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At least 721 records · Page 40Linked to original sources
USGS2014

Assessment of floodplain vulnerability during extreme Mississippi River flood 2011

Regional change in the variability and magnitude of flooding could be a major consequence of future global climate change. Extreme floods have the capacity to rapidly transform landscapes and expose landscape vulnerabilities through highly variable spatial patterns of inundation, erosion, and deposition. We use the historic activation of the Birds Point-New Madrid Floodway during the Mississippi and Ohio River Flooding of 2011 as a scientifically unique stress experiment to analyze indicators of floodplain vulnerability. We use pre- and postflood airborne Light Detection and Ranging data sets to locate erosional and depositional hotspots over the 540 km 2 agricultural Floodway. While riparian vegetation between the river and the main levee breach likely prevented widespread deposition, localized scour and deposition occurred near the levee breaches. Eroded gullies nearly 1 km in length were observed at a low ridge of a relict meander scar of the Mississippi River. Our flow modeling and spatial mapping analysis attributes this vulnerability to a combination of erodible soils, flow acceleration associated with legacy fluvial landforms, and a lack of woody vegetation to anchor soil and enhance flow resistance. Results from this study could guide future mitigation and adaptation measures in cases of extreme flooding.

Cairo, Illinois↗
USGS2022

Higher temperature sensitivity of flowering than leaf-out alters the time between phenophases across temperate tree species

Aim The aims of this study were to evaluate the changes in the length of the time period between leaf-out and flowering across temperate tree species, and associate these changes with potential physiological and environmental drivers to enhance mechanistic insight into these phenomena. Location Central Europe. Time period 1980–2016. Major taxa studied Six temperate woody species. Methods Statistical analyses were carried out based on long-term ground observations of both spring leaf-out and flowering across temperate tree species during 1980–2016, a period characterized by rapid warming. Results The temperature sensitivity of flowering (−5.4 ± 0.04 days/℃, mean ± SE ) was higher than that of leaf-out (−4.6 ± 0.04 days/℃) across all species, regardless of whether leaf-out occurred before or after flowering. This study postulates a hypothesis attributing the different temperature sensitivities to different thermal sensitivities, thermal requirements, and photoperiodic controls. Main conclusions The larger temperature sensitivity of flowering than leaf-out resulted in an extended time period between flowering and leaf-out in species that bloom before leafing out, but a shorter time period between these phenophases in species with the opposite strategy. We would like to emphasize the importance of changes in time period between different phenophases, and we recommend conducting experimental research to reveal the underlying mechanisms of plant phenology response to climate change, and to explore its potential ecological implications.

Global Ecology and Biogeography↗
USGS2024

Evidence on the ecological and physical effects of built structures in shallow, tropical coral reefs: A systematic map

Shallow, tropical coral reefs face compounding threats from climate change, habitat degradation due to coastal development and pollution, impacts from storms and sea-level rise, and pulse disturbances like blast fishing, mining, dredging, and ship groundings that reduce reef height and complexity. One approach toward restoring coral reef physical structure from such impacts is deploying built structures of artificial, natural, or hybrid (both artificial and natural) origin. Built structures range from designed modules and repurposed materials to underwater sculptures and intentionally placed natural rocks. Restoration practitioners and coastal managers increasingly consider incorporating – and in many cases have already begun to incorporate – built structures into coral reef-related applications, yet synthesized evidence on the ecological (coral-related; e.g., coral growth, coral survival) and physical performance of built structures in coral ecosystems across a variety of contexts (e.g., restoration, coastal protection, mitigation, tourism) is not readily available to guide decisions. To help fill this gap and inform management decisions, we systematically mapped the global distribution and abundance of published evidence on the ecological (coral-related) and physical performance of built structure interventions in shallow (≤ 30 m), tropical (35°N to 35°S) coral ecosystems.

