Patrick Megonigal, Smithsonian Institution

Firefighters battling the deadly wildfires that raced through the Los Angeles area in January 2025 have been hampered by a limited supply of freshwater. So, when the winds are calm enough, skilled pilots flying planes aptly named Super Scoopers are skimming off 1,500 gallons of seawater at a time and dumping it with high precision on the fires.

Using seawater to fight fires can sound like a simple solution – the Pacific Ocean has a seemingly endless supply of water. In emergencies like Southern California is facing, it’s often the only quick solution, though the operation can be risky amid ocean swells.

But seawater also has downsides.

Saltwater corrodes firefighting equipment and may harm ecosystems, especially those like the chaparral shrublands around Los Angeles that aren’t normally exposed to seawater. Gardeners know that small amounts of salt – added, say, as fertilizer – does not harm plants, but excessive salts can stress and kill plants.

While the consequences of adding seawater to ecosystems are not yet well understood, we can gain insights on what to expect by considering the effects of sea-level rise.

A seawater experiment in a coastal forest

As an ecosystem ecologist at the Smithsonian Environmental Research Center, I lead a novel experiment called TEMPEST that was designed to understand how and why historically salt-free coastal forests react to their first exposures to salty water.

Sea-level rise has increased by an average of about 8 inches globally over the past century, and that water has pushed salty water into U.S. forests, farms and neighborhoods that had previously known only freshwater. As the rate of sea-level rise accelerates, storms push seawater ever farther onto the dry land, eventually killing trees and creating ghost forests, a result of climate change that is widespread in the U.S. and globally.

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In our TEMPEST test plots, we pump salty water from the nearby Chesapeake Bay into tanks, then sprinkle it on the forest soil surface fast enough to saturate the soil for about 10 hours at a time. This simulates a surge of salty water during a big storm.

Our coastal forest showed little effect from the first 10-hour exposure to salty water in June 2022 and grew normally for the rest of the year. We increased the exposure to 20 hours in June 2023, and the forest still appeared mostly unfazed, although the tulip poplar trees were drawing water from the soil more slowly, which may be an early warning signal.

Things changed after a 30-hour exposure in June 2024. The leaves of tulip poplar in the forests started to brown in mid-August, several weeks earlier than normal. By mid-September the forest canopy was bare, as if winter had set in. These changes did not occur in a nearby plot that we treated the same way, but with freshwater rather than seawater.

The initial resilience of our forest can be explained in part by the relatively low amount of salt in the water in this estuary, where water from freshwater rivers and a salty ocean mix. Rain that fell after the experiments in 2022 and 2023 washed salts out of the soil.

But a major drought followed the 2024 experiment, so salts lingered in the soil then. The trees’ longer exposure to salty soils after our 2024 experiment may have exceeded their ability to tolerate these conditions.

Seawater being dumped on the Southern California fires is full-strength, salty ocean water. And conditions there have been very dry, particularly compared with our East Coast forest plot.

Changes evident in the ground

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

Tree leaves turning from green to brown well before fall was a surprise, but there were other surprises hidden in the soil below our feet.

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Rainwater percolating through the soil is normally clear, but about a month after the first and only 10-hour exposure to salty water in 2022, the soil water turned brown and stayed that way for two years. The brown color comes from carbon-based compounds leached from dead plant material. It’s a process similar to making tea.

Our lab experiments suggest that salt was causing clay and other particles to disperse and move about in the soil. Such changes in soil chemistry and structure can persist for many years.

Sea-level rise is increasing coastal exposure

While ocean water can help fight fires, there are reasons fire officials prefer freshwater sources – provided freshwater is available.

U.S. coastlines, meanwhile, are facing more extensive and frequent saltwater exposure as rising global temperatures accelerate sea-level rise that drowns forests, fields and farms, with unknown risks for coastal landscapes.

Patrick Megonigal, Associate Director of Research, Smithsonian Environmental Research Center, Smithsonian Institution

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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Colleen E. Reid, University of Colorado Boulder

When wildfires spread into neighborhoods, they burn all kinds of materials found in cars and houses and everything around them – electronics, paint, plastics, furniture.

Research shows that the mix of chemicals released when human-made materials like these burn is different from what is emitted during a vegetation fire and is potentially more toxic. The smoke and ash can blow under doors and around windows in nearby homes, bringing in chemicals that are absorbed into furniture, walls and other indoor surfaces and continue off-gassing for weeks to months.

As people return to smoke-damaged homes after a wildfire, there are several steps they can take to protect their health before starting to clean.

Elevated levels of metals and VOCs

In 2021, after the Marshall Fire swept through neighborhoods near Boulder, Colorado, my colleagues and I at Colorado universities and labs heard from many residents who were worried about the ash and lingering smells inside their homes that had otherwise survived the flames.

