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At least 55 records · Page 3Linked to original sources
USGS2012

Seasonal zooplankton dynamics in Lake Michigan: disentangling impacts of resource limitation, ecosystem engineering, and predation during a critical ecosystem transition

We examined seasonal dynamics of zooplankton at an offshore station in Lake Michigan from 1994 to 2003 and 2007 to 2008. This period saw variable weather, declines in planktivorous fish abundance, the introduction and expansion of dreissenid mussels, and a slow decline in total phosphorus concentrations. After the major expansion of mussels into deep water (2007–2008), chlorophyll in spring declined sharply, Secchi depth increased markedly in all seasons, and planktivorous fish biomass declined to record-low levels. Overlaying these dramatic ecosystem-level changes, the zooplankton community exhibited complex seasonal dynamics between 1994–2003 and 2007–2008. Phenology of the zooplankton maximum was affected by onset of thermal stratification, but there was no other discernable effect due to temperature. Interannual variability in zooplankton biomass during 1994 and 2003 was strongly driven by planktivorous fish abundance, particularly age-0 and age-1 alewives. In 2007–2008, there were large decreases in Diacyclops thomasi and Daphnia mendotae possibly caused by food limitation as well as increased predation and indirect negative effects from increases in Bythotrephes longimanus abundance and in foraging efficiency associated with increased light penetration. The Bythotrephes increase was likely driven in part by decreased predation from yearling and older alewife. While there was a major decrease in epilimnetic–metalimnetic herbivorous cladocerans in 2007–2008, there was an increase in large omnivorous and predacious calanoid copepods, especially those in the hypolimnion. Thus, changes to the zooplankton community are the result of cascading, synergistic interactions, including a shift from vertebrate to invertebrate planktivory and mussel ecosystem impacts on light climate and chlorophyll.

Journal of Great Lakes Research↗
USGS1998

The role of introduced species in the degradation of island ecosystems: A case history of Guam

The accidental introduction of the brown treesnake ( Boiga irregularis ) on Guam around 1950 induced a cascade of extirpations that may be unprecedented among historical extinction events in taxonomic scope and severity. Birds, bats, and reptiles were affected, and by 1990 most forested areas on Guam retained only three native vertebrates, all of which were small lizards. Of the hypotheses to account for the severity of this extinction event, we find some support for the importance of lack of coevolution between introduced predator and prey, availability of alternate prey, extraordinary predatory capabilities of the snake, and vulnerabilities of the Guam ecosystem. In addition, there were important interactions among these factors, especially the presence of introduced prey (possessing coevolutionary experience) that were thus able to maintain their populations and provide alternate prey to the introduced predator while it was driving the native prey species to extinction. This complex of vulnerabilities is common on oceanic islands.

Annual Review of Ecology and Systematics↗
USGS2007

Understanding Ecosystems and Predicting Ecosystem Change

In 2007, the U.S. Geological Survey (USGS) developed a science strategy outlining the major natural science issues facing the Nation in the next decade. The science strategy consists of six science directions of critical importance, focusing on areas where natural science can make a substantial contribution to the well-being of the Nation and the world. This fact sheet focuses on understanding ecosystems and predicting ecosystem change, and how USGS research can strengthen the Nation with information needed to meet the challenges of the 21st century.

Fact Sheet↗
USGS2011

Land-use planning for nearshore ecosystem services—the Puget Sound Ecosystem Portfolio Model

The 2,500 miles of shoreline and nearshore areas of Puget Sound, Washington, provide multiple benefits to people—"ecosystem services"—including important fishing, shellfishing, and recreation industries. To help resource managers plan for expected growth in coming decades, the U.S. Geological Survey Western Geographic Science Center has developed the Puget Sound Ecosystem Portfolio Model (PSEPM). Scenarios of urban growth and shoreline modifications serve as model inputs to develop alternative futures of important nearshore features such as water quality and beach habitats. Model results will support regional long-term planning decisions for the Puget Sound region.

Washington↗
USGS2013

Changing Arctic ecosystems--the role of ecosystem changes across the Boreal-Arctic transition zone on the distribution and abundance of wildlife populations

Arctic and boreal ecosystems provide important breeding habitat for more than half of North America’s migratory birds as well as many resident species. Northern landscapes are projected to experience more pronounced climate-related changes in habitat than most other regions. These changes include increases in shrub growth, conversion of tundra to forest, alteration of wetlands, shifts in species’ composition, and changes in the frequency and scale of fires and insect outbreaks. Changing habitat conditions, in turn, may have significant effects on the distribution and abundance of wildlife in these critical northern ecosystems. The U.S. Geological Survey (USGS) is conducting studies in the Boreal–Arctic transition zone of Alaska, an environment of accelerated change in this sensitive margin between Arctic tundra and boreal forest.

