The Disconnect Between Restoration Goals and Practices: A Case Study of Watershed Restoration in the Russian River Basin, California

Over the past two decades, watershed restoration has dramatically increased internationally. California has been at the forefront, allocating billions of dollars to restoration activities through legislation and voter-approved bonds. Yet, the implications of restoration remain ambiguous because there has been little examination of restoration accomplishments and almost no analysis of the political context of restoration. This article addresses these gaps, utilizing a case study of the Russian River basin in Northern California. We identify trends that shed light on both the ecological and the political implications of restoration at a basin scale by examining a database of 787 restoration projects implemented in the Russian River basin since the early 1980s. Although a total of over $47 million has been spent on restoration in the basin, dominant forms of restoration are limited in scope to small-scale projects that focus on technical solutions to site-specific problems. The majority of restoration efforts are devoted to road repair, riparian stabilization, and in-stream structures, accounting for 62% of all projects. These types of projects do not address the broader social drivers of watershed change such as land and water uses. We suggest that restoration can become more effective by addressing the entire watershed as a combination of social and ecological forces that interact to produce watershed conditions.     

The effects of macroinvertebrate taxonomic resolution in large landscape bioassessments: an example from the Mid-Atlantic Highlands, U.S.A.

1. During late spring 1993–1995, the U.S. Environmental Protection Agency's Environmental Monitoring and Assessment Program (EMAP) sampled 490 wadeable streams in the mid‐Atlantic Highlands (MAH) of the U.S. for a variety of physical, chemical and biological indicators of environmental condition. We used the resulting data set to evaluate the importance of differing levels of macroinvertebrate taxonomic resolution in bioassessments by comparing the ability of family versus genus to detect differences among sites classified by type and magnitude of human impact and by stream size. We divided the MAH into two physiographic regions: the Appalachian Plateau where mine drainage (MD) and acidic deposition are major stressors, and the Ridge and Valley where nutrient enrichment is a major stressor. Stream sites were classified into three or four impact classes based on water chemistry and habitat. We used stream order (first to third Strahler order) in each region as a measure of stream size. Ordination, 2 × 2 chi‐square and biotic metrics were used to compare the ability of family and genus to detect differences among both stressor and size classes. 2. With one notable exception, there were only a small number of different genera per family (interquartile range = 1–4). Family Chironomidae, however, contained 123 different genera. As a result, significant information loss occurred when this group was only classified to family. The family Chironomidae did not discriminate among the predefined classes but many chironomid genera did: by chi‐square analysis, 10 and 28 chironomid genera were significant in discriminating MD and nutrient impacts, respectively. 3. Family and genus data were similar in their ability to distinguish among the coarse impacts (e.g. most severe versus least severe impact classes) for all cases. Though genus data in many cases distinguished the subtler differences (e.g. mixed/moderate impacts versus high or low impacts) better than family, differences in significance levels between family and genus analyses were relatively minor. However, genus data detected differences among stream orders in ordination analyses that were not revealed at the family level. In the ordinations, both family and genus levels of analysis responded to similar suites of environmental variables. 4. Our results suggest that identification to the family level is sufficient for many bioassessment purposes. However, identifications to genus do provide more information in genera‐rich families like Chironomidae. Genus or finer levels of identification are important for investigating natural history, stream ecology, biodiversity and indicator species. Decisions about the taxonomic level of identification need to be study specific and depend on available resources (cost) and study objectives.     

Natural flow regime,temperature and the composition and richness of invertebrate assemblages in streams of the western United States

1. We tested how strongly aquatic macroinvertebrate taxa richness and composition were associated with natural variation in both flow regime and stream temperatures across streams of the western United States. 2. We used long‐term flow records from 543 minimally impacted gauged streams to quantify 12 streamflow variables thought to be ecologically important. A principal component analysis reduced the dimensionality of the data from 12 variables to seven principal component (PC) factors that characterised statistically independent aspects of streamflow: (1) zero flow days, (2) flow magnitude, (3) predictability, (4) flood duration, (5) seasonality, (6) flashiness and (7) base flow. K‐means clustering was used to group streams into 4–8 hydrologically different classes based on these seven factors. 3. We also used empirical models to estimate mean annual, mean summer and mean winter stream temperatures at each stream site. We then used invertebrate data from 63 sites to develop Random Forest models to predict taxa richness and taxon‐specific probabilities of capture at a site from flow and temperature. We used the predicted taxon‐specific probabilities of capture to estimate how well predicted assemblages matched observed assemblages as measured by RIVPACS‐type observed/expected (O/E) indices and Bray–Curtis dissimilarities. 4. Macroinvertebrate taxon richness was only weakly associated with streamflow and temperature variables, implying that other factors more strongly influenced taxa richness. 5. In contrast to taxa richness, taxa composition was strongly associated with streamflow and temperature. Predictions of taxa composition (O/E and Bray–Curtis) were most precise when both temperature and streamflow PC factors were used, although predictions based on either streamflow PC factors or temperature alone were also better than null model predictions. Of the seven aspects of the streamflow regime we examined, variation in baseflow conditions appeared to be most directly associated with invertebrate biotic composition. We were also able to predict assemblage composition from the conditional probabilities of hydrological class membership nearly as well as Random Forests models that were based directly on continuous PC factors. 6. Our results have direct implication for understanding the relative importance of streamflow and temperature in regulating the structure and composition of stream assemblages and for improving the accuracy and precision of biological assessments.     

