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At least 1,099 records · Page 61Linked to original sources
USGS2015

Modelling regional land change scenarios to assess land abandonment and reforestation dynamics in the Pyrenees (France)

Over the last decades and centuries, European mountain landscapes have experienced substantial transformations. Natural and anthropogenic LULC changes (land use and land cover changes), especially agro-pastoral activities, have directly influenced the spatial organization and composition of European mountain landscapes. For the past sixty years, natural reforestation has been occurring due to a decline in both agricultural production activities and rural population. Stakeholders, to better anticipate future changes, need spatially and temporally explicit models to identify areas at risk of land change and possible abandonment. This paper presents an integrated approach combining forecasting scenarios and a LULC changes simulation model to assess where LULC changes may occur in the Pyrenees Mountains, based on historical LULC trends and a range of future socio-economic drivers. The proposed methodology considers local specificities of the Pyrenean valleys, sub-regional climate and topographical properties, and regional economic policies. Results indicate that some regions are projected to face strong abandonment, regardless of the scenario conditions. Overall, high rates of change are associated with administrative regions where land productivity is highly dependent on socio-economic drivers and climatic and environmental conditions limit intensive (agricultural and/or pastoral) production and profitability. The combination of the results for the four scenarios allows assessments of where encroachment (e.g. colonization by shrublands) and reforestation are the most probable. This assessment intends to provide insight into the potential future development of the Pyrenees to help identify areas that are the most sensitive to change and to guide decision makers to help their management decisions.

Journal of Mountain Science↗
USGS2013

Spatial and temporal patterns of dust emissions (2004-2012) in semi-arid landscapes, southeastern Utah, USA

Aeolian dust can influence nutrient availability, soil fertility, plant interactions, and water-holding capacity in both source and downwind environments. A network of 85 passive collectors for aeolian sediment spanning numerous plant communities, soil types, and land-use histories covering approximately 4000 square kilometers across southeastern Utah was used to sample horizontal emissions of aeolian sediment. The sample archive dates to 2004 and is currently the largest known record of field-scale dust emissions for the southwestern United States. Sediment flux peaked during the spring months in all plant communities (mean: 38.1 g m −2 d −1 ), related to higher, sustained wind speeds that begin in the early spring. Dust flux was lowest during the winter period (mean: 5 g m−2 d−1) when surface wind speeds are typically low. Sites dominated by blackbrush and sagebrush shrubs had higher sediment flux (mean: 19.4 g m−2 d−1) compared to grasslands (mean: 11.2 g m−2 d−1), saltbush shrublands (mean: 10.3 g m −2 d −1 ), and woodlands (mean: 8.1 g m −2 d −1 ). Contrary to other studies on dust emissions, antecedent precipitation during one, two, and three seasons prior to sample collection did not significantly influence emission rates. Physical site-scale factors controlling dust emissions were complex and varied from one vegetation type to another.

Utah↗
USGS2007

Tracking environmental dynamics and agricultural intensification in southern Mali

The Office de la Haute Vallée du Fleuve Niger (OHVN) zone in southern Mali is a small but important agricultural production region. Against a background of environmental degradation including decades of declining rainfall, soil erosion, and human pressure on forest resources, numerous farming communities stand out through the use of improved soil and water management practices that have improved agricultural and environmental conditions. Field surveys conducted in 1998–2001 indicated that environmental and agricultural conditions have improved in the past decade. In an effort to better quantify environmental trends, we conducted a study using medium- and high-resolution remotely sensed images from 1965 to 2001 in order to analyze land use and land cover trends in 21 village territories. The trends show clear indications of agricultural intensification and diversification among villages that have received assistance from the OHVN agricultural development agency. Some communities have improved environmental conditions by protecting their forest resources through community management actions. Four decades of remotely sensed images played a practical role in tracking and quantifying environmental and agricultural conditions over time.

