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Land‐based mitigation strategies, such as afforestation and avoided deforestation, are critical to achieving the Paris Agreement's goal of limiting global warming to 1.5°C or 2°C. However, the biophysical impacts of anthropogenic land use and land cover change (LULCC), particularly deforestation and afforestation, on extreme weather events in West Africa remain poorly understood at the regional scale. In this study, we present the first high‐resolution LULCC experiments (at 3 km resolution, covering 2012–2022) using the advanced fully coupled atmosphere‐hydrology WRF‐Hydro model system to assess the potential impacts of idealized land use and land management scenarios on extreme events in the West African savannah region. By analyzing 18 extreme weather indices, we show that deforestation significantly affects temperature extremes (up to 0.45 ± 0.04°C), with effects on regional rainfall extremes being approximately twice as pronounced as those on mean rainfall conditions, along with a significant increase in the number of dry days. Conversely, afforestation generally leads to increases in both mean and extreme precipitation, along with fewer dry days and shorter drought durations. Notably, afforestation produces contrasting responses in temperature extremes depending on vegetation type: converting grassland to mixed or evergreen forest reduces extreme heat via increased transpiration, while conversion to savanna or woody savanna may intensify heat extremes due to albedo‐induced warming effects. Plain Language Summary West Africa is currently experiencing extensive agricultural intensification associated with rapid population growth. Those anthropogenic land use and land‐cover changes (LULCC) can have significant impacts on regional climate but also on extreme weather events, posing high vulnerability to human, natural, and economic systems. However, the effects of LULCC (including deforestation and afforestation) on extreme events in West Africa remain largely unexplored at the regional scale, lacking consensus. This study employs high‐resolution LULCC simulations (3 km resolution, 2012–2022) using an advanced coupled atmosphere‐hydrology model to evaluate the impacts of land cover transition scenarios on extreme events in the West African Savanna. The results indicate that deforestation significantly influences temperature extremes, while it consistently affects regional rainfall extremes—about twice as much as mean rainfall changes—and substantially increases the number of dry days. Conversely, afforestation scenarios generally lead to increases in both mean and extreme precipitation, fewer dry days, and shorter drought durations. Notably, afforestation with mixed or evergreen forests mitigates extreme heat through enhanced plant transpiration. However, certain forest types, such as woody savanna or savanna, can exacerbate heat extremes due to albedo‐induced warming effects. Key Points Deforestation of the West African savanna region significantly intensifies temperature extremes (up to 0.45 ± 0.04°C) and increases drought lengths Afforestation with mixed or evergreen forests mitigates extreme heat, while woody savanna or savanna may worsen it due to albedo induced warming effects Afforestation leads to increased mean and extreme precipitation, more frequent wet days, and shorter drought durations

The impacts of land use have been shown to have considerable influence on regional climate. With the recent international commitment to limit global warming to well below 2°C, emission reductions need to be ambitious and could involve major land‐use change (LUC). Land‐based mitigation efforts to curb emissions growth include increasing terrestrial carbon sequestration through reforestation, or the adoption of bioenergy crops. These activities influence local climate through biogeophysical feedbacks, however, it is uncertain how important they are for a 1.5° climate target. This was the motivation for HAPPI‐Land: the half a degree additional warming, prognosis, and projected impacts—land‐use scenario experiment. Using four Earth system models, we present the first multimodel results from HAPPI‐Land and demonstrate the critical role of land use for understanding the characteristics of regional climate extremes in low‐emission scenarios. In particular, our results show that changes in temperature extremes due to LUC are comparable in magnitude to changes arising from half a degree of global warming. We also demonstrate that LUC contributes to more than 20% of the change in temperature extremes for large land areas concentrated over the Northern Hemisphere. However, we also identify sources of uncertainty that influence the multimodel consensus of our results including how LUC is implemented and the corresponding biogeophysical feedbacks that perturb climate. Therefore, our results highlight the urgent need to resolve the challenges in implementing LUC across models to quantify the impacts and consider how LUC contributes to regional changes in extremes associated with sustainable development pathways. Plain Language Summary The motivation for the Intergovernmental Panel on Climate Change Special Report of 1.5°C stems from the need to understand how the impacts of climate change may evolve for half a degree of global warming. Most low‐emission scenarios involve substantial land‐use change (LUC) including the expansion of bioenergy and food crops, as well as afforestation. Future emission scenarios used as input to climate models are derived using integrated assessment models, and focus on greenhouse gas emissions. However, changes in land use also have a direct effect on local climate through the local water and energy balances, which is not considered in these models, and therefore, our understanding on how dependent these climate projections are to the choice of land‐use scenario is limited. Our study demonstrates that the land‐use scenario has a considerable influence on the projections of temperature extremes for low‐emission scenarios. In particular, for large land areas in the Northern Hemisphere, more than 20% of the change in temperature extremes can be attributed to LUC. However, our study also reveals that considerable uncertainty remains on what the feedbacks of land use may mean for land‐based mitigation activities. Key Points Land‐use change (LUC) accounts for 20% change in temperature extremes for low‐emission scenarios Multimodel results show projected temperature extremes depend on where and what land‐based mitigation activities are pursued For some regions and models, LUC can affect temperature extremes as much as a half degree change in global mean temperature

