Salt occurs naturally all over planet earth. When rain falls, the water flows into ponds, aquifers, and rivers, and as it flows, salt dissolves into the water. The salt then moves along and ends up wherever the water goes: typically, this is into the ocean. Our oceans have accumulated salts since Earth’s primeval stage, and salinity levels have changed in response to landmasses moving around, rivers discharging more or less water, and glaciers taking water in and out.

If surface water doesn't end up in an ocean, it will probably evaporate, leaving the salt behind on earth in a terminal "evaporite" basin. This is why terminal lakes—like Utah's Great Salt Lake and The Dead Sea, which do not drain to anywhere—can become salty. Salt in the landscape varies with geologic history and soil characteristics, but in general most places on earth are not defined by their saltiness. The unique cases, like salt lakes, salt "glaciers," and brine pools, are not very common. (However, there is a subfield of geology on salt tectonics!)

From Modern Farmer.

Despite this truth, many places on earth are undergoing a slow salinity crises, where the soil salt levels are increasing to levels unsurvivable by plants. Or, at least, the plants we want to survive, like food crops. Increasing salt levels in agricultural soils is happening for a few reasons:

1. Natural accumulation of salts in old landmasses with high evaporation rates.
2. Use of surface water or groundwater to irrigate crops. This water might be a little bit salty already (in contrast to rainwater), so using it to irrigate crops speeds up natural salinization.
3. Irrigating to a degree that groundwater table levels go up, which then mobilizes salts in the soil up to the surface, where crops are rooting.
4. Oceanic saltwater that makes its way inland, either with winds carrying sea spray or by saline water creeping into coastal aquifers.

In Australia, a particularly old continent with an evaporative climate and plenty of irrigation agriculture, this problem of cropland salinization is so severe that it is named the "white death" and has its own Wikipedia Page. Some of California's hottest and most-irrigated croplands are suffering similarly and merit targeted salinity counter-measures.

However, for some plants, salinity is no problem. Enter halophytes, or salt-loving plants. This is actually a broad and somewhat unspecified category, ranging from plants that can tolerate salinity to those who thrive in it (and, depending on your definition, even seaweed that lives in saltwater). But the excitement now is generally towards halophytes that can help deal with these terrestrial salty-soil problems.

Purslane, from this piece in The Guardian about halophytes and the Tidal Garden.

The item that made me want to write today came from a place suffering from basically all four of these problems: the Venice Lagoon. Venice has saltwater all around its agricultural lands, little freshwater, and an increasingly arid climate. Recent efforts, particularly The Tidal Garden, are celebrating forgotten practices of cultivating and foraging halophytes around Venice.

Necessary is a "rebranding" of various halophytes, which might otherwise be seen as warning signs of soil salinity or as weeds. But the same plants can be used as food (often as gourmet herbs or medicinals), as living tools to remove salinity from the soil (planted between typical crops permanently or temporarily), or even as oil sources for biodiesel or fish meal. The Tidal Garden and groups of farmers, chefs, agronomists, and academics are experimenting with ways to bring our halophytic friends to the foreground of the "future food garden," combating salinity problems wherever they are. There are also a handful of plants already in our diets that are halophytic, including quinoa, beets, barley, and chard; centering their salt tolerance in cultivation and may help reduce soil salinization and enhance some micronutrient density.

From this great Scientific American piece that echoes much of what I've written about.

Some halophytes simply prevent salt from entering them in their roots, some are tolerant of salts in their body, and some find ways to squeeze the salt out after ingesting saltwater. (The latter have been studied as potential bio-inspired-design for desalination.) It's crucial to know which are which depending on your goals, as some halophytes end up too salty for regular consumption, or might not actually remove salt from soil in the first place. Despite this, raising the water levels (pun intended) on public awareness of these plants will help them escape from only being considered as "famine food."

This work is happening all over. Mary Mattingly's project in New York City, "Ebb of a Spring Tide" details salt-tolerant plants for an edible, medicinal, and pollinator-friendly garden that works in the American Northeast. Back in California, pickleweed was and continues to be eaten by native groups and is under study for biofuel development. Here in the Baltic Sea, halophytes are common among the brackish edge, but I have yet to learn about efforts to celebrate their presence (and, salinization isn't really an issue).

I'm excited by these efforts because they are generative, forward-looking initiatives that address real and present problems in salt and land management. They help us celebrate place and unique affordances of certain species, rather than adopting a view that lands truly become desecrated by salt. It's another case of "living with" the environmental future that unfolds before us.

Salted,

Lukas

P.S. Thanks again to everyone who donated to help me present my poster in Glasgow. I saw friends, did a lot of networking, and got really inspired by a bunch of great science. Here's a photo of me there with my poster!

P.P.S., some bonus links:

1. A great explainer on evaporite geology.
2. A funky database of halophytes.
3. Past and Present of Halophyte Agriculture.
4. The Rooted Sea: Halophytic Futures (art project).