Agricultural Systems↗
USGS2009

Continental-scale patterns in soil geochemistry and mineralogy: results from two transects across the United States and Canada

In 2004, the US Geological Survey (USGS) and the Geological Survey of Canada (GSC) initiated a pilot study that involved collection of more than 1500 soil samples from 221 sites along two continental transects across Canada and the United States. The pilot study was designed to test and refine protocols for a soil geochemical survey of North America. The two transects crossed a wide array of soil parent materials, soil ages, climatic conditions, landforms, land covers and land uses. Sample sites were selected randomly at approximately 40-km intervals from a population defined as all soils of the continent. At each site, soils representing 0 to 5 cm depth, and the O, A, and C horizons, if present, were collected and analyzed for their near-total content of over 40 major and trace elements. Soils from 0–5 cm depth were also collected for analysis of organic compounds. Results from the transects confirm that soil samples collected at a 40-km spacing reveal coherent, continental- to subcontinental-scale geochemical and mineralogical patterns that can be correlated to aspects of underlying soil parent material, soil age and climate influence. The geochemical data also demonstrate that at the continental-scale the dominance of any of these major factors that control soil geochemistry can change across the landscape. Along both transects, soil mineralogy and geochemistry change abruptly with changes in soil parent materials. However, the chemical influence of a soil’s parent material can be obscured by changing climatic conditions. For the transects, increasing precipitation from west to east and increasing temperature from north to south affect both soil mineralogy and geochemistry because of climate effects on soil weathering and leaching, and plant productivity. Regional anomalous metal concentrations can be linked to natural variations in soil parent materials, such as high Ni and Cr in soils developed on ultramafic rocks in California or high P in soils formed on weathered Ordovician limestones in central Kentucky. On local scales, anomalous metal concentrations recognized in soil profiles, such as high P in soils from animal confinement sites, are consistent with local anthropogenic disturbances. At a larger scale, the distribution of Hg across the west to east transect demonstrates that it can be difficult to distinguish between natural or anthropogenic contributions and that many factors can contribute to an element’s spatial distribution. Only three samples in a subset of seventy-three 0–5 cm depth soil samples from the north to south transect had organochlorine pesticides values above the method detection limit, apparently related to historic usage of the pesticides DDT and dieldrin.

Applied Geochemistry↗
USGS2008

Satellite remotely-sensed land surface parameters and their climatic effects for three metropolitan regions

By using both high-resolution orthoimagery and medium-resolution Landsat satellite imagery with other geospatial information, several land surface parameters including impervious surfaces and land surface temperatures for three geographically distinct urban areas in the United States – Seattle, Washington, Tampa Bay, Florida, and Las Vegas, Nevada, are obtained. Percent impervious surface is used to quantitatively define the spatial extent and development density of urban land use. Land surface temperatures were retrieved by using a single band algorithm that processes both thermal infrared satellite data and total atmospheric water vapor content. Land surface temperatures were analyzed for different land use and land cover categories in the three regions. The heterogeneity of urban land surface and associated spatial extents were shown to influence surface thermal conditions because of the removal of vegetative cover, the introduction of non-transpiring surfaces, and the reduction in evaporation over urban impervious surfaces. Fifty years of in situ climate data were integrated to assess regional climatic conditions. The spatial structure of surface heating influenced by landscape characteristics has a profound influence on regional climate conditions, especially through urban heat island effects.

Advances in Space Research↗
USGS2026

Urbanization alters riverine fluorescent dissolved organic matter characteristics in a forested city – metropolitan Atlanta, Georgia (USA)

Streams and rivers in urban watersheds are predicted to export more bioreactive, autochthonous dissolved organic matter (DOM) relative to forested watersheds. However, the spatial and temporal variations of DOM quality in forested urban watersheds remain uncertain, and their relationships with socioeconomic conditions, biological characteristics, and the built environment are understudied. We measured optical properties of fluorescent DOM (FDOM) in 93 streams spanning a gradient of land-use and land cover during four seasons in metropolitan Atlanta, Georgia, USA. Streamwater FDOM was dominated by humic substances from anthropogenic (41%) and terrestrial origin (41.5%). Impervious surface cover was the strongest predictor, which was positively correlated with anthropogenically- and autochthonously-derived FDOM. Overwater canopy cover was positively associated with autochthonous FDOM, and housing age increased diagenetic FDOM. FDOM was more proteinaceous during low-flow conditions (fall, winter), and more allochthonous humic-like FDOM was detected during periods of higher flows (spring, summer). Interestingly, wastewater-related FDOM proxies were highest during low flows, suggesting that sewer exfiltration is a pervasive source and is diluted by other inputs during high flows. Overall, seasonal patterns in FDOM quality were associated with changes in hydrology, and FDOM was primarily humic throughout the year, a pattern likely driven by ubiquitous forest canopy cover. Our results highlight the importance of urban forests in mediating aquatic carbon cycling and provide a template for future studies that integrate sociodemographic and infrastructure information into studies of watershed biogeochemistry, especially in regions undergoing rapid, intense, and localized urban development.

