Hydraulic fracturing, or fracking, is a process of introducing liquid at high pressure to create fractures in shale rock formations, thus releasing natural gas. Flowback and produced water from ...fracking operations is typically stored in temporary open-air earthen impoundments, or frack ponds. Unfortunately, in the United States there is no public record of the location of impoundments, or the dates that impoundments are created or removed. In this study we use a dataset of drilling-related impoundments in Pennsylvania identified through the FrackFinder project led by SkyTruth, an environmental non-profit. For each impoundment location, we compiled all low cloud Landsat imagery from 2000 to 2016 and created a monthly time series for three bands: red, near-infrared (NIR), and the Normalized Difference Vegetation Index (NDVI). We identified the approximate date of creation and removal of impoundments from sudden breaks in the time series. To verify our method, we compared the results to date ranges derived from photointerpretation of all available historical imagery on Google Earth for a subset of impoundments. Based on our analysis, we found that the number of impoundments built annually increased rapidly from 2006 to 2010, and then slowed from 2010 to 2013. Since newer impoundments tend to be larger, however, the total impoundment area has continued to increase. The methods described in this study would be appropriate for finding the creation and removal date of a variety of industrial land use changes at known locations.
Object-oriented image classification has tremendous potential to improve classification accuracies of land use and land cover (LULC), yet its benefits have only been minimally tested in peer-reviewed ...studies. We aim to quantify the benefits of an object-oriented method over a traditional pixel-based method for the mixed urban-suburban-agricultural landscape surrounding Gettysburg, Pennsylvania. To do so, we compared a traditional pixel-based classification using maximum likelihood to the object-oriented image classification paradigm embedded in eCognition Professional 4.0 software. This object-oriented paradigm has at least four components not typically used in pixel-based classification: (1) the segmentation procedure, (2) nearest neighbor classifier, (3) the integration of expert knowledge, and (4) feature space optimization. We evaluated each of these components individually to determine the source of any improvement in classification accuracy. We found that the combination of segmentation into image objects, the nearest neighbor classifier, and integration of expert knowledge yields substantially improved classification accuracy for the scene compared to a traditional pixel-based method. However, with the exception of feature space optimization, little or no improvement in classification accuracy is achieved by each of these strategies individually.
Large recent fires in the western U.S. have contributed to a perception that fire exclusion has caused an unprecedented occurrence of uncharacteristically severe fires, particularly in lower ...elevation dry pine forests. In the absence of long-term fire severity records, it is unknown how short-term trends compare to fire severity prior to 20th century fire exclusion. This study compares historical (i.e. pre-1920) fire severity with observed modern fire severity and modeled potential fire behavior across 564,413 ha of montane forests of the Colorado Front Range. We used forest structure and tree-ring fire history to characterize fire severity at 232 sites and then modeled historical fire-severity across the entire study area using biophysical variables. Eighteen (7.8%) sites were characterized by low-severity fires and 214 (92.2%) by mixed-severity fires (i.e. including moderate- or high-severity fires). Difference in area of historical versus observed low-severity fire within nine recent (post-1999) large fire perimeters was greatest in lower montane forests. Only 16% of the study area recorded a shift from historical low severity to a higher potential for crown fire today. An historical fire regime of more frequent and low-severity fires at low elevations (<2260 m) supports a convergence of management goals of ecological restoration and fire hazard mitigation in those habitats. In contrast, at higher elevations mixed-severity fires were predominant historically and continue to be so today. Thinning treatments at higher elevations of the montane zone will not return the fire regime to an historic low-severity regime, and are of questionable effectiveness in preventing severe wildfires. Based on present-day fuels, predicted fire behavior under extreme fire weather continues to indicate a mixed-severity fire regime throughout most of the montane forest zone. Recent large wildfires in the Front Range are not fundamentally different from similar events that occurred historically under extreme weather conditions.
