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Assessing Effects of Sea-level Rise on Upstream Ecosystem Conditions Completed

By Chesapeake Bay Activities February 27, 2018

A synthesis published in Frontiers in Ecology and the Environment addresses what is known about the ecosystem consequences of freshwater tides extending upstream into formerly nontidal rivers.

The USGS and its partners, with support from the Climate and Land Use Change Mission Area, published an article that summarizes the known effects of sea-level rise pushing freshwater tides upstream into formerly non-tidal rivers. Tidal extension describes this gradual shift from non-tidal river flow to tidally influenced flow at the landward limit of tides.

This tidal extension may increase the area of tidal freshwater ecosystems and offset loss of ecosystem functions due to salinization downstream. Without considering how gains in ecosystem functions could offset losses, landscape-scale assessments of ecosystem functions may be biased toward worst-case scenarios of loss. To stimulate research on this concept, they address three fundamental questions about tidal extension: Where will tidal extension be most evident, and can we measure it? What ecosystem functions are influenced by tidal extension, and how can we measure them? How do watershed processes, climate change, and tidal extension interact to affect ecosystem functions?

Key Findings

  • There are 2850 km of tidal freshwater rivers in the eastern U.S. (Figure 1), and this tidal freshwater zone is advancing inland as sea-level rise pushes ocean tides farther upstream.
  • Tidally influenced river flow changes nutrient and carbon cycling, invertebrate and fish communities, and riparian wetland vegetation, but there are limited measurements of whether these ecosystem functions increase or decrease as tidal extension occurs. Figure 2 shows a hypothetical depiction of the cumulative consequences of tidal extension on landscape ecosystem functions and services.
  • Watershed sediment supply is important for tidal freshwater wetlands to offset sea level rise and prevent salinization. Sediment loading to tidal rivers located in the eastern U.S. Coastal Plain is low but has not changed over the past decades.

Implications and Next Steps

The findings will help managers consider more realistic management approaches to address wetland loss and the expectations of the consequences of sea level rise. Long-term sensor networks should be implemented to better detect tidal extension. More rigorous measurement of these changes in ecosystem function is needed to predict impacts from sea-level rise and help resource managers prioritize ecosystem conservation efforts. Their preliminary answers lead to recommendations that will advance tidal extension research, enable better predictions of the impacts of sea-level rise, and help balance the landscape-scale benefits of ecosystem function with costs of response.

More Information

The article is published in: Frontiers in Ecology and the Environment and available online at http://onlinelibrary.wiley.com/doi/10.1002/fee.1745/abstract.

 

figure 1 for Science Summary effects of sea-level rise
Sources/Usage: Public Domain. View Media Details
Figure 1. Length of tidal freshwater channel and watershed size for 22 Coastal Plain and Piedmont rivers on the U.S. East Coast, including the Chesapeake Bay.(Public domain.)

 

Figure 2 for Science Summary effects of seal-level rise
Sources/Usage: Public Domain. View Media Details
Figure 2. Conceptual figure showing (a) tidal extension up-slope in a river, (b) calculation of a rate of tidal extension, (c) hypothetical representation of differences in the rate of a process between habitat types, and (d) the change in ecosystem function over time as habitat areas change within the delimited boundaries of this river system. (Public domain.)

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  • Overview

    A synthesis published in Frontiers in Ecology and the Environment addresses what is known about the ecosystem consequences of freshwater tides extending upstream into formerly nontidal rivers.

    The USGS and its partners, with support from the Climate and Land Use Change Mission Area, published an article that summarizes the known effects of sea-level rise pushing freshwater tides upstream into formerly non-tidal rivers. Tidal extension describes this gradual shift from non-tidal river flow to tidally influenced flow at the landward limit of tides.

    This tidal extension may increase the area of tidal freshwater ecosystems and offset loss of ecosystem functions due to salinization downstream. Without considering how gains in ecosystem functions could offset losses, landscape-scale assessments of ecosystem functions may be biased toward worst-case scenarios of loss. To stimulate research on this concept, they address three fundamental questions about tidal extension: Where will tidal extension be most evident, and can we measure it? What ecosystem functions are influenced by tidal extension, and how can we measure them? How do watershed processes, climate change, and tidal extension interact to affect ecosystem functions?

    Key Findings

    • There are 2850 km of tidal freshwater rivers in the eastern U.S. (Figure 1), and this tidal freshwater zone is advancing inland as sea-level rise pushes ocean tides farther upstream.
    • Tidally influenced river flow changes nutrient and carbon cycling, invertebrate and fish communities, and riparian wetland vegetation, but there are limited measurements of whether these ecosystem functions increase or decrease as tidal extension occurs. Figure 2 shows a hypothetical depiction of the cumulative consequences of tidal extension on landscape ecosystem functions and services.
    • Watershed sediment supply is important for tidal freshwater wetlands to offset sea level rise and prevent salinization. Sediment loading to tidal rivers located in the eastern U.S. Coastal Plain is low but has not changed over the past decades.

    Implications and Next Steps

    The findings will help managers consider more realistic management approaches to address wetland loss and the expectations of the consequences of sea level rise. Long-term sensor networks should be implemented to better detect tidal extension. More rigorous measurement of these changes in ecosystem function is needed to predict impacts from sea-level rise and help resource managers prioritize ecosystem conservation efforts. Their preliminary answers lead to recommendations that will advance tidal extension research, enable better predictions of the impacts of sea-level rise, and help balance the landscape-scale benefits of ecosystem function with costs of response.

    More Information

    The article is published in: Frontiers in Ecology and the Environment and available online at http://onlinelibrary.wiley.com/doi/10.1002/fee.1745/abstract.

     

    figure 1 for Science Summary effects of sea-level rise
    Sources/Usage: Public Domain. View Media Details
    Figure 1. Length of tidal freshwater channel and watershed size for 22 Coastal Plain and Piedmont rivers on the U.S. East Coast, including the Chesapeake Bay.(Public domain.)

     

    Figure 2 for Science Summary effects of seal-level rise
    Sources/Usage: Public Domain. View Media Details
    Figure 2. Conceptual figure showing (a) tidal extension up-slope in a river, (b) calculation of a rate of tidal extension, (c) hypothetical representation of differences in the rate of a process between habitat types, and (d) the change in ecosystem function over time as habitat areas change within the delimited boundaries of this river system. (Public domain.)

    → Back to Sea-Level Rise and Wetlands 

    → Back to Land and Climate Change