Part 1: Wetlands Perceptions
Part 2: Riverine Processes
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We've discussed how wetlands have been perceived through time, across eras, and by different communities of people. We've discussed just how rivers work and build land and talked specifics of the Mississippi River in both cases. Next logical step is the value of wetlands. Intrinsic, economic, recreational, commercial, ecological, and everything in between.
In the past (as discussed
here) wetlands have been essentially abused. They've been logged, drained, filled, channeled, and destroyed in all manner of ways. All for the "good" of society. But it wasn't really for the good of the people but at the expense of the people. It just took us all these years to discover the true values of wetlands.
Everything is interconnected. Dredging a canal over there could allow salt water to intrude into a fresher water marsh over here and change the entire species community over time. Building levees blocks off the natural flow of water and may actually cause worse flooding, just in other and maybe unintended areas. The point is - we as humans have a habit of tinkering with a system that we don't fully understand before we even have a chance or take the time to fully understand it. The same with wetlands. We now understand the full values of the resources we have drastically altered, but often that information doesn't get relayed to the general public. So here's my shot at relaying all this!
Value 1: Water Filtration
Wetlands are a network of stems, leaves, and root masses. As water flows into a wetland, it's naturally slowed down by that network. As the water moves more slowly, sediments that were suspended in the water column begin to drop out and settle on the wetland surface instead of riding along the current. Larger sediments drop first (like sand) and smaller finer sediments drop last (like clay). The slower the water moves the finer the sediments that settle out.
Sediment trapping in this process is vital to wetland health. Wetlands naturally subside (compress or compact) over time, and the influx of fresh sediment naturally offsets that so that wetlands can maintain their elevation. Without accretion of sediments, wetlands sink and as a result are flooded more often because of the lower elevation. Increased flooding impacts plant health and eventually the wetland will just sink away and cease to exist. So when wetlands get access to water to remove sediment, its a win-win. Wetlands get fresh sediment, and the water gets to carry less material.
Not only do wetlands allow sediments to settle out by slowing water down, they also absorb nutrients from the water. The stems and leaves of wetland plants are capable of absorbing nutrients like nitrogen and phosphorous. Nitrogen and phosphorous commonly end up in riverine systems because they prevalent in agriculture areas. Phosphorous is used in most fertilizers and applied to crops and farms regularly. Nitrate is a form of nitrogen that also a byproduct of fertilization. Natural levels of nutrients can be absorbed by plants and regular levels of algae, but the excess in nutrients causes problems downstream.
The Mississippi River drains 41% of the United States, including nearly all of the Midwest, which has a very high concentration of farming and agriculture. Nutrient rich water in this region runs off the land, into streams and rivers, and ultimately into the Mississippi. That water flows down river into the Gulf of Mexico. All the extra nutrients in the water is a food source for phytoplankton, which leads to rapid population growth. This process of increased nutrients leading to algal blooms is called eutrophication. In the hot summers the water of the Gulf gets quite warm, nutrient levels are high, and algae blooms rapidly and unchecked, dissolved oxygen in the water is depleted, marine life cannot survive, and ultimately we end up with a "
dead zone". Historically, nutrient levels were not nearly as high as they are in modern times. Fertilizing for agriculture, manure runoff, and sewage all find their way into the river. It's too much for the system to handle naturally anymore and we end up with these crazy complications like the ever larger Gulf of Mexico Dead Zone.
Furthermore, historically water from the mighty Mississippi would have spread out and flowed across wetlands more gradually before ending up in the Gulf of Mexico. In the natural system, river water would get filtered, and the wetlands would get access to nutrients and sediment. These days, the river is channeled rather narrowly straight into the Gulf with limited connected flow, and even that flow is highly managed. As a result, wetlands don't get access to river water nutrients and sediment as much as historically, and river water doesn't get filtered naturally by the wetlands either. It's a lose-lose for the river and the wetlands.
Value 2: Storm Surge Protection and Buffering
It's difficult to put an economic value on an environmental service like storm surge reduction. There's many factors that go into play. What are the areas being protected? If it's coastal New Jersey versus a tiny community that's a vastly different economic amount, but still important protection either way. How much infrastructure damage was avoided? That includes roads, bridges, maybe oil and gas infrastructure, homes, businesses, etc. How many homes did not flood because of the storm surge reduction? If 1000 homes were at risk, but now 750 are now protected then that's a huge benefit (I made these numbers up for easy comparison).
