Firefighters battling the deadly wildfires that raced by means of the Los Angeles space in January 2025 have been hampered by a limited supply of freshwater. So when the winds are calm sufficient, expert pilots flying planes aptly named Super Scoopers are skimming off 1,500 gallons of seawater at a time and dumping it with excessive precision on the fires.
Utilizing seawater to battle fires can sound like a easy resolution—the Pacific Ocean has a seemingly countless provide of water. In emergencies like Southern California is going through, it’s usually the one fast resolution, although the operation could be risky amid ocean swells.
However seawater additionally has downsides.
Saltwater corrodes firefighting equipment and will hurt ecosystems, particularly these just like the chaparral shrublands round Los Angeles that aren’t usually uncovered to seawater. Gardeners know that small quantities of salt—added, say, as fertilizer—doesn’t hurt crops, however extreme salts can stress and kill crops.
Whereas the implications of including seawater to ecosystems will not be but properly understood, we will acquire insights on what to anticipate by contemplating the consequences of sea-level rise.
A seawater experiment in a coastal forest
As an ecosystem ecologist on the Smithsonian Environmental Analysis Heart, I lead a novel experiment called TEMPEST that was designed to know how and why traditionally salt-free coastal forests react to their first exposures to salty water.
Sea-level rise has increased by a median of about 8 inches globally over the previous century, and that water has pushed salty water into U.S. forests, farms and neighborhoods that had beforehand identified solely freshwater. As the speed of sea-level rise accelerates, storms push seawater ever farther onto the dry land, ultimately killing timber and creating ghost forests, a results of local weather change that’s widespread within the U.S. and globally.
In our TEMPEST test plots, we pump salty water from the close by Chesapeake Bay into tanks, then sprinkle it on the forest soil floor quick sufficient to saturate the soil for about 10 hours at a time. This simulates a surge of salty water throughout an enormous storm.
Our coastal forest confirmed little impact from the primary 10-hour publicity to salty water in June 2022 and grew usually for the remainder of the yr. We elevated the publicity to twenty hours in June 2023, and the forest nonetheless appeared principally unfazed, though the tulip poplar trees had been drawing water from the soil extra slowly, which can be an early warning sign.
Issues modified after a 30-hour publicity in June 2024. The leaves of tulip poplar within the forests began to brown in mid-August, a number of weeks sooner than regular. By mid-September the forest cover was naked, as if winter had set in. These adjustments didn’t happen in a close-by plot that we handled the identical manner, however with freshwater slightly than seawater.
The preliminary resilience of our forest could be defined partially by the comparatively low quantity of salt within the water on this estuary, the place water from freshwater rivers and a salty ocean combine. Rain that fell after the experiments in 2022 and 2023 washed salts out of the soil.
However a significant drought adopted the 2024 experiment, so salts lingered within the soil then. The timber’ longer publicity to salty soils after our 2024 experiment might have exceeded their capacity to tolerate these circumstances.
Seawater being dumped on the Southern California fires is full-strength, salty ocean water. And circumstances there have been very dry, significantly in contrast with our East Coast forest plot.
Adjustments evident within the floor
Our analysis group continues to be making an attempt to know all of the elements that restrict the forest’s tolerance to salty water, and the way our outcomes apply to different ecosystems resembling these within the Los Angeles space.
Tree leaves turning from inexperienced to brown properly earlier than fall was a shock, however there have been different surprises hidden within the soil beneath our ft.
Rainwater percolating by means of the soil is often clear, however a couple of month after the primary and solely 10-hour publicity to salty water in 2022, the soil water turned brown and stayed that manner for 2 years. The brown shade comes from carbon-based compounds leached from useless plant materials. It’s a course of much like making tea.
Our lab experiments counsel that salt was inflicting clay and different particles to disperse and transfer about within the soil. Such adjustments in soil chemistry and construction can persist for a few years.
Sea-level rise is growing coastal publicity
Whereas ocean water might help battle fires, there are causes hearth officers prefer freshwater sources—supplied freshwater is on the market.
U.S. coastlines, in the meantime, are going through extra intensive and frequent saltwater publicity as rising international temperatures speed up sea-level rise that drowns forests, fields, and farms, with unknown dangers for coastal landscapes.
Patrick Megonigal is an affiliate director of analysis on the Smithsonian Environmental Analysis Heart on the Smithsonian Institution.
This text is republished from The Conversation underneath a Artistic Commons license. Learn the original article.