Temporal dynamics of stream fish assemblages and the role of spatial scale in quantifying change

1. Spatial grain of studies of communities is often based on arbitrary convention. Few studies have examined how spatial scaling of grain size affects estimates of compositional change over time, despite its broad implications.
2. Fish assemblage structure was compared between 1974 and 2014 at 33 sampling locations in the Muddy Boggy River drainage, USA. The two main objectives for this comparison were to quantify change in assemblage structure and to test for a relationship between compositional change and spatial scale. Spatial scale was manipulated by pooling assemblage data into a continuous range of groups, which increased in size from K = 33 pairs (i.e., local scale) to K = 1 pair (i.e., global scale), via clustering algorithm based on pair‐wise fluvial distance.
3. Local assemblages (stream reaches) varied in the degree of assemblage change over time (range = 0.10–0.99 dissimilarity; mean = 0.66). The global assemblage (drainage), however, remained relatively similar. A discontinuity in the relationship between compositional change and spatial scale occurred at K = 15 (mean dissimilarity = 0.56; p = .062), and this grouping is roughly the size of the headwater/tributary drainages (i.e., stream order ≤ 3) in the study system.
4. Spatial scale can impact estimates of biodiversity change over time. These results suggest assemblages are more dynamic at individual stream reaches than at the scale of the entire drainage. The decline in assemblage change at the spatial scale of K = 15 deserves further attention given the marginal significance, despite a small sample size (n = 15). This pattern could suggest regional and meta‐community processes become more important in shaping assemblage dynamics at the scale of headwater drainages, whereas the factors responsible for driving individual stream reach dynamics (e.g., stochasticity) become less important. Defining assemblages at a larger scale will result in different estimates of species persistence. Biodiversity monitoring efforts must take the effect of spatial scaling into consideration.

     

Scale-dependent effects of rural activities on benthic macroinvertebrates and physico-chemical characteristics in headwater streams of the Mara River,Kenya

We studied streams in a rural landscape mosaic of the upper Mara River basin (Mau Forest, Kenya), where native forest has been converted to land uses dominated by various kinds of farming, agriculture and rural human settlements. We investigated scale-dependent effects of these anthropogenic rural activities on macroinvertebrates and physico-chemical variables by separately testing for effects of reach-scale disturbance and catchment-scale land use. Physico-chemical variables like conductivity, turbidity and total suspended solids reacted equally well to reach-scale disturbance and catchment-scale land use, demonstrating the high spatial integration potential of these variables and calling for farsighted large-scale water resource management. In contrast, macroinvertebrates reacted more sensitively at the reach-scale than at the catchment-scale, suggesting a stronger influence of local habitat conditions. These results highlight the importance of local stream ecosystem management, e.g., the restoration and protection of stream banks, to protect against agriculture-driven biodiversity losses. However, we also found responses of selected taxa to catchment-scale land use, suggesting that localized management efforts may not suffice to maintain full stream ecosystem integrity and regional biodiversity. Our results also suggest that macroinvertebrates may allow a scale-specific assessment of stream ecosystem integrity and pressures by a scale-dependent bioindicatory approach.     