Many spatially explicit studies of wildfire hazard focus on the wildland–urban interface (WUI), the area where natural vegetation intersects or mixes with structures. However, research suggests that ...the characteristics of a small portion of the WUI, the home ignition zone, largely determine potential for ignition from wildfire. The home ignition zone (HIZ) is the area that includes a structure and its surroundings out to 30–60 m. The primary goal of this study is to develop metrics to characterize land cover, burned area, and topography in the HIZ. Pre-fire metrics (i.e. related to land cover and topography) help identify relatively hazardous individual HIZes or neighborhoods of HIZes. Post-fire metrics can be used to assess the burned area across land cover types, inside and outside the HIZ. To calculate the HIZ metrics, multiple data sources (e.g. high resolution 8-band multispectral imagery and LiDAR point clouds) were integrated using an object-oriented image analysis. The setting for the study is the Fourmile Canyon area west of Boulder, Colorado, a data-rich area which experienced a large, destructive wildfire in September 2010. The land cover, burn area, and topography metrics were successfully and accurately calculated and then pre-fire metrics were combined into a simple HIZ hazard index. HIZ characteristics broadly mirror the characteristics of the WUI within the fire perimeter as a whole, though the HIZ on average contains more bare and less forest land, has more widely spaced canopies, and experienced less burning during the fire. The HIZ hazard index values were spatially heterogeneous, but with several distinct high and low hazard clusters. The methods described in this study, paired with in situ data collection, can be applied to other areas to inform hazard mitigation plans.
•Metrics to characterize the home ignition zone (HIZ) were developed.•The metrics were calculated for the area of the Fourmile Fire in Colorado.•The HIZ has less forest and greater spacing between canopies compared to the WUI.•A simple hazard index was used to identify clusters of relatively high risk HIZes.•The methods are broadly transferable to other WUI areas.
•We detected mountain pine beetle red attack in a time series of satellite imagery.•We analyzed the spatial structure and environmental predictors of the outbreak.•Outbreak spread was related to ...environmental characteristics and dispersal.•Beetle pressure increased in importance as the outbreak peaked.•Environmental factors characterizing infested locations also changed through time.
Over the past two decades, severe mountain pine beetle (MPB) outbreaks have affected several million hectares of forest in western North America. The extensive ecological and economic damage caused by widespread insect infestations make understanding the development and spread of MPB outbreaks critical. This study uses a time series of Landsat5 TM and Landsat7 ETM+images to map the spread of mortality due to MPB infestation in Arapaho–Roosevelt National Forest, Colorado, between 2003 and 2010. The Normalized Difference Vegetation Index (NDVI) and change in the Normalized Difference Moisture Index (NDMI) were used to classify red attack and non-red attack stands based on a maximum likelihood algorithm with manually selected training classes. The classification was validated by comparison with independent interpretations of aerial photography and high-resolution satellite imagery. The classification had good agreement (84.5–90.5% total accuracy). Cluster analysis for time series showed infestations originating in several different locations on the landscape early in the time series and subsequent infestations likely represent a combination of dispersal from outbreak populations and independent population growth. Analysis using conditional inference trees suggested that a combination of forest composition, topography, and dispersal predicted the distribution of MPB infestation on the landscape and that the importance of these variables changed as the outbreak developed. In early years, red attack was associated with forest and topographic characteristics known to influence susceptibility to MPB. Over time, beetle pressure became an increasingly important predictor of red attack, but in later years host tree availability played an important role in outbreak spread. If this pattern occurs consistently in MPB outbreaks, knowledge of these patterns could aid managers in targeting their efforts to reduce damage resulting from MPB outbreaks.
Himalayan communities that depend on rain-fed agriculture are disproportionately vulnerable to climate change. In this study, we compare local perceptions of climate change from a household survey (n ...= 251) to climate data obtained from the Global Land Data Assimilation System (GLDAS 2.1) and MODIS Terra Snow Cover data product datasets. The study is situated in and around the Kedarnath Wildlife Sanctuary, which is located within the Garhwal Himalayas in the Indian state of Uttarakhand. We found that a large majority of respondents perceive that rainfall is increasing and that snowfall is decreasing, while a smaller majority perceives an increase in summer temperatures and no change in winter temperatures. Agreeing with the perceptions of the majority, the climate data show an increase in summer temperature and winter rainfall. However, the climate data also show an increase in winter temperature, and no monotonic change in snowfall, findings which are contrary to the perception of the majority. Household perceptions of climate change were not associated with adaptation; while many households perceived change, very few reported that they were planning to adapt. To encourage adaptation, communities would benefit from locally appropriate climate data products, and collaboration on best practices with researchers, NGOs, and extension services.