Environmental Evidence↗
USGS2020

From pools to flow: The PROMISE framework for new insights on soil carbon cycling in a changing world

Soils represent the largest terrestrial reservoir of organic carbon, and the balance between soil organic carbon (SOC) formation and loss will drive powerful carbon‐climate feedbacks over the coming century. To date, efforts to predict SOC dynamics have rested on pool‐based models, which assume classes of SOC with internally homogenous physicochemical properties. However, emerging evidence suggests that soil carbon turnover is not dominantly controlled by the chemistry of carbon inputs, but rather by restrictions on microbial access to organic matter in the spatially heterogeneous soil environment. The dynamic processes that control the physicochemical protection of carbon translate poorly to pool‐based SOC models; as a result, we are challenged to mechanistically predict how environmental change will impact movement of carbon between soils and the atmosphere. Here, we propose a novel conceptual framework to explore controls on belowground carbon cycling: P robabilistic R epresentation of O rganic M atter I nteractions within the S oil E nvironment (PROMISE). In contrast to traditional model frameworks, PROMISE does not attempt to define carbon pools united by common thermodynamic or functional attributes. Rather, the PROMISE concept considers how SOC cycling rates are governed by the stochastic processes that influence the proximity between microbial decomposers and organic matter, with emphasis on their physical location in the soil matrix. We illustrate the applications of this framework with a new biogeochemical simulation model that traces the fate of individual carbon atoms as they interact with their environment, undergoing biochemical transformations and moving through the soil pore space. We also discuss how the PROMISE framework reshapes dialogue around issues related to SOC management in a changing world. We intend the PROMISE framework to spur the development of new hypotheses, analytical tools, and model structures across disciplines that will illuminate mechanistic controls on the flow of carbon between plant, soil, and atmospheric pools.

Global Change Biology↗
USGS2022

The impacts of mangrove range expansion on wetland ecosystem services in the southeastern United States: Current understanding, knowledge gaps, and emerging research needs

Climate change is transforming ecosystems and affecting ecosystem goods and services. Along the Gulf of Mexico and Atlantic coasts of the southeastern United States, the frequency and intensity of extreme freeze events greatly influences whether coastal wetlands are dominated by freeze-sensitive woody plants (mangrove forests) or freeze-tolerant grass-like plants (salt marshes). In response to warming winters, mangroves have been expanding and displacing salt marshes at varying degrees of severity in parts of north Florida, Louisiana, and Texas. As winter warming accelerates, mangrove range expansion is expected to increasingly modify wetland ecosystem structure and function. Because there are differences in the ecological and societal benefits that salt marshes and mangroves provide, coastal environmental managers are challenged to anticipate effects of mangrove expansion on critical wetland ecosystem services, including those related to carbon sequestration, wildlife habitat, storm protection, erosion reduction, water purification, fisheries support, and recreation. Mangrove range expansion may also affect wetland stability in the face of extreme climatic events and rising sea levels. Here, we review current understanding of the effects of mangrove range expansion and displacement of salt marshes on wetland ecosystem services in the southeastern United States. We also identify critical knowledge gaps and emerging research needs regarding the ecological and societal implications of salt marsh displacement by expanding mangrove forests. One consistent theme throughout our review is that there are ecological trade-offs for consideration by coastal managers. Mangrove expansion and marsh displacement can produce beneficial changes in some ecosystem services, while simultaneously producing detrimental changes in other services. Thus, there can be local-scale differences in perceptions of the impacts of mangrove expansion into salt marshes. For very specific local reasons, some individuals may see mangrove expansion as a positive change to be embraced, while others may see mangrove expansion as a negative change to be constrained.