In homes that my colleagues were able to quickly test, they found elevated levels of metals and PAHs – polycyclic aromatic hydrocarbons – in the ash. We also found elevated VOCs – volatile organic compounds – in airborne samples. Some VOCs, such as dioxins, benzene, formaldehyde and PAHs, can be toxic to humans. Benzene is a known carcinogen.

At the time, we could find no information about physical health implications for people who have returned to smoke-damaged homes after a wildfire. So, to look for patterns, we surveyed residents affected by the fire six months, one year and two years after the fire.

Even six months after the fire, we found that many people were reporting symptoms that aligned with health risks related to smoke and ash from fires.

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More than half (55%) reported that they were experiencing at least one symptom six months after the blaze that they attributed to the Marshall Fire. The most common symptoms reported were itchy or watery eyes (33%), headache (30%), dry cough (27%), sneezing (26%) and sore throat (23%).

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All of these symptoms, as well as having a strange taste in one’s mouth, were associated with people reporting that their home smelled differently when they returned to it one week after the fire.

Many survey respondents said that the smells decreased over time. Most attributed the improvement in smell to the passage of time, cleaning surfaces and air ducts, replacing furnace filters, and removing carpet, textiles and furniture from the home. Despite this, many still had symptoms.

We also found that living near a large number of burned structures was associated with these health symptoms. We found that for every 10 additional destroyed buildings within 820 feet (250 meters) of a person’s home, there was an associated 21% increase in headaches and a 26% increase in having a strange taste in their mouth.

These symptoms align with what could be expected from exposure to the chemicals that we found in the ash and measured in the air inside the few smoke-damaged homes that we were able to study in depth.

Lingering symptoms and questions

There are a still a lot of unanswered questions about the health risks from smoke- and ash-damaged homes.

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For example, we don’t yet know what long-term health implications might look like for people living with lingering gases from wildfire smoke and ash in a home. We found a significant decline in the number of people reporting symptoms one year after the fire. However, 33% percent of the people whose homes were affected and responded to a later survey still reported at least one symptom that they attributed to the fire. About the same percentage also reported at least one symptom two years after the fire.

We also could not measure the level of VOCs or metals that each person was exposed to. But we do think that reports of a change in the smell of a person’s home one week after the fire demonstrates the likely presence of VOCs in the home. That likely has health implications for people whose homes are exposed to smoke or ash from a wildfire.

Tips to protect yourself after wildfires

Wildfires are increasingly burning homes and other structures as more people move into the wildland-urban interface, temperatures rise and fire seasons lengthen.

If your home survives a wildfire nearby, here are some of the steps to think about before starting to clean:

• When you’re ready to clean your home, start by protecting yourself. Wear at least an N95 (or KN95) mask and gloves, goggles and clothing that covers your skin. Cleaning can send some of those gases and ash into the air again.
• Keep people with heart or lung diseases, older adults, pregnant women, children and pets away from cleanup activities.
• Vacuum floors, drapes and furniture. A recent scientific study documents how cleaning all surfaces within a home can reduce reservoirs of VOCs and lower indoor air concentrations of VOCs. Once the air outside has cleared, open windows to let clean air in.
• Avoid harsh chemical cleaners because they can react with the chemicals in the ash.
• Clean your HVAC filter and ducts to avoid spreading ash further, and change filters monthly until the smell is gone. Portable air cleaners with carbon filters can help remove VOCs and particles.
• If your car smells of smoke, consider changing the cabin air filter.

This is an update to an article first published Dec. 23, 2024.

Colleen E. Reid, Associate Professor of Geography, University of Colorado Boulder

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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Carlos Lopes, University of Cape Town

As we approach the global annual climate change conference, COP29, the need for increased public finance from the global north to address climate adaptation in Africa has become more urgent than ever.

However, framing the finance debate solely around this need risks deepening mistrust and downplaying the scale of the challenge. The financial burden of addressing climate change, coupled with limited fiscal space, creates a precarious situation for many African countries. African countries bear no historical responsibility for causing the climate crisis. However, they rely heavily on external financing to solve climate change problems.

Unfortunately, much external climate finance comes from loans rather than grants. This only worsens Africa’s debt burden. There is also not nearly enough money being channelled to Africa to pay for climate change adaptation.

At COP29, African negotiators will undoubtedly focus on reducing dependence on debt, and improving access to finance. I’m an economist who specialises in climate change and governance, with a long background at the United Nations and the African Union. Without robust commitments from public financial institutions, Africa will continue to face the dual crises of climate vulnerability and debt.

