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Research led by Associate Professor Tristan Salles shows ancient reefs have tuned Earth's climate recovery for millennia.

Coral reefs have long been celebrated as biodiversity hotspots – but new research shows they have also played a much deeper role: conducting the rhythm of Earth’s carbon and climate cycles for more than 250 million years.

Published this week in the Proceedings of the National Academy of Sciences (PNAS), the study reveals that the rise and fall of shallow-water reef habitats have governed how quickly the planet recovered from major carbon dioxide (CO?) shocks.

Researchers from the University of Sydney and Université Grenoble Alpes combined plate-tectonic reconstructions, global surface processes and climate simulations, with ecological modelling to reconstruct shallow-water carbonate production back to the Triassic Period. They found that the Earth system flips between two distinct modes that determine the pace of climate recovery.

Lead author Associate Professor Tristan Salles from the University of Sydney’s School of Geosciences said: “Reefs didn’t just respond to climate change – they helped set the tempo of recovery.”

In one mode, when tropical shelves are extensive and reefs thrive, carbonate accumulates in shallow seas, reducing chemical exchange with the deep ocean. This weakens the biological pump – the process by which marine organisms draw down carbon – and slows the planet’s recovery from carbon shocks.

In the other mode, when reef space collapses due to tectonic or sea-level change, calcium and alkalinity build up in the ocean. Carbonate burial then shifts to the deep sea, stimulating nannoplankton productivity and accelerating climate recovery.

The findings recast reefs and other shallow-water carbonate systems as active modulators of Earth’s buffering capacity rather than passive recorders of environmental change. This shifting balance between shallow- and deep-water carbonate burial also influenced the evolution of marine plankton and long-term ocean chemistry.

“These switches profoundly alter the biogeochemical equilibrium,” said co-lead author Dr Laurent Husson (CNRS - UGA).

“The big expansion of planktonic life happened exactly when shallow reefs were ‘turned down’ by the Earth system,” he said. Such changes modified the ocean’s biological pump and in turn, the climate and the speed at which it recovers from global perturbations.

This study suggests reefs have been central not only to marine biodiversity but also to the planet’s ability to stabilise climate.

Although this study focuses on Earth’s deep past, it offers clear lessons for the future. Modern reef systems are declining rapidly due to warming and ocean acidification. If this trajectory mirrors ancient episodes of reef collapse, carbonate burial may shift from shallow reefs to the deep ocean – a habitability-limited mode. In principle, this could help draw down atmospheric carbon.

However, the very organisms that drive deep-sea carbonate burial – plankton and other calcifying species – are themselves increasingly threatened by acidifying oceans and continued CO? emissions. Any potential stabilising effect would therefore come only after severe and irreversible ecological loss.

Associate Professor Salles said: “From our perspective on the past 250 million years, we know the Earth system will eventually recover from the massive carbon disruption we are now entering. But this recovery will not occur on human timescales. Our study shows that geological recovery requires thousands to hundreds of thousands of years.”

Salles, T. et al ‘Carbonate burial regimes, the Meso-Cenozoic climate and nannoplankton expansion’ (Proceedings of the National Academy of Sciences of North America 2025). DOI: 10.1073/pnas.2516468122

The authors declare no competing interests. Funding was received from the Australian Research Council and with support from the National Computational Infrastructure of the Australian Government.

Jakarta, 27 November 2025 - The Association of Southeast Asian Nations (ASEAN), the Government of Japan, and the United Nations Development Programme (UNDP) convened the ASEAN Regional Workshop on Blue Carbon and Finance Profiling on 27–28 November in Jakarta, to better connect science and policy for coastal and freshwater climate action.

Hosted at the Ministry of National Development Planning (BAPPENAS), the regional event is part of the ASEAN Blue Carbon and Finance Profiling (ABCF) Project, a Government of Japan-funded regional initiative implemented by UNDP Indonesia with the ASEAN Coordinating Task Force on Blue Economy (ACTF-BE). The project helps countries better understand the condition and economic value of their coastal and blue ecosystems so they can design more practical policies and attract financing for their protection and restoration.

30 technical experts from 11 ASEAN Member States gathered to compare data collection methods, review methodologies, and shape the development of 11 national Blue Carbon Profiles and 11 national Blue Finance Profiles, along with two corresponding regional profiles. The profiles are expected to be launched in March 2026, and will give governments clearer insights into their blue carbon assets and financing needs, supporting practical policymaking on coastal protection and restoration, strengthening climate strategies, and guiding investments in sustainable blue economy sectors.

