Many pathways to staying below 1.5C delay deep cuts in carbon dioxide (CO2) emissions and rely instead on huge amounts of CO2 removal (CDR) later this century.
Land-based CDR is used extensively in the 1.5C pathways presented by the Intergovernmental Panel on Climate Change (IPCC) and also features heavily in the climate plans of many governments and businesses.
Yet the large-scale deployment of land-based CDR could come with major challenges. These include significant ecological and societal risks – particularly to biodiversity loss, food security, freshwater use and human rights, among others – which have not been comprehensively assessed.
In our new paper, published in Science, we assess the level of sustainability risks that could be triggered by the use of various different land-based CDR techniques, such as bioenergy with carbon capture and storage (BECCS) and afforestation and reforestation (A/R).
We show that risks are triggered at much lower levels of deployment than previously thought. Moreover, many of the “Paris aligned” 1.5C pathways presented by the IPCC would exceed the CDR sustainability limits defined by our evaluation.
CDR deployment in mitigation pathways
Many mitigation pathways assessed by the IPCC envisage large deployments of CDR throughout the 21st century.
This is significant because, although the IPCC is not “policy prescriptive”, these pathways – and the policy options within them – strongly shape the “solution space” as seen by policymakers when considering how to meet the goals of the Paris Agreement.
The use of CDR is particularly widespread in the pathways labelled by the IPCC as “1.5C with high overshoot”. In these pathways, emissions cuts are not fast enough to avoid breaching the carbon budget for 1.5C and global temperatures temporarily overshoot the 1.5C limit, before extensive use of CDR brings temperatures down later this century.
Within these pathways, CDR is deployed up to 2050 to help compensate for a slower transition away from fossil fuels, to reduce net emissions. When emissions reach net-zero, CDR is being used to counterbalance large remaining residual emissions. Beyond this point, it is used to draw-down global temperature after exceeding 1.5C.
This type of pathway is typified by the IPCC’s “Neg” illustrative mitigation pathway. Here, – some 5.1bn tonnes of CO2 (GtCO2) is taken out of the atmosphere using CDR in 2050 and 15.1GtCO2 in 2100.
In this pathway, one of five outlined in the IPPC’s sixth assessment report (AR6), primary energy from fossil fuel drops only 36% below 2020 levels by 2050 and 73% by 2100, relative to 2020.
This CDR and emissions profile is in sharp contrast to the IPCC’s “Ren” pathway – which relies on rapid scale-up of renewable energy – primary energy from fossil fuel falls 85% by 2050 and 95% by 2100, relative to 2020. (IMP-Ren)
This means that this renewable energy pathway has much lower reliance on CDR, which is only used to take 2.6GtCO2 out of the atmosphere in 2050 and 3GtCO2 in 2100.
Sustainability limits
The large amounts of land-based CDR in many of the pathways assessed by the IPCC come with significant implications in terms of sustainability, with the potential for serious impacts on human livelihoods and food security.
Yet the IPCC report does not comprehensively assess the environmental feasibility of the scenarios, nor their associated sustainability risks. Nor does it put a figure on the scale of CDR that could be deployed without triggering major impacts.
To address this gap, we quantified the sustainability limits to the widespread deployment of BECCS, A/R and “nature-based” CDR, which includes limited reforestation, forest restoration, reduced forest harvest and agroforestry.
To do so, we draw from recent studies that give greater attention to the ecological, biological and societal impacts of land-based CDR.
Based on these studies, we calculated the levels of CDR deployment that would trigger “low”, “medium”, “high” and “very high” risks for sustainability. These risk levels are colour-coded from green through to dark red, for each type of land-based CDR in the figure below.
Reading from left to right, the figure shows increasing levels of CDR deployment in terms of GtCO2 removed per year. The grey bar shows the range of “technical mitigation potential” for each technique, as currently assessed by the IPCC. The upper end of this is the largest amount that could theoretically be deployed, if barriers to rapid scale-up, constraints on feasibility and sustainability risks are not taken into account.