Alaska↗
USGS2016

Ecosystem engineering of harvester ants: Effects on vegetation in a sagebrush-steppe ecosystem

Harvester ants are influential in many ecosystems because they distribute and consume seeds, remove vegetation, and redistribute soil particles and nutrients. Understanding the interaction between harvester ants and plant communities is important for management and restoration efforts, particularly in systems altered by fire and invasive species such as the sagebrush-steppe. Our objective was to evaluate how vegetation cover changed as a function of distance from Owyhee harvester ant ( Pogonomyrmex salinus ) nests within a sagebrush-steppe ecosystem. We sampled 105 harvester ant nests within southern Idaho, USA, that occurred in different habitats: annual grassland, perennial grassland, and native shrubland. The influence of Owyhee harvester ants on vegetation was larger at the edge of ant nests, but the relationship was inconsistent among plant species. Percent cover was positively associated with distance from harvester ant nests for plant species that were considered undesirable food sources and were densely distributed. However, percent cover was negatively associated with distance-from-nests for patchily distributed and desirable plant species. For some plant species, there was no change in cover associated with distance-from-nests. Total vegetation cover was associated with distance-from-nests in the shrubland habitat but not in the 2 grasslands. The dominant plant species in the shrubland habitat was a densely distributed shrub (winterfat, Krascheninnikovia lanata ) that was defoliated by harvester ants. Our results suggest that Owyhee harvester ants increase spatial heterogeneity in plant communities through plant clearing, but the direction and magnitude of effect will likely be contingent on the dominant vegetation groups. This information may inform future management and plant restoration efforts in sagebrush-steppe by directly considering the islands of influence associated with harvester ant engineering.

Idaho↗
USGS2026

Excessive phosphorus loading contributes to future vulnerability of mangrove ecosystems by reducing net ecosystem exchange of carbon

J.N. “Ding” Darling National Wildlife Refuge (DDNWR) is located on Sanibel Island along the southwestern coast of Florida, USA. There, eutrophication attributed to agricultural discharge along the Caloosahatchee River has affected the area’s aquatic habitat. In anticipation of additional nutrient loading, we experimentally fertilized mangrove forests with nitrogen (+N; NH4) and phosphorus (+P; P2O5) for 3 years, and monitored soil and pneumatophore CO2 fluxes and tree sap flow from two mangrove species. Furthermore, we modeled individual tree and stand water use, from which we developed carbon (C) budgets for +N and + P vs. control simulations based on a novel application of water use efficiency conversion. Many of the measured response variables provided hints of subtle changes in response to +P rather than +N, which were enhanced when scaled. From this, we found that additional P loading is expected to reduce both gross and net primary productivity as well as CO2 uptake via net ecosystem exchange of C, likely pressing the system beyond metabolic capacity and leading to a 48–62% decrease in projected lateral C export. Greater eutrophication will likely compound vulnerabilities to sea-level rise submergence, especially where P concentrations are high and already reducing soil surface elevations.

Florida↗
USGS2022

Higher temperature sensitivity of ecosystem respiration in low marsh compared to high elevation marsh ecosystems

Salt marsh habitats contain some of the highest quantities of soil organic carbon (C) per unit area, but increasing anthropogenic stressors threaten their ability to maintain themselves as large C reservoirs in some regions. We quantify rates of C gas exchange (methane [CH 4 ] and carbon dioxide [CO 2 ]) monthly across a 16-month period from a low nitrogen “reference” salt marsh on Cape Cod in New England using static chambers. While the summer period is the most dynamic period of marsh C gas exchange, we observed substantial fluxes in the early summer through late fall, highlighting the importance of including shoulder seasons in studies of marsh C exchange. We estimate annual ecosystem respiration between 108 and 252 g C m −2 yr −1 , which varied based on temperature and elevation. This flux is lower than in other nearby marshes, which we attribute to the frequently inundated, microtidal nature of the site, resulting in the majority of respired CO 2 being exported via lateral, not vertical, fluxes from this marsh. We observed significantly higher temperature sensitivity from the low elevation of the marsh compared to the high marsh. Recent acceleration in the rate of sea level rise is leading to a well-documented expansion of low marsh into high marsh vegetation zones in this marsh system and others in the region. While rates of C burial are higher in the low marsh compared to the high marsh, the higher temperature sensitivity of respiration in the low marsh may diminish the longevity of marsh C stocks with climate warming.

