Estimating biotic integrity to capture existence value of freshwater ecosystems.

The US Environmental Protection Agency (EPA) uses a water quality index (WQI) to estimate benefits of proposed Clean Water Act regulations. The WQI is relevant to human use value, such as recreation, but may not fully capture aspects of nonuse value, such as existence value. Here, we identify an index of biological integrity to supplement the WQI in a forthcoming national stated preference survey that seeks to capture existence value of streams and lakes more accurately within the conterminous United States (CONUS). We used literature and focus group research to evaluate aquatic indices regularly reported by the EPA's National Aquatic Resource Surveys. We chose an index that quantifies loss in biodiversity as the observed-to-expected (O/E) ratio of taxonomic composition because focus group participants easily understood its meaning and the environmental changes that would result in incremental improvements. However, available datasets of this index do not provide the spatial coverage to account for how conditions near survey respondents affect their willingness to pay for its improvement. Therefore, we modeled and interpolated the values of this index from sampled sites to 1.1 million stream segments and 297,071 lakes across the CONUS to provide the required coverage. The models explained 13 to 36% of the variation in O/E scores and demonstrate how modeling can provide data at the required density for benefits estimation. We close by discussing future work to improve performance of the models and to link biological condition with water quality and habitat models that will allow us to forecast changes resulting from regulatory options.

Correspondence between a recreational fishery index and ecological condition for U.S.A. streams and rivers.

Sport fishing is an important recreational and economic activity, especially in Australia, Europe and North America, and the condition of sport fish populations is a key ecological indicator of water body condition for millions of anglers and the public. Despite its importance as an ecological indicator representing the status of sport fish populations, an index for measuring this ecosystem service has not been quantified by analyzing actual fish taxa, size and abundance data across the U.S.A. Therefore, we used game fish data collected from 1,561 stream and river sites located throughout the conterminous U.S.A. combined with specific fish species and size dollar weights to calculate site-specific recreational fishery index (RFI) scores. We then regressed those scores against 38 potential site-specific environmental predictor variables, as well as site-specific fish assemblage condition (multimetric index; MMI) scores based on entire fish assemblages, to determine the factors most associated with the RFI scores. We found weak correlations between RFI and MMI scores and weak to moderate correlations with environmental variables, which varied in importance with each of 9 ecoregions. We conclude that the RFI is a useful indicator of a stream ecosystem service, which should be of greater interest to the USA public and traditional fishery management agencies than are MMIs, which tend to be more useful for ecologists, environmentalists and environmental quality agencies.

River metrics by the public, for the public.

Managing rivers in society's best interest requires data on river condition. However, the complexity of river ecosystems, combined with finite budgets for river monitoring and modeling, mean difficult choices are necessary regarding what information will be available. Typically, decisions of "what to measure" are left to natural scientists. However, knowledge of public appetite for different types of information helps ensure river data is useful to society. We investigated public interest in rivers directly, engaging nearly one hundred urban and rural participants in a combination of focus groups and semi-structured interviews. Drawing on concepts of "final" ecosystem services developed in environmental economics, we moved discussions past commonly mentioned stressors, such as pollution, to actual river features important in and of themselves. Participant feedback reflected extensive thought on river issues, in contrast to a stereotype that the public is ambivalent about environmental conditions. Interests were also broad, encompassing water quality and quantity, fish and wildlife, vegetation, and human features. Results show consolidation around relatively few themes despite diverse sociodemographics. Themes were interpreted into distilled, specific metrics to make public feedback as useful as possible for water resources monitoring, modeling, and management. Our research provides detailed, methodically generated hypotheses regarding river themes and metrics of public interest that should be considered as part of the tradeoffs inherent in river monitoring design. Results compared reasonably well to river attributes emphasized in river restoration environmental valuation reviews, with some differences. Future research could test our hypotheses with large-sample surveys.

Water clarity measures as indicators of recreational benefits provided by U.S. lakes: Swimming and aesthetics.

Lakes provide recreational benefits related to water quality. Using data from the 2007 and 2012 United States National Lake Assessments (N=2067 lake visits), we developed indicators for three benefits: swimming, general recreational value, and aesthetic appeal. For two combined ecoregions ("Mountains" and "Plains") we related objective measures of water clarity, including Secchi depth, turbidity, and water-column chlorophyll-a concentration to subjective visual assessments of recreational benefit quality. There were significant associations between water clarity measures and visual assessments from which we derived water-clarity based thresholds between benefit quality classes (exceptional, high, low, marginal) for each benefit type. More variation in Secchi depth and turbidity was explained by benefit quality than was variation in chlorophyll-a. Threshold values were different between combined ecoregions. Compared to lakes in the Mountains ecoregion, recreational users of Plains lakes have lower expectations for water clarity. Thresholds were generally in accord with water clarity thresholds and guidance derived from published regional studies. Including indicators of the quality of benefits humans receive from lakes in assessments of lake conditions can increase public participation in decision-making and reveal changes in benefit quality over time.

Index of alien impact: a method for evaluating potential ecological impact of alien plant species.

Alien plant species are stressors to ecosystems and indicators of reduced ecosystem integrity. The magnitude of the stress reflects not only the quantity of aliens present, but also the quality of their interactions with native ecosystems. We develop an Index of Alien Impact (IAI) to estimate the collective ecological impact of in situ alien species. IAI summarizes the frequency of occurrence and potential ecological impact (Invasiveness-Impact Score (I ( i ))) of individual alien species for all aliens present in a particular location or community type. A component metric, I (i), is based on ecological species traits (life history, ecological amplitude, and ability to alter ecosystem processes) that reflect mechanisms, which can increase impact to ecosystem structure and function. While I (i) is less complex than some other multi-metric rankings of alien impact, it compares well to these metrics and to qualitative judgments. IAI can be adapted for different ecological settings by modifying the set of species traits incorporated in I (i) to reflect properties likely to breach biotic and abiotic barriers or alter ecosystem function in a particular region or community type of interest. To demonstrate our approach, we created versions of IAI and I (i), applicable to the diverse streamside vegetation of a river basin (19,631 km(2)) spanning low-elevation arid to mesic montane habitats in eastern Oregon, USA. In this demonstration effort, we (1) evaluate relationships of IAI to metrics describing invasion level, and (2) illustrate the potential utility of IAI for prioritizing alien species management activities and informing restoration goals.

Evaluation of metric precision for a riparian forest survey.

This article evaluates the performance of a protocol to monitor riparian forests in western Oregon, United States based on the quality of the data obtained from a field survey. Precision is the criteria used to determine the quality of 19 field and 6 derived metrics. The derived metrics were calculated from the field data. The survey consisted of 110 riparian sites on public and private lands that were sampled during the summers of 1996 and 1997. In order to calculate metric precision, some of the field plots were re-measured. Metric precision was defined in terms of the coefficient of variability (CV) and standard deviation and then compared with a pre-defined data quality objective (DQO). A metric was considered precise if the CV met or exceeded the DQO. The geomorphology metrics were not precise while the forest stand inventory metrics and forest cover metrics, with some exceptions, were precise. The precision for many of the field and derived metrics compared favorably with the level of precision for similar metrics reported in the literature. Recommendations are made to improve the precision for some metrics and they include changing the way precision is calculated, re-defining the field protocol, or improving field training.