SEARCH · Geology Reports

Results for “Ecology and Society”

Search indexed USGS publications on groundwater, aquifers, geologic maps, mineral resources and earthquakes. Explore source records by subject and place.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 289 records · Page 16Linked to original sources

USGS2022

Human populations in the world’s mountains: Spatio-temporal patterns and potential controls

Changing climate and human demographics in the world's mountains will have increasingly profound environmental and societal consequences across all elevations. Quantifying current human populations in and near mountains is crucial to ensure that any interventions in these complex social-ecological systems are appropriately resourced, and that valuable ecosystems are effectively protected. However, comprehensive and reproducible analyses on this subject are lacking. Here, we develop and implement an open workflow to quantify the sensitivity of mountain population estimates over recent decades, both globally and for several sets of relevant reporting regions, to alternative input dataset combinations. Relationships between mean population density and several potential environmental covariates are also explored across elevational bands within individual mountain regions (i.e. sub-mountain range scale). Globally, mountain population estimates vary greatly from 0.344 billion (<5% of the corresponding global total) to 2.289 billion (>31%) in 2015. A more detailed analysis using one of the population datasets (GHS-POP) revealed that in 35% of mountain sub-regions, population increased at least twofold over the 40-year period 19752015. The urban proportion of the total mountain population in 2015 ranged from 6% to 39%, depending on the combination of population and urban extent datasets used. At sub-mountain range scale, population density was found to be more strongly associated with climatic than with topographic and protected-area variables, and these relationships appear to have strengthened slightly over time. Such insights may contribute to improved predictions of future mountain population distributions under scenarios of future climatic and demographic change. Overall, our work emphasizes that irrespective of data choices, substantial human populations are likely to be directly affected by and themselves affect mountainous environmental and ecological change. It thereby further underlines the urgency with which the multitudinous challenges concerning the interactions between mountain climate and human societies under change must be tackled.

PLoS ONE↗

USGS2002

Rangeland health attributes and indicators for qualitative assessment

Panels of experts from the Society for Range Management and the National Research Council proposed that status of rangeland ecosystems could be ascertained by evaluating an ecological site's potential to conserve soil resources and by a series of indicators for ecosystem processes and site stability. Using these recommendations as a starting point, we developed a rapid, qualitative method for assessing a moment-in-time status of rangelands. Evaluators rate 17 indicators to assess 3 ecosystem attributes (soil and site stability, hydrologic function, and biotic integrity) for a given location. Indicators include rills, water flow patterns, pedestals and terracettes, bare ground, gullies, wind scour and depositional areas, litter movement, soil resistance to erosion, soil surface loss or degradation, plant composition relative to infiltration, soil compaction, plant functional/structural groups, plant mortality, litter amount, annual production, invasive plants, and reproductive capability. In this paper, we detail the development and evolution of the technique and introduce a modified ecological reference worksheet that documents the expected presence and amount of each indicator on the ecological site. In addition, we review the intended applications for this technique and clarify the differences between assessment and monitoring that lead us to recommend this technique be used for moment-in-time assessments and not be used for temporal monitoring of rangeland status. Lastly, we propose a mechanism for adapting and modifying this technique to reflect improvements in understanding of ecosystem processes. We support the need for quantitative measures for monitoring rangeland health and propose some measures that we believe may address some of the 17 indicators.

Journal of Range Management↗

USGS2020

Assessing the ecological risks of per‐ and polyfluoroalkyl substances: Current state‐of‐the science and a proposed path forward

Per‐ and poly‐fluoroalkyl substances (PFAS) encompass a large, heterogenous group of chemicals of potential concern to human health and the environment. Based on information for a few relatively well‐understood PFAS such as perfluorooctane sulfonate and perfluorooctanoate, there is ample basis to suspect that at least a subset can be considered persistent, bioaccumulative, and/or toxic. However, data suitable for determining risks in either prospective or retrospective assessments are lacking for the majority of PFAS. In August 2019, the Society of Environmental Toxicology and Chemistry sponsored a workshop that focused on the state‐of‐the‐science supporting risk assessment of PFAS. The present review summarizes discussions concerning the ecotoxicology and ecological risks of PFAS. First, we summarize currently available information relevant to problem formulation/prioritization, exposure, and hazard/effects of PFAS in the context of regulatory and ecological risk assessment activities from around the world. We then describe critical gaps and uncertainties relative to ecological risk assessments for PFAS and propose approaches to address these needs. Recommendations include the development of more comprehensive monitoring programs to support exposure assessment, an emphasis on research to support the formulation of predictive models for bioaccumulation, and the development of in silico, in vitro, and in vivo methods to efficiently assess biological effects for potentially sensitive species/endpoints. Addressing needs associated with assessing the ecological risk of PFAS will require cross‐disciplinary approaches that employ both conventional and new methods in an integrated, resource‐effective manner.

