Declines in populations of Pacific salmon Oncorhynchus spp. in the Pacific Northwest have led to listings under the Endangered Species Act. One objective of current recovery efforts is the restoration of freshwater and estuarine habitats, which had been occurring prior to Endangered Species Act listing but increased dramatically afterwards. However, few listed populations are improving. We believe that there are five factors contributing to the lack of population response to habitat restoration: Not enough restoration has been done. We are not doing the right things in the right places at the right times. Ongoing habitat degradation is offsetting restoration benefits. Not enough time has passed. Monitoring has been inadequate to detect changes in Pacific salmon abundance.All factors contribute to the disappointing progress on Pacific salmon recovery, although their importance varies. Two factors are more consistently significant than the others. Resources available to address habitat damage remain insufficient. The scale of the problem is large, so the response needs to be correspondingly large to yield desired outcomes. Of equal significance is the failure of restoration programs to identify elements controlling fish production. Implementing the right projects in the right places is key to improving the outcomes of restoration.

Urban streams can provide amenities to people living in cities, but those benefits are reduced when streams become degraded, potentially even causing harm (disease, toxic compounds, etc.). Governments and institutions invest resources to improve the values and services provided by urban streams; however, the conception, development, and implementation of such projects may not include meaningful involvement of community members and other stakeholders. Consequently, project objectives may be misaligned with community desires and needs, and projects may fail to achieve their goals. In February 2020, the 5th Symposium on Urbanization and Stream Ecology, an interdisciplinary meeting held every 3 to 5 y, met in Austin, Texas, USA, to explore new approaches to urban stream projects, including ways to maximize the full range of potential benefits by better integrating community members into project identification and decision making. The symposium included in-depth discussion about 4 nearby field case studies, participation of multidisciplinary urban stream experts from 5 continents, and input from the Austin community. Institutional barriers to community inclusion were identified and analyzed using real-world examples, both from the case studies and from the literature, which clarified disparities in power, equity, and values. Outcomes of the symposium have been aggregated into a vision that challenges the present institutional approach to urban stream management and a set of strategies to systematically address these barriers to improve restoration solutions. Integrating community members and other stakeholders throughout the urban restoration process, and a transparent decision-making process to resolve divergent objectives, can help identify appropriate goals for realizing both the ecological and social benefits of stream restoration.

High-elevation alluvial river environments are little studied by geomorphologists despite their sensitivity to disturbance and their critical role as the landform supporting montane meadow ecosystems. Here, we establish the fundamental fluvial functioning and legacy factors inherent to the upper Tuolumne River in Tuolumne Meadows (elevation 2620 m asl), Yosemite National Park, USA. Evidence was drawn from structured field reconnaissance, morphological surveys, and sediment analysis; integrated with LiDAR monitoring and assess-ments of flood frequency, flood inundation, and sediment transport potential. Results indicate a sinuous single-thread channel in dynamic equilibrium with fluvial processes but with reduced rates of meander activity over the past century. Geomorphic processes are dominated by the influence of snowmelt discharge, partly because at-mospheric river events rarely influence this high elevation. Process intensity is thus directly related to snowpack depth with monitored bank erosion rates substantially higher following the deep snowpack of 2016-17. Diurnal cycling of flow means that bedload-transport potential scales very well with total annual discharge volume. The legacy of human activity is unique here, with perturbations caused primarily by early-to-mid twentieth century infrastructure development rather than typical patterns of watershed development. Pre-eminent was 1930s instream aggregate extraction for road improvements. In conjunction with naturally very low rates of sediment supply, the resulting pit is still only one-quarter full and could disconnect downstream sediment supplies for several centuries more. The gravel pit appears to explain incision of the upper channel reach and reduced rates of lateral activity farther downstream. Future impacts will be dominated by climate change, including the potential increased influence of atmospheric river events, reduced snowpack depth, and tradeoffs in sediment production and connectivity as headwater glaciers recede. The upper Tuolumne River and its meadow typify the unusual, but not singular, geomorphology of high-elevation alluvial rivers, whose high ecological and social values justify greater attention.

Urban rivers and streams, collectively 'urban watercourses', play a unique role in the ecology of urban environments. This chapter focuses on free-flowing urban rivers and streams and, in particular, the hydrological regime that determines much of their attributes and behavior. Recent research and practice have addressed both of these broad settings, which for convenience are distinguished here as 'urban streams' and 'urban rivers'. Nearly all of the impairments described in urban streams, except those that physically alter the channel itself, result from one underlying cause: loss of the water-retaining function of the soil and vegetation in the urban landscape. Despite the obvious consequences for natural channel form and biotic communities that result from putting small streams into large pipes, the most widespread and pervasive impacts to urban streams arise from the indirect effects of urban stormwater runoff. In urban streams these are normally expressed as instantaneous measurements of concentration, with threshold values intended to highlight particularly problematic levels.