Georgia↗
USGS2021

Remote sensing-based actual evapotranspiration assessment in a data-scarce area of Brazil: A case study of the Urucuia Aquifer System

The large groundwater reserves of the Urucuia Aquifer System (UAS) enabled agricultural development and economic growth in the western Bahia State, in northeastern Brazil. Over the last several years, concern has grown around the aquifer’s diminishing water levels, and water balance (WB) studies are in demand. Considering the lack of measured actual evapotranspiration (ET a ), a major component of the water cycle, this work uses the Operational Simplified Surface Energy Balance (SSEBop) model to estimate ET a , and compares it to basin-scale estimates from the Soil Moisture Accounting Procedure (SMAP) monthly model and from an annual WB closure method, based on gridded meteorological data and the Gravity Recovery and Climate Experiment (GRACE) product. Additionally, a comparative assessment of different versions of the SSEBop parameterization was performed. Moderate Resolution Imaging Spectroradiometer (MODIS) imagery was used to implement eight different versions of the SSEBop algorithm over the UAS between 2000 and 2013. SSEBop and SMAP ET a yielded similar seasonal patterns, with correlation coefficient (r) up to 0.65, mean difference (MD) of 0.8 mm/month and mean absolute difference (MAD) of 18.5 mm/month. Comparison of SSEBop annual ET a estimates to annual SMAP and WB closure estimates yielded low MD (12.1 and −7.3 mm/year, respectively) and MAD (82.5 and 82.8 mm/year, respectively), but also low r values (0.00 and 0.37, respectively). The comparison of the different SSEBop versions indicated the need to incorporate a calibration step of the aerodynamic heat resistance (r ah ) parameter. SSEBop results were also used for land cover and drought monitoring. Analysis indicates that agriculture, associated with an increasing trend of atmospheric evaporative demand, is responsible for the decrease in groundwater levels and streamflow in the studied time period.

Urucuia Aquifer System↗
USGS2016

Comparison of mercury mass loading in streams to atmospheric deposition in watersheds of Western North America: Evidence for non-atmospheric mercury sources

Annual stream loads of mercury (Hg) and inputs of wet and dry atmospheric Hg deposition to the landscape were investigated in watersheds of the Western United States and the Canadian-Alaskan Arctic. Mercury concentration and discharge data from flow gauging stations were used to compute annual mass loads with regression models. Measured wet and modeled dry deposition were compared to annual stream loads to compute ratios of Hg stream load to total Hg atmospheric deposition. Watershed land uses or cover included mining, undeveloped, urbanized, and mixed. Of 27 watersheds that were investigated, 15 had some degree of mining, either of Hg or precious metals (gold or silver), where Hg was used in the amalgamation process. Stream loads in excess of annual Hg atmospheric deposition (ratio > 1) were observed in watersheds containing Hg mines and in relatively small and medium-sized watersheds with gold or silver mines, however, larger watersheds containing gold or silver mines, some of which also contain large dams that trap sediment, were sometimes associated with lower load ratios (< 0.2). In the non-Arctic regions, watersheds with natural vegetation tended to have low ratios of stream load to Hg deposition (< 0.1), whereas urbanized areas had higher ratios (0.34–1.0) because of impervious surfaces. This indicated that, in ecosystems with natural vegetation, Hg is retained in the soil and may be transported subsequently to streams as a result of erosion or in association with dissolved organic carbon. Arctic watersheds (Mackenzie and Yukon Rivers) had a relatively elevated ratio of stream load to atmospheric deposition (0.27 and 0.74), possibly because of melting glaciers or permafrost releasing previously stored Hg to the streams. Overall, our research highlights the important role of watershed characteristics in determining whether a landscape is a net source of Hg or a net sink of atmospheric Hg.

