On Dams & Storm Surges

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What would you say if I told you there was a connection between dams and the damage coastal communities are faced with after a storm surge? It may not seem obvious at first but as you will see, plants form a major connection between the two. Now more than ever, our species is dealing with the collective actions of the last few generations. Rare storm events are becoming more and more of a certainty as we head deeper into a future wrought with man-made climate change. The reality of this will only become more apparent for those smart enough to listen. Rivers are complex ecosystems that, like anything else in nature, are dynamic. Changes upstream will manifest themselves in a multitude of ways further downstream.

The idea of a dam is maddeningly brilliant. Much like our cells utilize chemical concentration gradients to produce biological power, we have converged on a similar solution to generate the electricity that powers our modern lives. A wall is built to block a waterway and store massive quantities of water on one side. That water is then forced through a channel where it turns turbines, which generate power. The problem is that the reservoir created to store all of that water drowns out ecosystems and the organisms that rely upon them (including humans). 

 

Here in the United States, we got a little dam crazy in the last few decades. With an estimated 75,000 dams in this country, many of which are obsolete, these structures have had an immense impact. One major issue with dams is the sediment load. As erosion occurs upstream, all of the debris that would normally be washed downstream gets caught behind the dam. Far from merely an engineering issue, a dams nature to trap sediment has some serious ecological impacts as well. 

Until humans came along, all major rivers eventually made their way to the coast. A free flowing river continually brings sediments from far inland, down to the mouth where they build up to form the foundation of coastal wetlands. Vegetation such as sedges, grasses, and mangroves readily take root in these nutrient-rich sediments, creating an amazingly rich and productive ecosystem. Less apparent, however, is the fact that these wetlands provide physical protection.

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Storm surges caused by storms like hurricanes can send tons upon tons of water barreling towards the coast. In places where healthy wetland vegetation is present, these surges are absorbed and much of that water never has a chance to hit the coast. In areas where these wetlands have vanished, there is nothing stopping the full brunt of the surge and we end up with a situation like we saw following Katrina or Sandy and are facing now with Harvey and Irma. Coastal wetlands provide the United States alone with roughly $23 billion in storm protection annually

These wetlands rely on this constant supply of sediment to keep them alive, both literally and figuratively. As anyone who has been to Florida can tell you, erosion is a powerful force that can eat away an entire coastline. Without constant input of sediment, there is nowhere for vegetation to grow and thus coastal wetlands are rapidly eroded away. This is where dams come in. An estimated 970,000 km (600,000 mi) of rivers dammed translates into a lot of sediment not reaching our coasts. The wetlands that rely on these sediments are being starved and are rapidly disappearing as a result. Add to that the fact that coastal developments take much of the rest and we are beginning to see a very bleak future for coastal communities both in the US and around the world. 

Photo Credit: [1] [2] [3]

Further Reading: [1] [2] [3] [4]

Why You Should Never Buy Cypress Mulch

Gardening season is soon to be underway here in the northern hemisphere. This past weekend saw droves of people taking advantage of the nice weather by getting their hands dirty in the garden. A walk around the neighborhood brought with it a lot of smiles and a chance to reconnect with neighbors I haven't talked to in a while but it also brought with it something sinister. Lingering in the air was the scent of cypress mulch. Tons upon tons of it are being spread over gardens everywhere. One might ask "Whats the problem? Cypress mulch is more durable and more insect resistant than other mulches!"

WRONG!

Anymore today, these ideas are leftovers of a long gone era. Back when old growth cypress forests were still a thing, these centuries old trees did impart rot and pest resistance into their wood. Today, this is not the case. Because logging has taken most of the old growth cypress from places like Florida and Louisiana, mulch companies have had to resort to cutting down and mulching young, second and third growth cypress stands. Barely given the time to grow into the towering specimens their parents and grandparents once were, these young trees have not yet imparted the centuries worth of compounds into their wood that keep them from rotting and deter insect predators.

The saddest part of the cypress mulch industry is that they are destroying valuable and irreplaceable habitat for the myriad lifeforms that rely on cypress swamps for their existence. To add insult to injury, recovery of cypress trees is almost negligible anymore today due to the way we have managed our waterways. Cypress seedlings require inundation by freshwater and regular silt deposition in order to successfully germinate. A century of flood control, inundation by brackish water, as well as dam and ship canal building have completely upset this dynamic. Now, instead of building new habitat for cypress swamps, these sediments are washed away, far out into the Gulf of Mexico.

What staggeringly few people seem to care to realize is that cypress swamps are our first line of defense against hurricanes. Cypress swamps can cut the force of a storm surge by 90%. It has been estimated that the cypress swamps in Louisiana alone are worth a staggering $6.7 billion in storm protection every year. That is a lot of cash, people!

As with any other industry, the cypress mulch companies are driven by consumer demand. The simple act of individuals, communities, and local governments not purchasing this nasty product is all it will take to lessen the blow to these precious habitats. At the rate cypress is being cut, it will not take long for us to exhaust the resource entirely. As you are looking to do some gardening this year, and many years into the future, please keep these great trees in mind and stop buying cypress mulch. In lieu of wood and bark mulches, you should consider using shredded leaves from your property instead. They make excellent mulch and being locally sourced, the reduce the chances of introducing disease and other pests to your landscape. In the words of Captain Planet, "the power is yours!"

Photo Credit: Jesse Reeder (http://bit.ly/1wmQpn8)

Further Reading: [1] [2] [3] [4]