The rule of thumb from an US Army Corps of Engineers report is that storm surge is reduced by 1 foot for every 2.7 miles of marsh. That's a round number but many things influence whether that is true or not (like wind speed, storm speed, wind direction, precipitation, marsh health...). It's definitely situation and location dependent. But if we just ballpark and say 1 foot of storm surge is reduced for every 3 miles of marsh, then we still need a substantial amount of healthy contiguous marsh. Storm surge from hurricanes can often reach 15-20 feet high, so if we have a 15 foot storm surge we need 45 miles of marsh or more to fully absorb that surge and provide adequate protection.
Besides extreme storm surge events from named hurricanes, wetlands also absorb water from more regular high water events. In Louisiana, the Mississippi River has several diversions where water can be diverted from the river to the surrounding wetlands. That has a variety of benefits, but this is done to relieve flooding stress on levees and cities. These outlets funnel water into the wetlands where it is slowed down and absorbed. Water moves much slowly through a wetland ecosystem than a channeled river. Wetlands also absorb precipitation, overflow from rivers/bayous/creeks with natural boundaries, and any other surface water. They are effectively sponges.
Reduction in wetlands surrounding populated areas has many negative effects, many of which are only realized many years later when it's far too late to resolve immediately. I talked about this some in
Part 1: Wetlands Perceptions. But in this regard, the shorter distance from cities to open water is detrimental, particularly during hurricane season. Water simply has nowhere to go and is forced into human society instead of being completely or primarily captured by the natural wetlands.
Value 3: Fisheries
Wetlands play a vital role in fisheries, though it may not seem like it to the casual observer. Many species of marine (as in offshore) fish come inland to spawn in wetlands, because wetlands provide cover, protection, and food for young fish before they head back out to their marine homes. "Over 75% of Louisiana’s commercially harvested fish and shellfish species are dependent on wetlands. Coastal wetlands provide valuable breeding, spawning, feeding and nursery grounds for many of these species at some point during their life cycles" (
source).
Young fish and shellfish may feed on algae, plant matter, insects, other young fish, and the detritus (partially decomposed plant matter) present in the wetlands. Each species has different needs and the buffet offered up by wetlands is bountiful. As an example, small fish such as menhaden eat plant detritus. Bigger fish (tuna, trout, drums) may eat menhaden. Continuing with menhaden as my example, they are also food source for wildlife.
Admittedly I'm not much of a fisheries person myself, but I do know that without wetlands to provide habitat and cover for spawning, many species would be severely impacted. That would have a chain effect for fisheries, commercial and recreational fishing, and Louisiana's economy.
Value 4: Migratory Bird Habitat
Migratory birds worldwide use a system of routes, called flyways, to get from breeding grounds to wintering grounds and back again. The Mississippi River delta and alluvial valley overall is part of the Mississippi Flyway. Birds that winter in South America and breed in Northern Canada (and every midway distance in between) may use that to cross over the Gulf of Mexico. The coastal wetlands and barrier islands of Louisiana are important on the northward migration because they are literally the first land many birds meet after crossing the Gulf. If you time it right, and you bird watch from the beach in Grand Isle LA, you can see many species of birds diving into the first available vegetation as they finish the water crossing. As wetlands deteriorate and recede, the crossing becomes just that much longer.
Related barrier islands, which are part of the coastal wetlands system, provide critical habitat in the same manner. The disappearance of those vital strips of land is a whole other set of issues that I won't discuss in depth here. But suffice to say that loss of wetlands makes it harder for migratory birds as they land on their northerly journey.
Even with wetlands presence, habitat quality may suffer. There's a big difference between a happy healthy salt marsh full of native plants and a shrubby degraded patchy semi-wetland. If habitat suffers, then the whole food chain is probably suffering. Everything is interconnected. Birds that use this migratory flyway include everything from hummingbirds, songbirds, raptors such as my fave the swallow-tailed kite, waterfowl, and waterbirds.
And that's only migratory birds! There are also many resident species that use wetlands, including our relatively new nonmigratory experimental population of Whooping Cranes. There's also rails, waterbirds, and more that don't migrate and call Louisiana's wetlands home year round. Protecting, conserving, and managing habitat for migratory birds also will automatically encompass the needs of nonmigratory birds as well.
Value 5: Recreational Opportunities
There's a reason that Louisiana is called Sportsman's Paradise - we are flush in outdoor recreational opportunities of the aquatic kind. Hunting, fishing, swamp tours, offshore fishing, kayaking, even kayak fishing. The opportunities for recreation in the coastal wetlands are vast.