Environmental Toxicology and Chemistry↗

USGS2009

Effects of geolocation archival tags on reproduction and adult body mass of sooty shearwaters (Puffinus griseus)

We attached 11 g (1.4% body-mass equivalent) global location sensing (GLS) archival tag packages to tarsi of 25 breeding sooty shearwaters (Puffinus griseus, titi) on Whenua Hou (Codfish Island), New Zealand during the chick-rearing period in 2005. Compared with chicks reared by non-handled adults that did not carry tags, deployment of tags on one or both adult parents ultimately resulted in 35% reduction in chick body mass and significantly reduced chick skeletal size preceding fledging (19 April). However, body mass between chick groups was not significantly different after controlling for skeletal size. Effects on chicks were more pronounced in six pairs where both parents carried tags. Chick mass was negatively related to the duration that adults carried tags. In this study, none of the chicks reared by pairs where both parents were tagged, 54% of chicks reared by pairs where one parent was tagged, and 83% of chicks reared by non-handled and non-tagged parents achieved a previously determined pre-fledging mass threshold (564 g; Sagar & Horning 1998). Body mass of adults carrying tags and returning from transequatorial migration the following year were 4% lighter on average than non-tagged birds, but this difference was not statistically significant. Reduced mass among chicks reared by adults carrying tags during the chick-provisioning period indicated that adults altered "normal" provisioning behaviours to maintain their own body condition at the expense of their chicks. Population-level information derived from telemetry studies can reveal important habitat-linked behaviours, unique aspects of seabird foraging behaviours, and migration ecology. Information for some species (e.g., overlap with fisheries) can aid conservation and marine ecosystem management. We advise caution, however, when interpreting certain data related to adult provisioning behaviours (e.g., time spent foraging, provisioning rates, etc.). If effects on individuals are of concern, we suggest shorter-term deployments, smaller and lighter tags, and alternative attachment techniques, especially when investigating threatened or endangered species. ?? The Royal Society of New Zealand 2009.

New Zealand Journal of Ecology↗

USGS2007

Assessment of fecal pollution sources in a small northern-plains watershed using PCR and phylogenetic analyses of Bacteroidetes 16S rRNA gene

We evaluated the efficacy, sensitivity, host-specificity, and spatial/temporal dynamics of human- and ruminant-specific 16S rRNA gene Bacteroidetes markers used to assess the sources of fecal pollution in a fecally impacted watershed. Phylogenetic analyses of 1271 fecal and environmental 16S rRNA gene clones were also performed to study the diversity of Bacteroidetes in this watershed. The host-specific assays indicated that ruminant feces were present in 28-54% of the water samples and in all sampling seasons, with increasing frequency in downstream sites. The human-targeted assays indicated that only 3-5% of the water samples were positive for human fecal signals, although a higher percentage of human-associated signals (19-24%) were detected in sediment samples. Phylogenetic analysis indicated that 57% of all water clones clustered with yet-to-be-cultured Bacteroidetes species associated with sequences obtained from ruminant feces, further supporting the prevalence of ruminant contamination in this watershed. However, since several clusters contained sequences from multiple sources, future studies need to consider the potential cosmopolitan nature of these bacterial populations when assessing fecal pollution sources using Bacteroidetes markers. Moreover, additional data is needed in order to understand the distribution of Bacteroidetes host-specific markers and their relationship to water quality regulatory standards. ?? 2006 Federation of European Microbiological Societies.

