John Van Sickle

ALTERNATIVE FUTURES FOR THE WILLAMETTE RIVER BASIN, OREGON

Alternative futures analysis can inform community decisions regarding land and water use. We conducted an alternative futures analysis in the Willamette River Basin in western Oregon. Based on detailed input from local stakeholders, three alternative future landscapes for the year 2050 were created and compared to present-day (circa 1990) and historical (pre-EuroAmerican settlement) landscapes. We evaluated the likely effects of these landscape changes on four endpoints: water availability, Willamette River, stream condition, and terrestrial wildlife. All three futures assume a doubling of the 1990 human population by 2050. The Plan Trend 2050 scenario assumes current policies and trends continue. Because Oregon has several conservation-oriented policies in place, landscape changes and projected environmental effects associated with this scenario were surprisingly small (most #10% change relative to 1990). The scenario did, however, engender a debate among stakeholders about the reasonableness of assuming that existing policies would be implemented exactly as written if no further policy actions were taken. The Development 2050 scenario reflects a loosening of current policies, more market-oriented approach, as proposed by some stakeholders. Estimated effects of this scenario include loss of 24% of prime farmland; 39% more wildlife species would lose habitat than gain habitat relative to the 1990 landscape. Projected effects on aquatic biota were less severe, primarily because many of the land use changes involved conversion of agricultural lands into urban or rural development, both of which adversely impact streams. Finally, Conservation 2050 assumes that ecosystem protection and restoration are given higher priority, although still within the bounds of what stakeholders considered plausible. In response, most ecological indi- cators (both terrestrial and aquatic) recovered 20-70% of the losses sustained since EuroAmerican settlement. The one exception is water availability. Water consumed for out- of-stream uses increased under all three future scenarios (by 40-60%), with accompanying decreases in stream flow. Although the conservation measures incorporated into Conser- vation 2050 moderated the increase in consumption, they were not sufficient to reverse the trend. Results from these analyses have been actively discussed by stakeholder groups charged with developing a vision for the basins future and a basin-wide restoration strategy.

Classification strengths of ecoregions, catchments, and geographic clusters for aquatic vertebrates in Oregon

The usefulness of ecoregions and catchments (hydrologic units) as bases for classifying aquatic vertebrate assemblages in western Oregon was compared using samples collected by electrofishing from 137 wadeable stream sites distributed evenly throughout the region. The classification strengths of these regionalizations were also compared with neutral-model classifications that were based either on intersite proximities in geographic distance or on intersite similarities in the sampled vertebrate assemblages. The strength of each classification was assessed by the extent to which average within-class assemblage similarities exceeded the average similarity between classes. Mean similarity dendrograms were used as a concise graphical comparison of between- and within-class similarities for alternative classifications, whether they were specified a priori or constructed by clustering. For each a priori classification, a permutation test of the no class structure hypothesis was performed. Classification strengths were assessed using the Sorenson–Dice (presence/absence) and Bray–Curtis (relative abundance) similarity measures, applied to both species-level and family-level assemblage characterizations, as well as for the Bray–Curtis measure applied to a set of 5 assemblage metrics that were designed to reflect stream impairment. For all 5 measures of assemblage similarity, ecoregions had higher classification strengths than did large catchments, and large catchments had about the same strength as a stream-order classification. A catchment classification with 1 of the 3 catchments split into 2 ecoregions separated assemblages as strongly as ecoregions alone. A neutral-model classification based solely on geographic site proximity classified assemblages with about the same strength as ecoregions. Another neutral-model classification of sites, based solely on their sampled assemblages, was at least twice as strong as any of the geographic classifications. Intermediate strength was seen in site groupings derived from a composite measure of between-site assemblage and geographic dissimilarities. Our results suggest that ecoregions and large catchments do indeed have utility for classifying stream vertebrate assemblages. However, much of their classification strength may be a result of spatial autocorrelation effects, rather than ecological factors that determine their particular boundaries. Our similarity analyses also suggest that geographic partitions can be expected to account for only a minor portion of the total variation seen in stream vertebrate assemblages across a large region.

