Almost 60 countries, representing about a third of the global economy, met in the Colombian port city of Santa Marta last week for the first international summit on the transition away from fossil fuels.

It was hailed as a bold step to shift global dependence on hydrocarbons into an era of clean energy. The group of 57 countries, including Australia, Canada, Norway and Brazil, launched a new international process to coordinate the global phase out of coal, oil and gas. This historic shift brings us closer to the end of fossil fuels.

Irene Vélez Torres, Colombia’s environment minister and chair of the talks, said: “We decided that the transition away from fossil fuels could no longer remain a slogan but must become a concrete, political and collective endeavour.”

Here are five key developments from Santa Marta.

1. Moving beyond negotiating deadlocks

This meeting was a successful complement to the UN’s annual climate summits, not a replacement for them.

Decisions at UN climate meetings are made by consensus. Outcomes such as the 2015 Paris Agreement have huge legitimacy because they are agreed by nearly 200 countries. But the consensus rules also allow a handful of fossil fuel producers such as Saudi Arabia and Russia to block progress.

Holding a summit outside these formal UN talks brought much-needed fresh air to global climate diplomacy. Without petrostates blocking the way, willing countries were able to have pragmatic discussions about the legal, fiscal and economic measures needed for a coordinated wind down of fossil fuels.

These discussions will now feed back into the next UN climate talks, to be held in Turkey in November. They will, for example, raise expectations that countries include timelines to end fossil fuel use in national climate plans.

2. Paths away from coal, oil and gas

Working groups were established in Santa Marta to help countries develop national and regional plans to move away from fossil fuels, with targets and timelines to end the use of coal, oil and gas.

France launched its national roadmap at the summit, pledging to end the use of coal by 2030, oil by 2045 and gas by 2050. Europe’s second-largest economy plans to close its last coal-fired power plant next year, while replacing oil with electricity for transport and switching from gas to heat pumps for home heating. France wants two out of three new cars to be electric by 2030 and will ban the installation of gas boilers in new homes this year.

The ongoing US-Iran war has only added momentum for a shift to clean energy, as nations grapple with their dependence on imported fossil fuels amid the worst energy crisis in history.

Other nations are now expected to create plans to move away from fossil fuels and bring them to future summits.

3. A science panel to guide the transition

A new scientific panel launched in Santa Marta brings together experts in climate, economics, technology and law to advise policymakers as they draft plans to shift away from fossil fuels.

The panel will map out the most promising policies, regulations and financial arrangements to support the shift to clean energy. It is spearheaded by Professor Johan Rockstrom from the Potsdam Institute for Climate Impact Research.

Ahead of Santa Marta, a global group of researchers released a report listing 12 high-level actions nations can take to support a fossil-fuel phaseout.

4. Tuvalu to host next summit, with Irish support

Tuvalu will host the next meeting on ending fossil fuels in 2027. As a low-lying island nation, Tuvalu’s future is threatened by sea-level rise. The Pacific nation has led global climate diplomacy for decades.

“If we are to address the climate change issue, we have to address the root cause, and the root cause is the fossil fuel industry,” said Maina Talia, Tuvalu’s climate change minister.

That there are plans for a second summit is meaningful in itself. A single conference could be a flash in the pan. But a series marks the birth of a new international process with buy in from both wealthy nations and developing countries. This year’s summit was co-hosted with the Netherlands and next year will be co-hosted with Ireland.

5. Toward a fossil fuel treaty

Today, fossil fuel producers plan to dig up more than double the amount of coal, oil and gas in 2030 than would be consistent with meeting shared climate goals.

Tuvalu is part of a growing bloc of countries, including 11 Pacific nations, that wants a new treaty to phase out fossil fuel production. Such a treaty would have three elements: ending fossil fuel expansion; phasing down existing production; and supporting a just transition to clean energy.

It would be similar to global agreements to phase out weapons, harmful substances or hazardous waste.

Climate diplomacy now runs at two speeds

We will only appreciate the full significance of the Santa Marta summit in history’s rear-view mirror.

But what is clear is that climate diplomacy now has two operating speeds. André Corrêa do Lago, who headed last year’s UN COP30 climate talks in Brazil, calls this “two-tier multilateralism”.

The first speed is that of the UN climate talks, which are slower and anchored in consensus. They ensure legitimacy, universality and collective direction.

But what the Santa Marta conference shows is the existence of a second, much faster speed available to any country wanting to rapidly move to end the use of fossil fuels, once and for all.

