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The BlueFlux field campaign, supported by NASA’s Carbon Monitoring System, will develop prototype blue carbon products to inform coastal carbon management. While blue carbon has been suggested as a nature-based climate solution (NBS) to remove carbon dioxide (CO 2 ) from the atmosphere, these ecosystems also release additional greenhouse gases (GHGs) such as methane (CH 4 ) and are sensitive to disturbances including hurricanes and sea-level rise. To understand blue carbon as an NBS, BlueFlux is conducting multi-scale measurements of CO 2 and CH 4 fluxes across coastal landscapes, combined with long-term carbon burial, in Southern Florida using chambers, flux towers, and aircraft combined with remote-sensing observations for regional upscaling. During the first deployment in April 2022, CO 2 uptake and CH 4 emissions across the Everglades National Park averaged −4.9 ± 4.7 μ mol CO 2 m −2 s −1 and 19.8 ± 41.1 nmol CH 4 m −2 s −1 , respectively. When scaled to the region, mangrove CH 4 emissions offset the mangrove CO 2 uptake by about 5% (assuming a 100 year CH 4 global warming potential of 28), leading to total net uptake of 31.8 Tg CO 2 -eq y −1 . Subsequent field campaigns will measure diurnal and seasonal changes in emissions and integrate measurements of long-term carbon burial to develop comprehensive annual and long-term GHG budgets to inform blue carbon as a climate solution.

Terrestrial, aquatic, and marine ecosystems regulate climate at local to global scales through exchanges of energy and matter with the atmosphere and assist with climate change mitigation through nature‐based climate solutions. Climate science is no longer a study of the physics of the atmosphere and oceans, but also the ecology of the biosphere. This is the promise of Earth system science: to transcend academic disciplines to enable study of the interacting physics, chemistry, and biology of the planet. However, long‐standing tension in protecting, restoring, and managing forest ecosystems to purposely improve climate evidences the difficulties of interdisciplinary science. For four centuries, forest management for climate betterment was argued, legislated, and ultimately dismissed, when nineteenth century atmospheric scientists narrowly defined climate science to the exclusion of ecology. Today's Earth system science, with its roots in global models of climate, unfolds in similar ways to the past. With Earth system models, geoscientists are again defining the ecology of the Earth system. Here we reframe Earth system science so that the biosphere and its ecology are equally integrated with the fluid Earth to enable Earth system prediction for planetary stewardship. Central to this is the need to overcome an intellectual heritage to the models that elevates geoscience and marginalizes ecology and local land knowledge. The call for kilometer‐scale atmospheric and ocean models, without concomitant scientific and computational investment in the land and biosphere, perpetuates the geophysical view of Earth and will not fully provide the comprehensive actionable information needed for a changing climate. Plain Language Summary Terrestrial ecosystems provide a natural solution to planetary warming by storing carbon, dissipating surface heating through evapotranspiration, and other processes. That forests, in particular, influence climate is a centuries‐old premise, but its potential for planetary stewardship has not been realized. In an acrimonious controversy spanning several centuries, managing forests to purposely change climate was advocated, legislated, and resoundingly dismissed as unscientific. Similar intellectual bias is evident in today's Earth system science and the associated Earth system models, which are the state‐of‐the‐art models used to inform climate policy. The popular characterization of Earth system science lauds its interdisciplinary melding of physics, chemistry, and biology, but the models emphasize the physics and fluid dynamics of the atmosphere and oceans and present a limited perspective of terrestrial ecosystems in the Earth system. Ecologists studying the living world increasingly have a voice in Earth system science as we move beyond the physical basis for climate change to Earth system prediction for planetary stewardship. As we once again look to forests to solve a climate problem, we must surmount the disciplinary narrowness that failed to answer the forest‐climate question in the past and that continues to limit the interdisciplinary potential of Earth system science. Key Points Nature‐based climate solutions have been advocated for centuries, but have been distorted by academic bias and colonialist prejudice Earth system science, while recognizing the climate services of the biosphere, has a geophysical bias in interdisciplinary collaboration To realize the potential for planetary stewardship, Earth system models must embrace the living world equally with the fluid world