Global Change Biology↗
USGS2021

Spatiotemporal dynamics of insect pollinator communities in sagebrush steppe associated with weather and vegetation

The conservation of native insect pollinators is hampered by a lack of information about environmental factors influencing pollinator communities. We investigated how insect pollinator communities, composed of bees (Hymenoptera), butterflies and moths (Lepidoptera), and flies (Diptera), are influenced by spatial and temporal aspects of the environment in sagebrush steppe shrublands. We assessed hypotheses regarding spatial autocorrelation of communities, inter-annual variability in communities, influence of elevation on timing of emergence, and influence of weather on seasonal changes in relative abundance of different pollinator taxa. We captured 27,310 insects from 6 bee families, 27 butterfly and moth families, and 3 fly families. The occurrence of insect pollinators among sampling plots was not spatially autocorrelated, indicating that insect communities may be structured by habitat variation and microclimates over relatively fine spatial scales. Pollinator familial richness, diversity, abundance, and timing of emergence were most strongly positively associated with spatiotemporal variation in minimum daily temperatures at the ground surface during the active season. Emergence timing was positively correlated with growing degree days and percent humidity, regardless of elevation. All pollinator groups varied in abundance throughout their active season, peaking in early July (bees), late July (flies), or early August (butterflies and moths). Our findings suggest that changes in nighttime temperatures, which have been steadily increasing over the last several decades as a result of climate change, may have strong effects on sagebrush steppe pollinator communities. Also, non-bee pollinators may provide particularly important pollination in this vast ecosystem during the warmest time of the year.

Oregon↗
USGS2021

Divergent climate change effects on widespread dryland plant communities driven by climatic and ecohydrological gradients

Plant community response to climate change will be influenced by individual plant responses that emerge from competition for limiting resources that fluctuate through time and vary across space. Projecting these responses requires an approach that integrates environmental conditions and species interactions that result from future climatic variability. Dryland plant communities are being substantially affected by climate change because their structure and function are closely tied to precipitation and temperature, yet impacts vary substantially due to environmental heterogeneity, especially in topographically complex regions. Here, we quantified the effects of climate change on big sagebrush ( Artemisia tridentata Nutt.) plant communities that span 76 million ha in the western United States. We used an individual-based plant simulation model that represents intra- and inter-specific competition for water availability, which is represented by a process-based soil water balance model. For dominant plant functional types, we quantified changes in biomass and characterized agreement among 52 future climate scenarios. We then used a multivariate matching algorithm to generate fine-scale interpolated surfaces of functional type biomass for our study area. Results suggest geographically divergent responses of big sagebrush to climate change (changes in biomass of −20% to +27%), declines in perennial C 3 grass and perennial forb biomass in most sites, and widespread, consistent, and sometimes large increases in perennial C 4 grasses. The largest declines in big sagebrush, perennial C 3 grass and perennial forb biomass were simulated in warm, dry sites. In contrast, we simulated no change or increases in functional type biomass in cold, moist sites. There was high agreement among climate scenarios on climate change impacts to functional type biomass, except for big sagebrush. Collectively, these results suggest divergent responses to warming in moisture-limited versus temperature-limited sites and potential shifts in the relative importance of some of the dominant functional types that result from competition for limiting resources.

Global Change Biology↗
USGS2004

Contemporary carbon dynamics in terrestrial ecosystems in the Southeastern Plains of the United States

Quantifying carbon dynamics over large areas is frequently hindered by the lack of consistent, high-quality, spatially explicit land use and land cover change databases and appropriate modeling techniques. In this paper, we present a generic approach to address some of these challenges. Land cover change information in the Southeastern Plains ecoregion was derived from Landsat data acquired in 1973, 1980, 1986, 1992, and 2000 within 11 randomly located 20-km × 20-km sample blocks. Carbon dynamics within each of the sample blocks was simulated using the General Ensemble Biogeochemical Modeling System (GEMS), capable of assimilating the variances and covariance of major input variables into simulations using an ensemble approach. Results indicate that urban and forest areas have been increasing, whereas agricultural land has been decreasing since 1973. Forest clear-cutting activity has intensified, more than doubling from 1973 to 2000. The Southeastern Plains has been acting as a carbon sink since 1973, with an average rate of 0.89 Mg C/ha/yr. Biomass, soil organic carbon (SOC), and harvested materials account for 56%, 34%, and 10% of the sink, respectively. However, the sink has declined continuously during the same period owing to forest aging in the northern part of the ecoregion and increased forest clear-cutting activities in the south. The relative contributions to the sink from SOC and harvested materials have increased, implying that these components deserve more study in the future. The methods developed here can be used to quantify the impacts of human management activities on the carbon cycle at landscape to global scales.