Wesley Morgan is a Fellow with the Climate Council of Australia.

On the western side of Lake Macquarie in New South Wales, Australia, sits Myuna Bay, a quiet bay with meadows of seagrass waving beneath the water. The most common marine plant species you find there is Zostera muelleri. It has long ribbon-like leaves that grow from stems (called rhizomes) buried beneath the sediment and provides important shelter for small fish, shrimp and crabs.

Although Myuna Bay looks quite normal, it is actually a bit unusual. For decades, the nearby Eraring power station released warm water into the lake that was used to cool down their systems, causing water temperatures here to be consistently 1°C to 3°C higher than nearby sites.

This made the bay a rare natural laboratory for understanding what warming oceans might mean for coastal ecosystems.

In our new research, published today in the journal New Phytologist, we used this setting to investigate what happens to seagrass and the microbes living in the sediment when ocean temperatures increase in the way climate models predict they will in the future.

One of the most important coastal habitats

Seagrasses are often overlooked, but they are among the most important coastal habitats on Earth.

They are marine flowering plants that stabilise sediments, improve water clarity and provide food and shelter for many marine animals. They also store large amounts of carbon in the sediments beneath them, making them important for slowing climate change.

But seagrasses don’t function alone. Beneath the leaves, in the sediments, lives a hidden ecosystem of microbes: bacteria, fungi and other microscopic organisms that interact with the plant.

Just as plants on land depend on soil microbes, seagrasses rely on microbial communities in the sediment around their roots. These microbes carry out many important processes. Some provide nutrients that plants need to grow. Others break down organic matter or detoxify harmful compounds in the sediment.

In some ways, the relationship can be compared to the partnership between corals and the microscopic algae living inside them. Corals rely on those algae for energy, while seagrasses depend on microbes to help maintain a healthy environment around their roots.

But not all microbes are helpful. Some produce sulphide, a compound that can be toxic to seagrass roots when it accumulates in sediments. We are starting to find out that whether microbial communities help or harm the plant can depend strongly on environmental conditions, including increases in ocean temperatures due to climate change.

Simulating future ocean warming in the field

To understand how ocean warming might affect the relationship between seagrasses and microbes in the sediment under realistic future conditions, we designed a field experiment at Myuna Bay.

We collected seagrass plants and sediments from both warmer and “normal” temperature sites in Lake Macquarie. Some plants were grown in sediments with their microbial communities intact.

In other treatments, the sediments were heated to 121°C to disrupt the microbes; this reduces total bacterial abundance by more than 95%.

This allowed us to test how plants performed when the microbial community was intact versus when it had been disrupted. We then placed plants in pots with those different sediments and exposed the plants to warmer conditions at Myuna Bay, similar to those expected in the future.

After one month, we monitored how the plants responded. We measured how they survived, how many shoots they produced and how their biomass changed over time. At the same time, we analysed the bacterial communities in the sediment using DNA sequencing to see how they differed between treatments.

Looking beyond plants

When plants were grown in sediments from “normal” temperature sites, seagrass performed well whether the microbes were intact or disrupted. But when plants were grown in sediments from warmer sites, the outcome changed: plants growing with intact sediment microbial communities performed worse. These sediments from the warm areas also contained different bacterial communities, which may help explain the lower plant biomass we observed.

One possible explanation involves sulphide. In seagrass sediments, certain microbes produce sulphide as part of their metabolism. At high concentrations, sulphide can be toxic for seagrasses. Warmer temperatures may stimulate microbial activity, increasing sulphide production and tipping the balance from a supportive microbial community to one that harms the plant.

Our findings highlight an important idea: the impacts of climate change on seagrasses can’t be understood by looking at the plants alone. The microbial communities living in the sediment can also influence how these plants respond to warming.

This has important implications for conservation and restoration. Around the world, seagrass meadows are declining due to coastal development, pollution and climate change.

Restoration projects often focus on planting seagrass shoots or seeds. But the condition of the surrounding sediment, including its microbial community, may also determine whether restoration succeeds.

As oceans continue to warm, the future of seagrass meadows may depend not only on the plants we see when snorkelling, but also on the microscopic microbes living in the sediment beneath them.

Renske Jongen is a council member for the NSW Branch of the Australian Marine Sciences Association.

Ziggy Marzinelli is an Associate Professor at The University of Sydney and receives funding from the Australian Research Council, the Ian Potter Foundation and the NSW Environmental Trust.

Paul Gribben receives funding from Australian Research Council.