FEMS Microbiology Ecology↗

USGS2022

A biological condition gradient for Caribbean coral reefs: Part II. Numeric rules using sessile benthic organisms

The Biological Condition Gradient (BCG) is a conceptual model used to describe incremental changes in biological condition along a gradient of increasing anthropogenic stress. As coral reefs collapse globally, scientists and managers are focused on how to sustain the crucial structure and functions, and the benefits that healthy coral reef ecosystems provide for many economies and societies. We developed a numeric (quantitative) BGC model for the coral reefs of Puerto Rico and the US Virgin Islands to transparently facilitate ecologically meaningful management decisions regarding these fragile resources. Here, reef conditions range from natural, undisturbed conditions to severely altered or degraded conditions. Numeric decision rules were developed by an expert panel for scleractinian corals and other benthic assemblages using multiple attributes to apply in shallow-water tropical fore reefs with depths <30 m. The numeric model employed decision rules based on metrics (e.g., % live coral cover, coral species richness, pollution-sensitive coral species, unproductive and sediment substrates, % cover by Orbicella spp.) used to assess coral reef condition. Model confirmation showed the numeric BCG model predicted the panel’s median site ratings for 84% of the sites used to calibrate the model and 89% of independent validation sites. The numeric BCG model is suitable for adaptive management applications and supports bioassessment and criteria development. It is a robust assessment tool that could be used to establish ecosystem condition that would aid resource managers in evaluating and communicating current or changing conditions, protect water and habitat quality in areas of high biological integrity, or develop restoration goals with stakeholders and other public beneficiaries.

Ecological Indicators↗

USGS1997

Status, ecology, and management of the invasive plant, Miconia calvescens DC (Melastomataceae) in the Hawaiian islands

Miconia calvescens (Melastomataceae), native to montane forests of the neotropics, has now invaded wet forests of both the Society and Hawaiian Islands. This tree, which grows up to 15 m tall, is potentially the most invasive and damaging weed of rainforests of Pacific islands. In moist conditions, it grows rapidly, tolerates shade, and produces abundant seed that is effectively dispersed by birds and accumulates in a large, persistent soil seed-bank. Introduced to the Hawaiian Islands in 1961, M. calvescens appears to threaten much of the biological diversity in native forests receiving 1800–2000 mm or more annual precipitation. Currently, M. calvescens is found on 4 Hawaiian islands— Hawaii, Maui, Oahu, and Kauai. Widespread awareness of this invader began in the early 1990s. Although biological control is being pursued, conventional control techniques (mechanical and chemical) to contain and eradicate it locally are underway.

Hawaii↗

USGS2009

Bat Rabies and Other Lyssavirus Infections

Bat Rabies and Other Lyssavirus Infections offers readers an overview of the virus variants that cause bat rabies, and geographical patterns in occurrence of this disease. The section Species Susceptibility describes infection rates and trends among bats, humans, and other animals. Disease Ecology considers the biological and environmental dynamics of the disease in various species of bats. Points to Ponder: Interspecies Interactions in Potential Bat Rabies Transmission Settings discusses the narrowing interface of bat colonies and human society and how humans and domestic animals play a role in transmission of bat rabies. Disease Prevention and Control outlines how to limit exposure to rabid bats and other animals. Appendixes include extensive tables of reported infections in bat species and in humans, and a glossary of technical terms is included. The author, Denny G. Constantine, helped define rabies infection in insect-eating bats and has investigated bat rabies ecology for more than half a century. He has authored more than 90 papers during the course of his career and is widely considered to be the world's foremost authority on the disease. Currently, Dr. Constantine is a public health officer emeritus and veterinary epidemiologist for the California Department of Health Services Viral and Rickettsial Disease Laboratory. Milt Friend, first director of the USGS National Wildlife Health Center, wrote the foreword. David Blehert, a USGS microbiologist who is investigating the emergence and causes of bat white-nose syndrome, edited the volume. Bat Rabies is intended for scholars and the general public. Dr. Constantine presents the material in a simple, straightforward manner that serves both audiences. The goal of the author is to increase people's understanding of both bat and disease ecology and also provide a balanced perspective on human risks pertaining to bat rabies.

Circular↗

USGS2022

Grassland conservation supports migratory birds and produces economic benefits for the commercial beekeeping industry in the U.S. Great Plains

Although declines in grassland birds have been documented, national initiatives to conserve grasslands and their biota have fallen short in part because the non-market values of natural ecosystems and species are often not recognized in political decision making. Identifying shared, anthropogenic threats faced by market-valued and non-market-valued species may generate additional support for grassland conservation. We quantify the relationship between the market value of grasslands to commercial beekeepers and the importance of grasslands for birds of conservation concern in North and South Dakota. Our models estimated beekeeping annual revenue increased by $7525 USD and grassland bird abundances increased 2 to 7% per 10-km 2 increase in grassland area. We estimated grassland conversion from 2006 to 2012 resulted in a $2.0 to $2.8 M USD decrease in annual revenue for beekeepers in the Dakotas. Through this study we demonstrate both the market value of grasslands to commercial beekeepers and the non-market benefits of grasslands in supporting migratory birds and discuss the implications of future land-use change. As grassland conversion and subsequent biodiversity loss continue, understanding the co-benefits of grassland conservation may be necessary to illuminate their contributions to society.

