The Paris Agreement's goal of achieving net-zero greenhouse gas emissions necessitates carbon dioxide removal (CDR) to offset residual emissions. While existing assessments focus on the total amount of CO2 removed, they neglect the land area required for land-based CDR, which currently dominates. This study addresses this gap by analyzing Nationally Determined Contributions (NDCs) and Long-Term Low Emission Development Strategies (LT-LEDS) submitted to the UNFCCC up to the end of 2023 to estimate the global land demand for CDR. The researchers aim to quantify the aggregate land area required, analyze its geographical distribution and temporal allocation, and evaluate the implications for land-use change, particularly considering competing demands for land and potential conflicts with other societal priorities such as food production and biodiversity conservation. The lack of transparency and consistency in country pledges concerning land use is highlighted as a significant challenge, affecting the accuracy of assessments and the ability to address CDR governance questions effectively, as highlighted by the IPCC.

Existing literature demonstrates the inadequacy of current national climate pledges in meeting the Paris Agreement's goals. Many studies quantify CDR commitments in terms of tonnes of CO2 removed, without specifying the land requirements. The interplay between climate change, biodiversity loss, and land-use change is well-established, with land-use change being a primary driver of biodiversity loss. While land-based CDR methods like afforestation and BECCS offer climate mitigation potential, they may also exacerbate biodiversity loss due to increased land demand and resource consumption. Further, the potential for land-based CDR to negatively impact Indigenous Peoples and other vulnerable communities is also noted in the literature. The uncertainties surrounding the aggregate land demand for CDR, especially concerning the balance between competing land uses, are also discussed in existing studies. The importance of examining national pledges' implications for land use is highlighted, emphasizing transparency and integrity of pledges and considering the impacts on other societal priorities.

The study reviewed climate pledges from 194 countries (treating the EU as a single entity). Of these, 140 countries (including the EU) had quantifiable land-sector mitigation commitments. Three methods were used to estimate the land area required for CDR: 1) direct area pledges from the pledges themselves; 2) converting CO2 removal pledges into land area using IPCC removal factors; and 3) estimating land area from pledges expressed as the number of trees planted or percentage of forest cover expansion using external data sources. The pledged activities were categorized according to IPCC land activity categories (primary forest, old secondary forest, young secondary forest, plantations, mangroves, agroforestry, silvopasture). A key distinction was made between activities causing land-use change (reforestation, tree planting, energy crops) and those restoring existing land uses. For BECCS, country-specific yield values and a 60% conversion efficiency rate were assumed due to insufficient detail in pledges. Pledges for existing forest protection were noted but not quantified. Uncertainty analysis was conducted using a propagation of uncertainty approach. The study acknowledges limitations, including missing data for 51 countries, and the inherent vagueness of net-zero targets, which necessitate assumptions.

The study finds that meeting aggregate CDR commitments in national climate pledges from 2020 to 2060 would require 990 (892–1087) million hectares of land, exceeding the land area of the United States. Of this, 435 (395–475) million hectares would entail land-use change (conversion to forest or energy crops), while 555 (466–644) million hectares would involve restoration of degraded ecosystems. A few countries account for a large proportion of the total pledged land area; four countries (Russia, Saudi Arabia, the US, and Canada) contribute over 70%, and the top ten countries account for 85%. The temporal distribution shows a reliance on an additional 211 million hectares by 2030, scaling to 990 million hectares by 2060. The rate of land-use change implied by reforestation pledges (up to 13 million hectares per annum) is considered unprecedented compared to historical trends and comparable to rates in 1.5°C mitigation scenarios. The geographical distribution shows that many low-income nations, particularly in Africa, have pledged substantial portions of their land area for CDR, raising concerns about potential land rushes and displacement of communities. A significant portion of the land area is pledged for reforestation and tree planting (land-use change), raising concerns about biodiversity impacts and competition for land.

The findings reveal significant reliance on land-based CDR in national climate pledges, highlighting risks associated with over-reliance on this approach, including the potential for undermining near-term emission reductions and relying on non-permanent removals. The study's conservative estimate, due to data limitations and the vagueness of net-zero targets, suggests that the actual land demand might be even higher. Limitations include missing data from several countries and the inherent uncertainties associated with long-term pledges and technologies like BECCS. The temporal distribution of pledges suggests increasing land reliance as more countries set net-zero targets. The reliance on reforestation raises significant concerns about biodiversity loss and competition for land, while the geographical distribution highlights potential risks to vulnerable communities in low-income countries. The study's findings indicate that current national climate pledges embed an unrealistic expectation of the land sector's role in climate mitigation.

This research demonstrates a concerning over-reliance on land for CDR in national climate pledges. The scale of land-based removals, particularly reforestation, poses significant risks to biodiversity and food security, particularly in low-income nations. The study underscores the need for greater transparency and more ambitious near-term emission reduction targets, prioritizing land restoration over land-use change. Future research should focus on more detailed assessments of land-use change impacts, considering regional specificities and socio-economic contexts.

The study acknowledges several limitations. Data were unavailable for 51 countries, including several large forested nations. The vagueness of net-zero targets necessitates assumptions, leading to potential under- or overestimation of land demand. Uncertainty in removal factors and land-area conversion methods also contributes to the uncertainty of the findings. The focus on mitigation pledges excludes other factors influencing land use. The analysis assumes a linear scaling of reforestation efforts, which might not reflect real-world implementation.