Condition of stream ecosystems in the US: an overview of the first national assessment

Abstract The Wadeable Streams Assessment (WSA) provided the first statistically sound summary of the ecological condition of streams and small rivers in the US. Information provided in the assessment filled an important gap in meeting the requirements of the US Clean Water Act. The purpose of the WSA was to: 1) report on the ecological condition of all wadeable, perennial streams and rivers within the conterminous US, 2) describe the biological condition of these systems with direct measures of aquatic life, and 3) identify and rank the relative importance of chemical and physical stressors affecting stream and river condition. The assessment included perennial wadeable streams and rivers that accounted for 95% of the length of flowing waters in the US. The US Environmental Protection Agency, states, and tribes collected chemical, physical, and biological data at 1392 randomly selected sites. Nationally, 42% of the length of US streams was in poor condition compared to best available reference sites in their ecoregions, 25% was in fair condition, and 28% was in good condition. Results were reported for 3 major regions: Eastern Highlands, Plains and Lowlands, and West. In the West, 45% of the length of wadeable flowing waters was in good condition. In the Eastern Highlands, only 18% of the length of wadeable streams and rivers was in good condition and 52% was in poor condition. In the Plains and Lowlands, almost 30% of the length of wadeable streams and rivers was in good condition and 40% was in poor condition. The most widespread stressors observed nationally and in each of the 3 major regions were N, P, riparian disturbance, and streambed sediments. Excess nutrients and excess streambed sediments had the highest impact on biological condition; streams scoring poor for these stressors were at 2 to 3× higher risk of having poor biological condition than were streams that scored in the good range for the same stressors.

Striving for consistency in a national assessment: the challenges of applying a reference-condition approach at a continental scale

Abstract One of the biggest challenges when conducting a continental-scale assessment of streams is setting appropriate expectations for the assessed sites. The challenge occurs for 2 reasons: 1) tremendous natural environmental heterogeneity exists within a continental landscape and 2) reference sites vary in quality both across and within major regions of the continent. We describe the process used to set expectations for the multimetric index of biotic integrity (MIBI) and observed/expected (O/E) indices generated from predictive models used to assess stream condition for the US Wadeable Streams Assessment (WSA). The assessment was based on a reference-site approach, in which the least-disturbed sites in each region of the US were used to establish benchmarks for assessing the condition of macroinvertebrate assemblages at other sites. Reference sites were compiled by filtering WSA sample sites for disturbance using a series of abiotic variables. Additional reference sites were needed and were obtained from other state, university, and federal monitoring programs. This pool of potential reference sites was then assessed for uniformity in site quality and comparability of macroinvertebrate sample data. Ultimately, 1625 sites were used to set reference expectations for the WSA. Reference-site data were used to help define 9 large ecoregions that minimized the naturally occurring variation in macroinvertebrate assemblages associated with continental-wide differences in biogeography. These ecoregions were used as a basis for developing MIBI and O/E indices and for reporting results. A least-disturbed definition of reference condition was used nationally, but we suspect that the quality of the best extant sites in ecoregions, such as the Northern Plains and Temperate Plains, was lower than that of sites in other ecoregions. For the MIBI assessment, we used a simple modeling approach to adjust scores in ecoregions where gradients in reference-site quality could be demonstrated conclusively. The WSA provided an unparalleled opportunity to push the limits of our conceptual and technical understanding of how to best apply a reference-condition approach to a real-world need. Our hope is that we have learned enough from this exercise to improve the technical quality of the next round of national assessments.

PROJECTING THE BIOLOGICAL CONDITION OF STREAMS UNDER ALTERNATIVE SCENARIOS OF HUMAN LAND USE

We present regression models for estimating the status of fish and aquatic invertebrate communities in all second to fourth-order streams (1:100 000 scale; total stream length 5 6476 km) throughout the Willamette River Basin, Oregon (USA). The models project fish and invertebrate status as a function of physiographic, land-use/land-cover, and stream flow variables, with the latter two sets of variables subject to change under historical and alternative future scenarios of human development. Models are developed using sample data collected between 1993 and 1997 from 149 wadeable streams in the basin. Model uncertainties are propagated through model projections and into aggregated estimates of regional status. The projections show no significant change in basin-wide status in year 2050, relative to Circa 1990, for scenarios either of increased human development or continuation of current development trends, because landscape change under these scenarios is dominated by conversion of agricultural land to rural residential and urban uses, and because these changes affect only a small percentage of the basin. However, under a scenario of increased conservation, regional medians of biotic status indicators are projected to improve by 9-24% by year 2050. None of the changes projected between Circa 1990 and year 2050 is as large in magnitude as the decline in status projected to have occurred between the time of pre-European settlement and Circa 1990.

