Climate impacts on Atlantic and Great Lakes coastal and nearshore environments

The Northeast CSC region is unique in that it contains two coastal regions: the Atlantic Ocean and the Laurentian Great Lakes Basin. While there are some inherent differences (e.g., salt water influence of the Eastern Seaboard; 10,000 miles of freshwater coastline of the Great Lakes), both contain a wide array of estuaries (e.g., tidally-driven Hudson River Estuary, Narragansett, Delaware, and Chesapeake Bays) and bays/marshes (e.g., freshwater Black River Bay, Cecil Bay Marsh) that provide protection from hazards (e.g., reduction of flooding), and support highly valuable commercial fisheries. Coastal habitats including low-lying beaches, rocky shores, marshes, nearshore and barrier islands, have been identified by management agencies and interdisciplinary work-groups as being particularly vulnerable to climate change impacts. Climate-change associated sea level rise (Atlantic), and lake-level fluctuations (Great Lakes) in combination with more frequent and intense precipitation, drought, and extreme storm events (e.g., increasingly stronger coastal storms and more intense hurricanes), may strongly increase the risk of coastal flooding, shoreline instability, and erosion throughout the two coastal regions. 
 

Of primary importance on the Atlantic coast, are the impacts of sea level rise and extreme storm events, which threaten to flood coastal habitats, displace or eradicate some species, and increasingly place people and property at risk (Arkema et al., 2013). Saltwater intrusion into groundwater systems, exacerbated by groundwater withdrawal as coastal populations increase, is another concern. As mentioned in Theme 3, changes in climate are predicted to have significant effects on river discharge that will impact salinity levels, as well as sedimentation, contaminant, and nutrient inputs into coastal and nearshore habitats. Changes in freshwater inputs to coastal habitats can also exacerbate seasonal episodes of stratification, and the formation of dead zones, which have already been observed in major coastal water bodies in the region (e.g., Long Island Sound, Chesapeake Bay) as well as neighboring downstream systems (e.g., Gulf of Mexico hypoxic zone). The projected joint effects of these physical processes along with climate change-associated chemical changes such as ocean acidification and hypoxic or low oxygen events are expected to result in degradation or permanent loss of some habitats. Since many coastal habitats serve as nursery grounds and essential habitat to commercially and culturally valued fishes and invertebrates (e.g., shellfish), impacts are likely to be widespread and have economic consequences for the region (Griffis and Howard, 2012; Staudinger et al., 2012). 
 

Nearly one-quarter of the US population lives in the Northeast CSC region. The strong and increasing human footprint of coastal cities and residential areas plays an important role in the sustainability and resilience of surrounding Atlantic and Great Lakes coastal ecosystems. Urban development exacerbates nutrient inputs and increases the frequency and magnitude of runoff associated with impervious surfaces. In addition, commercial ports increase the spread of pollutants and invasive species, further stressing biotic assemblages already at risk to growing climate impacts. At the same time, an increasing human population along the two coasts places more people at risk of catastrophic storm and flood events, and significant property damage. Recent extreme weather events including Tropical Storm Irene (2011) and Hurricane Sandy (2012) have revealed how vulnerable coastal infrastructure and communities are to flooding and storm surge, causing billions of dollars in damages (Horton et al., 2012). Human responses to climate change can often have unintended consequences and exacerbate the impacts of climate change. For example, building seawalls and other structures that harden the coastline can impede the inland migration of coastal habitats and species trying to keep pace with sea level rise, as well as reduce the amount of protection that natural systems provide to people. Therefore, it will be increasingly important to raise local awareness (e.g., through decision analysis of the risks and uncertainties associated with different response strategies) and emphasize adaptation planning that decreases vulnerability, and improves resiliency without further compromising or exacerbating the impacts of climate change and other anthropogenic stressors on ecological systems. 
 
Predicting these effects and adapting to these vulnerabilities will drive NE CSC research in coastal and nearshore environments throughout the Atlantic and Great Lakes regions. A motivating question for this Science Theme is the extent to which management actions particularly in urban and suburban areas (e.g., reduction in nitrogen inputs, decreases in impervious surface, improved stormwater management) can buffer climate impacts to the coasts. Answering this question requires increasing the accuracy of sea level rise projections, runoff, and lake level fluctuations, and linking them to critical elements of Atlantic and Great Lakes coastal ecosystems such as the structure and function of estuarine wetlands. Resource managers need to understand the extent to which coastal zones can continue to provide habitat for valuable fisheries and at-risk wildlife under a changing climate (see Theme 5) and how management actions including conservation design and restoration can promote sustainability of natural systems while decreasing risks and increasing quality of life for human communities. 
 
Recommendations 
 
  • Evaluate the synergistic impacts of sea level rise (Atlantic) or lake level fluctuations (Great Lakes), flooding, extreme events, and anthropogenic stressors (e.g., land use/land cover change) on coastal and nearshore resources including wetlands, marshes, estuaries, beaches, and associated fish and wildlife populations. 

  • Evaluate the synergistic impacts of sea level rise (Atlantic) or lake level fluctuations (Great Lakes) and anthropogenic stressors (e.g., urban development) on water quality including nutrient-, sediment-, and contaminant-loading, and the resulting impacts on the structure and function of coastal and nearshore ecosystems. 

  • Understand the combined impacts of climate-associated physical (e.g., increased stratification and coastal erosion) and chemical changes (e.g., increased acidification and hypoxia) on coastal and nearshore ecosystems. 

  • Characterize and evaluate risks and uncertainty (e.g., through the use of decision analysis approaches) of increasing precipitation and extreme storm events on coastal ecological and human communities. 

  • Assess and predict the combined impacts of climate change and anthropogenic activities (e.g., urban development) on coastal and nearshore environments (e.g., rates and magnitude of wetland loss in coastal systems). 

  • Work with regional partners to develop decision support tools, alternative scenarios, and adaptation strategies that aid government and coastal landowners respond to the combined impacts of climate change and urban development, and increase resistance and resilience to future global change through selection and adoption of Best Management Practices as well as strategic coastal planning, conservation, restoration, and engineering efforts.