Holocene and Modern Drivers of Wetland Change
On a global scale, wetland systems have been affected by climate extremes, changing sea level, and population growth, reducing their capacity to moderate storm surge, filter contaminants, store carbon, and provide habitats for fish and wildlife. This research takes a long-term perspective on the resilience of wetlands to a range of climatic and human-induced changes and provides critical data to support decisions on wetland restoration and the use of wetlands as ‘nature-based’ solutions to climate mitigation strategies.
Wetlands serve many important functions: providing habitats for fish and wildlife, moderating storm surge, filtering contaminants, and storing carbon over long time periods. Over the last few centuries, the combined effects of human modification of the landscape, rising sea level, and climate variability have reduced wetland extent by nearly half across the United States. These reductions have been accompanied by changes in plant communities, fire regimes, and rates of carbon sequestration. 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 climatic 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 climate 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 and climate change.
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. Because wetlands also store carbon in their organic-rich soils such as peat, restoration of their original hydrology is an effective way to store carbon underground, making wetlands a nature-based mitigation strategy to climate change.
To develop effective wetland management and restoration strategies, resource managers and policy makers need data on wetland response to a wide range of stressors, from human changes (such as drainage, damming of rivers, coastal development) to 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 in climate and hydrology. To devise management strategies that are sustainable under a continually changing climate, resource managers need longer-term records that provide information on the conditions that allowed wetland formation and the timing and magnitude of wetland response to a range of environmental stressors.
Why this Research is Important
The nearly 40% of the U.S. population that lives on or near a coast relies on wetlands to protect them from storm surges, filter contaminants from water, and support industries such as fishing and recreation. Because wetlands sequester carbon in their organic soils, their restoration provides a nature-based opportunity to increase storage of carbon. This research provides a long-term perspective on wetland response to natural climate variability, changing sea level, and various water and land management actions by documenting variation in hydrology, vegetation, fire, and carbon accumulation over decades, centuries, and millennia. Such data are being provided to management agencies to develop sustainable strategies to preserve critical ecosystem services and maximize carbon sequestration in wetland systems.
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 wetlands and climate to better understand how changing climate, sea level, and land use have combined to shape wetlands and to better anticipate impacts of various 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) and long-term fire histories and impacts of changing sea level 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 of past changes. Integration of the resulting new data with existing datasets will enhance understanding of Holocene hydroclimate 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 climate variability and impacts of human modification of the landscape. The ages of sediments are determined using radiocarbon (14C) dating, lead-210 (210Pb) 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.
Past Perspectives of Water in the West
Impacts of coastal and watershed changes on upper estuaries: causes and implications of wetland ecosystem transitions along the US Atlantic and Gulf Coasts
Drivers and Impacts of North Pacific Climate Variability
Sea Level and Storm Hazards: Past and Present
Wetland Forest Regeneration Dynamics and Productivity in Southeastern Cypress Swamp Ecosystems
On a global scale, wetland systems have been affected by climate extremes, changing sea level, and population growth, reducing their capacity to moderate storm surge, filter contaminants, store carbon, and provide habitats for fish and wildlife. This research takes a long-term perspective on the resilience of wetlands to a range of climatic and human-induced changes and provides critical data to support decisions on wetland restoration and the use of wetlands as ‘nature-based’ solutions to climate mitigation strategies.
Wetlands serve many important functions: providing habitats for fish and wildlife, moderating storm surge, filtering contaminants, and storing carbon over long time periods. Over the last few centuries, the combined effects of human modification of the landscape, rising sea level, and climate variability have reduced wetland extent by nearly half across the United States. These reductions have been accompanied by changes in plant communities, fire regimes, and rates of carbon sequestration. 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 climatic 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 climate 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 and climate change.
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. Because wetlands also store carbon in their organic-rich soils such as peat, restoration of their original hydrology is an effective way to store carbon underground, making wetlands a nature-based mitigation strategy to climate change.
To develop effective wetland management and restoration strategies, resource managers and policy makers need data on wetland response to a wide range of stressors, from human changes (such as drainage, damming of rivers, coastal development) to 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 in climate and hydrology. To devise management strategies that are sustainable under a continually changing climate, resource managers need longer-term records that provide information on the conditions that allowed wetland formation and the timing and magnitude of wetland response to a range of environmental stressors.
Why this Research is Important
The nearly 40% of the U.S. population that lives on or near a coast relies on wetlands to protect them from storm surges, filter contaminants from water, and support industries such as fishing and recreation. Because wetlands sequester carbon in their organic soils, their restoration provides a nature-based opportunity to increase storage of carbon. This research provides a long-term perspective on wetland response to natural climate variability, changing sea level, and various water and land management actions by documenting variation in hydrology, vegetation, fire, and carbon accumulation over decades, centuries, and millennia. Such data are being provided to management agencies to develop sustainable strategies to preserve critical ecosystem services and maximize carbon sequestration in wetland systems.
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 wetlands and climate to better understand how changing climate, sea level, and land use have combined to shape wetlands and to better anticipate impacts of various 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) and long-term fire histories and impacts of changing sea level 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 of past changes. Integration of the resulting new data with existing datasets will enhance understanding of Holocene hydroclimate 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 climate variability and impacts of human modification of the landscape. The ages of sediments are determined using radiocarbon (14C) dating, lead-210 (210Pb) 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.