Explore the vast range of titles available.

Better land stewardship is needed to achieve the Paris Agreement's temperature goal, particularly in the tropics, where greenhouse gas emissions from the destruction of ecosystems are largest, and where the potential for additional land carbon storage is greatest. As countries enhance their nationally determined contributions (NDCs) to the Paris Agreement, confusion persists about the potential contribution of better land stewardship to meeting the Agreement's goal to hold global warming below 2°C. We assess cost-effective tropical country-level potential of natural climate solutions (NCS)—protection, improved management and restoration of ecosystems—to deliver climate mitigation linked with sustainable development goals (SDGs). We identify groups of countries with distinctive NCS portfolios, and we explore factors (governance, financial capacity) influencing the feasibility of unlocking national NCS potential. Cost-effective tropical NCS offers globally significant climate mitigation in the coming decades (6.56 Pg CO2e yr−1 at less than 100 US$ per Mg CO2e). In half of the tropical countries, cost-effective NCS could mitigate over half of national emissions. In more than a quarter of tropical countries, cost-effective NCS potential is greater than national emissions. We identify countries where, with international financing and political will, NCS can cost-effectively deliver the majority of enhanced NDCs while transforming national economies and contributing to SDGs. This article is part of the theme issue ‘Climate change and ecosystems: threats, opportunities and solutions’.

Constraining the climate crisis requires urgent action to reduce anthropogenic emissions while simultaneously removing carbon dioxide from the atmosphere. Improved information about the maximum magnitude and spatial distribution of opportunities for additional land-based removals of CO₂ is needed to guide on-the-ground decision-making about where to implement climate change mitigation strategies. Here, we present a globally consistent spatial dataset (approximately 500-m resolution) of current, potential, and unrealized potential carbon storage in woody plant biomass and soil organic matter. We also provide a framework for prioritizing actions related to the restoration, management, and maintenance of woody carbon stocks and associated soils. By comparing current to potential carbon storage, while excluding areas critical to food production and human habitation, we find 287 petagrams (PgC) of unrealized potential storage opportunity, of which 78% (224 PgC) is in biomass and 22% (63 PgC) is in soil. Improved management of existing forests may offer nearly three-fourths (206 PgC) of the total unrealized potential, with the majority (71%) concentrated in tropical ecosystems. However, climate change is a source of considerable uncertainty. While additional research is needed to understand the impact of natural disturbances and biophysical feedbacks, we project that the potential for additional carbon storage in woody biomass will increase (+17%) by 2050 despite projected decreases (−12%) in the tropics. Our results establish an absolute reference point and conceptual framework for national and jurisdictional prioritization of locations and actions to increase land-based carbon storage.

Nations of the world have, to date, pursued nature protection and climate change mitigation and adaptation policies separately. Both efforts have failed to achieve the scale of action needed to halt biodiversity loss or mitigate climate change. We argue that success can be achieved by aligning targets for biodiversity protection with the habitat protection and restoration necessary to bring down greenhouse gas concentrations and promote natural and societal adaptation to climate change. Success, however, will need much higher targets for environmental protection than the present 10% of sea and 17% of land. A new target of 30% of the sea given high levels of protection from exploitation and harm by 2030 is under consideration and similar targets are being discussed for terrestrial habitats. We make the case here that these higher targets, if achieved, would make the transition to a warmer world slower and less damaging for nature and people. This article is part of the theme issue ‘Climate change and ecosystems: threats, opportunities and solutions’.

