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At least 1,603 records · Page 89Linked to original sources
USGS2011

Estimating tiger abundance from camera trap data: Field surveys and analytical issues

Automated photography of tigers Panthera tigris for purely illustrative purposes was pioneered by British forester Fred Champion (1927, 1933) in India in the early part of the Twentieth Century. However, it was McDougal (1977) in Nepal who first used camera traps, equipped with single-lens reflex cameras activated by pressure pads, to identify individual tigers and study their social and predatory behaviors. These attempts involved a small number of expensive, cumbersome camera traps, and were not, in any formal sense, directed at “sampling” tiger populations.

Book chapter↗
USGS2011

Estimation of demographic parameters in a tiger population from long-term camera trap data

Chapter 7 (Karanth et al.) illustrated the use of camera trapping in combination with closed population capture–recapture (CR) models to estimate densities of tigers Panthera tigris. Such estimates can be very useful for investigating variation across space for a particular species (e.g., Karanth et al. 2004) or variation among species at a specific location. In addition, estimates of density continued at the same site(s) over multiple years are very useful for understanding and managing populations of large carnivores. Such multi-year studies can yield estimates of rates of change in abundance. Additionally, because the fates of marked individuals are tracked through time, biologists can delve deeper into factors driving changes in abundance such as rates of survival, recruitment and movement (Williams et al. 2002). Fortunately, modern CR approaches permit the modeling of populations that change between sampling occasions as a result of births, deaths, immigration and emigration (Pollock et al. 1990; Nichols 1992). Some of these early “open population” models focused on estimation of survival rates and, to a lesser extent, abundance, but more recent models permit estimation of recruitment and movement rates as well.

Book chapter↗
USGS2011

Patch reefs: Lidar morphometric analysis

Alina Reef is one of several thousand patch reefs that lie across the shallow carbonate platform seaward of Hawk Channel off the northern Florida Keys. The site is near the northern latitudinal fringe of the late Holocene western Atlantic coral reef distribution (Figure 1 ). The area is covered by calcareous sand and discontinuous Thalassia testudinum seagrass meadows and is studded with numerous scattered Holocene patch reefs. Most of the patch reefs are found in water depths of 2–9 m, are subcircular, elliptical, or irregular in plan view, and range up to about 8 m in vertical relief and 700 m in width. Coring has demonstrated thicknesses of 4.5–6 m and has revealed frameworks built by large, massive head corals.

Florida↗
USGS2011

Porosity variability in limestone sequences

Porosity is the state of being porous, as measured by the percentage of bulk volume of a rock or soil that is occupied by space, whether isolated or connected. In hydrocarbon-bearing limestone settings, subsurface porous strata containing the oil or gas usually underlie non-porous caprock through which hydrocarbons cannot pass. In settings, subsurface freshwater aquifers beneath caprock can become contaminated by saltwater intrusion during periods of drought. Islands of the Florida Keys consist of two types of emergent 125-ka limestone, a highly porous fossil coral reef with large voids and a less porous oolite with small grains and interstices. Both limestones are capped by impervious laminated Holocene calcrete whose dimensions differ greatly (Figure 1a and b). Porosity variability in the limestones is thought to be the cause. The less permeable oolite retained rainfall moisture longer, allowing longer periods of calcrete buildup. Reddish and brownish layers in both illustrated calcrete samples represent periods of influx of non-carbonate minerals on African dust. The hiatus or gap in these rock records represents an interval of >115 kyr during which no marine or terrestrial deposition is recorded.

Book chapter↗
USGS2009

Methodology for an integrative assessment of China's ecological restoration programs

While research projects have been conducted to examine the impacts and effectiveness of China's ecological restoration programs, few of them represent integrated, systematic efforts. The objective of this chapter is thus to articulate and outline a methodology for an integrative assessment, which, we believe, should embrace both the environmental and socioeconomic changes and engage investigations at multiple scales. Further, these investigations should be pursued through interdisciplinary collaboration with expertise from ecology, economics, hydrology, and geospatial, climate, and land change sciences. We argue that the deployment of geospatial capability, the use of longitudinal data, and the connection between science and policy should be the hallmarks of an integrative assessment. We also describe our general approach and specific models to quantify the environmental and socioeconomic impacts induced by implementing the restoration programs, and address the issue of how to overcome the challenges in generating the data needed for executing various empirical tasks. We hope that the adoption and application of this methodology will make a valuable contribution to a more robust and timely assessment as well as implementation of the ecological restoration programs in and outside of China.