Science of the Total Environment↗
USGS2022

Air, land, and water variables associated with the first appearance and current spatial distribution of toxic Prymnesium parvum blooms in reservoirs of the Southern Great Plains, USA

This study examined the association of air, land, and water variables with the first historical occurrence and current distribution of toxic Prymnesium parvum blooms in reservoirs of the Brazos River and Colorado River, Texas (USA). One impacted and one reference reservoir were selected per basin. Land cover and use variables were estimated for the whole watershed (WW) and a 0.5-km zone on either side of streams (near field, NF). Variables were expressed in annual values. Principal component and trend analyses were used to determine (1) differences in environmental conditions before and after the 2001 onset of toxic blooms in impacted reservoirs (study period, 1992–2017), and (2) traits that uniquely discriminate impacted from reference reservoirs (2001–2017). Of thirty-three variables examined, two positively aligned with the reoccurring appearance of blooms in impacted reservoirs (air CO 2 and herbicide Glyphosate) and another two negatively aligned (insecticides Terbufos and Malathion). Glyphosate use was observed throughout the study period but a turning point for an upward trend occurred near the year of first bloom occurrence. While the relevance of the decreased use of insecticides is uncertain, prior experimental studies reported that increasing concentrations of air CO 2 and water Glyphosate can enhance P. parvum growth. Consistent with prior findings, impacted reservoirs were of higher salinity than reference reservoirs. In addition, their watersheds had far lower wetland cover at NF and WW scales. The value of wetlands in reducing harmful algal bloom incidence by reducing nutrient inputs has been previously recognized, but wetlands can also capture pesticides. Therefore, a diminished wetland cover could magnify Glyphosate loads flowing into impacted reservoirs. These observations are consistent with a scenario where rising levels of air CO 2 and Glyphosate use contributed to the establishment of P. parvum blooms in reservoirs of relatively high salinity and minimal wetland cover over their watersheds.

Texas↗
USGS2017

Depth of the vadose zone controls aquifer biogeochemical conditions and extent of anthropogenic nitrogen removal

We investigated biogeochemical conditions and watershed features controlling the extent of nitrate removal through microbial dinitrogen (N 2 ) production within the surficial glacial aquifer located on the north and south shores of Long Island, NY, USA. The extent of N 2 production differs within portions of the aquifer, with greatest N 2 production observed at the south shore of Long Island where the vadose zone is thinnest, while limited N 2 production occurred under the thick vadose zones on the north shore. In areas with a shallow water table and thin vadose zone, low oxygen concentrations and sufficient DOC concentrations are conducive to N 2 production. Results support the hypothesis that in aquifers without a significant supply of sediment-bound reducing potential, vadose zone thickness exerts an important control of the extent of N 2 production. Since quantification of excess N 2 relies on knowledge of equilibrium N 2 concentration at recharge, calculated based on temperature at recharge, we further identify several features, such as land use and cover, seasonality of recharge, and climate change that should be considered to refine estimation of recharge temperature, its deviation from mean annual air temperature, and resulting deviation from expected equilibrium gas concentrations.

Water Research↗
USGS2001

The Landsat 7 mission: terrestrial research and applications for the 21st century

The Landsat Earth observation approach introduced in 1972 created a new way of monitoring land cover and land use globally. The Landsat 7 mission, successfully launched on April 15, 1999, continues those observations and demonstrates significant progress in precise numerical radiometry, spectral differentiation, and seasonally repetitive monitoring. Substantial improvements in calibration procedures, both prior to launch and during normal operations, have also been made to ensure long-term stability in the acquired spectral radiometry. Landsat 7 data acquisitions are being driven by a long-term data acquisition plan that was designed to ensure that substantially cloud-free, seasonal coverage would be recorded and archived in the US for all land areas of the globe. NASA competitively selected a Landsat Science Team, consisting of representatives from US universities and government agencies, to exploit the Landsat 7 record for global change research. This team is addressing the technical and analytical means to process and analyze the core of this observation record, and for the first time in the history of the Landsat mission, the technical and operational aspects of the mission are being driven by the goals of the US science community. The expected outcome of these efforts is a rapid improvement in understanding the Earth system, as well as conceptual knowledge that will underpin significant advancements in the application of this technology for commercial, operational, educational, and research purposes. Pathways to achieve effective Landsat continuity in the early decades of the 21st century are also being given careful attention, and there is no question that the lessons learned from the Landsat 7 mission will strongly influence these next-generation sensor systems.