Tropical forest loss currently exceeds forest gain, leading to a net greenhouse gas emission that exacerbates global climate change. This has sparked scientific debate on how to achieve natural climate solutions. Central to this debate is whether sustainably managing forests and protected areas will deliver global climate mitigation benefits, while ensuring local peoples’ health and well-being. Here, we evaluate the 10-y impact of a human-centered solution to achieve natural climate mitigation through reductions in illegal logging in rural Borneo: an intervention aimed at expanding health care access and use for communities living near a national park, with clinic discounts offsetting costs historically met through illegal logging. Conservation, education, and alternative livelihood programs were also offered. We hypothesized that this would lead to improved health and well-being, while also alleviating illegal logging activity within the protected forest. We estimated that 27.4 km² of deforestation was averted in the national park over a decade (∼70% reduction in deforestation compared to a synthetic control, permuted P = 0.038). Concurrently, the intervention provided health care access to more than 28,400 unique patients,with clinic usage and patient visitation frequency highest in communities participating in the intervention. Finally, we observed a dose–response in forest change rate to intervention engagement (person-contacts with intervention activities) across communities bordering the park: The greatest logging reductions were adjacent to the most highly engaged villages. Results suggest that this community-derived solution simultaneously improved health care access for local and indigenous communities and sustainably conserved carbon stocks in a protected tropical forest.

The climate mitigation potential of urban nature-based solutions (NBSs) is often perceived as insignificant and thus overlooked, as cities primarily pursue NBSs for local ecosystem services. Given the rising interest and capacities in cities for such projects, the potential of urban forests for climate mitigation needs to be better understood. We modelled the global potential and limits of urban reforestation worldwide, and find that 10.9 ± 2.8 Mha of land (17.6% of all city areas) are suitable for reforestation, which would offset 82.4 ± 25.7 MtCO 2 e yr −1 of carbon emissions. Among the cities analysed, 1189 are potentially able to offset >25% of their city carbon emissions through reforestation. Urban natural climate solutions should find a place on global and local agendas.

Purpose of Review Despite covering only 3% of the land surface, peatlands represent the largest terrestrial organic carbon stock on the planet and continue to act as a carbon sink. Managing ecosystems to reduce greenhouse gas (GHG) emissions and protect carbon stocks provide nature-based climate solutions that can play an important role in emission reduction strategies, particularly over the next decade. This review provides an overview of peatland management pathways that can contribute to natural climate solutions and compiles regional and global estimates for the size of potential GHG emission reductions. Recent Findings Degraded peatlands may account for 5% of current anthropogenic GHG emissions and therefore reducing emissions through rewetting and restoration offer substantial emission reductions. However, as a majority of peatland remains intact, particularly in boreal and subarctic regions, protection from future development is also an important peatland management pathway. Literature compilation indicates a global potential for peatland nature–based climate solutions of 1.1 to 2.6 Gt CO 2 e year −1 in 2030. Summary Peatland management can play an important role in GHG emission reductions while also providing many additional co-benefits such as biodiversity protection, reduced land subsidence, and fire-severity mitigation. Yet, climate warming will hinder the ability of peatland ecosystems to continue to act as carbon sinks indicating the importance of reducing future warming through rapid decarbonization of the economy to protect these globally significant carbon stocks.

Large‐scale re‐/afforestation projects afford sizable atmospheric CO2 removals yet questions loom surrounding their potentially offsetting biogeophysical radiative forcings. Forest area change alters not only the surface albedo but also heat, moisture, and momentum fluxes, which in turn modify the atmosphere's radiative, thermodynamical, and dynamical properties. These so‐called radiative forcing “adjustments” have been little examined in re‐/afforestation contexts, and many questions remain surrounding their relevance in relation to the instantaneous forcing from the surface albedo change—and whether they can affect Earth's radiative energy balance in regions remote from where the re‐/afforestation occurs. Here, we quantified biogeophysical radiative forcings and adjustments from realistically scaled re‐/afforestation in Europe at high spatial resolution and found that adjustments with high signal‐to‐noise were largely confined to only a few months and to the region of re‐/afforestation. Adjustments were dominated by perturbed low‐level clouds and rarely exceeded ±25% of the annual albedo change forcing. Plain Language Summary Increased forest area can boost carbon stores in the terrestrial biosphere and benefit global climate. At the same time, this modifies several biogeophysical properties of the surface that impact Earth's energy balance. The extent to which these so‐called “biogeophysical” radiative forcings are important has not been comprehensively evaluated, with much of the research focusing on only a single mechanism—or the change to the surface's reflective properties (i.e., its albedo). Other mechanisms can dampen or reinforce the albedo change forcing and can even lead to remote effects, but these are much less understood. Focusing on Europe, we used a regional climate model combined with other analytical tools to quantify these additional mechanisms and understand their relevance in relation to the local forcing caused by surface albedo changes. We found that these other mechanisms rarely manifested in regions outside the region of re‐/afforestation, and further, that they are far less important than the forcing attributable to the surface albedo change. Key Points Biogeophysical radiative forcings and adjustments of European afforestation were quantified using a climate model and radiative kernels Radiative adjustments with high signal‐to‐noise were highly localized, dominated by low cloud cover change, and heavily confined in space and time Annual effective radiative forcings were largely driven by surface albedo change

