Firefighters battling the lethal wildfires that raced via the Los Angeles space in January 2025 have been hampered by a restricted provide of freshwater. So, when the winds are calm sufficient, expert pilots flying planes aptly named Tremendous Scoopers are skimming off 1,500 gallons of seawater at a time and dumping it with excessive precision on the fires.
Utilizing seawater to struggle 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 typically the one fast resolution, although the operation will be dangerous amid ocean swells.
However seawater additionally has downsides.
Saltwater corrodes firefighting gear and should 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 vegetation, however extreme salts can stress and kill vegetation.
Whereas the results of including seawater to ecosystems usually are not but effectively understood, we are able to achieve insights on what to anticipate by contemplating the results of sea-level rise.
A seawater experiment in a coastal forest
As an ecosystem ecologist on the Smithsonian Environmental Analysis Middle, I lead a novel experiment referred to as TEMPEST that was designed to grasp how and why traditionally salt-free coastal forests react to their first exposures to salty water.
Sea-level rise has elevated by a mean 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 recognized solely freshwater. As the speed of sea-level rise accelerates, storms push seawater ever farther onto the dry land, finally killing timber and creating ghost forests, a results of local weather change that’s widespread within the U.S. and globally.
In our TEMPEST check 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.
Scientists work in a check plot the place saltwater experiments are exhibiting the affect of sea-level rise on coastal forests.
Alice Stearns/Smithsonian Environmental Analysis Middle
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 timber have 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 method, however with freshwater quite than seawater.
The preliminary resilience of our forest will be defined partly 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 capability to tolerate these situations.
Seawater being dumped on the Southern California fires is full-strength, salty ocean water. And situations there have been very dry, notably in contrast with our East Coast forest plot.
Adjustments evident within the floor
Our analysis group continues to be attempting to grasp all of the components that restrict the forest’s tolerance to salty water, and the way our outcomes apply to different ecosystems corresponding to these within the Los Angeles space.
Tree leaves turning from inexperienced to brown effectively earlier than fall was a shock, however there have been different surprises hidden within the soil beneath our toes.
Rainwater percolating via the soil is generally 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 method for 2 years. The brown colour comes from carbon-based compounds leached from useless plant materials. It’s a course of just like making tea.
Water drawn from the soil after one saltwater experiment is the colour of tea, reflecting plentiful compounds leached from useless plant materials. Usually, soil water would seem clear.
Alice Stearns/Smithsonian Environmental Analysis Middle, CC BY-ND
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 rising coastal publicity
Whereas ocean water might help struggle fires, there are causes hearth officers want freshwater sources – offered freshwater is on the market.
U.S. coastlines, in the meantime, are going through extra in depth and frequent saltwater publicity as rising world temperatures speed up sea-level rise that drowns forests, fields and farms, with unknown dangers for coastal landscapes.