A null model for the expected macroinvertebrate assemblage in streams

Abstract Predictive models such as River InVertebrate Prediction And Classification System (RIVPACS) and AUStralian RIVer Assessment System (AUSRIVAS) model the natural variation across geographic regions in the occurrences of macroinvertebrate taxa in data from streams that are in reference condition, i.e., minimally altered by human-caused stress. The models predict the expected number of these taxa at any stream site, assuming that site also is in reference condition. A significant difference between the ratio of observed (O) and expected (E) taxa (O/E) and 1.0 indicates that the site is not in reference condition. The standard deviation (SD) of O/E values estimated for a set of reference sites is a measure of predictive-model precision, with a small SD indicating that the model accounts for much of the variability in E that is associated with natural factors such as stream size and elevation. We propose a null model for E that assumes fixed occurrence probabilities for individual taxa across reference sites. The null model explains none of the variability in E caused by natural factors, so the SD of its O/E predictions is the upper limit attainable by any predictive model. We also derive a theoretical lower limit for SD of O/E that is caused only by replicate-sampling variation among predictions from a perfect model. Together, the null-model and replicate-sampling SDs estimate the minimum and maximum precision, respectively, attainable by any predictive model for a given set of reference-site data. A predictive model built from data at 86 reference sites in the Mid-Atlantic Highlands region, USA, had SD = 0.18 for O/E across those sites, while the corresponding null model had SD = 0.20, indicating relatively little gain from the predictive-model effort. In contrast, a model built from 209 sites in North Carolina, USA, had predictive- and null-model SDs of 0.13 and 0.28, respectively, indicating that the North Carolina predictive model had relatively high gain in precision over the null model. Replicate-sampling SDs of O/E for the Mid-Atlantic and North Carolina data were 0.09 and 0.11, respectively, suggesting that the North Carolina predictive model had little room for further improvement, in contrast to the Mid-Atlantic model. The precisions of null-model estimates were lower than those of predictive models, so null models somewhat underestimated the percentages of 447 and 1773 test assemblages from the Mid-Atlantic region and North Carolina, respectively, that differed significantly from reference conditions. The estimates illustrate how a simple and easily built null model provides a lower bound for the prevalence of impaired streams within a region.

The effect of wastewater phosphorus removal on shagawa lake, Minnesota: phosphorus supplies, lake phosphorus and chlorophyll a

Abstract In early 1973, the phosphorus supply to Shagawa Lake, Minnesota, was reduced by about 80% when a tertiary wastewater treatment plant began operating. Significant reductions in total and soluble reactive phosphorus concentrations have occurred in the lake since that time. By 1976 the average (volume weighted over the entire lake) total and soluble reactive phosphorus concentrations had declined from about 51 and 21 μg l −1 to about 30 and 4.5 μg l −1 , respectively, corresponding to 40 and 80% reductions. During 1975 and 1976, chlorophyll a (averaged over the top 5 m) had decreased to less than 50% of the pretreatment level during May-June but during July-August little change had occurred. A phosphorus residence time model projected equilibrium total phosphorus concentrations of about 12 μg l −1 within 1.5 years. The fact that this level was not reached is attributed to a feedback of phosphorus from the sediments, primarily during summer. This phenomenon has been incorporated into a modified total phosphorus mass balance model which projects the phosphorus pattern through 1976 quite accurately. The close fit of the modified mass balance model implies that the phosphorus supply from the sediments has not diminished since treatment since treatment began, and that further recovery of the lake will depend upon how long this feedback of phosphorus from the sediments continues.

