Holocene and Modern Drivers of Wetland Change
On a global scale, wetland systems are affected by precipitation extremes, changing sea level, and population growth, influencing their capacity to moderate storm surge, filter contaminants, and provide habitats for fish and wildlife. This research takes a long-term perspective on the resilience of wetlands to a range of environmental- and human-induced changes and supports wetland management by providing critical data to support decisions on use of wetlands in ‘nature-based’ mitigation strategies.
Wetlands serve many important functions: providing habitats for fish and wildlife, moderating storm surge, and filtering contaminants over long time periods. Over the last few centuries, the combined effects of human modification of the landscape, precipitation and temperature variability, and rising sea level have reduced wetland extent by nearly half across the United States. These reductions have been accompanied by changes in plant communities, fire regimes, and sedimentation. This project integrates new paleoenvironmental data with monitoring and instrumental data from long term study sites in wetlands in the Gulf Coast, Alaska, Hawaii, and the Pacific Islands to advance understanding of wetland resilience to a range of environmental and human-induced changes. Results of this effort are advancing understanding of the underlying processes that influence wetland systems and provide critical data to support decisions on wetland restoration and the use of wetlands as ‘nature-based’ solutions to mitigation strategies.
Statement of Problem
Wetlands, such as marshes, bogs, and swamps (forested wetlands), have water-logged soil that remains under water for at least part of each year. In the conterminous United States, most are freshwater wetlands, with about 5% of wetlands occurring on the coasts. The extent of wetlands in the United States has been reduced by half since the 18th century, largely due to drainage for agriculture and urbanization, but also due to changes in sea level, temperature, and precipitation.
Wetland loss has increased the vulnerability of communities to floods, droughts, and pollution from nutrient runoff. Fish and wildlife populations that provide recreational opportunities and help maintain biodiversity also have been altered through loss of habitat. drained
Resource managers and policy makers need data on wetland response to a wide range of stressors to develop effective wetland management strategies. These stressors include impacts of human changes (such as drainage, damming of rivers, coastal development) and natural disturbances (such as droughts, floods, storms, and rising sea level). Monitoring records span only the last few years to decades and are too short to capture the full range of natural variability and hydrology. Longer-term records, which provide information on the conditions that initiated and maintained wetlands and the timing and magnitude of wetland response to other environmental stressors, provide an important context to devise management strategies that are sustainable under a continually changing environment.
Why this Research is Important
Wetlands protect coastal communities from storm surges and provide other services such as filtering contaminants from water and supporting fishing, hunting, and recreational industries. This research supports management agencies by providing new datasets on the impacts of different environmental stressors on the distribution and composition of wetland habitats. Our long-term perspective documents how resilient wetlands are to specific changes in hydrology and land management, and these data are helping resource managers develop sustainable strategies to preserve critical habitats for fish and wildlife populations along with other benefits.
Objectives
This project has several over-arching goals:
- Establish long-term patterns, magnitudes, and impacts of hydroclimate variability that influenced wetlands in the southeastern United States, Alaska, and Hawaii;
- Document wetland response to human activities such as ditching, damming, and other land-use changes; and
- Integrate geologic and instrumental records of wetland change to better understand how changing precipitation, sea level, and land use have combined to shape wetlands and to better anticipate impacts of different mitigation and restoration strategies.
These goals are addressed with an initial network of sites in the Gulf Coast, Alaska, and Hawaii. In these regions, we focus specifically on reconstruction of extreme hydrologic events (droughts, storm events), long-term fire histories, changing salinity, and human activities on wetland composition and extent. The datasets span the period from today to the full glacial (~21,000 years ago), and high-resolution sampling will allow evaluation of the timing and impacts of past environmental changes on these wetland systems. Integration of the resulting new data with existing datasets will enhance understanding of Holocene precipitation and hydrologic variability across the North American continent.
Methods
The project produces paleoenvironmental datasets from wetland sediment cores. We analyze a range of proxies, including pollen, plant macrofossils, charcoal, cellulose oxygen isotopes, sedimentary properties, and geochemistry to reconstruct both natural patterns of variability and impacts of human modification of the landscape. The ages of sediments are determined using radiometric dating and pollen biostratigraphy. The resulting reconstructions of past vegetation, fire, and hydrology are being integrated with instrumental and monitoring records to create continuous records from modern time throughout the Holocene.
