Over the past decade, research has emerged suggesting that ramping up reforestation around the world could make a substantial contribution to tackling climate change.
Studies have estimated that the CO2-absorbing power of newly planted trees could add up to mitigation “potential” of 10bn tonnes (GtCO2) per year – more than the annual emissions of the US.
Achieving this would require planting trees across 678m hectares – an area twice the size of India.
But the uncertainty around those figures is large due to a range of factors, such as where sufficient trees already exist, how much climate mitigation those trees offer and where people actually want additional trees to be planted.
In our new study, published in Nature Communications, we unpack eight years of research into reducing these uncertainties.
We have quantified, for example, how the carbon-sucking power of trees changes when you let forests grow back naturally versus planting monoculture or mixed-species plantations.
We figured out how much carbon could be removed at different price points and mapped where trees – somewhat counterintuitively – actually act to warm, rather than cool, our climate.
But, as we shrank the uncertainty, we also shrank the estimate itself.
Our research provides the most precise estimate of global reforestation area to date – 195m hectares, or 71% less than earlier estimates.
Reforesting an area this size could capture 2GtCO2 per year.
Mapping reforestation opportunity
Maps of global reforestation potential have been cited in thousands of scientific publications, inspired large-scale tree-planting movements and been used by the International Panel on Climate Change (IPCC) in its flagship reports.
However, they have also been very controversial.
Critics have pointed out, for example, that these maps failed to account for natural disturbances that prevent forest growth, ignored existing trees and overlooked the people that live, steward and often depend on those lands for their wellbeing.
In our new study, we resolved to produce a map that addresses these past critiques.
We began by searching for existing maps of reforestation “opportunity”.
Our search uncovered 89 such maps, although most of those we identified are national or sub-national. Some places – such as Brazil’s Atlantic Forest – have many maps, but we found that most of the globe was only covered by a single older, more controversial map.
The map below shows where we found existing maps at the global, regional, national and sub-national levels.
Thus, we set about creating a new global map that built upon the methods of past efforts, tackled prominent critiques and incorporated newly available layers.
Our new map accounts for albedo, for example – how restoring tree cover can, in some locations, actively heat the Earth, rather than cool it, by affecting how much sunlight is absorbed or reflected.
It excludes native grasslands and other ecosystems where carpeting the land with trees would harm biodiversity and exacerbate the risk of wildfire. And it layers in additional safeguards, such as food security, to ensure that reforestation outcomes are more likely to be beneficial to people.
These constraints left us with up to 195m hectares of reforestation opportunity across the world.
A reforestation ‘menu’
Not all reforestation opportunities are created equal – different communities may want to implement reforestation for different reasons, such as restoring floodplains or re-establishing iconic ecosystems that have been lost.
So, alongside the reforestation opportunity, our map shows other factors that communities or decisionmakers may use to help them prioritise areas for reforestation.
We show, for example, where natural regeneration may be most likely to occur and where biodiversity benefits may be greatest, given proximity to existing forest. We show where reforestation opportunity exists on slopes and floodplains – and therefore is more likely to provide benefits for the local watershed. We show places where people have strong rights and secure land tenure, to avoid exacerbating social inequities.
Perhaps unsurprisingly, it is hard to find places that tick all of these complex boxes. But, it is still possible to achieve multiple objectives in one location.
In fact, our study finds that 83% of reforestation opportunities occur close to existing forest, while 81% occur in places that are expected to have low conflicts with rural livelihoods.
More than half of the opportunity that we identify also occurs in countries with explicit restoration goals – places such as Brazil’s Atlantic Forest, where we are working with local partners and communities to restore 1.2m hectares of forest. Forest restoration there contributes to national climate goals, supports sustainable economic development and connects habitat for wildlife.
Alongside the paper, we present the Global Reforestation Hub, which allows users to explore this menu of reforestation options, drill down to reforestation potential at county level and see what opportunities meet a given set of objectives.
For example, a government interested in climate mitigation and protection from floods might use the tool to find the places within their country where both goals might be achieved via reforestation.
The screenshot below shows the Global Reforestation Hub. Countries are coloured by their total reforestation opportunity, from low (white) to high (dark blue). The table shows the amount of land available for – and the CO2 mitigation potential of – reforestation given different priorities and constraints.
Smaller can be better
Reforestation remains one of the most cost-effective climate removal options, but it cannot – and should not – happen everywhere.
While there are certainly opportunities to plant and regrow trees beyond what we have mapped here, we created these maps to show where the climate mitigation opportunities – and their co-benefits – are most concentrated.
Prioritising other motivations, such as human health, habitat for specific wildlife species or local considerations, would also increase the total reforestation opportunity area. For example, our maps don’t include the potential for reforestation in dense urban areas, but trees in those areas can be highly beneficial for human health.
Our study prioritised mapping opportunities for climate change mitigation – and we were deliberately conservative, erring on the side of caution when determining which places to include.
The result is a map that shows the places where reforestation offers both the greatest climate benefits and the fewest downsides for both people and nature.
During a year when the UN climate COP will be hosted in the most iconic forest of all, our study is less a critique of the pre-existing numbers and more an effort to create the most precise and pragmatic maps of reforestation potential. This can help ensure that we get the reforestation part of the climate equation right.
The post Guest post: Why the global area for regrowing trees is 71% smaller than thought appeared first on Carbon Brief.
Guest post: Why the global area for regrowing trees is 71% smaller than thought
A new storm recovery charge could soon hit Georgia Power customers’ bills, as climate change drives more destructive weather across the state.
Hurricane Helene may be long over, but its costs are poised to land on Georgians’ electricity bills. After the storm killed 37 people in Georgia and caused billions in damage in September 2024, Georgia Power is seeking permission from state regulators to pass recovery costs on to customers.