Coastal ecosystems, including mangroves, seagrass meadows and peatlands remain among the region’s most valuable yet vulnerable natural assets. They provide significant carbon storage capacity, support fisheries, protect coastlines from erosion, and underpin coastal livelihoods. However, they continue to face pressure from land conversion, pollution, and climate-related impacts. The ABCFP aims to close critical knowledge and financing gaps by mapping blue ecosystem potential, identifying enabling policy conditions, and outlining pathways for public, private, and innovative financing solutions.

Opening the workshop on behalf of ASEAN as the Shepherd of the ACTF-BE, Dr. Eka Chandra Buana, Deputy Minister for Macro Development Planning of BAPPENAS, underscored that advancing blue carbon and blue finance is central to ASEAN’s broader blue economy agenda. “This workshop demonstrates how ASEAN Member States can work collectively to strengthen shared knowledge and develop approaches that support sustainable development across the region,” he stated.

In his remarks, Mr. Chujo Kazuo, Minister/Deputy Chief of Mission, Mission of Japan to ASEAN, reaffirmed Japan’s long-standing partnership with ASEAN and its commitment to support ASEAN’s efforts in advancing a sustainable blue economy. He stated, “Japan places great value on collaboration with regional partners and local experts. We believe that expertise must be grounded in local knowledge, and policy must be shaped through regional ownership.” He further emphasized Japan’s outlook for the partnership moving forward: “The work ahead is complex, but the potential impact is transformative. Through this project, we are taking a crucial step to protect vital ecosystems, strengthen climate resilience, create sustainable economic opportunities, and uphold the prosperity and security of our region.”

UNDP Indonesia Deputy Resident Representative, Ms. Sujala Pant, highlighted the depth of regional collaboration behind the profiling effort. She noted: “The profiling work has engaged 98 individual experts, representing 35 academic and research institutions across ASEAN and Timor-Leste. This is a significant scientific community for the region, and the network that has emerged through this initiative can continue to support the ACTF-BE as it advances its work.” She also underscored the purpose of the two-day working session: “This workshop is designed as a working space—an opportunity to refine the drafts, strengthen assumptions, and identify linkages between the carbon and finance analyses, while also understanding regional commonalities and trends.”

Throughout the event, participants engaged in technical exchanges on data integration, valuation methods, and financing frameworks, ensuring that the final products become practical tools for national and regional decision-making.

The ABCFP forms part of the broader Japan–ASEAN Blue Economy Cooperation initiative, which aims to enhance regional collaboration, scale nature-based climate solutions, and support a resilient and inclusive blue economy across ASEAN.

Media Contacts:Nabilla Rahmani, Head of Communications, UNDP Indonesia, [email protected]

In the run-up to COP30 in Belém, we hosted “Capital, Carbon and Conservation: Investing in Brazil for Net Zero Gains,” a roundtable discussion in association with the Financial Services Committee and the Energy and Decarbonization Committee of the Brazilian Chamber of Commerce in Great Britain.

The session addressed opportunities in carbon credit–generating assets, and the future outlook for Brazil/UK bilateral opportunities in the voluntary carbon market.

The panel discussion was moderated by Simon Davies, entrepreneur and head of the Financial Services Committee at the Brazilian Chamber of Commerce; and featured Ciaran Kelly, CEO of carbon offset provider Go Balance; Alexandre Leite, co-founder and CEO of UK-based climate fintech start-up NaturAll Carbon; and Henry Waite, COO of institutional debt finance software provider Kumo.

Ken Rivlin, A&O Shearman’s co-head of the environmental and climate law group, co-head of the international trade group, and board member, closed the panel with remarks on Brazil’s potential leadership on carbon credits and shifts to U.S. climate policy.

Here is a summary of the key themes.

1. Corporate demand for high-quality voluntary carbon credits today is driven by a mix of compliance, reputation and genuine sustainability commitments.

Compliance and voluntary carbon markets are two routes to reduce greenhouse gas emissions. The former are mandatory and regulated, driven by legal obligations under government policies such as emissions trading schemes. The latter are optional, enabling participants to buy credits to offset their emissions to meet corporate climate goals such as net zero targets.

Future regulatory frameworks, such as CORSIA (a global market-based carbon market program for international aviation created by the International Civil Aviation Organization to offset emissions growth) and Article 6 of the Paris Agreement (which allows countries to cooperate voluntarily to achieve emission reduction targets by transferring carbon credits) are influencing strategic interest, with trading houses positioning for potential compliance-driven markets.

Currently, most businesses make decisions to purchase carbon credits through their sustainability offices—rather than their treasury teams—thus limiting their scale.