Environmental Management↗
USGS2019

Trace metal and nutrient loads from groundwater seepage into the South Fork Coeur d’Alene River near Smelterville, northern Idaho, 2017

The Coeur d’Alene mining district in northern Idaho historically was a globally important source of lead, zinc, and silver, but over 100 years of mining has left a legacy of metals contamination in the Coeur d’Alene River valley. Previous studies by the U.S. Geological Survey (USGS) and others have indicated that groundwater discharging into the South Fork Coeur d’Alene River between Kellogg and Smelterville, Idaho, is a substantial source of dissolved zinc, dissolved cadmium, and total phosphorus. As part of its ongoing cleanup efforts, the U.S. Environmental Protection Agency is constructing a groundwater collection and treatment system to intercept and treat this contaminated water before it reaches the river. To establish conditions prior to construction, the USGS conducted a seepage study in September 2017 to quantify the rate and quality of groundwater discharging into the South Fork Coeur d’Alene River between Kellogg and Smelterville. Repeated measurements of streamflow were taken at multiple locations in the river and tributaries, and water-quality samples were collected and analyzed for trace metals and nutrients. Results showed consistent increases in streamflow (5.8 ± 1.3 cubic feet per second); and in dissolved zinc (85 ± 9.3 kilograms per day [kg/d]), dissolved cadmium (0.58 ± 0.10 kg/d) and total phosphorus (6.3 ± 0.45 kg/d) loads in a discrete segment of the reach. These gains exceeded tributary inputs, thereby implicating groundwater discharge as the main source of loading. Zinc and cadmium loads from groundwater in 2017 were less than those measured in 1999 but comparable to those measured from 2003 to 2008. This suggests that remedial actions in the late 1990s and early 2000s decreased trace-metal loading from 1999 to 2003, but that conditions remained similar from 2003 to 2017. A second seepage study will be conducted after construction and treatment plant system optimization are complete; this second study will evaluate changes in groundwater discharge to and water quality in the South Fork Coeur d’Alene River compared to the pre-construction conditions.

Idaho↗
USGS2020

Mercury export from Arctic great rivers

Land–ocean linkages are strong across the circumpolar north, where the Arctic Ocean accounts for 1% of the global ocean volume and receives more than 10% of the global river discharge. Yet estimates of Arctic riverine mercury (Hg) export constrained from direct Hg measurements remain sparse. Here, we report results from a coordinated, year-round sampling program that focused on the six major Arctic rivers to establish a contemporary (2012–2017) benchmark of riverine Hg export. We determine that the six major Arctic rivers exported an average of 20 000 kg y –1 of total Hg (THg, all forms of Hg). Upscaled to the pan-Arctic, we estimate THg flux of 37 000 kg y –1 . More than 90% of THg flux occurred during peak river discharge in spring and summer. Normalizing fluxes to watershed area (yield) reveals higher THg yields in regions where greater denudation likely enhances Hg mobilization. River discharge, suspended sediment, and dissolved organic carbon predicted THg concentration with moderate fidelity, while suspended sediment and water yields predicted THg yield with high fidelity. These findings establish a benchmark in the face of rapid Arctic warming and an intensifying hydrologic cycle, which will likely accelerate Hg cycling in tandem with changing inputs from thawing permafrost and industrial activity.

