Why dumping seawater at fire sites isn’t the solution to California’s wildfire problem

Our coastal forests had little impact during the first 10 hours of salt water exposure in June 2022 and grew normally for the rest of the year. We increased the exposure time to 20 hours in June 2023, which slowed down the rate at which the tulip poplar trees drew water from the soil, although the forest still appeared largely unperturbed. could be an early warning signal.

After 30 hours of exposure in June 2024, things changed. The leaves of the forest’s tulip poplars began turning brown in mid-August, several weeks earlier than usual. By mid-September, the forest canopy was bare, as if winter had begun. These changes did not occur in nearby plots that we treated similarly, but using freshwater rather than seawater.

The early resilience of our forests can be partially explained by the relatively low salinity in the water of this estuary, where freshwater rivers and salty ocean water mix. Rains that fell after the 2022 and 2023 experiments washed salts from the soil.

However, a major drought occurred after the 2024 experiment, leaving salt residue in the soil. Since the 2024 experiment, the trees may have been exposed to saline soil for longer periods of time, potentially exceeding their ability to tolerate these conditions.

The seawater being dumped on the Southern California fires is fully salted seawater. And conditions there are very dry, especially compared to the forested areas of the east coast.

obvious changes in the ground

Our research group is still trying to understand all the factors that limit forest tolerance to salty water and how our results apply to other ecosystems, such as the Los Angeles region. I’m trying.

It was a surprise to see the leaves on the trees turn from green to brown long before fall, but the soil beneath our feet held another surprise.

Rainwater that percolates into the soil is normally clear, but in 2022, about a month after the initial exposure to salt water for just 10 hours, the soil water turned brown and remained that way for two years. The brown color comes from carbon-based compounds that leach from dead plant matter. The process is similar to making tea.