At the same time, our experts also felt that carbon credits must become mandatory for demand to grow significantly. Until then, CFOs and treasury teams are more likely to see them as a potential risk.

2. Buyers are demanding higher quality and more demonstrable impact from carbon credits.

Corporate buyers of carbon credits are seeking immediate and tangible climate benefits as well as long-term impact and high-quality partnerships. Due diligence processes are becoming longer and more detailed, even in the case of voluntary credits. Sustainability departments are pushing for quality and longevity, including to protect against reputational risk.

CFOs and finance departments, for their part, are seeking reassurance that they can book credits as an asset. Being able to demonstrate co-benefits (positive outcomes beyond the primary goal of a policy or action, such as improvements to public health, economic growth like job creation), energy security, biodiversity, and community well-being) is a strong selling point here.

3. Successful carbon projects require genuine community buy-in and must deliver tangible co-benefits.

In markets such as Brazil, it is impossible to carry out high-quality, high-integrity climate projects without buy-in from local communities. For example, the Trocano project—which aims to prevent deforestation across 1.3 million hectares of the Amazonas region—is nine times the size of Greater London, and includes 10,700 residents living in 100 different communities.

While achieving buy-in takes longer, following the lead of local people with first-hand knowledge of an area enables providers to deliver solutions to real problems while also developing incentives such as income-generation potential. However, some buyers are focused on targeting the lowest-priced assets that provide the greatest climate impact—which are likely be the cheapest to deliver and therefore not involve as many co-benefits. One route to offer the best co-benefits is to price this element into the carbon itself, which by its nature is more easily measured than environmental benefit.

Some members of the panel felt that buyers should remain focused on the primary goal of reducing emissions, meaning therefore that the community angle is less relevant. However, another highlighted that engaging with communities through nature-based initiatives such as afforestation, reforestation and restoration (ARR) and REDD+ (a framework that financially rewards developing countries for preventing deforestation and forest degradation, with the goal of converting these actions into carbon) offer longer-term benefits than technologies that remove carbon.

4. Quality assurance in carbon credits is complex and time-consuming, requiring robust certification and verification.

To determine the quality and integrity of a carbon credit, it’s important to consider who is promoting the underlying project and which group is certifying it. In Brazil this process is time-consuming, and in the case of agricultural land management (ALM) can take two years from first discussing an opportunity with a farmer until the carbon credit is registered and verified.

The first step is to find out whether the relevant land was part of a native forest in the last ten years—if so, the project cannot proceed. Then the parties must determine whether the project is completely new (a requirement) and would create additionality (a benefit that would not have happened otherwise, or a measure of the value added), given that Brazil is home to a sophisticated agricultural sector.

Once the land, the forest and the process are verified, the project design must be audited and certified before buyers can begin due diligence. From there, it usually takes another 12 months to sell the credit.

5. A lack of standardization and the proliferation of registries are obstacles to scaling the market.

Because of this complexity, it is hard to standardize the process, meaning that only specialist players—or buyers’ clubs (coalitions of companies that pool their resources to purchase carbon removal credits collectively)—may be able to afford to conduct due diligence.

Another perspective is that there are two types of voluntary carbon credits: avoidance (the prevention of new greenhouse gas emissions) and removals (the extraction of existing carbon dioxide from the atmosphere), which could each be considered a form of standard. There are various categories of typical avoidance projects, and buying this type of credit tends to be cheaper than purchasing removals. Key to creating demand is providing clarity on quality and price.

The number of verifying bodies, all of which provide different levels of standardization, and the difficulty of transferring from one registry to another, are further obstacles to increased corporate investment in voluntary credits. Additionally, lenders and buyers tend to join a limited number of registries, meaning they can only access the projects listed there.

Northern Trust was highlighted as a registry that may seek to set an industry standard—if successful, this would enable money to flow and bankers to find innovative ways to create products such as credit derivatives and securitization. Following a correction in 2021, more trustworthy methodologies will also contribute to a more functional, pragmatic market—even if this doesn’t deliver the ultimate goal of cross-registry standardization.

6. Technology is improving transparency but must be applied carefully.

Emerging technologies can provide better data, which in turn leads to higher-quality carbon credits. For example, the Brazilian geospatial system has provided extremely accurate deforestation data for ten years, while the European Space Agency is open source and thus more affordable. Developing risk maps would enable buyers to make their own judgement of a project, in addition to using a professional verification report.

Other technologies likely to contribute to standardization include satellites, blockchain and artificial intelligence.

Geospatial technology works better for REDD+ because of the need to monitor, modify, and model carbon, but there is no technology able to measure carbon in the soil. The best strategy is to develop proven methodologies – something that can take years—before trying to run on technology.