Book chapter↗
USGS2009

Seismic monitoring to assess performance of structures in near-real time: Recent progress

Earlier papers have described how observed data from classical accelerometers deployed in structures or from differential GPS with high sampling ratios deployed at roofs of tall buildings can be configured to establish seismic health monitoring of structures. In these configurations, drift ratios are the main parametric indicator of damage condition of a structure or component of a structure. Real-time measurement of displacements are acquired either by double integration of accelerometer time-series data, or by directly using GPS. Recorded sensor data is then related to the performance level of a building. Performance-based design method stipulates that for a building the amplitude of relative displacement of the roof of a building (with respect to its base) indicates its performance. Usually, drift ratio is computed using relative displacement between two consecutive floors. When accelerometers are used, determination of displacement is possible by strategically deploying them at a select number of pairs of consecutive floors. For these determinations, software is used to compute displacements and drift ratios in real-time by double integration of accelerometer data. However, GPS-measured relative displacements are limited to being acquired only at the roof with respect to its reference base. Thus, computed drift ratio is the average drift ratio for the whole building. Until recently, the validity of measurements using GPS was limited to long-period structures (T>1 s) because GPS systems readily available were limited to 10–20 samples per seconds (sps) capability. However, presently, up to 50 sps differential GPS systems are available on the market and have been successfully used to monitor drift ratios [1, Panagitou et al. (Seismic Response of ReinForced Concrete Wall Buildings, 2006)], (Restrepo, pers. comm. 2007) – thus enabling future usefulness of GPS to all types of structures. Several levels of threshold drift ratios can be postulated in order to make decisions for inspections and/or occupancy. Experience with data acquired from both accelerometers and GPS deployments indicates that they are reliable and provide pragmatic alternatives to alert the owners and other authorized parties to make informed decisions and select choices for pre-defined actions following significant events. Furthermore, recent adoption of such methods by financial and industrial enterprises is testimony to their viability.

Book chapter↗
USGS2009

Passive seismic monitoring of natural and induced earthquakes: Case studies, future directions and socio-economic relevance

An important discovery in crustal mechanics has been that the Earth’s crust is commonly stressed close to failure, even in tectonically quiet areas. As a result, small natural or man-made perturbations to the local stress field may trigger earthquakes. To understand these processes, Passive Seismic Monitoring (PSM) with seismometer arrays is a widely used technique that has been successfully applied to study seismicity at different magnitude levels ranging from acoustic emissions generated in the laboratory under controlled conditions, to seismicity induced by hydraulic stimulations in geological reservoirs, and up to great earthquakes occurring along plate boundaries. In all these environments the appropriate deployment of seismic sensors, i.e., directly on the rock sample, at the earth’s surface or in boreholes close to the seismic sources allows for the detection and location of brittle failure processes at sufficiently low magnitude-detection threshold and with adequate spatial resolution for further analysis. One principal aim is to develop an improved understanding of the physical processes occurring at the seismic source and their relationship to the host geologic environment. In this paper we review selected case studies and future directions of PSM efforts across a wide range of scales and environments. These include induced failure within small rock samples, hydrocarbon reservoirs, and natural seismicity at convergent and transform plate boundaries. Each example represents a milestone with regard to bridging the gap between laboratory-scale experiments under controlled boundary conditions and large-scale field studies. The common motivation for all studies is to refine the understanding of how earthquakes nucleate, how they proceed and how they interact in space and time. This is of special relevance at the larger end of the magnitude scale, i.e., for large devastating earthquakes due to their severe socio-economic impact.