Peatlands cover only about 3% the global land area, but store about twice as much carbon as global forest biomass. If intact peatlands are drained for agriculture or other human uses, peat oxidation can result in considerable CO2 emissions and other greenhouse gases (GHG) for decades or even centuries. Despite their importance, emissions from degraded peatlands have so far not been included explicitly in mitigation pathways compatible with the Paris Agreement. Such pathways include land-demanding mitigation options like bioenergy or afforestation with substantial consequences for the land system. Therefore, besides GHG emissions owing to the historic conversion of intact peatlands, the increased demand for land in current mitigation pathways could result in drainage of presently intact peatlands, e.g. for bioenergy production. Here, we present the first quantitative model-based projections of future peatland dynamics and associated GHG emissions in the context of a 2 °C mitigation pathway. Our spatially explicit land-use modelling approach with global coverage simultaneously accounts for future food demand, based on population and income projections, and land-based mitigation measures. Without dedicated peatland policy and even in the case of peatland protection, our results indicate that the land system would remain a net source of CO2 throughout the 21st century. This result is in contrast to the outcome of current mitigation pathways, in which the land system turns into a net carbon sink by 2100. However, our results indicate that it is possible to reconcile land use and GHG emissions in mitigation pathways through a peatland protection and restoration policy. According to our results, the land system would turn into a global net carbon sink by 2100, as projected by current mitigation pathways, if about 60% of present-day degraded peatlands would be rewetted in the coming decades, next to the protection of intact peatlands.

The land-use sector can contribute to climate change mitigation not only by reducing greenhouse gas (GHG) emissions, but also by increasing carbon uptake from the atmosphere and thereby creating negative CO2 emissions. In this paper, we investigate two land-based climate change mitigation strategies for carbon removal: (1) afforestation and (2) bioenergy in combination with carbon capture and storage technology (bioenergy CCS). In our approach, a global tax on GHG emissions aimed at ambitious climate change mitigation incentivizes land-based mitigation by penalizing positive and rewarding negative CO2 emissions from the land-use system. We analyze afforestation and bioenergy CCS as standalone and combined mitigation strategies. We find that afforestation is a cost-efficient strategy for carbon removal at relatively low carbon prices, while bioenergy CCS becomes competitive only at higher prices. According to our results, cumulative carbon removal due to afforestation and bioenergy CCS is similar at the end of 21st century (600-700 GtCO2), while land-demand for afforestation is much higher compared to bioenergy CCS. In the combined setting, we identify competition for land, but the impact on the mitigation potential (1000 GtCO2) is partially alleviated by productivity increases in the agricultural sector. Moreover, our results indicate that early-century afforestation presumably will not negatively impact carbon removal due to bioenergy CCS in the second half of the 21st century. A sensitivity analysis shows that land-based mitigation is very sensitive to different levels of GHG taxes. Besides that, the mitigation potential of bioenergy CCS highly depends on the development of future bioenergy yields and the availability of geological carbon storage, while for afforestation projects the length of the crediting period is crucial.