Environmental Science & Technology↗
USGS2025

Shifting baselines of coral-reef species composition from the Late Pleistocene to the present in the Florida Keys

The ongoing global-scale reassembly of modern coral reefs is unprecedented compared with the observed stability of most late Quaternary reef assemblages. One notable exception is the marine isotope stage (MIS) 5e ( ca 130–116 thousand years ago [ka]) reefs in the Florida Keys, where the ubiquitous shallow-water coral, Acropora palmata , was near absent. Little is known, however, about reefs that grew during MIS5d–a ( ca 116–74 ka), between MIS5e and the Holocene. It is therefore unclear whether Florida's unique MIS5e coral assemblages represent a geologically brief anomaly or a more persistent departure from the western Atlantic coral-reef archetype. We addressed that question by reconstructing the composition of MIS5d–a reefs within 29 coral-reef cores collected throughout the Florida Keys. We then compared the relative composition of corals during MIS5d–a to existing datasets from MIS5e, Holocene and modern (1996 and 2022) reefs to evaluate how far today's reef assemblages have diverged from geological baselines. We show that although the proportion of reef frameworks built by corals was remarkably consistent ( ca 38%), species composition changed significantly through time. Acropora palmata was rare throughout MIS5, which we hypothesise was due to greater cold-temperature stress in Florida's subtropical reefs compared with the more climatically stable tropics. In contrast, the massive reef-building coral, Orbicella spp., was regionally dominant throughout the late Quaternary, but has become increasingly rare on modern reefs. By 2022, reefs in the Florida Keys were characterised by a truly novel coral assemblage dominated by Porites astreoides and Siderastrea siderea . In many ways, Florida's reefs defy the concept of a natural baseline; instead, their most persistent characteristic since the Late Pleistocene is their uniqueness. Yet, as reefs are increasingly subjected to unprecedented levels of environmental change, the exceptions to what was normal in the past could, paradoxically, provide the best geological analogues for the future.

Florida↗
USGS2013

Public lakes, private lakeshore: Modeling protection of native aquatic plants

Protection of native aquatic plants is an important proenvironmental behavior, because plant loss coupled with nutrient loading can produce changes in lake ecosystems. Removal of aquatic plants by lakeshore property owners is a diffuse behavior that may lead to cumulative impacts on lake ecosystems. This class of behavior is challenging to manage because collective impacts are not obvious to the actors. This paper distinguishes positive and negative beliefs about aquatic plants, in models derived from norm activation theory (Schwartz, Adv Exp Soc Psychol 10:221–279, 1977 ) and the theory of reasoned action (Fishbein and Ajzen, Belief, attitude, intention, and behavior: an introduction to theory and research, Addison-Wesley, Boston 1975 ), to examine protection of native aquatic plants by Minnesota lakeshore property owners. We clarify how positive and negative evaluations of native aquatic plants affect protection or removal of these plants. Results are based on a mail survey ( n = 3,115). Results suggest that positive evaluations of aquatic plants (i.e., as valuable to lake ecology) may not connect with the global attitudes and behavioral intentions that direct plant protection or removal. Lakeshore property owners’ behavior related to aquatic plants may be driven more by tangible personal benefits derived from accessible, carefully managed lakeshore than intentional action taken to sustain lake ecosystems. The limited connection of positive evaluations of aquatic plants to global attitudes and behavioral intentions may reflect either lack of knowledge of what actions are needed to protect lake health and/or unwillingness to lose perceived benefits derived from lakeshore property.

Minnesota↗
USGS2000

Monitoring beach morphology changes using small-format aerial photography and digital softcopy photogrammetry

Current methods of monitoring beach morphology changes commonly involve the establishment of Global Positioning System profiles that are surveyed on a regular basis. Although this method produces precise measurements of coastal topography, it is costly in time and effort and may result in large data gaps between profiles. Much of our understanding of coastal dynamics is thus limited by profile spacing and survey frequency. Softcopy photogrammetry is increasingly being used as an alternative to assess shoreline change and study beach morphodynamics. This method of producing three-dimensional topographic models and orthophotographs from digitized aerial photography can aid in filling in the gaps between established profiles. A limiting factor to this technology is the cost of obtaining high-resolution aerial photography. We have developed an aerial mapping system designed to collect data in an efficient and cost-effective way. We use a small-format aerial photography system that can be mounted on a variety of small aircraft on short notice. After a flight, the photographs are scanned, and softcopy photogrammetry software is used to create both DTMs (Digital Terrain Models) and orthophotographs. The DTMs can be compared with existing profiles for accuracy, and volumetric changes can be computed. The orthophotos are used to make precise measurements of the position and morphology of shoreline features. This aerial mapping system is advantageous over previous methods of beach morphology change monitoring because it allows for rapid response to storm events and provides a cost-effective method of establishing a continual monitoring program in erosion hazard areas.