Natural climate solutions (NCS) in the Arctic hold the potential to be implemented at a scale able to substantially affect the global climate. The strong feedbacks between carbon-rich permafrost, climate and herbivory suggest an NCS consisting of reverting the current wet/moist moss and shrub-dominated tundra and the sparse forest–tundra ecotone to grassland through a guild of large herbivores. Grassland-dominated systems might delay permafrost thaw and reduce carbon emissions—especially in Yedoma regions, while increasing carbon capture through increased productivity and grass and forb deep root systems. Here we review the environmental context of megafaunal ecological engineering in the Arctic; explore the mechanisms through which it can help mitigate climate change; and estimate its potential—based on bison and horse, with the aim of evaluating the feasibility of generating an ecosystem shift that is economically viable in terms of carbon benefits and of sufficient scale to play a significant role in global climate change mitigation. Assuming a megafaunal-driven ecosystem shift we find support for a megafauna-based arctic NCS yielding substantial income in carbon markets. However, scaling up such projects to have a significant effect on the global climate is challenging given the large number of animals required over a short period of time. A first-cut business plan is presented based on practical information—costs and infrastructure—from Pleistocene Park (northeastern Yakutia, Russia). A 10 yr experimental phase incorporating three separate introductions of herds of approximately 1000 individuals each is costed at US$114 million, with potential returns of approximately 0.3–0.4% yr−1 towards the end of the period, and greater than 1% yr−1 after it. Institutional friction and the potential role of new technologies in the reintroductions are discussed. This article is part of the theme issue ‘Climate change and ecosystems: threats, opportunities and solutions'.

It is clear that reducing greenhouse gas emissions alone is insufficient to avoid large global temperature increases. To avoid atmospheric concentrations of greenhouse gases that result in dangerous alterations of the climate, large reductions in carbon dioxide emissions from fossil fuel combustion and land use changes must be accompanied by an increase in atmospheric carbon dioxide sequestration. Natural Climate Solutions have become a major focus of climate policy. Land and ocean ecosystems remove and store atmospheric carbon, and forests play a major role. This focus collection includes papers that address three important aspects of the role for forests in meeting climate change mitigation goals: (i) Carbon Accounting of forest sinks and reservoirs, process emissions and carbon storage in forest products, (ii) the carbon dioxide dynamics of using Forest Bioenergy and (iii) the carbon cycle of Tropical Forests.

Trawling the seafloor can disturb carbon that took millennia to accumulate, but the fate of that carbon and its impact on climate and ecosystems remains unknown. Using satellite-inferred fishing events and carbon cycle models, we find that 55-60% of trawling-induced aqueous CO2 is released to the atmosphere over 7-9 years. Using recent estimates of bottom trawling’s impact on sedimentary carbon, we found that between 1996-2020 trawling could have released, at the global scale, up to 0.34-0.37 Pg CO2 yr-1 to the atmosphere, and locally altered water pH in some semi-enclosed and heavy trawled seas. Our results suggest that the management of bottom-trawling efforts could be an important climate solution.