Emergingresearch points to large greenhouse gas mitigation opportunities for activities that are focused on the preservation and maintenance of ecosystems, also known as natural climate solutions (NCS). Despite large quantifications of the potential biophysical and carbon benefits of these activities, these estimates hold large uncertainties and few capture the socio-economic bounds. Furthermore, the uptake of NCS remains slow and information on the enabling factors needed for successful implementation, co-benefits, and trade-offs of these activities remain underrepresented at scale. As such, we present a systematic review that synthesizes and maps the bottom-up evidence on the contextual factors that influence the implementation of NCS in the peer-reviewed literature. Drawing from a large global collection of (primarily case study-based, N = 211) research, this study (1) clarifies the definition of NCS, including in the context of nature-based solutions and other ecosystem-based approaches to addressing climate change; (2) provides an overview of the current state of literature, including research trends, opportunities, gaps, and biases; and (3) critically reflects on factors that may affect implementation in different geographies. We find that the content of the reviewed studies overwhelmingly focuses on tropical regions and activities in forest landscapes. We observe that implementation of NCS rely, not on one factor, but a suite of interlinked enabling factors. Specifically, engagement of indigenous peoples and local communities, performance-based finance, and technical assistance are important drivers of NCS implementation. While the broad categories of factors mentioned in the literature are similar across regions, the combination of factors and how and for whom they are taken up remains heterogeneous globally, and even within countries. Thus our results highlight the need to better understand what trends may be generalizable to inform best practices in policy discussions and where more nuance may be needed for interpreting research findings and applying them outside of their study contexts.

Forests-based measures such as afforestation/reforestation (A/R) and reducing deforestation (RDF) are considered promising options to mitigate climate change, yet their mitigation potentials are limited by economic and biophysical factors that are largely uncertain. The range of mitigation potential estimates from integrated assessment models raises concerns about the capacity of land systems to provide realistic, cost-effective and permanent land-based mitigation. We use the Global Change Analysis Model to quantify the economic mitigation potential of forests-based measures by simulating a climate policy including a tax on greenhouse gas emissions from agriculture, forestry, and other land uses. In addition, we assess how constraining unused arable land (UAL) availability, forestland expansion rates, and global bioenergy demand may influence the forests-based mitigation potential by simulating scenarios with alternative combinations of constraints. Results show that the average forests-based mitigation potential in 2020–2050 increases from 738 MtCO 2 .yr −1 through a forestland increase of 86 Mha in the fully constrained scenario to 1394 MtCO 2 .yr −1 through a forestland increase of 146 Mha when all constraints are relaxed. Regional potentials in terms of A/R and RDF differ strongly between scenarios: unconstrained forest expansion rates mostly increase A/R potentials in northern regions (e.g., +120 MtCO 2 .yr −1 in North America); while unconstrained UAL conversion and low bioenergy demand mostly increase RDF potentials in tropical regions (e.g., +76 and +68 MtCO 2 .yr −1 in Southeast Asia, respectively). This study shows that forests-based mitigation is limited by many factors that constrain the rates of land use change across regions. These factors, often overlooked in modelling exercises, should be carefully addressed for understanding the role of forests in global climate mitigation and defining pledges towards the Paris Agreement.

Methane (CH4) is a major and potent greenhouse gas (GHG), and its emissions from agricultural activities, particularly rice cultivation, are a significant concern for climate change. Due to the high demand for food security, driven by rapid population growth and national initiatives to reduce dependency on rice imports, rice cultivation is intensified in West Africa. However, its contribution to atmospheric CH4 remains largely unknown. Here, for the first time, cutting-edge eddy covariance tower measurements were conducted parallelly in a rice field (Janga) and a reserve forest (Mole National Park), both located in the Guinea savanna region of West Africa. Using CH4 measurement data from June to October 2023 (rice cultivation period), the dynamic interplay between methane emissions from rice cultivation and its potential mitigation through forest methane uptake was assessed. Our results show that the rice field acted as a net source of CH4 at a rate of 2037 mgCH4m−2, whereas the most intense flooded period (August) accounted for 70% of the total emissions. On the other hand, the forest reserve acted as a sink, with a net uptake of −560 mgCH4m−2, and the highest uptake observed in October. Accounting for the global warming potential (GWP) of CH4 over a 20 year period, the forest had a wet season negative GWP of −47.04 gCO2eq, while the rice field emitted CH4 of 171.36 gCO2eq. This implies that under similar conditions during the measurement campaigns, the forest per square area needs approximately a factor of ∼4 to balance the positive radiative effect per square area of rice cultivated. This work emphasizes the need to integrate forests to compensate for methane released by rice cultivation in the semi-arid West African savannah region.