Societal Impact Statement Human interactions with forests have shaped Earth's climate for millennia and will continue to do so as we target net‐zero emission goals. Accurately characterizing these climate impacts requires making reliable forest carbon data available for forest monitoring and planning. Here, we develop a semi‐automated process for submitting forest carbon measurements from the largest relevant scientific database to the International Panel on Climate Change's Emission Factor Database, which currently has sparse forest carbon data. Building this bridge from scientific research to international policy is an important step towards managing forests in a net‐zero motivated future. Humans have been influencing Earth's climate via transformative impacts on forests for millennia, and forests are now recognized as critical to climate change mitigation under the Paris Agreement. The efficacy of climate change mitigation planning and reporting depends on quality data on forest carbon (C) stocks and changes. The Emission Factor Database (EFDB) of the International Panel on Climate Change (IPCC) is intended to be a definitive source for such data, but needs comprehensive and well‐documented data to be so. To facilitate submission of forest C estimates from scientific studies to EFDB, we develop and document a process for semi‐automated data submission from the Global Forest C database (ForC v4.0), which is the largest compilation of ground‐based forest C estimates. We then assess the data currently available through ForC and provide recommendations for improving forest data collection, analysis, and reporting. As of September 2024, ForC contained ~19,286 records potentially relevant to EFDB, 1068 of which had been submitted and posted to EFDB. These represented 19% of the total EFDB records for forest land. Records were unevenly distributed across variables and geographic regions. ForC records (37%) reviewed could not be submitted because the original publication lacked required information. In the future, ground‐based forest C estimates should target gaps in the record, and studies should ensure that they report all information necessary for inclusion in EFDB. Given that climate change is rapidly impacting the world's forests, timely reporting of recent estimates will be critical to accurate forest C inventories. As interações humanas com as florestas têm moldado o clima da Terra por milênios e continuarão a fazer isto, enquanto nos tentamos alcançar emissões líquidas zero. Para caracterizar com precisão esses impactos climáticos, é necessário disponibilizar dados confiáveis sobre o carbono florestal. Aqui, desenvolvemos um processo semiautomatizado para enviar medições de carbono florestal do maior banco de dados científico relevante para o Banco de Dados de Fatores de Emissão do IPCC (Painel Internacional sobre Mudanças Climáticas), que atualmente possui dados esparsos sobre carbono florestal. A construção dessa ponte entre a pesquisa científica e a política internacional é uma etapa importante para o gerenciamento das florestas em um futuro com motivação líquida zero. Human interactions with forests have shaped Earth's climate for millennia and will continue to do so as we target net‐zero emission goals. Accurately characterizing these climate impacts requires making accurate forest carbon data available for forest monitoring and planning. Here, we develop a semi‐automated process for submitting forest carbon measurements from the largest relevant scientific database to the International Panel on Climate Change's Emission Factor Database, which currently has sparse forest carbon data. Building this bridge from scientific research to international policy is an important step towards managing forests in a net‐zero motivated future.

Societal Impact Statement India has a long history of planting trees to restore ecosystem services providing an opportunity to evaluate long‐term ecosystem restoration processes. We show that these programs have shifted over time in response to public demands as well as through changes in the government's vision for forests. These shifts point towards opportunities and limits for political responsiveness in the design and implementation of restoration programs. Independent evaluations have shown that the tree planting programs we study often fail to achieve their goals, raising questions about their benefits, and risks from positioning tree planting as a panacea for social and environmental problems. Summary Aims: Interest in forest restoration has increased in recent years with the goal of increasing carbon storage, protecting biodiversity, and improving the delivery of ecosystem services to aid rural livelihoods. However, there is little systematic analysis of how this trend relates to broader histories of landscape interventions. Methods: We analyze a dataset comprising 36 years of government plantation records from the forest department of the Indian Himalayan state of Himachal Pradesh. Findings: Restoration‐oriented tree planting peaked in the 1980s and 1990s with heavy domestic funding. Counter to dominant policy narratives, most plantation programs did not formally involve the participation of local people and were not funded by donors or carbon markets. Over time, planting shifted away from commercial timber species towards a more diverse set of native broadleaf species, reflecting local preferences for the production of firewood, fodder, and other non‐timber forest products and ecosystem services as well as changing conceptions by government agencies about what and who a forest is meant to serve. Over time, the number of programs sponsoring tree planting has proliferated, reflecting the ways that tree planting has been framed as the solution to a growing number of problems, ranging from poverty alleviation to climate adaptation. Conclusion: The current global focus on forest restoration and nature‐based climate solutions represents a reframing of long‐existing policies and programs in this region. As with past policy changes, restoration practices are likely to be influenced by long‐term histories, entrenched practices, and local political influences. India has a long history of planting trees to restore ecosystem services providing an opportunity to evaluate long‐term ecosystem restoration processes. We show that these programs have shifted over time in response to public demands as well as through changes in the government's vision for forests. These shifts point towards opportunities and limits for political responsiveness in the design and implementation of restoration programs. Independent evaluations have shown that the tree planting programs we study often fail to achieve their goals, raising questions about their benefits, and risks from positioning tree planting as a panacea for social and environmental problems.

