A comparison of survey method efficiencies for estimating densities of zebra mussels (Dreissena polymorpha).

Abundance surveys are commonly used to estimate plant or animal densities and frequently require estimating detection probabilities to account for imperfect detection. The estimation of detection probabilities requires additional measurements that take time, potentially reducing the efficiency of the survey when applied to high-density populations. We conducted quadrat, removal, and distance surveys of zebra mussels (Dreissena polymorpha) in three central Minnesota lakes and determined how much survey effort would be required to achieve a pre-specified level of precision for each abundance estimator, allowing us to directly compare survey design efficiencies across a range of conditions. We found that the required sampling effort needed to achieve our precision goal depended on both the survey design and population density. At low densities, survey designs that could cover large areas but with lower detection probabilities, such as distance surveys, were more efficient (i.e., required less sampling effort to achieve the same level of precision). However, at high densities, quadrat surveys, which tend to cover less area but with high detection rates, were more efficient. These results demonstrate that the best survey design is likely to be context-specific, requiring some prior knowledge of the underlying population density and the cost/time needed to collect additional information for estimating detection probabilities.

Analyzing ecosystem services as part of ecological networks in three salt marsh ecosystems.

Biodiversity plays important roles in nature's contributions to people (i.e., ecosystem services), but the critical details of how biodiversity contributes are challenging to determine. Efforts to identify the components of an ecosystem that provide services have improved our understanding of which species, functional groups, population, or habitats directly provide services. However, species do not exist in isolation and considerably less is known about how species indirectly influence ecosystem services through interacting with those species directly providing services. This uncertainty is even greater when considering that species interact in complex networks. As such, detailed analyses of species interdependencies are rarely included in ecosystem services assessments or conservation decisions. To date, most studies on food webs and on ecosystem services have developed largely in parallel for many services, but these fields and data are ripe for empirical integration. To further this integration, we compiled data sets that linked three existing ecological networks to seven ecosystem functions and services: wave attenuation, shoreline stabilization, carbon sequestration, water filtration, fisheries, birdwatching, and waterfowl hunting. We leveraged high-resolution ecological interaction network data sets from three coastal salt marsh ecosystems including detailed species information (e.g., consumer strategy, body size, biomass) on several hundred species from Carpinteria Salt Marsh in California, USA, and for Estero de Punta Banda and Bahia Falsa in Baja, Mexico from Hechinger et al. (2011). Through an extensive literature synthesis and use of citizen science data, we identified which species in the Hechinger et al. (2011) data provided each ecosystem services directly. We augmented the Hechinger et al. (2011) data published in Ecology, particularly the link (or edge) list to include species-service links to indicate a species providing a service, in which species are listed as "Resources" and services are listed as "Consumers." Connecting these data to the previously published ecological networks with species interactions (i.e., trophic, parasitism) formed a topological network with species and service nodes. We also provided a protocol for assigning services to ecological networks that can be used in other ecosystems. This data set provides a step toward advancing the knowledge of important supporting species for ecosystem services and to developing new ecological network methods for ecosystem services. There are no copyright restrictions; please cite this data paper when the data are used in publications.

Conceptualizing ecosystem services using social-ecological networks.

Social-ecological networks (SENs) represent the complex relationships between ecological and social systems and are a useful tool for analyzing and managing ecosystem services. However, mainstreaming the application of SENs in ecosystem service research has been hindered by a lack of clarity about how to match research questions to ecosystem service conceptualizations in SEN (i.e., as nodes, links, attributes, or emergent properties). Building from different disciplines, we propose a typology to represent ecosystem service in SENs and identify opportunities and challenges of using SENs in ecosystem service research. Our typology provides guidance for this growing field to improve research design and increase the breadth of questions that can be addressed with SEN to understand human-nature interdependencies in a changing world.

An ecological network approach to predict ecosystem service vulnerability to species losses.

Human-driven threats are changing biodiversity, impacting ecosystem services. The loss of one species can trigger secondary extinctions of additional species, because species interact-yet the consequences of these secondary extinctions for services remain underexplored. Herein, we compare robustness of food webs and the ecosystem services (hereafter 'services') they provide; and investigate factors determining service responses to secondary extinctions. Simulating twelve extinction scenarios for estuarine food webs with seven services, we find that food web and service robustness are highly correlated, but that robustness varies across services depending on their trophic level and redundancy. Further, we find that species providing services do not play a critical role in stabilizing food webs - whereas species playing supporting roles in services through interactions are critical to the robustness of both food webs and services. Together, our results reveal indirect risks to services through secondary species losses and predictable differences in vulnerability across services.