Hunting is a big deal here, and waterfowl is probably the most common type of hunting taking place in Louisiana's wetlands. It's a big deal when the first teal start to show up in August and September because winter is coming! Avid duck hunters wait excitedly for this time of year and every hunter I know will keep records, report retrieved bands, buy ammo and guns, buy gear, buy duck stamps/WMA permits/hunting licenses. Hunters pay taxes (11% on guns/ammo, for example) that directly funds wildlife and habitat conservation and management through programs like the
Pittman-Robertson Act. Hunters have to buy federal duck stamps, and nearly 98% of that money goes directly to the Migratory Bird Conservation Fund, which uses that money to create, expand, and manage National Wildlife Refuges. So money from hunting goes directly to protecting wildlife habitat, so it's a self fulfilling system in a way. Hunters are the original conservationists - they want to hunt wildife, so they want to conserve habitat and the species in the long term to protect the species, habitat, and sustainable hunting opportunities.
But waterfowl hunting isn't the only hunting taking place. There's waterfowl, deer, hogs, alligators in a strict season, nutria... It's practically a buffet out there. Responsible population management will provide hunting opportunities for interested people, keep populations to a manageable level, and bring in money from taxes and sales.
Fishing is also a big deal. I talked some above about fisheries and habitat, but commercial and recreational fishing is a big market. People travel from all over to go on a guided fishing trip in the wetlands of Louisiana. People fish inland and offshore, for speckled trout and red snapper, guided or not, in a motorized boat or kayak, and in any number of ways. Commercial fishing is also important because it is an important part of our economy. According to Louisiana Seafood, the industry is worth $2.4 BILLION annual for Louisiana's economy (
source). That includes shrimp, oysters, crabs, crawfish (that's farmed & wild caught), and alligator (farmed and wild caught). The seafood fishing industry is built into the culture, the diet, the festivals, and the mentality of the coastal population.
Summary
As you can see there are so many ways to value wetlands. It's difficult to put an exact monetary value on something like storm surge protection, but you can put an economic value on the house that didn't get destroyed because of the extra 10 miles of wetlands providing protection. It's not exactly a black and white system, but more wetlands = more benefits. There's really no downside to more wetlands. You just can't have too many wetlands. So no matter which aspect of these few that I listed you value the most, providing for that value often provides for all the other values. It's similar to managing for a keystone species in wildlife ecology. If you want to provide habitat for migratory birds and don't much care about alligator hunting, you'll still provide alligators with good habitat by providing habitat for migratory birds. They use different parts of the wetlands but both benefit from habitat conservation or restoration. More wetlands please!
Additional Reading and Sources:
Water Filtering of Wetlands National Park Service, accessed 1/25/2019
Fertilizer Runoff Overwhelms Streams and Rivers--Creating Vast "Dead Zones" Scientific American, 3/14/2008
Eutrophication Wikipedia, accessed 1/25/2019
Dead Zone (Ecology) Wikipedia, accessed 1/25/2019
Nitrogen and Water USGS, accessed 1/25/2019
The Gulf of Mexico Dead Zone Carleton College, accessed 1/25/2019
What Causes Ocean "Dead Zones"? Scientific American, accessed 1/25/2019
How Do Wetlands Filter Water? Sciencing.com, accessed 1/25/2019
Cleaner Water The Wetlands Initiative, accessed 1/25/2019
Louisiana Coastal Wetland Functions and Values LAcoast.gov, accessed 1/25/2019
Menhaden Wikipedia, accessed 1/25/2019
Storm Surge Reduction by Wetlands accessed 2/1/2019
Wetlands Provide Hundreds Of Millions Of Dollars In Storm Protection Fast Company, 10/2/2017
Understand - Conserving Coastal Wetlands for Sea Level Rise Adaptation NOAA, accessed 2/1/2019
Wetlands and barrier islands: Our communities’ first line of defense RESTORE, accessed 2/1/2019
The Value of Wetlands in Protecting Southeast Louisiana from Hurricane Storm Surges E Barbier et al, 2013, PLOS One
Mississippi Flyway Wikipedia, accessed 2/1/2019
Mississippi Flyway Audubon, accessed 2/1/2019
Pittman-Robertson Act Wikipedia, accessed 2/1/2019
Duck Stamp Dollars at Work US Fish and Wildife Service, accessed 2/1/2019
Whooping Cranes Louisiana Department of Wildlife and Fisheries, accessed 2/1/2019
Louisiana Seafood Industry Louisiana Seafood, accessed 2/1/2019
What Does the Economy Stand to Lose If We Don’t Restore Louisiana’s Coast? RESTORE, accessed 2/1/2019
Coastal Wetlands: Too Valuable to Lose NOAA Fisheries, accessed 2/1/2019
Louisiana seafood industry's economic impact compared to other states NOLA.com, 3/11/2013
Value of Wetlands The Wetlands Initiative, accessed 2/1/2019
Why are Wetlands Important? EPA, accessed 2/1/2019