Scale-dependence of fish habitat associations in a North American river system

1. Determining the appropriate measurement scale to assess habitat variables is critical for ecologists assessing biological or ecological conditions. Depth, velocity, substrate, woody debris and other fish cover variables occur on both reach and microhabitat scales, and fish habitat associations with these variables may be scale-dependent. The aim of this work was to better understand the importance of scale for fish–habitat associations with these variables in a framework consistent with environmental filtering and to test the hypothesis that habitat variable importance is scale-dependent.
2. I used prepositioned areal electrofishing in wadeable streams of the Delaware River basin to evaluate the associations of fish with the same variables summarised on different reach and microhabitat scales. The importance of scale for fish–habitat associations was assessed using two approaches that approximate an environmental filtering framework: variance partitioning with (1) ordination and (2) generalised linear mixed models.
3. Variables on both the reach and microhabitat scales explained a significant fraction of the total variation in fish community composition (p < 0.05). Variation decomposition of reach- and microhabitat-scale effects revealed 20.2% and 2.0% of all variation were due uniquely to reach and microhabitat scales, respectively. Measures of coarseness, embeddedness, amount of riffle and areal coverage of five fish cover variables were significant explanatory variables of community composition at the reach scale only (p < 0.05). Velocity and mesohabitat (amount or presence of riffle) were the only two habitat features that were significant explanatory variables of fish community composition at both the reach and microhabitat scales (p < 0.05). Individual models of species occurrence revealed similar patterns as seen with analyses of community composition.
4. For many fishes, habitat features quantified at the reach scale were more explanatory than at the microhabitat scale. Longnose dace (Rhinichthys cataractae) were more dependent upon microhabitat variables than reach-scale variables, relative to other fishes. Mean velocity at the reach scale was the most important explanatory variable for explaining fish community composition and indicated support for the concept of environmental filtering at the reach and microhabitat scales.
5. Few studies of fish occurrence have incorporated a study design and analytical framework that approximates the hierarchical nature of habitat. This study identifies important scales and predictors, demonstrates the importance of a multiscale approach, and provides support for the environmental filtering concept at the reach and microhabitat scales. These findings will allow ecologists to better account for scale-dependent habitat associations and justify the use of fish habitat associations on reach and microhabitat scales for assessing biotic integrity, restoration and conservation of fishes.

     

Use of benthic macroinvertebrates to assess the biological status of Pampean streams in Argentina

Macro-invertebrate communities and environmental variables were assessed seasonally for two years in seven streams in North-Eastern of Buenos Aires province (Argentina) in order to analyse changes in their structure and composition in relation with the quality of the water. The study includes pristine streams and others affected by urban and industrial effluents with high conductivity, nitrates, nitrites, phosphates and low oxygen content. Organisms with well-known pollution tolerance were identified to assess biological water quality, using a new Biotic Index (IBPAMP: Biotic Index for PAMPean rivers and streams) in comparison with other existing biotic indices. The usefulness of principal component analysis (PCA) and correlation matrices were examined to evaluate the efficiency of the method to assess disturbances. In general IBPAMP did well correlate with several classical measures of biological water quality (taxon richness, diversity and several biotic indices). The El Gato stream was the most disturbed ecosystem among all studied sites. It was characterised by low dissolved oxygen levels, high turbidity in the middle course, high BOD5 (>30 mg l^–1) and COD (>40 mg l^–1) values. The Buñirigo stream has a bad quality in the industrial area, but varying according to the dry and wet periods. In general, in the mountainous areas the water quality of streams was good with the exception of the stations located downstream of cities like Ayacucho on the Tandileofú stream.     

Habitat associations of imperilled fishes after conservation intervention in the Cape Fold Ecoregion,South Africa

The aim of this study was to examine the habitat associations of a native cyprinid community of the recovering Rondegat River in the Cape Fold Ecoregion of South Africa as part of a long-term native fish abundance monitoring project. Relative abundance data were extracted from underwater video camera footage across the longitudinal gradient of the river in three sampling instances. Using multivariate methods the authors assessed community composition with respect to habitat, its overlap with a protected area and species-specific abiotic predictors of relative abundance. Distance from the uppermost site in the river was the most significant predictor of species abundance, indicating spatial segregation and varying overlap between species. The protected status of sites in the upper reaches, vegetated substrates and the size of individual sites were the most impactful on the relative abundance of the endangered fiery redfin Pseudobarbus phlegethon. The results of this study indicate that underwater video monitoring is an effective and low-cost approach that can inform conservation recommendations. Reducing agricultural runoff and sedimentation in the lower reaches may be useful further interventions to maintain key habitats of submerged vegetation.     

Dispersal of organisms in a patchy stream environment under different settlement scenarios

1.  Previous work in streams, where many organisms disperse downstream by drifting in the water column, has suggested dispersal distances could be related to the overall proportion of the stream within dead water zones (DWZ), places such as backwaters, pools or behind large obstacles, where the water is out of the main flow and is stored temporarily. However, dispersal distances might also be influenced by the spatial organization of DWZ within a reach; this would require us to distinguish between reaches containing many small DWZ compared with those having a few large ones in order to understand fully differences in dispersal patterns among reaches differing in this regard.
2.  We constructed a spatial model of flow in stream reaches, in which we varied the density and size distribution of DWZ distributed through the reach. We defined flow conditions under which stream organisms, modelled as passive particles, would settle or continue to drift downstream. We then examined the horizontal dispersal profiles of such particles through reaches differing in arrays of DWZ.
3.  Our results support those of previous studies, but suggest that the spatial arrangement of DWZ may be just as important as the overall proportion of DWZ within a reach. On a more general note, the importance of patch configuration observed in this study reflects the growing view that a thorough understanding of population and ecosystem processes will require the explicit consideration of spatial pattern in the environment.