The figure shows that sustainability risks start well below the technical mitigation potential.
For BECCS, the IPCC reports an average technical potential of 5.9GtCO2 per year. Yet we find that deploying more than 1.2GtCO2 of BECCS per year would tip over from “low risk” into “medium” or higher risk levels.
(This figure is based on BECCS plants capturing a “medium” share of their associated CO2 emissions, below 70%. For a “low” capture rate below 50%, the low-risk threshold drops to just 0.7GtCO2 per year.)
Correspondingly, BECCS would cross the high sustainability risk threshold (shown in red) if used to remove 1.3GtCO2 with a low capture rate – or 2.8GtCO2 with a medium rate.
Even these limited levels of BECCS assume significant bioenergy policy reforms that governments have not yet addressed. These include addressing gaps in emissions accounting and ensuring bioenergy is not causing deforestation, either directly or indirectly.
For A/R, the IPCC average technical potential is 3.9GtCO2 a year. Our research shows that associated sustainability risks remain low or medium below 3.8GtCO2 per year, with high risks beyond that point.
We find that nature-based CDR (which includes limited reforestation) carries the lowest sustainability risks. Deployment would trigger high risks beyond 5.1GtCO2 a year (including 3.8GtCO2 per year of non-monoculture reforestation).
Having defined risk levels for each type of CDR, we then mapped those indicators onto the amount of CDR deployed in each of the IPCC’s five “illustrative mitigation pathways” (IMPs).
(These pathways are: gradual strengthening of climate policy, GS; widespread use of CDR, Neg; low energy demand, LD; shifting pathways towards sustainable development, SP; and heavy use of renewables, Ren.)
Our results, illustrated in the table below, show that the three pathways that limit warming to 1.5C with limited to no overshoot are able to do so without greatly overstepping our sustainability risk thresholds.
In contrast, Neg limits warming in 2100 to 1.5C with high temperature overshoot, but exceeds high and even very high sustainability risk thresholds. The GS pathway only limits warming to 2C and still carries significant levels of sustainability risks.
Reading the table from top to bottom, the first set of rows list the change in CO2 emissions, energy demand and fossil fuel use in 2050 and 2100.
The second set of rows show the amount of each type of CDR deployed in 2050 and 2100, colour-coded according to our sustainability risk levels.
The third set of rows show the amount of land needed for CDR deployment – the land footprint. Again, these are colour-coded according to our sustainability risk levels.
Notably, our findings show that the amount of land needed for CDR in the Neg pathway could reach 7.2m square kilometres in 2050 and 13.3m square kilometres in 2100. For comparison, the land area of the US is just 9.1m square kilometres.
Risk assessment
Our findings suggest there is an urgent need to consider sustainability risks when choosing between different mitigation pathways.
One way to do this would be to define a “sustainable CDR budget”, as the amount of CDR that could be deployed sustainably across all CDR methods.
While our research only considered land-based CDR, alternative CDR options are also likely to come with sustainability and deployment risks, which could limit their potential. These include direct air carbon capture and storage (DACCS) or ocean-based CDR.
Another option would be for scientists to identify Paris-aligned scenarios that do not overstep sustainability limits. Our research suggests that this could be a key priority for the IPCC’s seventh assessment cycle, as well as integrating environmental risks and feasibility throughout the IPCC’s work.
Moreover, our findings suggest that delaying fossil fuel cuts, in the hope that emissions can be drawn down later this century using CDR, would come with high sustainability risks.
If, on the other hand, countries wish to account for biodiversity considerations alongside climate goals, while still limiting temperatures to 1.5C, then they would need to follow a mitigation pathway with more rapid cuts in fossil fuel use, our research suggests.
Many of these pathways include behaviour changes and reductions in energy demand.
Countries could take up our findings in their next nationally-determined contributions (NDCs) under the Paris Agreement, due in 2025. For example, they could address sustainability risks by setting separate, transparent targets for CDR, in addition to headline emissions goals.
