1. What is the geologic history of the US that gave this continent so many wetlands? Do you think that the eastern seaboard of the US which is a passive margin attributes to the huge coastal wetland complex there? Why?
The geological history of the United States explains its configuration of wetlands. Wetland formation occurred as glaciers created pits, valleys and floodplains that could retain water. Additional wetlands were created as the glaciers left behind large ice pieces, leading to depressions in the landscape that collected water. From there, plate boundaries is a crucial factor that distinguishes some sections of the United States from others in terms of wetlands (“Geology and Wetlands”).
There is not a lot of tectonic activity in the mid-oceanic ridge (“Geology and Wetlands”). Specifically, in the United States, wetlands are plentiful in regions with flatter terrain as opposed to mountainous regions (Mitsh and Gosselink 2015). So, there is a huge coastal wetland complex along the eastern seaboard as opposed to in the western United States. Due to the passive quality of the eastern seaboard, it’s a haven for wetland formation and movement across the landscape (“Geology and Wetlands”). As wetlands fill up, they need to move laterally across the landscape in order to sustain themselves (“Geology and Wetlands”). Without the seismic activity, the water in wetlands at the eastern seaboard can meander as there is no interruption in flow (“Riparian/Riverine Ecosystems”). However, there is major earthquake activity at the western seaboard which is an active margin with a convergent boundary (“Geology and Wetlands”). One example is the San Andreas transform fault. On the other hand, the gradual rising sea level at the eastern seaboard has led to a consistent increase in flooding of its coastal lowlands. All in all, the eastern seaboard’s passive margin allows for the necessary lateral water movement that is a key characteristic of wetlands and therefore attributes to the huge coastal wetland complex there.
2. What is the hydroperiod of the wetland you have observed?
Living in Asheville, I found bogs to be an intriguing type of wetland in western North Carolina. According to the N.C. Wildlife Resources Commission, mountain bogs are considered among the rarest and most imperiled habitat types in the Southeast, with an estimated 80-90 percent of bogs lost due to development (Chavez 2020). They are iconic for having long-term ground saturation. The substrate is saturated for extended periods during the growing season, but standing water is rarely present (Mitsh and Gosselink 2015, 115). Organic matter accumulates in the soil as a result of the anaerobic conditions created by poor drainage (Mitsh and Gosselink 2015). The organic matter cannot decompose. As a result, nutrients are bound up and unavailable to plants (Chavez 2020).
I observed the Jonas Ridge Bog in Burke County. It borders the Pisgah Loop Scenic Byway. Specifically, cranberries and peat moss are known to thrive in this wetland (Chavez 2020). The former is defined as a threatened species by the North Carolina National Heritage Program (Chavez 2020). Since cranberries are not tall plants, they need a place where taller plants don’t grow and shade them out (Chavez 2020). So, they do well in this type of wetland because most trees can’t grow in bogs due to intolerance of having their roots continually saturated (Chavez 2020). As organic content increases in a wetland, both the percentage and the amount of exchangeable hydrogen ions increase (Mitsh and Gosselink 2015). For moss peat, the high cation capacity may be caused by long-chain polymers of uronic acid (Mitsh and Gosselink 2015). Further, mountain bogs have a natural capacity to regulate water flow, holding floodwaters like giant sponges and slowly releasing water to nearby streams (Chavez 2020). The Jonas Ridge Bog property drains to headwaters of Upper Creek, designated a high-quality trout stream by the N.C. Department of Environmental Quality (Chavez 2020).
3. I worked in a cypress-hardwood, forested wetland where the Army Corps of Engineers wanted to dam to make permanent, standing water for recreation. With your knowledge of the hydroperiod and primary production – why did we stop the project?
The Army Corps of Engineers (ACE) wanted to make standing water as humans tend to value permanence (“Geology and Wetlands”). The decision to dam prioritized other interests as opposed to conservation of wetlands that have a short duration of life and need a lot of room to move. As wetlands traverse, they let go of the sediment that has been collected by the force of moving water, depositing sediments onto the land behind them (Mitsh and Gosselink 2015). In general, water movement enables a wetland to sustain high primary productivity (Mitsh and Gosselink 2015). The dam would severely disturb the area’s natural hydro period by preventing water inflow and outflow. Since the dam diverts the water flow so that it goes over the banks instead of into the wetland, it directly contradicts the project because the decrease in flooding would dry out the floodplain and result in a negative impact on the entire cypress-hardwood, forested wetland ecosystem (“Riparian/Riverine Ecosystems”).
The cypress-hardwood, forested woodlands are not capable of absorbing the water from the flooding and then gradually draining the flood waters back into the river (“Riparian/Riverine Ecosystems”;). Cypress-hardwood forests are most productive in systems that are neither too wet nor too dry because a surplus in soil saturation alters oxygen content and limits vegetation growth in the area (Mitsh and Gosselink 2015). Also, eventually, sediment accumulation would take over the wetland and transform it into dry terrain such as a grassland or meadow (Mitsh and Gosselink 2015).