Core Vema 28-238 preserves an excellent oxygen isotope and magnetic stratigraphy and is shown to contain undisturbed sediments deposited continuously through the past 870,000 yr. Detailed correlation with sequences described by Emiliani in the Caribbean and Atlantic Ocean is demonstrated. The boundaries of 22 stages representing alternating times of high and low Northern Hemisphere ice volume are recognized and dated. The record is interpreted in terms of Northern Hemisphere ice accumulation, and is used to estimate the range of temperature variation in the Caribbean. Oxygen isotopic composition of G. sacculijera in core X28-238 complete record to 1600 cm, expressed as deviation so from Emiliani Bl standard. Denton, G.H., Karlén, W. 1973. Holocene climatic variations–Their pattern and possible cause. Quaternary Research 3, 155–205. Cited 580 times. ABSTRACT In the northeastern St. Elias Mountains in southern Yukon Territory and Alaska, C-dated fluctuations of 14 glacier termini show two major intervals ofHolocene glacier expansion, the older dating from3300–2400 calendar yrBPand theyounger corresponding to theLittle IceAge of the last several centuries. Both were about equivalent in magnitude. In addition, a less-extensive and short-lived advance occurred about 1250–1050 calendar yr BP (A.D. 700–900). Conversely, glacier recession, commonly accompanied by rise in altitude of spruce tree line, occurred 5975–6175, 4030–3300, 2400–1250, and 1050–460 calendar yr BP, and fromA.D. 1920 to the present. Examination of worldwide Holocene glacier fluctuations reinforces this scheme and points to a thirdmajor interval of glacier advances about 5800–4900 calendar yr BP; this interval generallywas less intense than the two younger major intervals. Finally, detailed mapping and dating of Holocene moraines fronting 40 glaciers in the Kebnekaise and Sarek Mountains inSwedishLapland reveals again that theHolocenewaspunctuatedby repeated intervalsofglacierexpansion that correspond to those found in the St. EliasMountains and elsewhere. The twoyoungest intervals,whichoccurred during theLittle IceAge and again about 2300–3000 calendar yr BP, were approximately equal in intensity. Advances of the two older intervals, which occurred approximately 5000 and 8000 calendar yr BP, were generally less extensive. Minor glacier fluctuations were superimposed on all four broad expansion intervals; those of the Little Ice Age culminatedIn the northeastern St. Elias Mountains in southern Yukon Territory and Alaska, C-dated fluctuations of 14 glacier termini show two major intervals ofHolocene glacier expansion, the older dating from3300–2400 calendar yrBPand theyounger corresponding to theLittle IceAge of the last several centuries. Both were about equivalent in magnitude. In addition, a less-extensive and short-lived advance occurred about 1250–1050 calendar yr BP (A.D. 700–900). Conversely, glacier recession, commonly accompanied by rise in altitude of spruce tree line, occurred 5975–6175, 4030–3300, 2400–1250, and 1050–460 calendar yr BP, and fromA.D. 1920 to the present. Examination of worldwide Holocene glacier fluctuations reinforces this scheme and points to a thirdmajor interval of glacier advances about 5800–4900 calendar yr BP; this interval generallywas less intense than the two younger major intervals. Finally, detailed mapping and dating of Holocene moraines fronting 40 glaciers in the Kebnekaise and Sarek Mountains inSwedishLapland reveals again that theHolocenewaspunctuatedby repeated intervalsofglacierexpansion that correspond to those found in the St. EliasMountains and elsewhere. The twoyoungest intervals,whichoccurred during theLittle IceAge and again about 2300–3000 calendar yr BP, were approximately equal in intensity. Advances of the two older intervals, which occurred approximately 5000 and 8000 calendar yr BP, were generally less extensive. Minor glacier fluctuations were superimposed on all four broad expansion intervals; those of the Little Ice Age culminated aboutA.D. 1500–1640, 1710, 1780, 1850, 1890, and 1916. In themountains of SwedishLapland,Holocenemean summer temperature rarely, if ever, was lower than 1°C below the 1931–1960 summermean and varied by less than 3.5°Cover the last two broad intervals of Holocene glacial expansion and contraction. Viewed as awhole, therefore, the Holocene experienced alternating intervals of glacier expansion and contraction that probably were superimposed on the broad climatic trends recognized in pollen profiles and deep-sea cores. Expansion intervals lasted up to 900 yr and contraction intervals up to 1750 yr. Dates of glacial maxima indicate that the major Holocene intervals of expansion peaked at about 200–330, 2800, and 5300 calendar yr BP, suggesting a recurrence of major glacier activity about each 2500 yr. If projected further into the past, this Holocene pattern predicts that alternatingglacierexpansion-contraction intervals shouldhavebeen superimposedon theLate-Wisconsinglaciation,withglacier readvancespeaking about 7800, 10,300, 12,800, and15,300calendar yrBP.Thesemajor readvances shouldhavebeen separatedby intervals ofgeneral recession, some of which might have been punctuated by short-lived advances. Furthermore, the time scales of Holocene events and their Late-Wisconsin analogues should be comparable. Considering possible errors in C dating, this extended Holocene scheme agrees reasonably well with the chronology and magnitude of such Late-Wisconsin events as the Cochrane-Cockburn readvance (8000–8200 C yr BP), the Pre-Boreal interstadial, the Fennoscandian readvances during the Younger Dryas stadial (10,850–10,050 varve yr BP), the Alleröd interstadial (11,800–10,900 C yr BP), the Port Huron readvance (12,700–13,000C yrBP), theCary/PortHuron interstadial (centered about 13,300C yrBP), and theCarystadial (14,000–15,000C yr BP). Moreover, comparison of presumed analogues such as the Little Ice Age and the Younger Dryas, or the Alleröd and the Roman Empire-Middle 2 D. B. Booth et al.

