given the lack of comprehensive surveys. In an attempt to determine these boundaries, we conducted a literature survey of 98 studies that either stated the range limits and/or included field-based studies/observations of the two grass species. We then produced an interactive map that summarizes the locations of the surveyed papers and books. The literature review suggests that the current southern range limit for A. breviligulata is Cape Fear, NC, and the northern range limit for U. paniculata is Assateague Island, on the Maryland and Virginia border. Our data suggest a northward expansion of U. paniculata, possibly associated with warming trends observed near the northern range limit in Painter, VA. In contrast, the data regarding a range shift for A. breviligulata remain inconclusive. We also compare our literature-based map with geolocated records from the Global Biodiversity Information Facility and iNaturalist research grade crowd-sourced observations. We intend for our literature-based map to aid coastal researchers who are interested in the dynamics of these two species and the potential for their ranges to shift as a result of climate change

Using cultural ecosystem services to inform restoration priorities in the Laurentian Great Lakes

Ecological restoration programs often attempt to maintain or enhance ecosystem services (ES), but fine-scale maps of multiple ES are rarely available to support prioritization among potential projects. Here we use agency reports, citizen science, and social media as data sources to quantify the spatial distribution of five recreational elements of cultural ES (CES) - sport fishing, recreational boating, birding, beach use, and park visitation - Across North America\u27s Laurentian Great Lakes, where current restoration investments exceed US$1.5 billion. These recreational CES are widely yet unevenly distributed, and spatial correlations among all except park visitation indicate that many locations support multiple CES benefits. Collectively, these five service metrics correlate with tourism gross domestic product, indicating that local economies benefit from ecosystem conditions that support CES. However, locations of high recreational CES delivery are often severely affected by environmental stressors, suggesting that either ecosystem condition or human enjoyment of these recreational CES is resilient even to substantial levels of stress. Our analyses show that spatial assessments of recreational CES are an informative complement to ecosystem stress assessments for guiding large-scale restoration efforts