They could also aim to limit their reliance on CDR – and its corresponding land footprint – in order to avoid climate actions that have negative consequences for their national biodiversity plans under the global biodiversity framework (NBSAPs).
The post Guest post: Heavy use of CO2 removal would trigger high sustainability risks appeared first on Carbon Brief.
Guest post: Heavy use of CO2 removal would trigger high sustainability risks
KOROR, PALAU, Friday 4 September 2026 – At the closing of the 55th Pacific Islands Forum Leaders Meeting in Palau overnight, Greenpeace Australia Pacific called out Australia for promising climate action while expanding fossil fuel production, and is urging Pacific leaders to unite ahead of the Pacific Pre-COP.
The meeting was rocked by the UN’s 1.5°C overshoot report a day before Australia approved the extension of one of the country’s largest coal mines.
Speaking from Palau, Shiva Gounden, Head of Pacific at Greenpeace Australia Pacific, said:
“Against the backdrop of the 1.5°C UNEP report, this Forum was a vital opportunity for Pacific leadership to shine by firmly calling out fossil fuels and banding together for our shared Pacific future. While the final communique reaffirmed the need to accelerate the transition away from fossil fuels, Pacific leaders missed the opportunity to hold the Australian government accountable for their continued approval of new coal and gas projects.
“At Pacific Pre-COP in Nadi, we are calling for Pacific priorities to be centred and respected by Australia and our global partners: they must support the ambition of a Fossil Fuel Free Pacific, ensure access to adequate climate finance and lead a global push to hold the line on 1.5°C as a matter of Pacific survival.
“Leaders fell short at the Pacific Islands Forum, and Pacific Pre-COP is the opportunity to match the ambition with urgency, and set the vaka on course toward a peaceful, just Pacific future.”
Speaking from Palau, Dr Simon Bradshaw, COP31 Lead and climate expert at Greenpeace Australia Pacific, said:
“The Pacific Islands Forum was an opportunity for Prime Minister Albanese to show real commitment to climate action and to its Pacific partnership. Instead, this week the Australian Government ‘celebrated’ the first extraction of polluting gas from the Beetaloo Basin and approved an extension of one of Australia’s largest coal mines. All amidst a still unfolding flood crisis in Nepal-Tibet and the devastating news that the world will blow through 1.5°C of warming — a survival line for Pacific communities.
“These are not the actions of a government aspiring to be a global climate leader and effective middle power in turbulent times, they are the actions of a government still beholden to the fossil fuel industry. Australia, get it together.
“As we head towards the Pacific Pre-COP, our Prime Minister and Government must remember the responsibility we have taken on. We must hold the line on returning warming to 1.5°C as our legal and moral obligation. This means doing everything possible to accelerate the global transition away from fossil fuels, starting at home.”
—ENDS—
Australia blows PIF climate opportunity as Pacific leaders urged to band together
As efforts to expand energy access across Africa grow, experts and policymakers have called this week for greater coordination and investment to power food production with renewables, arguing the sector has been treated separately from energy policy and therefore faces barriers in going green.
Hailemariam Desalegn, former prime minister of Ethiopia, said energy is critical across the food value chain – from irrigation and processing to cold storage and transport – and should therefore be considered a key pillar of strengthening food systems for the future.
“Energy is not separate from the nutrition challenge. Irrigation needs energy. Cold storage, transport, processing, as well as markets – all need reliable energy,” Desalegn told a panel at the 20th session of the Africa Food Systems Forum in Kigali. He said investments in sustainable energy systems could help reduce post-harvest losses and make nutritious food more accessible and affordable.
Africa loses up to 30% of its food before it reaches markets annually, largely due to poor roads, weak storage and inadequate cold chains, according to a 2025 report by the Alliance for a Green Revolution in Africa (AGRA).