Environmental Geosciences↗
USGS2023

Investigating permafrost carbon dynamics in Alaska with artificial intelligence

Positive feedbacks between permafrost degradation and the release of soil carbon into the atmosphere impact land–atmosphere interactions, disrupt the global carbon cycle, and accelerate climate change. The widespread distribution of thawing permafrost is causing a cascade of geophysical and biochemical disturbances with global impacts. Currently, few earth system models account for permafrost carbon feedback (PCF) mechanisms. This research study integrates artificial intelligence (AI) tools and information derived from field-scale surveys across the tundra and boreal landscapes in Alaska. We identify and interpret the permafrost carbon cycling links and feedback sensitivities with GeoCryoAI, a hybridized multimodal deep learning (DL) architecture of stacked convolutionally layered, memory-encoded recurrent neural networks (NN). This framework integrates in-situ measurements and flux tower observations for teacher forcing and model training. Preliminary experiments to quantify, validate, and forecast permafrost degradation and carbon efflux across Alaska demonstrate the fidelity of this data-driven architecture. More specifically, GeoCryoAI logs the ecological memory and effectively learns covariate dynamics while demonstrating an aptitude to simulate and forecast PCF dynamics—active layer thickness (ALT), carbon dioxide flux (CO 2 ), and methane flux (CH 4 )—with high precision and minimal loss (i.e. ALT RMSE : 1.327 cm [1969–2022]; CO 2 RMSE : 0.697 µ molCO 2 m −2 s −1 [2003–2021]; CH 4 RMSE : 0.715 nmolCH 4 m −2 s −1 [2011–2022]). ALT variability is a sensitive harbinger of change, a unique signal characterizing the PCF, and our model is the first characterization of these dynamics across space and time.

Alaska↗
USGS2021

Changes in seabed mining

Chapter 23 of the First World Ocean Assessment (WOA I) focused on marine mining, and particularly on established extractive industries, which are predominantly confined to near-shore areas, where shallow-water, near-shore aggregate and placer deposits, and somewhat deeper water phosphate deposits are found (United Nations, 2017a). At the time of publication, there were no commercially developed deep-water seabed mining (DSM) deposits but an assessment of mining leases and exploration activity was included. Since WOA I, the number of deep-water (depths greater than 200 m below the ocean surface) seabed exploration licenses has increased both within national jurisdictions of coastal, island and archipelagic States, and beyond in the Area (the seabed, ocean floor and subsoil thereof beyond the limits of national jurisdiction) under the administration of the International Seabed Authority (ISA). For the first time, in 2017 deep-water seabed test-mining was carried out by Japan at a water depth of 1,600 m within its exclusive economic zone (EEZ) (METI, 2017). The update in the present Chapter will focus on the nascent deep-water seabed mining industry and mineral deposits. Hereafter, we use seabed for deep-water seabed. Environmental issues focused on impacts from dredging activities and a list of references for some mining operations were provided. However, WOA I could not provide an environmental baseline for DSM and considered that environmental, social and economic aspects were often not adequately understood with available data. Data on potential environmental impacts are still scarce and can differ greatly between mineral extraction from near-shore and seabed mining sites. Information on economic benefits, and to some extent social impacts, of mining is becoming progressively more accessible due to several initiatives promoting an increase in transparency of extractive industries. In 2015, the 2030 Agenda for Sustainable Development was adopted by all United Nations Member States. It includes 17 Sustainable Development Goals (SDGs) to be addressed on the basis of a global partnership. DSM activities may have implications for the achievement of SDGs 1, 5, 7–10, 12–14, and 17.

