This week is National Estuaries week. Estuaries occur where freshwater from a river meets the saltwater of the ocean. Here in Louisiana we have one of the largest, most productive estuaries in the world. The extensive Mississippi River basin meets the saltwater of the Gulf of Mexico at several places along the Louisiana coast, building a network of estuaries. A salinity gradient results from the mixing of the water, and provides a bountiful array of habitats for plants, wildlife, and fisheries. Without freshwater, there is no estuary. Estuaries serve several functions that we in Louisiana enjoy immensely and have built a big part of our culture around.
Estuaries provide habitat and food sources for birds that need to rest and refuel for their migration. As a result, Louisiana is a wonderful duck hunting destination.
Another important function that an estuary provides is water filtration. In a natural system, when flood waters rise above the banks of the river they reach out into the surrounding estuary. The water then nourishes the marsh, providing the soil with important nutrients.
Estuaries, and wetlands in general, also act as storm buffers. This is a particularly important function in Louisiana. When a storm moves from water to land, the intensity of the storm is greatly reduced. The more extensive our estuaries are, the more the strength of the storm can be reduced before it hits a densely populated area.
Commercially important marine species need estuaries, even though they are marine! Nearly 735 species use an estuary at some point in their life cycle. The mixing of the fresh and salt water creates a unique habitat that many species use as a refuge or nursery to escape marine predators that cannot withstand the salinity gradients.
Louisiana is battling wetland and estuary loss at the rate of one football field an hour. The State Coastal Master Plan calls for a variety of project types to keep our coast working. Many of these projects involve moving sediment, building barrier islands, creating marsh, etc. And while each of these is important for a sustainable coast, they all only address the lack of sediment making it to the wetlands. The only strategy that addresses the lack of freshwater making it to the estuaries, and the only strategy that mimics the natural process that built this landscape, is diversions. River diversions are an important way to reintroduce freshwater (and sediment) into the estuary- the very thing that makes an estuary what it is.
Since the levees have cut off the river from the wetlands for decades, not only has Louisiana experienced land loss at an astonishing rate, we’ve also experienced saltwater intrusion. Salinity levels are higher closer to shore than would naturally occur, and we are losing our freshwater marsh and our swamps. We have seen some consequences of this so far, but some see this as a benefit- commercially important marine species are occurring closer to shore. However, even these same species need the estuary with freshwater at important points in their lifecycle. Ultimately, these resources will not be able to endure the complete loss of the estuarine habitat. The big hang-up on diversions is how they will affect our fisheries- people are worried that the salinity changes might change some resources. One can almost guarantee that they will. The resources will move further offshore where the salinity level suits them better. But, many of these resources are where they are artificially because of saltwater intrusion. The discussion about what will happen to our fisheries if we DON’T build diversions is a much more compelling one- without the mixing of freshwater and saltwater in the nursery of a fishery, there is a much greater unknown.
So, in honor or National Estuaries Week get out and appreciate an estuary. Experience the very special phenomenon of the mixing of two worlds- fresh and salt. Join the Camo Coalition and become an advocate for Louisiana’s estuaries. Go to the Take Action page and sign up for information and opportunities to take action for our wetlands.