Quaternary Research is an international journal devoted to the advancement of the interdisciplinary understanding of the Quaternary Period.We aim to publish articles of broad interest with relevance to more than one discipline,

Successful river restoration requires understanding and integration of multiple disciplinary perspectives, including evaluations of past and ongoing watershed processes, local geomorphic response, and impacts unique to human activity. Nowhere is this more apparent than along the Merced River in Yosemite National Park, USA, where both an outstanding natural landscape and the consequences of over a century of human disturbances continue to interact. An intact upstream watershed highlights the importance here of local impacts on geomorphic response. Incision and the resulting decoupling of the channel from its adjacent late-Holocene floodplain are consequences of reduced channel roughness, likely from de-snagging the river, and instream gravel mining in the 19th and early 20th century. Riparian-zone disturbance by visitor use has damaged riparian vegetation and soils, inducing channel widening. Revetments and channel-spanning bridges, the latter being visible and oft-cited impacts to fluvial processes, have distorted the natural evolution of meanders and induced local channel narrowing. The historical rate of sediment export from Yosemite Valley has greatly exceeded replenishment from upstream and lateral sources, creating a deficit that now inhibits recovery via passive restoration of more natural channel form and function. Climate change may amplify now-diminished fluvial processes but also exacerbate the rate of sediment export. These conditions, reflecting a complex intersection of geologic history, modern geomorphic processes, and human interactions, demonstrate how a limited influx of sediment coupled with intensive human use can have long-term consequences for riverine conditions, restoration opportunities, and social engagement with the riverine landscape.

Cover photo.Despite a magnitude 6.9 earthquake (2015-07-27, 04:49:46 UTC) ~50 km south-southeast of the Islands of Four Mountains, the steam plume never wavered from the summit of Mt.Cleveland volcano (center).The scanty steaming of fumaroles within the summit caldera of Herbert volcano (left) testifies to its recent dormancy.Distant Carlisle Island is visible beyond the isthmus of Chuginadak Island that separates Cleveland from the slopes of larger Tana volcano (foreground).Later that night and for the next several days, the team of archaeologists, paleoecologists, and geologists felt aftershocks as they pursued the first characterization of this region of the Aleutian archipelago.Photo by K. Nicolaysen.

Cover photo.Aeolian Quaternary loess and Late Miocene-Pliocene Red Clay at Shilou section on the eastern Chinese Loess Plateau, North China.The climate and environment of the Shilou area are dominated by seasonal reversal of Asian winter monsoon (AWM) and Asian summer monsoon (ASM) circulations, with a mean annual temperature of ~9°C and mean annual precipitation

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Cover photo.Glacial activity in Andean Peru associated with the last ice age formed many lakes, such as Laguna Las Quinuas, which lies at 3467 m elevation in an east-facing valley that receives >3000 mm of Amazonian precipitation each year.Lakes lying at the lowest limit of glacial activity were targeted by Paul Colinvaux in South America and in Africa by Dan Livingstone, as they offered greater palynological sensitivity to climate change than lakes further upslope.Below the lower limit of moraines, ancient lakes are very rare, and especially prized by paleoecologists.During their careers Dan and Paul worked on a number of these rare lowland lakes.