Book chapter↗
USGS2018

Canopy volume removal from oil and gas development activity in the upper Susquehanna River basin in Pennsylvania and New York (USA): An assessment using lidar data

Oil and gas development is changing the landscape in many regions of the United States and globally. However, the nature, extent, and magnitude of landscape change and development, and precisely how this development compares to other ongoing land conversion (e.g. urban/sub-urban development, timber harvest) is not well understood. In this study, we examine land conversion from oil and gas infrastructure development in the upper Susquehanna River basin in Pennsylvania and New York, an area that has experienced much oil and gas development over the past 10 years. We quantified land conversion in terms of forest canopy geometric volume loss in contrast to previous studies that considered only areal impacts. For the first time in a study of this type, we use fine-scale lidar forest canopy geometric models to assess the volumetric change due to forest clearing from oil and gas development and contrast this land change to clear cut forest harvesting, and urban and suburban development. Results show that oil and gas infrastructure development removed a large volume of forest canopy from 2006 to 2013, and this removal spread over a large portion of the study area. Timber operations (clear cutting) on Pennsylvania State Forest lands removed a larger total volume of forest canopy during the same time period, but this canopy removal was concentrated in a smaller area. Results of our study point to the need to consider volumetric impacts of oil and gas development on ecosystems, and to place potential impacts in context with other ongoing land conversions.

New York, Pennsylvania↗
USGS2025

RAD (Resist-Accept-Direct) switch points and triggers for adaptation planning

Climate change is transforming ecosystems globally. The Resist-Accept-Direct (RAD) framework has gained traction within many natural resource management institutions to help consider the decision space in response to this transformation. Because RAD helps manage for directional change, RAD choices entail considering which RAD pathway to implement and for how long. For example, one may accept a slowly changing ecosystem, but at a certain point, decide to begin resisting or directing the change an ecosystem is experiencing. Alternatively, one may begin resisting an ecosystem transformation, but ultimately realize resistance is no longer feasible based on cost or efficacy. These choices are challenging and encompass broad domains of cultural, ecological, financial, organizational, public, regulatory, and technological considerations to determine when to switch RAD pathways. We introduce the concepts of RAD switch points and triggers to help support these decision processes. We illustrate these concepts using case studies on walleye ( Sander vitreus ) stocking decisions in Wisconsin, wildfire response in the Greater Yellowstone Ecosystem, and bull trout ( Salvelinus confluentus ) management in Oregon, USA. Synthesizing across these examples, we delineate key points for decision makers as they (iteratively) reevaluate among the RAD pathways as conditions continue to change.

Journal of Environmental Management↗
USGS2012

Concentrations, loads, and yields of organic carbon in streams of agricultural watersheds

Carbon is cycled to and from large reservoirs in the atmosphere, on land, and in the ocean. Movement of organic carbon from the terrestrial reservoir to the ocean plays an important role in the global cycling of carbon. The transition from natural to agricultural vegetation can change the storage and movement of organic carbon in and from a watershed. Samples were collected from 13 streams located in hydrologically and agriculturally diverse watersheds, to better understand the variability in the concentrations and loads of dissolved organic carbon (DOC) and particulate organic carbon (POC) in the streams, and the variability in watershed yields. The overall annual median concentrations of DOC and POC were 4.9 (range: 2.1–6.8) and 1.1 (range: 0.4–3.8) mg C L −1 , respectively. The mean DOC watershed yield (± SE) was 25 ± 6.8 kg C ha −1 yr −1 . The yields of DOC from these agricultural watersheds were not substantially different than the DOC yield from naturally vegetated watersheds in equivalent biomes, but were at the low end of the range for most biomes. Total organic carbon (DOC + POC) annually exported from the agricultural watersheds was found to average 0.03% of the organic carbon that is contained in the labile plant matter and top 1 m of soil in the watershed. Since the total organic carbon exported from agricultural watersheds is a relatively small portion of the sequestered carbon within the watershed, there is the great potential to store additional carbon in plants and soils of the watershed, offsetting some anthropogenic CO2 emissions.

California;Indiana;Iowa;Maryl;Mississippi;Nebraska↗