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  • Writer's pictureAllan Dyen-Shapiro

On the Everglades Part 3: the science behind the salty language

To the Buddha's proverb, "A spoon of salt in a glass of water makes the water undrinkable. A spoon of salt in a lake is almost unnoticed," a resident of Florida would answer that it depends on the size of the spoon. Much invective has been heaped upon the Water Management District lately for the decision to maximize flow rates out of Lake Okeechobee (returned to normal as of March 4th). One of the claims was that diluting the salinity of the estuarine enviroments into which Lake O water ultimately dumps would wreck havoc with the environment. To this, I answer, partially true. With the deplorable state of waste management (especially on the East Coast) leading to dumping of sewage into the Saint Lucie estuary, enteric bacteria have proliferated and closed much of the area to public use. Had high salinity been maintained, this never would have happened. Enteric bacteria die with standard estuarine levels of salt. Estuaries naturally fluctuate to some extent in salt concentration. It rains, the salt concentration goes down. Submerged aquatic vegetation, invertebrates, fish--all have to tolerate some level of variation. So I decry as falsehood the claim that the fresh water killed fish by dilution. Brown water (due to the dirt kicked up) blocking photosynthesis, killing plant/algal life, leading to decay via bacteria, which overgrew and used up the oxygen, the lack of oxygen killing fish--that I'll buy. However, some areas did reach very low levels of salinity, and it's possible that some damage to seagrasses and oyster beds was suffered. Bottom line: estuarine dilution was not the major cause of damage recently suffered in the ecosystem as a result of upping Lake O discharges. (See Part 2 of this series for a more in depth discussion of what was.)

On the other hand, too much salt is a huge issue for Florida. At the point in my life when I was a scientist studying seagrass productivity, I went out on water sampling runs up the Caloosahatchie, starting in the tidal region and progressing all the way to Lake O. I didn't do that a lot--I was much more the guy who sat at a computer and crunched numbers--but I did need to have a feel for what the numbers meant, so I went out with my collaborators a few times. What struck me was the abruptness of the transition between salt water and fresh water. Around the bridges between Fort Myers and North Fort Myers, the conductivity was the same as the Gulf of Mexico, roughly 35 ppt (parts per thousand, that's grams of salt per kilogram of water). At the very next sampling site, just outside of the Fort Myers city limit, the reading on our sensors was 0.1 ppt. Fresh water. At the first couple sampling locations, we were in the tidal Caloosahatchie, the parts that water coming in with the tide from the Gulf of Mexico reaches. Just outside of Fort Myers, the water was largely run-off from the land (largely agricultural) and outflow from Lake O. Our route was on the "superhighway" of water from Lake O to the Gulf. By contrast, Estero Bay (and several other estuaries) averages 23 ppt. Water percolates in slowly from the land, through an intact mangrove swamp, and then drains out into the Gulf. Slowing flow down allows for the brackish water that supports shore birds and hatcheries for fish.

All is well and good as long as the salt stays in the coastal and estuarine areas. However, when flow out of Lake O. is dramatically reduced, as it was in 2006/2007 because of the dry winter, salt concentrations can rise in parts of the rivers that are normally fresh water. My former collaborators traveled the length of the Caloosahatchie that year, and found that the aquatic plant upon which the entire ecosystem is based, Valisneria americanum, was nonexistant in every site they looked. Lack of discharge from Lake O. completely killed the river.

It recovered. Seeds travel. Plants grow.

In the future, with seawater encroaching due to global climate change-related sea level rise, it may not recover. In addition to threatening the highest value real estate and development in the world put at risk due to climate change (Miami, ignoring for the moment how that oft-reported statistic is a pretty stupid way to look at the problem, as the residents of Coral Gables are unlikely to be made homeless refugees under even worst-case scenarios--they will merely move in-land, even if they are left second homeless--but the residents of Bangladesh will likely perish in the tens to hundreds of thousands), salt water in the underground aquifer means no drinking water for South Florida. Salt water moving into the Everglades means the death of the entire ecosystem.

In the novel I am hoping to have in a finished state by the end of the summer, I had to do some climate change predictions, as near-future Southwest Florida was one of three settings for the book. Back in 2008, when I was first thinking this out, I predicted that the Keys and low-lying areas in the Caribbean would be submerged, leading to a movement of population into South Florida proper. I predicted a disruption in agriculture (Immokalee lies just west of the Everglades and currently supplies most of the winter vegetables to the entire East Coast of the United States), leading to food riots, leading to disruption of work on the seawalls protecting Miami. I'd used the word dike rather than seawall, a word chosen based on the origin of the character who introduced this backstory. I'd predicted corruption would lead to faulty construction.

So far, so good, in terms of my ability as a futurist. In the real world, the seawalls to protect Miami have been planned. They are awaiting funding. Corruption in Florida? Check. Increased salinity in Immokalee soils? Not yet seen, but I'd still stand by this as plausible. Submerging of Caribbean lowlands: many islands have been hit very hard by hurricanes. That will get worse.

I further predicted salt water moving in from both ends of the state, leading to a near-island resulting. Widening of the rivers, swampy areas--I'd still say possible. The question of whether there would be a true circulation of salt water from the Atlantic Ocean all the way to the Gulf of Mexico would depend on how badly the humans mess things up in the next 40 years or so.

I think we are capable of that level of ecocide. I think we are also capable of much better environmental management.

And again, I end a post by saying the part I'm leaving out is the politics. I really have to get around to an environmental politics post soon. But I prefer to ground such a discussion on solid science. It's who I am. It's the way I think. And if you've read this far, it's at least a perspective in which you are interested.

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