Salt Pond Magic: How to see them differently

Exploring around the BVI you’ll see crazy turquoise waters and deep green hills, colourful coral reefs and white sand beaches so bright you can hardly look at them. And then, occasionally, your eye will fall on a brown, muddy pond. Or maybe, after no rain and plenty of sun, an off-white and dull-grey salt pan. Not so pretty.

But I’m here to urge you to look again.

We know these as salt ponds. When it rains they fill up with fresh water and silt, and when it’s dry, they’re empty, with hard-packed black mud and salt-crusted surfaces. Occasionally they smell, especially as the last water is evaporating out of them. But sometimes, too, they are full of shocking pink flamingoes and even brighter scarlet ibis, offering eye candy that makes up for the yuck.

You’ll encounter salt ponds on shorelines, tucked away behind coral berms or mangroves, and some even hidden in the bush inland. Only a few offer us actual salt to collect. The most famous of these are on Salt Island, of course, where, over several centuries the two ponds supplied salt for both flavouring and all-important curing before refrigeration.

But that’s another story. Aside from eye candy and rock salt, these ponds do a whole bunch of jobs for us that are not well understood, and as the climate continues to change, we need to start appreciating them a lot more than we have in the past.

Most of our salt ponds started as mangrove lagoons. Not all. Some were small bays or curves in the coastline. But all of them became ponds when coral, sand and other natural material built up so much that it cut the inner area off from the sea.

So, take a mangrove lagoon, for instance. Most have one or two entrances where they join the ocean and where tides and currents flow in and out. Over hundreds of years those entrances become shallower as sand slowly builds up, coral on the reefs outside dies and washes in, and of course on occasion, huge events like hurricanes dump large amounts of this kind of debris the sea floor.

All this helps to make the entrance to a mangrove lagoon more and more shallow until eventually it ceases to be an entrance at all and the water inside gets trapped. In our climate, trapped sea water will soon evaporate in the hot sun. But salt? Salt won’t evaporate, so it stays behind and lays on the floor.

This new ecosystem is of course more intensely salty than the ocean-flushed mangrove lagoon. Concentrations of salt are highest in the dry seasons and lower in the wet seasons when rainwater dilutes it. Wet or dry, the pond now plays host to some of the same and some different creatures and species. Red, black and white mangroves all grow on the edges of salt ponds, with the reds – the ones most famous for growing in the sea itself – still thriving despite the increased saltiness. Fiddler crabs, shrimps and other salt specialists also live here and these attract the flamingos, ibis, ducks, wading birds and migrants like the least terns which nest around the ponds’ edges and feed salty critters to their fledglings.

Not all salt ponds are equal. Some may never go dry because water can still seep in from the sea. Cane Garden Bay has one of these on its northern edge at Cannon Point. In the case of Salt Island, the ponds have just enough incoming seawater to refresh them regularly, meaning that in the driest season, large blocks of salt crystals form in impressive piles when the bulk of the water has evaporated.

Most ponds in the BVI, however, are separate from the sea so salt rarely builds up enough to collect. That said, after hurricane Irma broke all the rules and records in September 2017, enough new ocean water was thrown into the pond in Bluff Bay on Beef Island that, for a few years afterwards, it offered collectible lumps of salt when the dry season arrived. On those occasions people came from all over the island to fill up buckets and bags. I spoke with many and only one older gentleman remembered seeing enough salt on that pond to collect. Most, even other elderly, couldn’t remember it ever offering salt.

Like most, the Bluff Bay pond would have been a mangrove lagoon in its previous life. How long ago is hard to tell, but a good way to estimate is to look at how thick or thin the narrowest point is between pond and sea. Usually this is the last point where the two connected and the further from the sea, the older the pond is. Beef Island has many ponds of many ages. Right in the middle, below Mount Alma, there are areas barely recognisable as salt ponds in the thick bush of kasha trees, wild tamarinds and loblolly. These would have been ponds long ago and probably part of an extensive mangrove network on the island even further back in time.

We may not notice it, but all of these ponds, whether seasonal, permanently filled with water or high and dry on the land, are working for us. As well as the salt, and the living ecosystems, these ponds are providing unsung services we can’t do without. First, they help prevent flash floods by offering somewhere for rainwater to collect instead of destroying communities. And they are often described as ‘the kidneys of the land’ because they literally cleanse the natural water system for us. When heavy rains fall they absorb tons of topsoil and other sediment that would otherwise run into the sea, smothering the reefs and seagrass beds and overloading our coastal system with nutrients like nitrogen and phosphorus. This would kill the coral and fish and leave the BVI with dead, brown waters.

Arguably the most important thing that salt ponds do is serve as a lock-box for carbon that has been taken out of the atmosphere and the ocean and returned underground where it belongs. That sticky, black mud on the floor of all salt ponds is rotted organic matter and in terms of our planet, it matters. Here’s why:

Some of that black goo comes from the land when it rains. Leaves and sticks and other living things pile up on the floor of the pond and break down. But the majority of it was put there in the pond’s previous life, when it was a mangrove lagoon. Mangrove and seagrass beds extract more carbon from the sea and the air than any other ecosystem on Earth – by a very large amount. Research it and you’ll find numbers range between 3.5-10 times more carbon is being grabbed by these systems than by the Amazon rainforest.

How does it do this? Well, mangroves have extremely clever techniques for dealing with the salt in salt water. One of these is the red mangrove’s ability to suck in salt water, separate the salt and dump it by sending it to a chosen ‘sacrificial’ leaf. These leaves die and drop to the floor of the lagoon. It doesn’t take long for them to be buried by shifting sands and more leaves. All that organic matter being buried 24-7, 365, rots slowly, undisturbed over hundreds and hundreds of years.

Since all living things are made of cells whose key building block is carbon, these leaves can be considered packets of carbon. As one scientist explained to me, if those leaves are falling in an Amazon rainforest, they will be eaten by small creatures. The carbon in their cells goes into those creatures and maybe those creatures will be eaten by others and it will take a long time for the carbon from the leaves to be buried in the ground. In the mangrove lagoon, nothing eats the leaves. They rot slowly, sand covers them and they form a dense black goo that, hundreds of years later, when the mangrove lagoon has turned into a salt pond, forms the sticky black mud on the salt pond floor.

Dig up a salt pond and you release centuries of work capturing carbon, so not only do we lose all those other benefits that salt ponds bring us, it also dramatically sets us back in the race to pull the extra carbon out of the atmosphere that we’ve put there by burning coal and oil. Instead of slowing climate change, we drastically help to accelerate it.

I look at it this way: In the days before Europeans came to these islands, indigenous people like Taino and Kalinago Indians lived in and around mangrove lagoons. In the 1980s Belmont Pond, between Long Bay and Smuggler’s Cove, was explored by archaeologists from the Institute of Archaeology in London, the University of Virginia and local BVI students. They uncovered a complex and long-lasting native American settlement dating from 1000 BC. They uncovered pottery, tools and enough fish bones and shells to verify that these people relied on the ocean for much of their sustenance.

And of course, in days past, that brown salt pond we now call Belmont Pond would have been a beautiful, sparkling mangrove inlet, complete with canoe access to the sea via Smuggler’s Cove. I grew up living above this brown pond and it was the ugly duckling in a view of green islands and turquoise sea that could hardly be matched anywhere in the world. Nowadays when I see that, or any salt pond in the BVI, I don’t see ugly. I see something once thriving with life and now serving us all in its afterlife in ways we’re only just beginning to understand.