Massachusetts↗
USGS1999

Ecosystem history: Terrestrial and fresh-water ecosystems of southern Florida

Introduction Plant and animal communities of the historic Everglades have undergone striking changes over the last few decades, including declines in wading bird populations, invasion by exotic (non-native) plant and animal species, and areal expansion of cattails into sawgrass marshes. Many of these changes have been attributed to human activities in the region, and efforts are underway to restore the Everglades to a more pristine state. Restoration plans include alteration of the present levee and canal system that controls water flow throughout southern Florida and changes in agricultural and land development activities. However, can we be sure that the observed changes are related to human practices rather than representing an extreme in the natural variability of the system? This question should be answered before changing current land-use practices to alleviate environmental concerns. To address this question, it is necessary to look at patterns of floral and faunal change over the last century as well as over the last few millennia. This project aims to reconstruct floral and faunal composition at selected time intervals throughout southern Florida to determine: 1) detailed biotic changes over the last 150 years; 2) the natural range of biotic variability over the last few thousand years; and 3) determine whether any cause-and-effect relationships exist between biotic and environmental changes. Such questions are being addressed by scientists in the South Florida Initiative of the Ecosystem Program at the U.S. Geological Survey.

Florida↗
USGS2016

Clawpack: Building an open source ecosystem for solving hyperbolic PDEs

Clawpack is a software package designed to solve nonlinear hyperbolic partial differential equations using high-resolution finite volume methods based on Riemann solvers and limiters. The package includes a number of variants aimed at different applications and user communities. Clawpack has been actively developed as an open source project for over 20 years. The latest major release, Clawpack 5, introduces a number of new features and changes to the code base and a new development model based on GitHub and Git submodules. This article provides a summary of the most significant changes, the rationale behind some of these changes, and a description of our current development model.

PeerJ Computer Science↗
USGS1999

Fire and aquatic ecosystems in forested biomes of North America

Synthesis of the literature suggests that physical, chemical, and biological elements of a watershed interact with long‐term climate to influence fire regime, and that these factors, in concordance with the postfire vegetation mosaic, combine with local‐scale weather to govern the trajectory and magnitude of change following a fire event. Perturbation associated with hydrological processes is probably the primary factor influencing postfire persistence of fishes, benthic macroinvertebrates, and diatoms in fluvial systems. It is apparent that salmonids have evolved strategies to survive perturbations occurring at the frequency of wildland fires (10°–10 2 years), but local populations of a species may be more ephemeral. Habitat alteration probably has the greatest impact on individual organisms and local populations that are the least mobile, and reinvasion will be most rapid by aquatic organisms with high mobility. It is becoming increasingly apparent that during the past century fire suppression has altered fire regimes in some vegetation types, and consequently, the probability of large stand‐replacing fires has increased in those areas. Current evidence suggests, however, that even in the case of extensive high‐severity fires, local extirpation of fishes is patchy, and recolonization is rapid. Lasting detrimental effects on fish populations have been limited to areas where native populations have declined and become increasingly isolated because of anthropogenic activities. A strategy of protecting robust aquatic communities and restoring aquatic habitat structure and life history complexity in degraded areas may be the most effective means for insuring the persistence of native biota where the probability of large‐scale fires has increased.

Transactions of the American Fisheries Society↗
USGS2012

Changing Arctic ecosystems - measuring and forecasting the response of Alaska's terrestrial ecosystem to a warming climate

The Arctic Coastal Plain of northern Alaska is a complex landscape of lakes, streams, and wetlands scattered across low relief tundra that is underlain by permafrost. This region of the Arctic has experienced a warming trend over the past three decades, leading to thawing of on-shore permafrost and the disappearance of sea ice at an unprecedented rate. The loss of sea ice has increased ocean wave action, leading to higher rates of erosion and salt water inundation of coastal habitats. Warming temperatures also have advanced the overall phenology of the region, including earlier snowmelt, lake ice thaw, and plant growth. As a result, many migratory species now arrive in the Arctic several days earlier in spring than in the 1970s. Predicted warming trends for the future will continue to alter plant growth, ice thaw, and other basic landscape processes. These changes will undoubtedly result in different responses by wildlife (fish, birds, and mammals) and the food they rely upon (plants, invertebrates, and fish). However, the type of response by different wildlife populations and their habitats-either positively or negatively-remains largely unknown.