African countries must use COP29 to tackle systemic biases that inflate risk perceptions, minimise African achievements and inflate its problems. These biases drive up borrowing costs, and worsen commodity dependence.

The climate finance gap

The African Development Bank has estimated that Africa needs between US$1.3 trillion and US$1.6 trillion in total climate financing every year between 2020 and 2030. This will enable African countries to meet their commitments to reduce greenhouse gas emissions, known as nationally determined contributions.

The Global Center for Adaptation estimates that Africa requires at least US$52.7 billion annually for adaptation every year until 2035. However, this figure could rise to US$106 billion. This is because data gaps allow for double counting of financial contributions. There is also very little transparency about the real amounts of climate finance being disbursed. Because nationally determined contributions are focused on mitigation, carbon depletion tends to be measured without accurate calculations of the amount of emissions that are captured, or carbon that is conserved.

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The United Nations Development Programme says that Africa’s nationally determined contributions mean the continent needs about US$2.8 trillion by 2030 for climate mitigation. However, Africa contributes only 4% of all greenhouse gas emissions currently. It needs funds for adaptation to adjust to climate change that is already changing the lives of many, rather than for mitigation.

But only about half of the climate finance received by Africa in 2022 was for adaptation (US$4.6 billion). The rest of the climate finance addressed mitigation or a mix of both, in line with the global north’s agenda.

Worse still, 64.5% of adaptation financing came from loans, which need to be repaid. This will increase the financial strain on African nations.

Loans versus grants for climate change adaptation

Multilateral financial institutions such as the International Monetary Fund (IMF) and the World Bank, and the Organisation for Economic Co-operation and Development through their Development Assistance Committee, handed out US$8.33 billion to Africa in 2022 for climate action. But most of this – US$5.4 billion – was loans. Only US$2.9 billion was grants, with a small fraction in equity investments.

These loans come with lower-than-market rates or extended repayment terms. But they still add to Africa’s external debt, which reached US$1.12 trillion in 2022. African countries’ debt repayments are twice what they get as climate finance.

The United Nations Framework Convention on Climate Change says developed countries are responsible for financing climate adaptation in vulnerable regions. But loans that create a huge debt burden only enrich global financial institutions at the expense of African countries.

The effects of climate change are causing unprecedented floods, drought and other disasters across Africa. Yet it is becoming more difficult for African countries to access the climate finance they need to adapt to a warming world.

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Why is the situation worsening?

First, access to climate finance remains a bureaucratic nightmare with complex application processes. There also needs to be more transparency in fund allocation. The recently established Loss and Damage Fund could assist. It is meant to channel money to countries worst affected by climate change to pay for the damage caused.

Second, the focus on reforming Bretton Woods institutions and development finance institutions is shifting attention away from the obligations developed countries have signed up for. This distracts developing nations from making reforms in trade, taxation and financial regulations that could drive more meaningful results.

Third, there is a lack of liquidity (access to fresh money) needed to propel investment or allow countries to bridge their budget deficits. African countries are forced to juggle paying for healthcare, education and infrastructure development with paying back debt. Some spend more on debt repayments than healthcare.

Increased tax efficiency and domestic savings, such as the savings maintained by pension funds, could be used. This should be the priority while the fight for better international conditions continues.

Fourth, the distinction between development finance and climate finance is becoming an impediment to progress. The conversation should move away from getting African countries to prioritise greenhouse gas emission reductions at the expense of other development priorities. Climate action is under-implemented and underfunded. The focus must be on excessive dependency on aid and rather promote market incentives to encourage the private sector to invest in climate adaptation in Africa.

Fifth, African negotiators must address the structural barriers that limit access to finance. For example, biased risk perceptions by credit rating agencies prevent African countries from securing finance. Restrictive prudential rules from the Bank for International Settlements intended to preserve international financial system integrity have proven unfavourable to the transformation of the African economies.

Sixth, Africa should make use of regional climate finance platforms and set up cross-border climate change adaptation projects that benefit more than one country.

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This will allow Africa to pool resources, coordinate demands and make it easier to negotiate better terms for climate finance. Just energy transition partnerships create an opportunity for countries to secure renewable energy funding for the transition from fossil fuel. Success will depend on effective coordination and regional solidarity in international climate negotiations.

Seventh, African countries have strong potential to use carbon markets to finance climate initiatives, provided they have control over them. Nature-based solutions can go hand in hand with reforestation, sustainable land management or conservation, while generating carbon credits. These are additional funding opportunities for climate adaptation efforts in Africa.

This moment demands bold leadership and a united front to rewrite the rules. African countries must secure the commitments and resources at COP29 that are needed to build a sustainable future.

Carlos Lopes, Professor at the Nelson Mandela School of Public Governance, University of Cape Town

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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