On a global scale, wetland systems are affected by precipitation extremes, changing sea level, and population growth, influencing their capacity to moderate storm surge, filter contaminants, and provide habitats for fish and wildlife. This research takes a long-term perspective on the resilience of wetlands to a range of environmental- and human-induced changes and supports wetland management by providing critical data to support decisions on use of wetlands in ‘nature-based’ mitigation strategies.
Wetlands serve many important functions: providing habitats for fish and wildlife, moderating storm surge, and filtering contaminants over long time periods. Over the last few centuries, the combined effects of human modification of the landscape, precipitation and temperature variability, and rising sea level have reduced wetland extent by nearly half across the United States. These reductions have been accompanied by changes in plant communities, fire regimes, and sedimentation. This project integrates new paleoenvironmental data with monitoring and instrumental data from long term study sites in wetlands in the Gulf Coast, Alaska, Hawaii, and the Pacific Islands to advance understanding of wetland resilience to a range of environmental and human-induced changes. Results of this effort are advancing understanding of the underlying processes that influence wetland systems and provide critical data to support decisions on wetland restoration and the use of wetlands as ‘nature-based’ solutions to mitigation strategies.
Statement of Problem
Wetlands, such as marshes, bogs, and swamps (forested wetlands), have water-logged soil that remains under water for at least part of each year. In the conterminous United States, most are freshwater wetlands, with about 5% of wetlands occurring on the coasts. The extent of wetlands in the United States has been reduced by half since the 18th century, largely due to drainage for agriculture and urbanization, but also due to changes in sea level, temperature, and precipitation.
Wetland loss has increased the vulnerability of communities to floods, droughts, and pollution from nutrient runoff. Fish and wildlife populations that provide recreational opportunities and help maintain biodiversity also have been altered through loss of habitat. drained
Resource managers and policy makers need data on wetland response to a wide range of stressors to develop effective wetland management strategies. These stressors include impacts of human changes (such as drainage, damming of rivers, coastal development) and natural disturbances (such as droughts, floods, storms, and rising sea level). Monitoring records span only the last few years to decades and are too short to capture the full range of natural variability and hydrology. Longer-term records, which provide information on the conditions that initiated and maintained wetlands and the timing and magnitude of wetland response to other environmental stressors, provide an important context to devise management strategies that are sustainable under a continually changing environment.
Why this Research is Important
Wetlands protect coastal communities from storm surges and provide other services such as filtering contaminants from water and supporting fishing, hunting, and recreational industries. This research supports management agencies by providing new datasets on the impacts of different environmental stressors on the distribution and composition of wetland habitats. Our long-term perspective documents how resilient wetlands are to specific changes in hydrology and land management, and these data are helping resource managers develop sustainable strategies to preserve critical habitats for fish and wildlife populations along with other benefits.
Objectives
This project has several over-arching goals:
- Establish long-term patterns, magnitudes, and impacts of hydroclimate variability that influenced wetlands in the southeastern United States, Alaska, and Hawaii;
- Document wetland response to human activities such as ditching, damming, and other land-use changes; and
- Integrate geologic and instrumental records of wetland change to better understand how changing precipitation, sea level, and land use have combined to shape wetlands and to better anticipate impacts of different mitigation and restoration strategies.
These goals are addressed with an initial network of sites in the Gulf Coast, Alaska, and Hawaii. In these regions, we focus specifically on reconstruction of extreme hydrologic events (droughts, storm events), long-term fire histories, changing salinity, and human activities on wetland composition and extent. The datasets span the period from today to the full glacial (~21,000 years ago), and high-resolution sampling will allow evaluation of the timing and impacts of past environmental changes on these wetland systems. Integration of the resulting new data with existing datasets will enhance understanding of Holocene precipitation and hydrologic variability across the North American continent.
Methods
The project produces paleoenvironmental datasets from wetland sediment cores. We analyze a range of proxies, including pollen, plant macrofossils, charcoal, cellulose oxygen isotopes, sedimentary properties, and geochemistry to reconstruct both natural patterns of variability and impacts of human modification of the landscape. The ages of sediments are determined using radiometric dating and pollen biostratigraphy. The resulting reconstructions of past vegetation, fire, and hydrology are being integrated with instrumental and monitoring records to create continuous records from modern time throughout the Holocene.