Gov. Mikie Sherrill says she supports both AI and lowering her constituents’ bills.
With New Jersey’s cost-of-living “crisis” at the center of Gov. Mikie Sherrill’s agenda, her administration has inherited a program that approved a $250 million tax break for an artificial intelligence data center.
Amid Affordability Crisis, New Jersey Hands $250 Million Tax Break to Data Center
Gabrielle Dreyfus is chief scientist at the Institute for Governance and Sustainable Development, Thomas Röckmann is a professor of atmospheric physics and chemistry at Utrecht University, and Lena Höglund Isaksson is a senior research scholar at the International Institute for Applied Systems Analysis.
This March scientists and policy makers will gather near the site in Italy where methane was first identified 250 years ago to share the latest science on methane and the policy and technology steps needed to rapidly cut methane emissions. The timing is apt.
As new tools transform our understanding of methane emissions and their sources, the evidence they reveal points to a single conclusion: Human-caused methane emissions are still rising, and global action remains far too slow.
This is the central finding of the latest Global Methane Status Report. Four years into the Global Methane Pledge, which aims for a 30% cut in global emissions by 2030, the good news is that the pledge has increased mitigation ambition under national plans, which, if fully implemented, could result in the largest and most sustained decline in methane emissions since the Industrial Revolution.
The bad news is this is still short of the 30% target. The decisive question is whether governments will move quickly enough to turn that bend into the steep decline required to pump the brake on global warming.
What the data really show
Assessing progress requires comparing three benchmarks: the level of emissions today relative to 2020, the trajectory projected in 2021 before methane received significant policy focus, and the level required by 2030 to meet the pledge.
The latest data show that global methane emissions in 2025 are higher than in 2020 but not as high as previously expected. In 2021, emissions were projected to rise by about 9% between 2020 and 2030. Updated analysis places that increase closer to 5%. This change is driven by factors such as slower than expected growth in unconventional gas production between 2020 and 2024 and lower than expected waste emissions in several regions.
Gas flaring soars in Niger Delta post-Shell, afflicting communities
This updated trajectory still does not deliver the reductions required, but it does indicate that the curve is beginning to bend. More importantly, the commitments already outlined in countries’ Nationally Determined Contributions and Methane Action Plans would, if fully implemented, produce an 8% reduction in global methane emissions between 2020 and 2030. This would turn the current increase into a sustained decline. While still insufficient to reach the Global Methane Pledge target of a 30% cut, it would represent historical progress.
Solutions are known and ready
Scientific assessments consistently show that the technical potential to meet the pledge exists. The gap lies not in technology, but in implementation.
The energy sector accounts for approximately 70% of total technical methane reduction potential between 2020 and 2030. Proven measures include recovering associated petroleum gas in oil production, regular leak detection and repair across oil and gas supply chains, and installing ventilation air oxidation technologies in underground coal mines. Many of these options are low cost or profitable. Yet current commitments would achieve only one third of the maximum technically feasible reductions in this sector.
Recent COP hosts Brazil and Azerbaijan linked to “super-emitting” methane plumes
Agriculture and waste also provide opportunities. Rice emissions can be reduced through improved water management, low-emission hybrids and soil amendments. While innovations in technology and practices hold promise in the longer term, near-term potential in livestock is more constrained and trends in global diets may counteract gains.
Waste sector emissions had been expected to increase more rapidly, but improvements in waste management in several regions over the past two decades have moderated this rise. Long-term mitigation in this sector requires immediate investment in improved landfills and circular waste systems, as emissions from waste already deposited will persist in the short term.
New measurement tools
Methane monitoring capacity has expanded significantly. Satellite-based systems can now identify methane super-emitters. Ground-based sensors are becoming more accessible and can provide real-time data. These developments improve national inventories and can strengthen accountability.
However, policy action does not need to wait for perfect measurement. Current scientific understanding of source magnitudes and mitigation effectiveness is sufficient to achieve a 30% reduction between 2020 and 2030. Many of the largest reductions in oil, gas and coal can be delivered through binding technology standards that do not require high precision quantification of emissions.
The decisive years ahead
The next 2 years will be critical for determining whether existing commitments translate into emissions reductions consistent with the Global Methane Pledge.
Governments should prioritise adoption of an effective international methane performance standard for oil and gas, including through the EU Methane Regulation, and expand the reach of such standards through voluntary buyers’ clubs. National and regional authorities should introduce binding technology standards for oil, gas and coal to ensure that voluntary agreements are backed by legal requirements.
One approach to promoting better progress on methane is to develop a binding methane agreement, starting with the oil and gas sector, as suggested by Barbados’ PM Mia Mottley and other leaders. Countries must also address the deeper challenge of political and economic dependence on fossil fuels, which continues to slow progress. Without a dual strategy of reducing methane and deep decarbonisation, it will not be possible to meet the Paris Agreement objectives.
Mottley’s “legally binding” methane pact faces barriers, but smaller steps possible
The next four years will determine whether available technologies, scientific evidence and political leadership align to deliver a rapid transition toward near-zero methane energy systems, holistic and equity-based lower emission agricultural systems and circular waste management strategies that eliminate methane release. These years will also determine whether the world captures the near-term climate benefits of methane abatement or locks in higher long-term costs and risks.
The Global Methane Status Report shows that the world is beginning to change course. Delivering the sharper downward trajectory now required is a test of political will. As scientists, we have laid out the evidence. Leaders must now act on it.
The post Curbing methane is the fastest way to slow warming – but we’re off the pace appeared first on Climate Home News.
Curbing methane is the fastest way to slow warming – but we’re off the pace
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