Stemming biodiversity loss requires greater investment in conservation and more efficient use of available resources. Prioritizing conservation actions that yield the most biodiversity benefit for the least cost can help maximize return on investment. Actions that have co‐benefits for other objectives, such as climate change mitigation, can also help mobilize additional funds for conservation. We used Priority Threat Management to identify actions to secure the greatest number of species groups of conservation concern for the least cost in the Lake Simcoe‐Rideau ecoregion, Ontario—one of Canada's biodiversity crisis ecoregions. We also estimated the carbon sequestration benefits of actions related to land protection and restoration. We found that without additional investment in conservation, 13 of 16 species groups were expected to have <50% probability of persistence in this ecoregion by 2050. Implementing all proposed strategies would yield the greatest biodiversity benefits and secure 12 of the 16 species groups with ≥60% probability of persistence, at a cost of CA $113 million per year over 27 years. In comparison, investing CA$ 97 million per year in landowner stewardship, habitat protection and restoration and regeneration strategies could secure 10 species groups and improve the probability of persistence of one additional group from 39% to 55%. The habitat protection and restoration strategies also deliver direct carbon benefits of around 11.2 Mt in total avoided CO2 emissions and 137.6 Mt CO2 in total potential sequestration, respectively, over the long‐term, thus supporting alignment with climate change mitigation targets and delivering co‐benefits that may further justify investment. Practical implication. By estimating the costs and demonstrating the expected benefits and potential carbon co‐benefits of conservation actions, Priority Threat Management can help maximize return on investment and identify actions that address multiple environmental crises. We worked with a diverse group of local experts to identify cost‐effective and complementary management strategies that could help secure the persistence of species of conservation concern for the least cost in the Lake Simcoe‐Rideau ecoregion of Southern Ontario. We found that without additional investment in conservation, 130 out of 133 species of conservation concern in the region could be lost by 2050. Investing up to $113 million more per year on strategies informed by local experts can help reverse this outcome, securing up to 100 species while also delivering significant co‐benefits for climate change mitigation objectives.

Societal Impact Statement Novel forest ecosystems consist of forest ecosystems dominated by non‐native tree species that are difficult to restore to their pre‐human disturbance states. Nevertheless, novel forests can provide numerous ecosystem services, such as carbon sequestration and storage. We quantified the aboveground living tree and soil carbon stocks in four novel forest sites in Singapore using forest inventory and airborne LiDAR data, and soil core data, respectively. We found that the carbon stored in the four sites is comparable to tropical secondary forests elsewhere. Our results show that novel forests can be protected as carbon stores. Summary Forest succession after the cessation of intense human land use may result in ecosystems with biotic or abiotic properties that differ from their historical states before anthropogenic activities. These ‘novel ecosystems’ often consist of communities dominated by non‐native species that are costly to restore to their original state. As novel ecosystems become more ubiquitous, there is a need to understand the opportunities and challenges in managing these ecosystems and the implications for the ecosystem services they provide. Here, we evaluated the role of novel forest ecosystems in Singapore, a tropical city‐state in Southeast Asia, in regulating carbon stocks and flows. Specifically, we mapped the distribution of aboveground carbon density (ACD) in living trees of four post‐agricultural, non‐native‐dominated forest sites across two time periods using a combination of field measurements (2013, 2023) and airborne LiDAR scans (2014, 2019). Soil carbon stock was estimated from soil cores collected at each site. We find that field‐estimated ACD in our plots can reach 129.8 Mg C ha−1, with a mean sequestration rate for each site ranging between 0.3 and 2.6 Mg C ha−1 yr−1. Soil carbon can be as high as 127.9 Mg C ha−1 down to 200 cm, comparable to the soil carbon found in other non‐wetland forest ecosystems in the region. Our study highlights the role of novel forests as carbon stores. Therefore, there is a need to consider management options for these ecosystems in highly urbanized landscapes. Novel forest ecosystems consist of forest ecosystems dominated by non‐native tree species that are difficult to restore to their pre‐human disturbance states. Nevertheless, novel forests can provide numerous ecosystem services, such as carbon sequestration and storage. We quantified the aboveground living tree and soil carbon stocks in four novel forest sites in Singapore using forest inventory and airborne LiDAR data, and soil core data, respectively. We found that the carbon stored in the four sites is comparable to tropical secondary forests elsewhere. Our results show that novel forests can be protected as carbon stores.

