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
Next week, diplomats from around the world will descend on Yerevan, Armenia, to negotiate a series of decisions under the UN Convention on Biological Diversity (CBD).
Between 19 and 30 October, 196 parties will gather to hammer out the precise wording of the dozens of legal texts that make up the decisions under the Conference of the Parties (COP) to the CBD.
This year’s summit is particularly significant, as it marks the halfway point between the agreement of the Kunming-Montreal Global Biodiversity Framework and the deadline for achieving its targets.
The CBD has found that countries are currently not on track to meet 22 out of the framework’s 23 targets.
During the fortnight, delegates will also be negotiating decisions relating to the two supplemental protocols to the CBD: the Cartagena Protocol, which covers biosafety; and the Nagoya Protocol, which covers access and benefit-sharing for the use of genetic resources.
(The Cartagena and Nagoya Protocols, which are each governed by a “meeting of the parties”, or “MOP”, have fewer parties than the CBD as a whole, with 173 and 141, respectively.)
Carbon Brief is tracking the progress of countries towards consensus on dozens of negotiating texts using the interactive table below.
The tracker includes texts from the COP, as well as the MOPs for the Cartagena and Nagoya protocols. It also includes draft decisions from the most recent subsidiary body meetings, as these form the starting point for the negotiations in Yerevan.
The CBD has three subsidiary bodies: the subsidiary body on scientific, technical and technological advice (SBSTTA), the subsidiary body on implementation (SBI) and the subsidiary body on article 8(j) and other provisions (SB8J).
SB8J focuses on issues related to the Indigenous peoples and local communities. It was established at COP16 in Cali, Colombia, in 2024.
The first two columns of the interactive tracker list the topic of each agenda item and the relevant body, with subsequent columns including dates, page counts and links to the original documents.
The table is searchable and can be sorted using the arrows in the header.
Areas of disagreement in UN draft texts are denoted by square brackets. Counting the brackets in a particular iteration of a text therefore gives a sense of how far parties are from reaching consensus.
The bracket column is colour-coded, with dark green indicating a low number of brackets and red indicating a high number of brackets remaining.
Texts can also present parties with choices using “options” or alternatives (“alt”), which are counted together in the sixth column of the table.
The key discussions in Yerevan will centre around two agenda items in particular. The first is the global review, which will assess progress towards the GBF and make recommendations for accelerating action.
The second is finance, which can be separated into two parts: resource mobilisation and the financial mechanism. On resource mobilisation, biodiverse global south countries are likely to push for an increased amount of international finance for conservation.
Disagreement over the creation of the financial mechanism led to the suspension of COP16 in Cali in October 2024, as parties failed to find agreement on the mobilisation of finance before the end of the summit.
Global south countries want the establishment of a separate financial mechanism under the control of the CBD; global north countries largely prefer to maintain the existing mechanism, which sits under the Global Environment Facility.
At the resumed session of COP16 in Rome in early 2025, countries agreed on a roadmap that would lead to the establishment of a permanent mechanism.
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The post Interactive: Tracking negotiating texts at the COP17 biodiversity summit appeared first on Carbon Brief.
Interactive: Tracking negotiating texts at the COP17 biodiversity summit
A beacon of love
On an outer island of Fiji, two thousand nautical miles from Sydney, is a shining light of hope and resilience for our troubled world.
The island of Kioa is home to a Tuvaluan community who migrated from their atoll of Vaitupu in the late 1940s. It is a land of warm hearts, big smiles, and deep cultural roots; a place where the sound of a conch still summons the island together, where islanders paddle out to fish in carved outrigger canoes, and healthy happy children walk barefoot to school.
Here, culture is life. Kioans live sustainably through their traditional knowledge and practices. The island is alive with song, dance and the rhythms of a life tied to the tides, the winds, and the seasons.
Facing the future
Greenpeace has been lucky to have a relationship with Kioa for a number of years now, and we are continually learning from this remarkable community.
Last week, as part of our Voyaging Oceania project, we returned to the island. Our purpose was twofold —- to carry messages from the island to leaders gathering in Nadi this week for the Pacific Pre-COP, and to support the Kioa community in their efforts to improve water security for the island.
Unlike Tuvalu itself, with its eight atolls, Kioa is a mountainous, forested and richly fertile island. It will remain habitable far into the future. Kioans did not initially migrate from Vaitupu due to climate change, but the move was prophetic. They now have a lifeboat.
However, even Kioa faces challenges on our rapidly warming planet, in particular when it comes to water. Climate change is shifting once reliable rainfall patterns. On top of this, the island is already feeling the effect of this year’s intensifying El Niño event, which for Fiji means reduced rainfall and prolonged dry spells.
Right now, fresh water has to be carefully rationed, and is only available for a few hours a day. During last week’s visit aboard our campaigning ship Oceania, Greenpeace was privileged to work with the Kioa community on a new solar-powered water distribution project for the island.
Designed and led by the island, the project involves using a solar pump to move water from a reliable source to a storage tank and then using gravity to distribute the water around the village.
It was a lesson in how local knowledge and ingenuity can be the backbone of today’s climate solutions. To build a dam around the source, the local community knew the exact spot where they could gather gravel at low tide to mix with the cement. They took only what was needed, knowing that all resources must be carefully conserved. Kioa has no roads and no machinery, and it was an all-of-island effort to carry the materials up to the project site, including many heavy bags of sand and rock.
Such projects truly bring to life the vision of a resilient, locally-led, fossil fuel free Pacific.