Local governmental agencies are increasingly undertaking potentially costly “status‐and‐trends” monitoring to evaluate the effectiveness of stormwater control measures and land‐use planning strategies or to satisfy regulatory requirements. Little guidance is presently available for such efforts, and so we have explored the application, interpretation, and temporal limitations of well‐established hydrologic metrics of runoff changes from urbanization, making use of an unusually long‐duration, high‐quality data set from the Pacific Northwest (USA) with direct applicability to urban and urbanizing watersheds. Three metrics previously identified for their utility in identifying hydrologic conditions with biological importance that respond to watershed urbanization—T Qmean (the fraction of time that flows exceed the mean annual discharge), the Richards‐Baker Index (characterizing flashiness relative to the mean discharge), and the annual tally of wet‐season day‐to‐day flow reversals (the total number of days that reverse the prior days' increasing or decreasing trend)—are all successful in stratifying watersheds across a range of urbanization, as measured by total contributing area of urban development. All metrics respond with statistical significance to multidecadal trends in urbanization, but none detect trends in watershed‐scale urbanization over the course of a single decade. This suggests a minimum period over which dependable trends in hydrologic alteration (or improvement) can be detected with confidence. The metrics also prove less well suited to urbanizing watersheds in a semi‐arid climate, with only flow reversals showing a response consistent with prior findings from more humid regions. We also explore the use of stage as a surrogate for discharge in calculating these metrics, recognizing potentially significant agency cost savings in data collection with minimal loss of information. This approach is feasible but cannot be implemented under current data‐reporting practices, requiring measurement of water‐depth values and preservation of the full precision of the original recorded data. With these caveats, however, hydrologic metrics based on stage should prove as or more useful, at least in the context of status‐and‐trends monitoring, as those based on subsequent calculations of discharge.

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Cover photo.View of a sand ramp exposed in the Leh valley of Ladakh Himalaya.This and many such others are composed of alternating units of aeolian sand

Urban streams commonly express degraded physical, chemical, and biological conditions that have been collectively termed the "urban stream syndrome". The description of the syndrome highlights the broad similarities among these streams relative to their less-impaired counterparts. Awareness of these commonalities has fostered rapid improvements in the management of urban stormwater for the protection of downstream watercourses, but the focus on the similarities among urban streams has obscured meaningful differences among them. Key drivers of stream responses to urbanization can vary greatly among climatological and physiographic regions of the globe, and the differences can be manifested in individual stream channels even through the homogenizing veneer of urban development. We provide examples of differences in natural hydrologic and geologic settings (within similar regions) that can result in different mechanisms of stream ecosystem response to urbanization and, as such, should lead to different management approaches. The idea that all urban streams can be cured using the same treatment is simplistic, but overemphasizing the tremendous differences among natural (or human-altered) systems also can paralyze management. Thoughtful integration of work that recognizes the commonalities of the urban stream syndrome across the globe has benefitted urban stream management. Now we call for a more nuanced understanding of the regional, subregional, and local attributes of any given urban stream and its watershed to advance the physical, chemical, and ecological recovery of these systems.

Urban stormwater runoff is a critical source of degradation to stream ecosystems globally. Despite broad appreciation by stream ecologists of negative effects of stormwater runoff, stormwater management objectives still typically center on flood and pollution mitigation without an explicit focus on altered hydrology. Resulting management approaches are unlikely to protect the ecological structure and function of streams adequately. We present critical elements of stormwater management necessary for protecting stream ecosystems through 5 principles intended to be broadly applicable to all urban landscapes that drain to a receiving stream: 1) the ecosystems to be protected and a target ecological state should be explicitly identified; 2) the postdevelopment balance of evapotranspiration, stream flow, and infiltration should mimic the predevelopment balance, which typically requires keeping significant runoff volume from reaching the stream; 3) stormwater control measures (SCMs) should deliver flow regimes that mimic the predevelopment regime in quality and quantity; 4) SCMs should have capacity to store rain events for all storms that would not have produced widespread surface runoff in a predevelopment state, thereby avoiding increased frequency of disturbance to biota; and 5) SCMs should be applied to all impervious surfaces in the catchment of the target stream. These principles present a range of technical and social challenges. Existing infrastructural, institutional, or governance contexts often prevent application of the principles to the degree necessary to achieve effective protection or restoration, but significant potential exists for multiple co-benefits from SCM technologies (e.g., water supply and climate-change adaptation) that may remove barriers to implementation. Our set of ideal principles for stream protection is intended as a guide for innovators who seek to develop new approaches to stormwater management rather than accept seemingly insurmountable historical constraints, which guarantee future, ongoing degradation.