Book chapter↗
USGS2009

Real-time decision support systems: the famine early warning system network

A multi-institutional partnership, the US Agency for International Development’s Famine Early Warning System Network (FEWS NET) provides routine monitoring of climatic, agricultural, market, and socioeconomic conditions in over 20 countries. FEWS NET supports and informs disaster relief decisions that impact millions of people and involve billions of dollars. In this chapter, we focus on some of FEWS NET’s hydrologic monitoring tools, with a specific emphasis on combining “low frequency” and “high frequency” assessment tools. Low frequency assessment tools, tied to water and food balance estimates, enable us to evaluate and map long-term tendencies in food security. High frequency assessments are supported by agrohydrologic models driven by satellite rainfall estimates, such as the Water Requirement Satisfaction Index (WRSI). Focusing on eastern Africa, we suggest that both these high and low frequency approaches are necessary to capture the interaction of slow variations in vulnerability and the relatively rapid onset of climatic shocks.

Book chapter↗
USGS2010

Submarine mass transport within Monterey Canyon: Benthic disturbance controls on the distribution of chemosynthetic biological communities

Documenting mass transport within Monterey Canyon and Fan has been a focus of remotely operated vehicle (ROV) observations, sampling, monitoring, and multibeam mapping studies. These efforts indicate that major mass transport events occur within upper Monterey Canyon (<2 km water depths) with a sub-annual recurrence frequency. However, 14 C-stratigraphies indicate that a sand carrying event has not penetrated through lower Monterey Canyon (>2 km water depths) and onto Monterey Fan for ~100 years. Simultaneous efforts to document the distribution of benthic taxa observed in the video records from 668 ROV dives conducted by the Monterey Bay Aquarium Research Institute (MBARI) provide a uniquely detailed record of the occurrence of chemosynthetic biological communities (CBC). The combined results of these studies provide an understanding of the relationship between disturbance caused by episodic mass wasting events and the distribution of CBC. CBC are common within the canyon's axis below ~2.5 km water depth, but have not been found within the canyon's axis at depths shallower than 2 km. Moreover, CBC occur on the canyon walls at essentially any depth, primarily within young (~hundreds of years old) slump scars. The distribution of CBC provides evidence about the disturbance history of the seafloor. Major mass transport events will destroy communities that lie in their path. Erosion associated with major mass transport events can create environments to support CBC by exposing methane-bearing strata. This can happen as a result of slumping events on the sidewalls of the canyon or where major gravity flow events have excavated the base of canyon walls. Once fresh strata are exposed, geochemical conditions to support CBC will persist for a few centuries. Because CBC are composed of slow-growing and long-lived organisms, it will take decades for these communities to be established. Their existence indicates that environmental stability has occurred over a similar time scale.

California↗
USGS2010

The Block composite submarine landslide, southern New England slope, U.S.A.: A morphological analysis

Recent multibeam surveys along the continental slope and rise off southeast New England has enabled a detailed morphological analysis of the Block composite landslide. This landslide consists of at least three large debris lobes resting on a gradient less than 0.5 °. The slide took place on gradients of between 1 ° and 5 ° in Quaternary sediments likely deposited at the time of low sea level and high sedimentation rates associated with glaciations. The slide debris lobes are very close to each other and cover an area of about 1.125 km 2 of the sea floor. With an average thickness of 50 m, the total volume of the deposit is estimated at 36 km 3 . In some cases, the departure zone appears to be near the crest of the continental slope, at a water depth between 500 and 2,000 m with debris spreading over about 20 km at a depth ranging from 2,500 to 2,600 m. From preliminary analysis, at least one lobe of the Block Composite slide (lobe 2) would require further study to evaluate its tsunamigenic potential.

Book chapter↗
USGS2010

Estimating the empirical probability of submarine landslide occurrence

The empirical probability for the occurrence of submarine landslides at a given location can be estimated from age dates of past landslides. In this study, tools developed to estimate earthquake probability from paleoseismic horizons are adapted to estimate submarine landslide probability. In both types of estimates, one has to account for the uncertainty associated with age-dating individual events as well as the open time intervals before and after the observed sequence of landslides. For observed sequences of submarine landslides, we typically only have the age date of the youngest event and possibly of a seismic horizon that lies below the oldest event in a landslide sequence. We use an empirical Bayes analysis based on the Poisson-Gamma conjugate prior model specifically applied to the landslide probability problem. This model assumes that landslide events as imaged in geophysical data are independent and occur in time according to a Poisson distribution characterized by a rate parameter &lambda;. With this method, we are able to estimate the most likely value of &lambda; and, importantly, the range of uncertainty in this estimate. Examples considered include landslide sequences observed in the Santa Barbara Channel, California, and in Port Valdez, Alaska. We confirm that given the uncertainties of age dating that landslide complexes can be treated as single events by performing statistical test of age dates representing the main failure episode of the Holocene Storegga landslide complex.

