Author: Kiley Price Pubished: 3/18/2025 Climate News
Rising Seas and Land-Based Salt Pollution Pose Dual Threats for Drinking Water
Global sea levels rose faster than expected last year, largely due to warming ocean temperatures, a new NASA analysis found.
As seawater creeps further into coastlines, salt threatens to pollute the freshwater reserves that people depend on. But this brine isn’t just coming from the ocean: New research shows freshwater ecosystems are facing widespread dual threats of salt contamination from the sea and land, made worse by climate change.
Humans are a salty species, using the mineral for a vast number of reasons—from de-icing the roads during snowstorms to seasoning food.
But our salty habits, coupled with rising seas, pose major threats to human health, infrastructure, agriculture and wildlife. Now, scientists are trying to help water managers better understand the salt risks that crucial water supplies face from land to sea as global temperatures warm.
A Salty Future: When it comes to climate change, scientists are learning to expect the unexpected. Even so, 2024’s rate of sea level rise was unusual, according to NASA.
“Every year is a little bit different, but what’s clear is that the ocean continues to rise, and the rate of rise is getting faster and faster,” Josh Willis, a sea level researcher at NASA’s Jet Propulsion Laboratory in Southern California, said in a statement.
Using an ocean-observing satellite, scientists measured last year’s global rate of sea level rise at 0.23 inches, compared to the expected rate of 0.17 inches annually. This may seem tiny, but bear in mind that even small increases in sea levels can have major consequences for coastal communities, including worsening storm surges during hurricanes.
Around two-thirds of 2024’s rise can be attributed to ocean warming, because seawater expands as it heats. The rest of the rise is due to an influx of water coming from ice sheets and glaciers, which are melting at unprecedented rates around the world due to climate change. Last year’s El Niño weather event may have also been to blame for warming up the water by impacting how heat travels vertically through the ocean, NASA scientists said.
Overall, the rate of annual sea level rise has more than doubled since 1993. Global sea level has increased by 4 inches in that timeframe.
“It used to be that we could predict the future based on the past trends, but now we know that there are all these changes happening,” Sujay Kaushal, a geologist at the University of Maryland, told me. “Nothing is shocking anymore.”
Kaushal mostly studies the ecology of watersheds outside the ocean, such as wetlands, streams and rivers, which provide roughly 70 percent of humanity’s drinking water. However, in a newly published study, he teamed up with oceanographers to see how salt from the ocean and land are affecting tidal fresh waters. Spoiler alert: It’s not looking good.
Essentially, salt is coming from both directions—land and the ocean—and meeting in the middle, representing a “double trouble” issue for freshwater tidal basins, Kaushal said. The salt on land is mostly coming from wastewater, fertilizers, resource extraction and road salt.
I interviewed Kaushal for a newsletter I wrote in January about how road salt is threatening water supplies and wildlife, and the data is staggering: The U.S. alone uses about 25 million tons of salt on roads each year, according to one estimate. This salt can leach into watersheds when snow melts. Typically, “dilution is the solution of pollution,” Kaushal says, referring to the fact that heavy rainfall or releasing fresh water from dams into ecosystems can decrease salinity.
But climate-fueled droughts and rising temperatures are making this strategy more difficult. During parched periods, there is less water available to dilute the system and flush out the salt, while rising seas push salt into the watershed, a process known as saltwater intrusion.
“The interaction between human activities and climate change and climate variability is very, very important,” Kaushal said. “It amplifies the salt pulses that we see from human activity.”
This issue is particularly prevalent in the Delaware River, a 330-mile waterway that winds from New York to the Atlantic Ocean at the Delaware Bay. The river supplies about 60 percent of drinking water to Philadelphia’s 1.5 million people, but saltwater intrusion and pollution is threatening this crucial resource.
The Delaware River Basin Commission has a plan in place to release water from upstream reservoirs if needed to dilute the salt. But a report released in February found that this plan may no longer be viable due to the rate of sea level rise and frequent droughts, which reporter Jon Hurdle covered for ICN earlier this month.