Remote Sensing of Environment↗
USGS2004

Urbanization impacts on the structure and function of forested wetlands

The exponential increase in population has fueled a significant demographic shift: 60% of the Earth's population will live in urban areas by 2030. While this population growth is significant in its magnitude, the ecological footprint of natural resource consumption and use required to sustain urban populations is even greater. The land use and cover changes accompanying urbanization (increasing human habitation coupled with resource consumption and extensive landscape modification) impacts natural ecosystems at multiple spatial scales. Because they generally occupy lower landscape positions and are linked to other ecosystems through hydrologic connections, the cascading effects of habitat alteration on watershed hydrology and nutrient cycling are particularly detrimental to wetland ecosystems. I reviewed literature relevant to these effects of urbanization on the structure and function of forested wetlands. Hydrologic changes caused by habitat fragmentation generally reduce species richness and abundance of plants, macroinvertebrates, amphibians, and birds with greater numbers of invasives and exotics. Reduction in soil saturation and lowered water tables result in greater nitrogen mineralization and nitrification in urban wetlands with higher probability of NO − 3 export from the watershed. Depressional forested wetlands in urban areas can function as important sinks for sediments, nutrients, and metals. As urban ecosystems become the predominant human condition, there is a critical need for data specific to urban forested wetlands in order to better understand the role of these ecosystems on the landscape.

Urban Ecosystems↗
USGS2009

Quantifying the spatial details of carbon sequestration potential and performance

Upscaling the spatial and temporal changes of carbon stocks and fluxes from sites to regions is challenging owing to the spatial and temporal variances and covariance of driving variables and the uncertainties in both the model and the input data. Although various modeling approaches have been developed to facilitate the upscaling process, few deal with error transfer from model input to output, and error propagation in time and space. The author has developed the General Ensemble Biogeochemical Modelling System (GEMS) for upscaling carbon stocks and fluxes from sites to regions with measures of uncertainty. This chapter describes the GEMS model, its application to regional- and larger-scale areas, and the new results that demonstrate the challenges of upscaling. GEMS relies on site-scale biogeochemical models to simulate carbon dynamics at the site scale. The spatial deployment of the site-scale model in GEMS is based on the spatial and temporal joint frequency distribution of major driving variables (e.g., land cover and land use change, climate, soils, disturbances, and management). At the site scale, GEMS uses stochastic ensemble simulations to incorporate input uncertainty to quantify uncertainty transfer from input to output, and to identify trends in both input data and simulation results. It permits one to simulate the range of possible permutations of input values and identify the trends and variance in both the input data and results. Using data assimilation techniques, GEMS simulations can be constrained by field and satellite observations, including estimates of net primary production (NPP) from the Moderate Resolution Imaging Spectroradiometer (MODIS), grain yield and cropping practices, and forest inventories. The modeling philosophy embedded in GEMS makes it ideal for assimilating information with various uncertainties to support estimating the spatial details of carbon sequestration potential as well as dynamic monitoring of the performance of carbon sequestration activities over large areas. As a case study, GEMS is applied to simulate the spatial and temporal details of carbon sources, sinks, and uncertainty in the Ridge and Valley ecoregion in the eastern United States

Book chapter↗
USGS2024

Changes in landscape and climate in Mexico and Texas reveal small effects on migratory habitat of monarch butterflies (Danaus plexippus)

The decline of the iconic monarch butterfly ( Danaus plexippus ) in North America has motivated research on the impacts of land use and land cover (LULC) change and climate variability on monarch habitat and population dynamics. We investigated spring and fall trends in LULC, milkweed and nectar resources over a 20-year period, and ~ 30 years of climate variables in Mexico and Texas, U.S. This region supports spring breeding, and spring and fall migration during the annual life cycle of the monarch. We estimated a − 2.9% decline in milkweed in Texas, but little to no change in Mexico. Fall and spring nectar resources declined < 1% in both study extents. Vegetation greenness increased in the fall and spring in Mexico while the other climate variables did not change in both Mexico and Texas. Monarch habitat in Mexico and Texas appears relatively more intact than in the midwestern, agricultural landscapes of the U.S. Given the relatively modest observed changes in nectar and milkweed, the relatively stable climate conditions, and increased vegetation greenness in Mexico, it seems unlikely that habitat loss (quantity or quality) in Mexico and Texas has caused large declines in population size or survival during migration.