Book chapter↗
USGS2010

Historic and paleo-submarine landslide deposits imaged beneath Port Valdez, Alaska: Implications for tsunami generation in a glacial fiord

During the 1964 M9.2 great Alaskan earthquake, submarine-slope failures resulted in the generation of highly destructive tsunamis at Port Valdez, Alaska. A high-resolution, mini-sparker reflection profiler was used to image debris lobes, which we attribute to slope failures that occurred both during and prior to the 1964 megathrust event. In these reflection profiles, debris lobe deposits are indicated by acoustically opaque units that are separated by undisturbed parallel-layered reflectors. Near-surface debris lobes attributed to the 1964 earthquake include: (1) a debris lobe over 30 m thick that emanates from the fiord-head delta in eastern Port Valdez; and (2) debris flow lobes incorporating large, intact blocks up to 40 m high in western Port Valdez, off the Shoup Glacier moraine. In addition to the near-surface debris lobes, we imaged at least five additional debris lobe deposits buried beneath the 1964 deposit. The debris lobe directly beneath the 1964 deposit has a similar thickness and spatial distribution as the 1964 deposit. However, the older, deeper, debris lobes are thinner, less extensive, and separated by thinner sequences of parallel-layered reflectors. Glacier retreat and concomitant build-up of the fiord-head delta combined with longer time intervals between megathrust events may have resulted in more extensive delta failures and thus thicker debris lobes through time.

Alaska↗
USGS2009

Applications of stable isotopes for regional to national-scale water quality and environmental monitoring programs

Isotopes are a potentially powerful component of monitoring and assessment programs aimed at quantifying and mitigating alterations to environments from human activities. In particular, isotopic techniques have proved useful for tracing sources and sinks of various pollutants in large river basins, wetlands, and airsheds. Many of these studies have been conducted at the regional to national scale by building on existing large-scale water, air, and ecological monitoring programs managed by federal and state agencies, and demonstrate the usefulness of isotopes as a complement to standard chemical and hydrological mass balance methods. This chapter presents an overview of how nitrate, particulate organic matter, and water isotopes can be used to interpret spatial patterns and temporal changes in pollution sources, biogeochemical processes, and ecosystem function in watersheds, at the regional to national scale. Examples from several recent and ongoing studies are presented. From the insights developed using varied sampling strategies and isoscapes, we suggest guidelines for future studies in biologically active and human-impacted rivers.

Book chapter↗
USGS2010

Interpolating a consumption variable for scaling and generalizing potential population pressure on urbanizing natural areas

Measures of population pressure, referring in general to the stress upon the environment by human consumption of resources, are imperative for environmental sustainability studies and management. Development based on resource consumption is the predominant factor of population pressure. This paper presents a spatial model of population pressure by linking consumption associated with regional urbanism and ecosystem services. Maps representing relative geographic degree and extent of natural resource consumption and degree and extent of impacts on surrounding areas are new, and this research represents the theoretical research toward this goal. With development, such maps offer a visualization tool for planners of various services, amenities for people, and conservation planning for ecologist. Urbanization is commonly generalized by census numbers or impervious surface area. The potential geographical extent of urbanism encompasses the environmental resources of the surrounding region that sustain cities. This extent is interpolated using kriging of a variable based on population wealth data from the U.S. Census Bureau. When overlayed with land-use/land-cover data, the results indicate that the greatest estimates of population pressure fall within mixed forest areas. Mixed forest areas result from the spread of cedar woods in previously disturbed areas where further disturbance is then suppressed. Low density areas, such as suburbanization and abandoned farmland are characteristic of mixed forest areas.

Missouri↗