Land-based mitigation technologies and practices (LMTs) are critical for achieving the Paris Agreement’s aim of avoiding dangerous climate change by limiting the rise in average global surface temperatures. We developed a detailed two-level classification and analysis of the barriers to the adoption and scaling up of LMTs. The review suggests that afforestation/reforestation and forest management are LMTs with wide application and high potential across all continents. BECCS (bioenergy with carbon capture and storage) and biochar have a higher potential in higher-income countries in the short term, due to the availability of technology, funding, and low-cost biomass value chains. Although most LMTs can be cost-effective across multiple world regions, limited knowledge concerning their implementation and insufficient financing appear to be the main barriers to their large-scale deployment. Without considering gender and the rights of marginalised and Indigenous Peoples, the large-scale deployment of LMTs can further aggravate existing inequalities. Therefore, the social and institutional implications of LMTs need to be better understood to improve their public acceptance and reduce negative impacts. An integrated system approach is necessary to strike a balance between ambitious land-based mitigation targets and socioeconomic and environmental goals.

Human intervention in forested ecosystems is hoped to perform a fundamental shift within the next decade by reverting current forest loss—a major source of CO 2 emissions—to net forest gain taking up carbon and thus aiding climate change mitigation. The demanded extensive establishment of forests will change the local surface energy fluxes, and with it the local climate, in addition to competing with food and fiber production for land and water. Scenario building models encompass this competition for resources but have turned a blind eye to the biogeophysical (BGP) local surface energy flux disturbance so far. We combine the benefit of CO 2 sequestration of afforestation/reforestation (A/R) with the additional incentive or penalty of local BGP induced cooling or warming by translating the local BGP induced temperature change to a CO 2 equivalent. We then include this new aspect in the land-use model Model for Agricultural Production and their Impact on the Environment (MAgPIE) via modifying the application of the price on greenhouse gases (GHGs). This enables us to use MAgPIE to produce A/R scenarios that are optimized for both their potential CO 2 sequestration and the CO 2 equivalent local BGP effect, as well as the socio-economic trade-offs of A/R. Here we show that optimal A/R patterns are substantially altered by taking the local BGP effects into account. Considering local cooling benefits of establishing forests triples (+203.4%) the viable global A/R area in 2100 from 116 to 351 Mha under the conditions of the shared socioeconomic pathway 2 (SSP2) scenario driven by the same GHG price. Three quarters (76.0%, +179 Mha) of the additionally forested area is established in tropical climates alone. Therefore, a further neglect of BGP effects in scenario building models undervalues the benefit of tropical forests while simultaneously running the risk of proposing counterproductive measures at high latitudes. However, the induced focus on tropical forestation intensifies the competition with food production where forests contribute most to mitigation. A/R related trade-offs need to be considered alongside their climate benefit to inhibit unintentional harm of mitigation efforts.

Most socioeconomic pathways compatible with the aims of the Paris Agreement include large changes to land use and land cover. The associated vegetation changes can interact with the atmosphere and climate through numerous mechanisms. One of these is emissions of biogenic volatile organic compounds (BVOCs), which may lead to the formation of secondary organic aerosols (SOAs) and atmospheric chemistry changes. Here, we use a modeling framework to explore potential future global and regional changes in SOA and tropospheric ozone following idealized, large-scale vegetation perturbations, and their resulting radiative forcing (RF). Guided by projections in low-warming scenarios, we modify crop and forest cover, separately, and in concurrence with changes in anthropogenic emissions and CO2 level. We estimate that increasing global forest cover by 30% gives a 37% higher global SOA burden, with a resulting forcing of −0.13 W m−2. The effect on tropospheric ozone is relatively small. Large SOA burden changes of up to 48% are simulated for South America and Sub-Saharan Africa. Conversely, increasing crop cover at the expense of tropical forest, yields similar changes but of opposite sign. The magnitude of these changes is strongly affected by the concurrent evolution of anthropogenic emissions. Our land cover perturbations are representative of energy crop expansion and afforestation, two key mitigation measures in 1.5 °C compatible scenarios. Our results hence indicate that depending on the role of these two in the underlying mitigation strategies, scenarios with similar long-term global temperature levels could lead to opposite effects on SOA. Combined with the complexity of factors that control SOA, this highlights the importance of including BVOC effects in further studies and assessments of climate and air quality mitigation involving the land surface.