North Dakota, South Dakota↗

USGS2004

Geochemical control of microbial Fe(III) reduction potential in wetlands: Comparison of the rhizosphere to non-rhizosphere soil

We compared the reactivity and microbial reduction potential of Fe(III) minerals in the rhizosphere and non-rhizosphere soil to test the hypothesis that rapid Fe(III) reduction rates in wetland soils are explained by rhizosphere processes. The rhizosphere was defined as the area immediately adjacent to a root encrusted with Fe(III)-oxides or Fe plaque, and non-rhizosphere soil was 0.5 cm from the root surface. The rhizosphere had a significantly higher percentage of poorly crystalline Fe (66??7%) than non-rhizosphere soil (23??7%); conversely, non-rhizosphere soil had a significantly higher proportion of crystalline Fe (50??7%) than the rhizosphere (18??7%, P<0.05 in all cases). The percentage of poorly crystalline Fe(III) was significantly correlated with the percentage of FeRB (r=0.76), reflecting the fact that poorly crystalline Fe(III) minerals are labile with respect to microbial reduction. Abiotic reductive dissolution consumed about 75% of the rhizosphere Fe(III)-oxide pool in 4 h compared to 23% of the soil Fe(III)-oxide pool. Similarly, microbial reduction consumed 75-80% of the rhizosphere pool in 10 days compared to 30-40% of the non-rhizosphere soil pool. Differences between the two pools persisted when samples were amended with an electron-shuttling compound (AQDS), an Fe(III)-reducing bacterium (Geobacter metallireducens), and organic carbon. Thus, Fe(III)-oxide mineralogy contributed strongly to differences in the Fe(III) reduction potential of the two pools. Higher amounts of poorly crystalline Fe(III) and possibly humic substances, and a higher Fe(III) reduction potential in the rhizosphere compared to the non-rhizosphere soil, suggested the rhizosphere is a site of unusually active microbial Fe cycling. The results were consistent with previous speculation that rapid Fe cycling in wetlands is due to the activity of wetland plant roots. ?? 2004 Federation of European Microbiological Societies. Published by Elsevier B.V. All rights reserved.

FEMS Microbiology Ecology↗

USGS2013

The quality of our Nation’s waters--Ecological health in the Nation's streams, 1993-2005

This report summarizes a national assessment of the ecological health of streams done by the U.S. Geological Survey's (USGS) National Water-Quality Assessment Program (NAWQA). Healthy functioning stream ecosystems provide society with many benefits, including water purification, flood control, nutrient recycling, waste decomposition, fisheries, and aesthetics. The value to society of many of these benefits is substantial; for example, sportfishing in the United States generates an estimated annual economic output of $125 billion, including more than 1 million jobs (National Research Council, 2005; American Sportfishing Association, 2008). Continued monitoring and assessment of the Nation’s streams is needed to support informed decisions that will safeguard this important natural and economic resource. The quality of streams and rivers is often assessed with measures of the chemical or physical properties of water. However, a more comprehensive perspective is obtained if resident biological communities are also assessed. Guidelines to protect human health and aquatic life have been established for specific physical and chemical properties of water and have become useful yardsticks with which to assess water quality. Biological communities provide additional crucial information because they live within streams for weeks to years and therefore integrate through time the effects of changes to their chemical or physical environment. In addition, biological communities are a direct measure of stream health—an indicator of the ability of a stream to support aquatic life. Thus, the condition of biological communities, integrated with key physical and chemical properties, provides a comprehensive assessment of stream health.

conterminous United States↗

USGS2002

A model project for exploring the role of sustainability science in a citizen-centered, collaborative decision-making process

The role of science in society is evolving as we enter the 21st century. The report, Science — The Endless Frontier (Bush 1990[1945]), outlined a model of national scientific research that served the country for 50 years. The contract between science and society established in that report stipulated that science is essential and that basic research meets national needs (Pielke and Byerly 1998). This stipulation and the abundant — seemingly unlimited and unquestioned — funding for research during the Cold War caused many scientists to come to believe that funding for science was an entitlement independent of societal needs. Implicit in this belief is that science alone can solve society’s problems. We now are learning that many policy issues that involve science involve diverse economic, political, social, and aesthetic values as well, and rarely, if ever, is scientific information alone the basis of public policy (e.g., see Sarewitz 1996a, 1996b; Frodeman 1997). Moreover, resources are increasingly more limited and many in society are questioning the value of public-supported science.