References:
Chavez, Karen. 2020. “Foothills Conservancy permanently protects rare Southern Appalachian mountain bog land”. Asheville Citizen Times. https://www.citizen-times.com/story/news/2020/01/09/rare-mountain-bog-land-forever-protected-western-north-carolina/2834942001/
Flannagan, Kathryn. 2021. “Geology and Wetlands.” Wetland Ecology and Management. Lecture, June 21.
Flannagan, Kathryn. 2021 “Riparian/Riverine Ecosystems.” Wetland Ecology and Management. Lecture, June 22.
Mitsch, William J., and James G. Gosselink. 2015. Wetlands. John Wiley & Sons, Inc.
Comment by Jenny Kelley:
Hi Mary –
I am responding to Q1
The information you provided about coastal flooding on the eastern seaboard is really true. Having lived in coastal Georgia and spent most vacations in my lifetime somewhere between the coastal regions of Maine all the way down to Miami, I have seen gradual change. Storms seem more damaging, hurricanes more frequent, and overdevelopment is everywhere. I once stayed in Hilton Head – every bit of beachfront was bordered in by hotel after hotel after hotel or apartment/condo complex. There are little bridges over creeks and tidal canals but the edges of the canals are stripped bare of vegetation generally. If I were to put my systems thinking cap on, I see the input – storm water, has no where to go and the output, flooding. Dr. Flanagan noted that in riparian systems floodplains and wetlands absorb excess water like a sponge and then slowly let the water back out and when these systems are compromised or destroyed, a flood can be catastrophic for both human and natural world (“Riparaian/Riverine Ecosystems”). I think in the case of places I have been, like Hilton Head, there is no wetland or floodplain or very little, in some areas now and thus, nothing to absorb storm waters. Also, maybe with the influences of the effects of climate change, there is just too much water coming in and overdevelopment in the area is not helping. So much to consider! Thanks for writing a post that got me thinking!
Jenny
References
Flannagan, Kathryn. 2021 “Riparian/Riverine Ecosystems.” Wetland Ecology and Management. Lecture, June 22. https://canvas.du.edu/courses/128480/pages/riparian-slash-riverine-ecosystems
My Reply:
Hi Jenny,
I’m glad to see you’re bringing personal experience into the concepts we’re discussing! Great point that overdevelopment strips out the vegetation that would otherwise soak up the stormwater.
Comment by Laurel Golden:
Hi Jenny and Mary,
Responding to the Question 1 discussion-
Coastal cities need to plan for sea level rise, extremes in weather, and increased resilience. Mangroves and salt marshes are a living shoreline: soft barriers that absorb and calm coastal flooding as opposed to hard barriers like sea walls that redirect the energy. The mangrove root systems stabilize the shore, trap sediment and organic matter, increasing the shore height (Bennington-Castro 2017). The salt marsh’s benefits could be increased by adding oyster-shell bags or coconut-fiber logs to slow the wave intensity and storm surges. If there are existing seawalls, coastal cities could add wire cages to attract marsh plants to create a slope will lessen the wave impact against the wall (Bennington-Castro 2017).
Norfolk, Virginia, a coastal town anticipating a sea level rise of 14 inches, developed and implemented changes to reduce the effects of increased rainfall and sea rise by strategies to hold more rainwater and minimize storm surges. In addition to installing a living shoreline, they created bioswales, rain gardens, and installed permeable pavers to gather rainwater and keep it from overwhelming the storm water system (Naturally Resilient Communities 2016). The new living shoreline and bioswales create new habitat, expand wetlands, and increase ecosystem services. These are strategies to build resilience.
References
Bennington-Castro. 2017. “Walls Won’t Save Our Cities From Rising Seas. Here’s What Will.” NBC News. July 27. Accessed November 11, 2020. https://www.nbcnews.com/mach/science/walls-won-t-save-our-cities-rising-seas-here-s-ncna786811.
Naturally Resilient Communities. 2016. “Using Low Impact Development Concepts to Reduce Flooding, Norfolk, Virginia.” NRCSolutions. Accessed November 11, 2020. http://nrcsolutions.org/using-low-impact-development-concepts-to-reduce-flooding-norfolk-va/.
Comment by Kayla Sizemore:
Mary,
In response to question 3, you did an amazing job at thoroughly describing why the project was stopped. As you mentioned, with humans valuing permanence, an area of standing water would be ideal in contrast to flowing water. Great point regarding the dam leading to a dried floodplain, I had not immediately considered that in my analysis of the question, but it is a super important point. As the cypress trees are incapable of survival in an extreme environment, whether that be too wet or too dry, the project would have resulted in their detriment. Sediment accumulation as a result of the dam is another great point as to why this project would be a failure in the future. Great post!
My Reply to Kayla:
Kayla,
Thanks for the comment! It is interesting to consider the combination of the dam leading to the dried floodplain, cypress trees being incapable of survival in the extreme environment, and sediment accumulation. It reveals that ecological balance is based on a series of factors that all have chain reactions. One decision can lead to so many drawbacks in terms of wetland survival.