Scientific Reports↗
USGS2011

Estimation of volumetric runoff coefficients for Texas watersheds using land-use and rainfall-runoff data

The rational method for peak discharge ( Q p "> Q p ) estimation was introduced in the 1880s. Although the rational method is considered simplistic, it remains an effective method for estimating peak discharge for small watersheds. The runoff coefficient ( C "> C ) is a key parameter for the rational method and can be estimated in various ways. Literature-based C "> C values ( C lit "> C lit ) are listed for different land-use/land cover (two words, no hyphen) (LULC) conditions in various design manuals and textbooks; however, these C lit "> C lit values were developed with little basis on observed rainfall and runoff data. In this paper, C lit "> C lit values were derived for 90 watersheds in Texas by using LULC data for 1992 and 2001; the C lit "> C lit values derived from the two data sets were essentially the same. Also for this study, volumetric runoff coefficients ( C v "> C v ) were estimated by using observed rainfall and runoff depths from more than 1,600 events observed in the watersheds. Watershed-median and watershed-average C v "> C v values were computed, and both are consistent with data from the National Urban Runoff Program. In addition, C v "> C v values were estimated by using rank-ordered pairs of rainfall and runoff depths (i.e., frequency matching). As anticipated, C "> C values derived by all three methods (literature based, event totals, and frequency matching) consistently had larger values for developed watersheds than for undeveloped watersheds. Two regression equations of C v "> C v versus percent impervious area were developed and combined into a single equation that can be used to rapidly estimate C v "> C v values for similar Texas watersheds.

Texas↗
USGS2019

Modeling the morphological response of a barrier island to Hurricane Matthew

Surge and wave forcing from Hurricane Matthew caused a breach south of Matanzas Inlet (FL, USA) on a complex barrier island, including sandy dunes, hard structures (residential buildings and a highway), wetlands, and the US Intracoastal Waterway. In this paper, the skill of the XBeach model to predict hurricane-induced barrier island overwash, dune erosion, and breaching is demonstrated. The location of the breach is predicted correctly if bottom roughness based on land cover is used to calculate bed shear stresses. While the dunes are initially lowered by wave attack and surge from the ocean side, the main driver for breach formation is the water level difference between the back-barrier and nearshore, causing an ocean-directed outflow of water after the peak of the storm.

Florida↗
USGS2003

Geographic analysis and monitoring at the United States Geological Survey

The Geographic Analysis and Monitoring (GAM) Program of the U.S. Geological Survey assesses the Nation's land surface at a variety of spatial and temporal scales to understand the rates, causes, and consequences of natural and human-induced processes and their interactions that affect the landscape over time. The program plays an important role in developing National Map tools and application. The GAM is a science and synthesis program that not only assesses the rates of changes to the Earth's land surface, but also provides reports on the status and trends of the Nation's land resources on a periodic basis, produces a land-use and land- cover database for the periodically updated map and data set-the Geographic Face of the Nation, and conducts research leading to improved understanding and knowledge about geographic processes. Scientific investigations provide comprehensive information needed to understand the environmental, resource, and economic consequences of landscape change. These analyses responds to the needs of resource managers and offers the American public baseline information to help them understand the dynamic nature of our national landscape and to anticipate the opportunities and consequences of our actions.

Cartography and Geographic Information Science↗
USGS2005

Correlates of vernal pool occurrence in the Massachusetts USA, landscape

Vernal pool wetlands are at risk of destruction across the northeast United States, due in part to their diminutive size and short hydroperiolds. These characteristics make it difficult to locate vernal pool habitats in the landscape during much of the year, and no efficient method exists for predicting their occurrence. A logistic regression procedure was used to identify large-scale variables that influence the presence of a potential vernal pool, including surficial geology, land use and land cover, soil classification, topography, precipitation, and surficial hydrologic features. The model was validated with locations of field-verified vernal pools. The model demonstrated that the probability of potential vernal pool occurrence is positively related to slope, negatively related to till/bedrock surficial geology, and negatively related to the proportion of cropland, urban/commercial, and high density residential development in the landscape. The relationship between vernal pool occurrence and large-scale variables suggests that these habitats do not occur at random in the landscape, and thus, protection in situ should be considered.

Massachusetts↗