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Akinyi Walender, Africa director at development charity Practical Action, said poor energy supply in rural communities – where much of Africa’s food is produced – is also limiting productivity. Across the continent, about 600 million people currently live without access to electricity.
“The lack of energy access goes well beyond the inconvenience of not having lighting at home,” Walender said, adding that renewable energy has the potential to power local economies. “When people can access this sort of energy, it can raise rural incomes, improve food security, improve resilience, empower women and stimulate enterprise while creating jobs,” she added.
Breaking down silos
Unlocking the potential of energy across food systems requires greater coordination, Walender argued, pointing to institutional fragmentation and isolated pilot projects as major barriers.
“Organisations working on agriculture and energy often operate according to different modalities and the interdependence between agricultural and energy markets is often overlooked,” Walender said, adding that finance institutions also tend to work in silos.
Dana Rysankova, global lead for energy access at the World Bank, told a separate event at the forum that the bank is working to break down those barriers through its newly established Productive Use of Energy (PUE) Centre of Excellence based in Nairobi, which has a mandate to foster collaboration and help develop and design programmes across different sectors.
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In June, the World Bank Group and the African Development Bank Group said that over 50 million people had been connected to electricity across 40 African countries under their Mission 300 initiative, which aims to provide electricity access to 300 million Africans by 2030.
Rysankova said the programme has shown that energy access is just the foundation for linking with other sectors to deliver real economic transformation by boosting productivity and local incomes.
Mission 300 also aims to electrify schools and healthcare services, as well as bringing power to farmers so that they can use it for irrigation, cold storage and other agricultural activities, she added.
Bridging the finance and infrastructure gap
Experts said bigger investments are needed in infrastructure and finance to turn energy access into increased productivity and economic value.
AGRA’s 2026 foresight report, launched at the forum, puts the annual agrifood financing gap at $180 billion, while estimating that closing Africa’s yearly $67 billion-$108 billion shortfall in infrastructure finance could halve post-harvest losses and increase farmer incomes by up to 40%.
However, the cost of transitioning to clean energy is still a major barrier for farmers and agribusinesses.
Atinuke Lebile, CEO of Nigerian food processing company Cato Foods, told Climate Home News she would like to switch to using renewables but has been held back by the upfront cost of setting up the systems the firm needs.
Rwandan farmer Gezel also said she would like to invest in a solar irrigation pump, but “it is so expensive”.
Practical Action’s Walender said the challenge is no longer whether solutions exist, but how financial support can reach the communities and businesses where it could have the greatest impact.
“Customers are dispersed and have low incomes. Markets are fragmented, and there are high upfront costs for much energy equipment,” Walender said, adding that financial institutions also often perceive agriculture as a high-risk sector.
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For food processing, the business case for using cleaner energy more efficiently is particularly strong, said Vivian Maduekeh of Partners in Food Solutions, which has worked with more than 2,000 companies across Africa.
Maduekeh said food processing firms account for between 42 and 70% of energy use across food systems, while energy represents 15-22% of their total production costs. African food businesses also use roughly twice as much energy per kilogramme of product as their global competitors, putting them at a competitive disadvantage.
The problems they face in shifting to clean energy are “risk, perception of risk and the cost”, she explained, adding that financial mechanisms are needed to help businesses overcome those issues.
Maduekeh encouraged policymakers to consider measures like tax rebates on imported equipment and spending more on research and development to bring down the cost of productive-use technologies.
Making a range of affordable equipment available – such as smaller irrigation pumps – could also help make the transition more accessible, she said. The evidence in favour “is very clear”, she added. “We just need to package it and communicate it to the priorities of investors.”
The post More support needed to power Africa’s food systems with renewables, experts say appeared first on Climate Home News.
More support needed to power Africa’s food systems with renewables, experts say
Andy Burnham, the UK’s latest prime minister, has suggested reducing the amount the British government gives as climate finance grants and providing some of its climate finance through loans instead, in a move it anticipates will save £400 million.