7. Order and progress: how Brazil can position itself as a global leader in supply and carbon credits.

Many banks are considering funding projects in Brazil, thanks to its well-structured policy frameworks for carbon. The country is also well-positioned to be a leader in the voluntary carbon market because its climate commitments are written into law. Recent high-profile deals—such as the Brazil-UAE climate partnership, the Brazil-California climate agreement, Standard Chartered’s plans to turn rainforest protection into climate finance, and Brazil announcing a USD1 billion investment in a tropical forest facility—provide confidence for financiers and corporates.

It can learn from other jurisdictions by balancing regulatory integrity with market efficiency, maintaining strong enforcement, and ensuring long-term certainty for investors.

8. Despite significant policy headwinds in the U.S., the voluntary carbon market is expected to continue growing globally.

While U.S. carbon markets are facing obstacles amid the federal government’s policy shift on decarbonization, large U.S. companies continue to buy carbon credits, and more than 70% of Fortune 500 companies still invest in offsets. Legal and compliance teams at financial institutions with a presence in the U.S. are navigating how best to enter and remain in emissions credit investments, amid a fragmentation of global environmental and ESG rules.

One potential driver of growth is a U.S. General Accounting Office (GAO) report on emissions credit and voluntary trading, which hints at ways to expand the market in a more challenging political climate. It also covered cross-jurisdictional approach to promoting transparency and preventing fraud in carbon investing.

Despite the federal government’s stance, the panel felt that voluntary trading would continue to grow, supported by technological advances and ongoing demand from multinational businesses.

Long-term exposure to fine particulate matter like PM_2.5 components in polluted air can not only cause respiratory diseases, but also increase the risk of depression in older people, especially in those living with preexisting heart, metabolic and neurological conditions.

Depression has caused more loss of healthy life worldwide than any other mental health condition. This disorder has snatched away people's will to perform the basics of daily activities. An analysis of global health data in 2021 showed that all the years people lived with disability or reduced quality of life because of depression added up to about 56.3 million years.

A recent population-based cohort study collected data from nearly 23.7 million U.S. Medicare beneficiaries aged 65 years and older between 2000 and 2018 to examine specific components of PM_2.5 exposure, both individually and in combination, and its associations with the risk of developing depression. Among those tracked, more than 5.5 million developed depression during the follow-up period. These findings are published in JAMA Network Open.

Diving deeper into the data revealed that those people living in areas with higher levels of fine air pollution were more likely to develop depression. A combination of specific components was more strongly linked to depression than overall pollution levels alone, and with every quartile increase in exposure to this mixture, the risk of developing depression rose by about 7%.

Fine particulate matter strikes again

Air pollution isn't caused by a single type of pollutant, it's a cocktail of invisible gases and fine particulate matter released from anthropogenic activities. Among them, PM_2.5—fine particulate matter that is less than 2.5 micrometers in diameter—is the most damaging when inhaled. Particles classified as are so small that they can penetrate the bloodstream and the lungs and even bypass the blood–brain barrier.

They can also trigger inflammation and oxidative stress, which is even more dangerous for people with existing comorbidities.

A growing body of research suggests that air pollution may play a role in depression. Several studies have linked exposure to polluted air to a higher risk of developing the condition, with many pointing to PM_2.5 as a key concern. However, not much was known about the specific components that were behind the increased odds of developing depression.

To find an answer, the researchers analyzed nationwide Medicare data from older adults across the United States. The team estimated each participant's yearly exposure to PM_2.5 and other air pollution components based on where they lived and then identified new cases of depression. The data was then fed through different statistical tools to reveal the links between air pollution and depression.

They found that long-term exposure to PM_2.5, particularly its sulfate, elemental carbon, and soil dust components, was associated with an increased risk of depression. The results also indicated that the association was more pronounced among older adults with existing metabolic, cardiovascular, or brain-related conditions.

The findings exposed one more pathway by which air pollution can affect a person's quality of life. Ensuring better public health requires stricter regulation of ambient PM_2.5, particularly from fossil-fuel combustion and vehicular emissions.

Written for you by our author Sanjukta Mondal, edited by Lisa Lock, and fact-checked and reviewed by Andrew Zinin—this article is the result of careful human work. We rely on readers like you to keep independent science journalism alive. If this reporting matters to you, please consider a donation (especially monthly). You'll get an ad-free account as a thank-you.

Yanling Deng et al, Exposure to Multiple Fine Particulate Matter Components and Incident Depression in the US Medicare Population, JAMA Network Open (2025). DOI: 10.1001/jamanetworkopen.2025.51042