Less than 6% of US farmlands are cover cropped, an on‐farm management practice with potential to sequester carbon and provide environmental co‐benefits (e.g., improved soil health and water quality). Despite their promise as a nature‐based climate solution that can enhance soil carbon storage, cover crops remain underutilized, in part due to farmer perceptions that benefits are not assured and management risk is high. This scoping review synthesizes research from multiple disciplines to identify persistent knowledge gaps that limit both the effectiveness and sustained adoption of cover cropping. We focus on Midwestern US agroecosystems, where scientists generally agree that cover cropping has the potential to increase soil organic carbon and contribute to long‐term carbon sequestration. Our synthesis reveals critical challenges across domains: carbon outcomes are highly variable across space and time; water and nutrient dynamics exhibit tradeoffs and context dependence; economic returns remain difficult to quantify; and adoption patterns are shaped by feedbacks between perceived risk, observed outcomes, system constraints, and social factors such as norms and identity. We use Ostrom's social‐ecological systems framework to structure our analysis across biophysical, economic, and social domains, linking scientific uncertainty to real‐world implementation barriers. The review culminates in a set of research priorities designed to advance transdisciplinary work on cover cropping, clarify its climate mitigation potential, improve the design of private and public interventions, and support adaptive management. Plain Language Summary This review looks at why only a small percentage of US farmers use cover crops, which are crops grown to improve soil health, benefit the natural environment (like water quality and biodiversity), and store carbon to slow climate change. Many farmers hesitate to adopt cover cropping because they are unsure about the benefits and risks. This leads to low initial use and frequent abandonment. Our scoping review of previous research focuses on the Midwestern US, where scientists generally agree that cover cropping can help store carbon in the soil over time. We use the social‐ecological systems framework, developed by Elinor Ostrom, to review research studies from different fields on the ecological and social aspects of cover cropping. We find that the unanswered questions about the ecological impacts of cover cropping are closely linked to social factors that lead to limited adoption (like how much farmland should be planted with cover crops and how often). We suggest that future research should focus on closing key knowledge gaps, such as how to measure long‐term carbon outcomes and understand farm‐level decision‐making, to design better tools, policies, and incentives that support effective and lasting use of cover crops. Key Points The social‐ecological system framework helps explain how biophysical and socioeconomic interactions constrain cover crop adoption Major knowledge gaps persist in measuring carbon outcomes, evaluating tradeoffs, and linking environmental benefits to on‐farm decisions We outline an interdisciplinary research agenda to address these gaps and effectuate cover cropping as a nature‐based climate solution

Purpose of review This review aims to identify the key factors, methods, and spatial units used in the development and validation of the heat vulnerability index (HVI) and discuss the underlying limitations of the data and methods by evaluating the performance of the HVI. Recent findings Thirteen studies characterizing the factors of the HVI development and relating the index with validation data were identified. Five types of factors (i.e., hazard exposure, demographic characteristics, socioeconomic conditions, built environment, and underlying health) of the HVI development were identified, and the top five were social cohesion, race, and/or ethnicity, landscape, age, and economic status. The principal component analysis/factor analysis (PCA/FA) was often used in index development, and four types of spatial units (i.e., census tracts, administrative area, postal code, grid) were used for establishing the relationship between factors and the HVI. Moreover, although most studies showed that a higher HVI was often associated with the increase in health risk, the strength of the relationship was weak. Summary This review provides a retrospect of the major factors, methods, and spatial units used in development and validation of the HVI and helps to define the framework for future studies. In the future, more information on the hazard exposure, underlying health, governance, and protection awareness should be considered in the HVI development, and the duration and location of validation data should be strengthened to verify the reliability of HVI.

Growing political pressure to find solutions to climate change is leading to increasing calls for multiple disciplines, in particular those that are not traditionally part of climate change research, to contribute new knowledge systems that can offer deeper and broader insights to address the problem. Recognition of the complexity of climate change compels researchers to draw on interdisciplinary knowledge that marries natural sciences with social sciences and humanities. Yet most interdisciplinary approaches fail to adequately merge the framings of the disparate disciplines, resulting in reductionist messages that are largely devoid of context, and hence provide incomplete and misleading analysis for decision-making. For different knowledge systems to work better together toward climate solutions, we need to reframe the way questions are asked and research pursued, in order to inform action without slipping into reductionism. We suggest that interdisciplinarity needs to be rethought. This will require accepting a plurality of narratives, embracing multiple disciplinary perspectives, and shifting expectations of public messaging, and above all looking to integrate the appropriate disciplines that can help understand human systems in order to better mediate action.

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’.