Human Ecology Review↗

USGS2018

Ecosystem service flows from a migratory species: Spatial subsidies of the northern pintail

Migratory species provide important benefits to society, but their cross-border conservation poses serious challenges. By quantifying the economic value of ecosystem services (ESs) provided across a species’ range and ecological data on a species’ habitat dependence, we estimate spatial subsidies —how different regions support ESs provided by a species across its range. We illustrate this method for migratory northern pintail ducks in North America. Pintails support over \$101 million USD annually in recreational hunting and viewing and subsistence hunting in the U.S. and Canada. Pintail breeding regions provide nearly \$30 million in subsidies to wintering regions, with the “Prairie Pothole” region supplying over \$24 million in annual benefits to other regions. This information can be used to inform conservation funding allocation among migratory regions and nations on which the pintail depends. We thus illustrate a transferrable method to quantify migratory species-derived ESs and provide information to aid in their transboundary conservation.

Ambio↗

USGS2020

Influence of niche breadth and position on the historical biogeography of seafaring scincid lizards

Niche breadth and position can influence diversification among closely related species or populations, yet limited empirical data exist concerning the predictability of the outcomes. We explored the effects of these factors on the evolution of the Emoia atrocostata species group, an insular radiation of lizards in the western Pacific Ocean and Indo-Australasia composed of both endemic and widespread species that differ in niche occupancy. We used molecular data and phylogeographical diffusion models to estimate the timing and patterns of range expansion, and ancestral reconstruction methods to infer shifts in ecology. We show evidence of multidirectional spread from a centre of origin in western Micronesia, and that the phyletic diversity of the group is derived from a putative habitat specialist that survives in the littoral zone. This species is composed of paraphyletic lineages that represent stages or possible endpoints in the continuum toward speciation. Several descendant species have transitioned to either strand or interior forest habitat, but only on remote islands with depauperate terrestrial faunas. Our results suggest that the atrocostata group might be in the early phases of a Wilsonian taxon cycle and that the capacity to tolerate salt stress has promoted dispersal and colonization of remote oceanic islands. Divergence itself, however, is largely driven by geographical isolation rather than shifts in ecology.

Biological Journal of the Linnean Society↗

USGS2021

Coastal Tree-Ring Records for Paleoclimate and Paleoenvironmental Applications in North America

For more than a century, tree-ring research has identified relationships between climatic and ecological conditions and tree growth to describe past environments and constrain future ecosystem vulnerabilities. Tree-ring records are frequently used as environmental proxies that extend knowledge of past climate and ecology on millennial scales. Many of the most pressing global change questions facing North America concern the rate of climate change and vulnerability of ecosystems and society along the coast. The opportunities and applications in dendrochronology continue to grow with advancing methodologies, faster computational ability, and the cost-reduction of many chemical and anatomical analyses. Here, we propose that many pressing global change questions that affect coastal communities can be addressed using dendrochronological techniques. We review coastal tree-ring studies that demonstrate the utility and potential for future tree-ring studies in the northeastern, southeastern, northwestern, and southwestern North American coasts. Additionally, we show that tree-ring chronologies along the coast give insight into local and regional climate phenomena that are distinct from nearby, inland tree-ring chronologies of the same species. Lastly, we identify opportunities for coastal dendrochronology and encourage the collection of more tree-ring records that are directly impacted by coastal phenomena.