Risk Management: Consuming salty water has been linked to a number of negative health impacts in people, including high blood pressure, chronic kidney disease, dementia and reproductive risks.
One of the key points in the new study is that salty water can also trigger chain reactions in ecosystems that can impact drinking water quality, infrastructure and energy and food production. If saltwater reaches the intake areas that supply freshwater to communities, it could corrode pipes used for the distribution system, power generation and heating or contaminate soils used for farming, which can kill crops.
The brine can exacerbate existing issues associated with climate change, according to the study. For example, salt can release nitrogen or phosphorus from sediments in a watershed, which act as nutrients for plants—potentially leading to an overgrowth of algae and bacteria in the system, Kaushal said. Research shows that climate change can increase harmful algal blooms, which can change water’s oxygen levels for fish and block sunlight from underwater plants.
Currently, there are few plans or comprehensive guidance on salinization threats for people who oversee rivers, estuaries and drinking water supplies. To change this, the researchers developed a risk management framework to help officials understand where and when salinization might happen along their waterways as climate change accelerates. They zero in on methods to determine the types of hazards, probability, salt exposure and vulnerability a freshwater ecosystem may face. The Patuxent River, a tributary of the Chesapeake Bay in Maryland, for instance, has experienced high rates of salinization in recent years.
“Most of the management we do with water resources is reactive,” Kaushal said. “We’re starting to realize with climate change and climate variability that we have to be proactive.”
More Top Climate News
In the latest installment of the Trump administration layoff saga, the U.S. Environmental Protection Agency plans to get rid of its scientific research arm, potentially firing more than 1,100 chemists, biologists, toxicologists and other scientists, Lisa Friedman reports for The New York Times, based on documents reviewed by Democrats on the House Committee on Science, Space and Technology. The Office of Research and Development is the EPA’s largest department, and the agency relies on it to use the best available science to inform regulation.
Molly Vaseliou, a spokeswoman for the EPA, said in a statement to the Times that the agency “is taking exciting steps as we enter the next phase of organizational improvements” and stressed that changes had not been finalized. The EPA is also moving to roll back major environmental and public health rules, including the “endangerment” finding that underpins its efforts to combat climate change.
A new report from the Asthma and Allergy Foundation of America lists the most challenging places for living with seasonal allergies—and stresses how climate change is adding to the pollen problem in many regions. Wichita, Kansas, tops the list because of its “higher-than-average tree and grass pollen, higher-than-average medicine use, and limited access to allergy specialists.” However, New Orleans is also a close contender, jumping 32 spots in the rankings, mostly due to higher weed pollen counts, which were exacerbated by climate change, said Kenneth Mendez, president and CEO of AAFA.
“November was the warmest on record in Louisiana, extending the weed pollen season that was also boosted by moisture from Hurricane Francine,” he said in a statement. “Across the nation, growing seasons start earlier and last longer—leading to longer and more intense pollen allergy seasons.”
At least 42 people died in the severe storms and tornadoes that tore through eight states over the weekend. My colleagues Keerti Gopal and Lee Hedgepeth reported on the destruction left behind by this extreme weather, which decimated hundreds of homes and buildings and caused more than 100,000 power outages in states like Alabama and Oklahoma. As my colleagues pointed out, the storms came amid the Trump administration’s layoffs at the National Weather Service, which is responsible for forecasting and communicating extreme weather risks across the U.S.
Today, more than 30 conservation groups, including the Center for Biological Diversity, Fridays For Future and the Sierra Club, released a letter of support urging UNESCO and the International Union for Conservation of Nature to take action against the Saguaro liquified natural gas project proposed in Sonora, Mexico. They say that the fossil fuel plant’s construction and operations could harm marine life like whales and dolphins in the Islands and Protected Areas of the Gulf of California World Heritage Site.