Alaska↗
USGS2013

U.S. Geological Survey ecosystems science strategy—Advancing discovery and application through collaboration

Executive Summary Ecosystem science is critical to making informed decisions about natural resources that can sustain our Nation’s economic and environmental well-being. Resource managers and policymakers are faced with countless decisions each year at local, regional, and national levels on issues as diverse as renewable and nonrenewable energy development, agriculture, forestry, water supply, and resource allocations at the urban-rural interface. The urgency for sound decisionmaking is increasing dramatically as the world is being transformed at an unprecedented pace and in uncertain directions. Environmental changes are associated with natural hazards, greenhouse gas emissions, and increasing demands for water, land, food, energy, mineral, and living resources. At risk is the Nation’s environmental capital, the goods and services provided by resilient ecosystems that are vital to the health and wellbeing of human societies. Ecosystem science—the study of systems of organisms interacting with their environment and the consequences of natural and human-induced change on these systems—is necessary to inform decisionmakers as they develop policies to adapt to these changes. This Ecosystems Science Strategy is built on a framework that includes basic and applied science. It highlights the critical roles that U.S. Geological Survey (USGS) scientists and partners can play in building scientific understanding and providing timely information to decisionmakers. The strategy underscores the connection between scientific discoveries and the application of new knowledge, and it integrates ecosystem science and decisionmaking, producing new scientific outcomes to assist resource managers and providing public benefits. We envision the USGS as a leader in integrating scientific information into decisionmaking processes that affect the Nation’s natural resources and human well-being. The USGS is uniquely positioned to play a pivotal role in ecosystem science. With its wide range of expertise, the Bureau can bring holistic, cross-scale, interdisciplinary capabilities to the design and conduct of monitoring, research, and modeling and to new technologies for data collection, management, and visualization. Collectively, these capabilities can be used to reveal ecological patterns and processes, explain how and why ecosystems change, and forecast change over different spatial and temporal scales. USGS science can provide managers with options and decision-support tools to use resources sustainably. The USGS has long-standing, collaborative relationships with the Department of the Interior (DOI) and other partners in the natural sciences, in both conducting science and applying the results. The USGS engages these partners in cooperative investigations that otherwise would lack the necessary support or be too expensive for a single bureau to conduct. The heart of this strategy is a framework for USGS ecosystems science that focuses on five long-term goals, which are seen as interconnected components that reinforce our vision of the USGS providing science that is at the forefront of decisionmaking: Improve understanding of ecosystem structure, function, and processes. The focus for this goal is an understanding of how ecosystems work, including the dynamics of species, their populations, interactions, and genetics, and how they change across spatial and temporal scales. Advance understanding of how drivers influence ecosystem change. The challenges here are explaining the drivers of ecosystem change, their spatio-temporal patterns, their uncertainties and interactions, and their influence on ecosystem processes and dynamics. Improve understanding of the services that ecosystems provide to society. Here the emphasis is on the measurement of environmental capital and ecosystem services, and the identification of sources and patterns of change in space and time. Develop tools, technologies, and capacities to inform decisionmaking about ecosystems. This includes developing new technologies and approaches for conducting applications-oriented ecosystem science. A principal challenge will be how to quantify uncertainty and incorporate it in decision analysis. Apply science to enhance strategies for management, conservation, and restoration of ecosystems. These challenges include development of novel approaches to monitoring, assessment, and restoration of ecosystems; new methods to address species of concern and communities at risk; and innovations in decision analysis and support to address imminent ecosystem changes or those that are underway. Closely integrated with the five goals are four strategic approaches that provide the path forward for the USGS Ecosystems Mission Area. These approaches cross-cut all of the goals and are seen as essential to the implementation of this strategy: Assess information needs for ecosystem science through enhanced partnerships. Work with the DOI and other agencies and institutions to identify, design, and implement priority decision-driven ecological research. Promote the use of interdisciplinary ecosystem science. Design and conduct interdisciplinary process-oriented research in ecosystem science. Enhance modeling and forecasting. Build models to forecast ecosystem change, assess future management scenarios, and reduce uncertainties through an adaptive learning process. Support decisionmaking. Use quantitative approaches to assess the vulnerabilities of ecosystems, habitats, and species, and evaluate strategies for adaptation, restoration, and sustainable management. Following the four strategic approaches are a set of proposed actions that represent a sampling of specific USGS activities that align with this strategy and that address the Nation’s most pressing environmental needs. The strategy emphasizes coordination of activities across the USGS mission areas pursuant to these goals. Ecosystem science is inherently interdisciplinary and requires a broad perspective that incorporates the biological and physical sciences, climate science, information technology, and scientific capacity in mission areas across the Bureau. With its emphasis on coordination, this strategy can provide a critical underpinning for integrated science efforts with scientists from multiple mission areas of the USGS working together. Of course, the USGS will continue to conduct discipline-specific and interdisciplinary investigations, and both will continue to be vital parts of the ecosystem science portfolio. Finally, the strategy stresses the importance of coordination with other Federal agencies and organizations in the natural resources community. The USGS collaborates with resource agencies in the DOI and other organizations throughout the world to meet societal needs for species and ecosystem management. Working with these agencies and organizations, the USGS will play a key role in guiding sound decisionmaking during the next decade by advancing the scientific foundation for sustaining the natural resources that diverse, productive, resilient ecosystems provide.

Circular↗