Culverts and water - the lifeblood of salt marshes Salt marshes need a daily dose of seawater in order to thrive. Humans have interfered with the natural flow of seawater to and from marshes by building roads, railroads, and dikes over marshes. Water is then channelized into culverts, many of which are too small to allow adequate seawater to inundate the marshes or to drain from the marsh at low tide. Small culverts in the Great Marsh region area are being replaced with larger ones that let more water pass through. This allows the salt marsh to expand and thrive.
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Invasive Species Invasive species are one of the most profound threats to the natural world. The Great Marsh is threatened by several aggressive, nonnative, invasive plants. Common Reed (also known as Phragmites) generally spreads from the upper edge of the salt marsh out over the marsh surface. A more recent invasive threat to the Great Marsh is Perennial Pepperweed. This grows at the upper edge of marshes and at the top of creek banks, where its seeds can be spread by the tides. The Great Marsh Coalition has active programs to control these two invasive plants: restoring the natural hydrology where it has been altered by humans, herbiciding, prescribed burning, mowing and pulling out invasives by hand.
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Sea level rise Coastal communities are bracing for a sea level rise anticipated by scientists to be somewhere between one to four feet by the end of this century, possibly higher. Rising seas will likely cause profound changes in both the ecology and culture of coastal communities. Cherished landmarks, such as Motif # 2 in Essex, along with houses, businesses, and roads that cannot be moved back, may succumb to the ravages of these higher sea levels combined with the predicted more intensive coastal storms. Similarly, salt marshes that cannot migrate into an adjacent upland area or build up in elevation as fast as seas rise will be lost.
Marsh migration into uplands Since the beginning of the Industrial Revolution, 150 years ago, the rate of sea level rise in New England has tripled. Some marshes in New England are already drowning and eroding rapidly under rising sea levels. Land protection has an important role to play in insuring the future of salt marshes. As sea level rises, the land between low and high tide will move into upland areas that currently border marshes. Marshes can move into these new intertidal areas if the land is undeveloped and has no barriers to marsh migration such as seawalls. The key is to make sure that lands that could support future salt marshes remain undeveloped.