The wildland-urban interface (WUI) is the area where human-built structures and infrastructure abut or mix with naturally occurring vegetation types. Wildfires are of particular concern in the WUI ...because these areas comprise extensive flammable vegetation, numerous structures, and ample ignition sources. A priority of federal wildland fire policy in the United States is to help protect communities threatened by wildfire, creating a demand for maps of the WUI. In this study, five models of the WUI are compared for four counties in the United States. The models are all based on the widely cited characteristics of the WUI published in the Federal Register, although they differ slightly in their focus (vegetation or housing) and implementation (the details of the WUI definition). For models that differ in focus, I describe how the purpose of the map led to different results. For conceptually similar models, I assess how different effects-the "dasymetric effect," the "settlement representation effect," and the "merging buffer effect"-influence the extent of the WUI in different counties. The differences between the WUI maps can be more or less pronounced depending on the spatial distribution of housing, vegetation, and public land. No single mapping approach is unequivocally superior, and each has tradeoffs that need to be fully understood for use in management. PUBLICATION ABSTRACT
Mussels (
Mytilus edulis
) build massive, spatially complex, biogenic structures that alter the biotic and abiotic environment and provide a variety of ecosystem services. Unlike rocky shores, where ...mussels can attach to the primary substrate, soft sediments are unsuitable for mussel attachment. We used a simple lattice model, field sampling, and field and laboratory experiments to examine facilitation of recruitment (i.e., preferential larval, juvenile, and adult attachment to mussel biogenic structure) and its role in the development of power-law spatial patterns observed in Maine, USA, soft-bottom mussel beds. The model demonstrated that recruitment facilitation produces power-law spatial structure similar to that in natural beds. Field results provided strong evidence for facilitation of recruitment to other mussels-they do not simply map onto a hard-substrate template of gravel and shell hash. Mussels were spatially decoupled from non-mussel hard substrates to which they can potentially recruit. Recent larval recruits were positively correlated with adult mussels, but not with other hard substrates. Mussels made byssal thread attachments to other mussels in much higher proportions than to other hard substrates. In a field experiment, mussel recruitment was highest to live mussels, followed by mussel shell hash and gravel, with almost no recruitment to muddy sand. In a laboratory experiment, evenly dispersed mussels rapidly self-organized into power-law clusters similar to those observed in nature. Collectively, the results indicate that facilitation of recruitment to existing mussels plays a major role in soft-bottom spatial pattern development. The interaction between large-scale resource availability (hard substrate) and local-scale recruitment facilitation may be responsible for creating complex power-law spatial structure in soft-bottom mussel beds.
Abstract
In the Western US, area burned and fire size have increased due to the influences of climate change, long-term fire suppression leading to higher fuel loads, and increased ignitions. ...However, evidence is less conclusive about increases in fire severity within these growing wildfire extents. Fires burn unevenly across landscapes, leaving islands of unburned or less impacted areas, known as fire refugia. Fire refugia may enhance post-fire ecosystem function and biodiversity by providing refuge to species and functioning as seed sources after fires. In this study, we evaluated whether the proportion and pattern of fire refugia within fire events have changed over time and across ecoregions. To do so, we processed all available Landsat 4–9 satellite imagery to identify fire refugia within the boundaries of large wildfires (405 ha+) in 16 forested ecoregions of the Western US. We found a significant change in % refugia from 1986–2021 only in one ecoregion—% refugia increased within fires in the Arizona/New Mexico Mountain ecoregion (AZ/NM). Excluding AZ/NM, we found no significant change in % refugia across the study area. Furthermore, we found no significant change in mean refugia patch size, patch density, or mean distance to refugia. As fire size increased, the amount of refugia increased proportionally. Evidence suggests that fires in AZ/NM had a higher proportion of reburns and, unlike the 15 other ecoregions, fires did not occur at higher elevation or within greener areas. We suggest several possibilities for why, with the exception of AZ/NM, ecoregions did not experience a significant change in the proportion and pattern of refugia. In summary, while area burned has increased over the past four decades, there are substantial and consistent patterns of refugia that could support post-fire recovery dependent on their spatial patterns and ability to function as seeds sources for neighboring burned patches.
Cutter et al. offer a reflection on Gilbert F. White (1911-2006) who is among the most distinguished and honored American geographers of the 20th century. Among his many contributions, he stimulated ...efforts by geographers and others to foster human adjustments to the risks of endangered planet through better-informed policies and decisions at all levels of society. As executive editor of Environment from 1983-1992, Gilbert helped to guide the publication into a position as the venue for high-quality, policy-relevant environmental research that was widely read by many officials in Washington DC, who often displayed copies of Environment in their waiting rooms.
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