Exclusion of rare taxa affects performance of the O/E index in bioassessments

Abstract The contribution of rare taxa to bioassessments based on multispecies assemblages is the subject of continued debate. As a result, users of predictive models such as River InVertebrate Prediction and Classification System (RIVPACS) disagree on whether to exclude locally rare taxa from the O/E index, where O is the number of taxa observed in a sampled assemblage, and E is the number that would be expected if the site were in a minimally disturbed reference condition. We assessed how the bioassessment performance of O/E was affected by the exclusion of taxa with site-specific, model-predicted occurrence probabilities that did not exceed thresholds of PT = 0+, 0.1, 0.2, … , 0.7. We assessed O/E performance for each of 10 predictive models applied to a total of 5685 stream and lake samples from throughout the contiguous USA. For 5 of the 10 cases, the standard deviation (SD) of O/E across reference sites was reduced by at least 0.02 O/E units when locally rare and uncommon taxa were excluded (PT = 0.5) from O/E, as compared with all taxa being included (PT = 0+). These reductions in SD denote increases in precision of the O/E index. We also assessed the sensitivity of O/E, measured by the % of test sites (that is, sites independently assessed as not being in reference condition) that were declared to be outside the reference distribution of O/E scores. Five of our 10 cases showed increases in sensitivity of ≥10% at PT = 0.5 as compared with PT = 0+. All cases that did not show increases in sensitivity or precision also showed no decrease in either of these performance measures as PT increased. A comparison of observed occurrence frequencies of taxa at reference and test sites qualitatively explained the size of the O/E sensitivity response in all 10 cases. This result suggests that effects of rare-taxa exclusion are a direct consequence of these occurrence frequencies rather than of predictive-model structures. Thus, we predict that other assemblage-based bioassessment tools are likely to show improved sensitivity when rare taxa are excluded.

Continental-Scale Increase in Lake and Stream Phosphorus: Are Oligotrophic Systems Disappearing in the United States?

We describe continental-scale increases in lake and stream total phosphorus (TP) concentrations, identified through periodic probability surveys of thousands of water bodies in the conterminous U.S. The increases, observed over the period 2000-2014 were most notable in sites in relatively undisturbed catchments and where TP was initially low (e.g., less than 10 μg L(-1)). Nationally, the percentage of stream length in the U.S. with TP ≤ 10 μg L(-1) decreased from 24.5 to 10.4 to 1.6% from 2004 to 2009 to 2014; the percentage of lakes with TP ≤ 10 μg L(-1) decreased from 24.9 to 6.7% between 2007 and 2012. Increasing TP concentrations appear to be ubiquitous, but their presence in undeveloped catchments suggests that they cannot be entirely attributed to either point or common non-point sources of TP.

Effects of regionalization decisions on an O/E index for the US national assessment

Abstract We examined the effects of different regionalization schemes on the performance of River InVertebrate Prediction and Classification System (RIVPACS)-type predictive models in assessing the biological conditions of streams of the US for the National Wadeable Streams Assessment (WSA). Three regionalization schemes were considered: a single national predictive model (MOD1), separate predictive models for each of the 9 WSA aggregated Omernik level III ecoregions (MOD9), and 3 predictive models roughly corresponding to the western US, the Appalachian Mountains, and the Central and Coastal Plains (MOD3). The goal of the WSA was to assess stream condition at the national scale and at the scale of WSA aggregated ecoregions, so we compared the performance of the ratio of the observed number of taxa to the expected number of taxa (O/E) index estimated using different regionalization schemes at both of these spatial scales. We assessed model performance with a randomized resampling procedure, in which we set aside 10% of the reference sites, calibrated the model with the remaining sites, and applied the model to the set-aside sites. Performance statistics for the set-aside reference sites were accumulated over 10 iterations. When summarized at the national scale, mean model predictions of O/E for set-aside reference sites from the 3 different regionalization schemes were all reasonably close to 1. When summarized by the 9 aggregated ecoregions, MOD1 and MOD3 predictions of O/E differed systematically from 1 in certain aggregated ecoregions. Over all 9 ecoregions, the magnitude of these differences was significantly greater than observed with MOD9 predictions. Results from our analysis suggest that O/E values at test sites should be interpreted with respect to mean and SD of O/E of reference sites from the same region to minimize the effects of systematic biases in the predictions. RIVPACS-type predictive models also should be calibrated at a spatial scale similar to the scale at which summary statistics are reported.