The government plans to use the savings to fund a cap on bus fares in the UK, triggering accusations from the development sector that Burnham’s proposal “throws Global South countries under the bus”. One likely destination for these new loans is the Tropical Forest Forever Facility (TFFF).
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The TFFF is a new initiative designed to provide payments to countries that protect their rainforests by raising money from governments and private investors, channeling that money into riskier and therefore higher return assets, and using the returns it earns to fund forest protection. But there is a catch.
The UK has committed to provide around £6 billion in climate finance funded through aid (or official development assistance, ODA) over the next three years. If switching from grants to a loan to the TFFF reduces government spending, it will likely reduce the amount that counts as ODA as well.
In other words, the government can make the £400 million saving, or meet its £6 billion aid budget-funded climate finance commitment, but it probably cannot do both. The UK cannot have its cake and eat it.
How will it score as ODA?
Whether any loan to the TFFF scores as ODA depends on the OECD’s Development Assistance Committee (DAC) which is currently deliberating on this topic.
A plain reading of the DAC’s current reporting rules suggests that the TFFF would count as a multilateral organisation: the independent investment arm, the Tropical Forest Investment Fund, would ultimately be a global, official entity (with sovereign governments appointing the board and being sole equity holders), which pools capital from sponsor governments. This would mean that to count as ODA, any loan to it would have to charge less than 5% interest.
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The current concept note suggests a return for sponsor capital equivalent to US borrowing costs of a similar duration: currently around 5.2%, which would make any such loans ineligible. The UK could choose to charge less, but if the UK charges less than it borrows (also above 5%), the difference will add to the deficit in future years. And ODA accounting is not binary: if the UK charges just under 5%, only a small fraction of the loan would count.
At the same time, the risk profile of TFFF is not the same as your average multilateral, and there is speculation that the DAC could allow higher interest loans to TFFF to partially count (by changing the ‘discount rate’ used to measure how concessional the loan is). The TFFF’s own modelling suggests that the risk of the UK losing money on the loan would be fairly limited: roughly a 1% chance of some capital impairment in the riskiest scenario. But some analysts doubt the accuracy of this model and view the risk as much greater.
Would it really save money?
If the risk really is higher, then it might justify counting more ODA on a loan to the TFFF, but it also undermines the arguments that this would create savings for the government. Loans generally don’t count towards the deficit because they create an asset. But that only works if the loan is expected to be fully repaid. If there is a material risk of losing money, then at least some of the transaction will also count towards the deficit.
One possibility is that the loan will be ‘partitioned’ into a financial asset (the part which is expected to be repaid and wouldn’t count towards the deficit) and a ‘capital transfer’ (the part not expected to be repaid). The greater the risk, the larger that second component, and the bigger the impact on the deficit.
This would be the ODA and public accounting rules working as intended. ODA is a measure of ‘donor effort’, usually taken to mean fiscal impact. If it counts as ODA, it should have an impact on the deficit. And the fiscal treatment itself is governed by numerous international accounting standards, a key purpose of which is preventing politically motivated obfuscation of how governments spend their money. If it costs money, there should be an impact on the deficit even if it is a loan. If it doesn’t, it shouldn’t count as ODA (even if there have been exceptions in the past).
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We still know too little about the details to be sure how a loan to the TFFF (or a more exotic transaction) would count towards either ODA or the UK’s headline measures of debt and deficit. The key parameter for each is risk: the lower risk, the more likely it is that the transaction will save money, but the greater the chance that the government would have to spend more ODA elsewhere to meet its climate finance target.
If the UK believes in the TFFF business model and wants to preserve tropical forests, then it should invest. But this decision should not be driven by optimistic accounting tricks. The government cannot expect to reduce the real value of climate finance to partner countries by giving less in grant money, without this having an impact on commitments to spend that money.
The post UK’s budget juggling trick with rainforest loan for bus-fare cap needs transparency appeared first on Climate Home News.
UK’s budget juggling trick with rainforest loan for bus-fare cap needs transparency
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