Quaternary Science Reviews↗

USGS2022

Causes, responses, and implications of anthropogenic versus natural flow intermittence in river networks

Rivers that do not flow year-round are the predominant type of running waters on Earth. Despite a burgeoning literature on natural flow intermittence (NFI), knowledge about the hydrological causes and ecological effects of human-induced, anthropogenic flow intermittence (AFI) remains limited. NFI and AFI could generate contrasting hydrological and biological responses in rivers because of distinct underlying causes of drying and evolutionary adaptations of their biota. We first review the causes of AFI and show how different anthropogenic drivers alter the timing, frequency and duration of drying, compared with NFI. Second, we evaluate the possible differences in biodiversity responses, ecological functions, and ecosystem services between NFI and AFI. Last, we outline knowledge gaps and management needs related to AFI. Because of the distinct hydrologic characteristics and ecological impacts of AFI, ignoring the distinction between NFI and AFI could undermine management of intermittent rivers and ephemeral streams and exacerbate risks to the ecosystems and societies downstream.

BioScience↗

USGS2011

USDA conservation program and practice effects on wetland ecosystem services in the Prairie Pothole Region

Implementation of the U.S. Department of Agriculture (USDA) Conservation Reserve Program (CRP) and Wetlands Reserve Program (WRP) has resulted in the restoration of >2 million ha of wetland and grassland habitats in the Prairie Pothole Region (PPR). Restoration of habitats through these programs provides diverse ecosystem services to society, but few investigators have evaluated the environmental benefits achieved by these programs. We describe changes in wetland processes, functions, and ecosystem services that occur when wetlands and adjacent uplands on agricultural lands are restored through Farm Bill conservation programs. At the scale of wetland catchments, projects have had positive impacts on water storage, reduction in sedimentation and nutrient loading, plant biodiversity, carbon sequestration, and wildlife habitat. However, lack of information on the geographic location of restored catchments relative to landscape‐level factors (e.g., watershed, proximity to rivers and lakes) limits interpretation of ecosystem services that operate at multiple scales such as floodwater retention, water quality improvement, and wildlife habitat suitability. Considerable opportunity exists for the USDA to incorporate important landscape factors to better target conservation practices and programs to optimize diverse ecosystem services. Restoration of hydrologic processes within wetlands (e.g., hydroperiod, water level dynamics) also requires a better understanding of the influence of conservation cover composition and structure, and management practices that occur in uplands surrounding wetlands. Although conservation programs have enhanced delivery of ecosystem services in the PPR, the use of programs to provide long‐term critical ecosystem services is uncertain because when contracts (especially CRP) expire, economic incentives may favor conversion of land to crop production, rather than reenrollment. As demands for agricultural products (food, fiber, biofuel) increase, Farm Bill conservation programs will become increasingly important to ensure provisioning of ecosystem services to society, especially in agriculturally dominated landscapes. Thus, continued development and support for conservation programs legislated through the Farm Bill will require a more comprehensive understanding of wetland ecological services to better evaluate program achievements relative to conservation goals.

Ecological Applications↗

USGS2005

Aquatic assemblages of the highly urbanized Santa Ana River Basin, California

We assessed the structure of periphyton, benthic macroinvertebrate, and fish assemblages and their associations with environmental variables at 17 sites on streams of the highly urbanized Santa Ana River basin in Southern California. All assemblages exhibited strong differences between highly urbanized sites in the valley and the least-impacted sites at the transition between the valley and undeveloped mountains. Results within the urbanized area differed among taxa. Periphyton assemblages were dominated by diatoms (>75% of total taxa). Periphyton assemblages within the urbanized area were not associated with any of the measured environmental variables, suggesting that structure of urban periphyton assemblages might be highly dependent on colonization dynamics. The number of Ephemeroptera, Trichoptera, and Plecoptera (EPT) taxa included in macroinvertebrate assemblages ranged from 0 to 6 at urbanized sites. Benthic macroinvertebrate assemblages had significant correlations with several environmental variables within the urban area, suggesting that stream size and permanence were important determinants of distribution among the species able to survive conditions in urban streams. Only 4 of 16 fish species collected were native to the drainage. Fish assemblages of urbanized sites included two native species, arroyo chub Gila orcuttii and Santa Ana sucker Catostomus santaanae, at sites that were intermediate in coefficient of variation of bank-full width, depth, bed substrate, and water temperature. Alien species dominated urbanized sites with lesser or greater values for these variables. These results suggest that urban streams can be structured to enhance populations of native fishes. Continued study of urban streams in the Santa Ana River basin and elsewhere will contribute to the basic understanding of ecological principles and help preserve the maximum ecological value of streams in highly urbanized areas.

American Fisheries Society Symposium↗