Governments worldwide are adopting ambitious policies to reduce greenhouse gas (GHG) emissions. A New York State (NYS) legislative mandate requires net zero statewide GHG emissions by 2050 in part through decarbonizing electricity generation. However, increasing renewable energy capacity, including utility scale solar (USS), competes with land-uses such as agriculture and forestry. This case study evaluates USS historic land use to project future demand for land to meet NYS’s 2050 GHG goal. Data collected from open-source solar databases were combined with USS boundaries obtained through manual and automated digitization and Monte-Carlo and Maximum Entropy modeling were used to project the likely area and land use characteristics of future sites built to meet the projected 2050 demand for electricity. Demand for solar energy in NYS is projected to reach 116–125 terawatt hours per year by 2050, when electrification of current fossil-fueled heating and transportation sectors is taken into account. By analyzing the performance of over 300 existing USS sites across NYS, we project that approximately 100 GW _DC of USS capacity can meet this demand. We found an average power density of 0.62 MW _DC /ha of land for fixed axis sites and 0.59 MW _DC /ha for single axis tracked sites. Stochastic modeling of power density trends over time indicates that the 2050 mandate will require between 71,072 and 128,784 hectares (ha) depending on siting variables. If trends continue, we project that between 21 386 and 27 233 ha of cropland and between 14,985 and 18,463 ha of forest could be converted to USS. For future scenarios in which conversion of annual row crop land and high-quality soils were limited, there was an increase in distance to transmission lines, number of parcels required, and complexity of site shapes, which would likely increase solar development costs. These results help bound the likely land use changes that will occur to meet electric sector GHG mitigation mandates. These results also provide information about the benefits and trade-offs of restricting the conversion of current agricultural land to solar energy production. Additionally, the approach we developed, combining analysis of fenced area, capacity factors, trends in power density over time, and projecting likely future locations for solar stochastically is applicable to many global regions with solar development on agricultural lands.

Integrated conservation and development efforts in low- and middle-income countries have emphasized the devolution of forest management to local communities. This approach is posited to benefit both communities and conservation, but those benefits may depend on community capacity to capture value added, e.g., by processing forest products. In Mexico, most forests are under community management, but only some communities have vertically integrated their wood products supply chain through the establishment of community sawmills. The different timing of sawmill construction allows us to test the hypothesis that vertical integration of the wood products supply chain under community management is protective of forests. We use detailed, spatially explicit panel data from southern Mexico that allow us to examine impacts on land use change (deforestation and forest regrowth) separately from temporary changes in tree cover within forest areas. We find that vertical integration, as indicated by the presence of community sawmills and corroborated by a government classification of ejidos, reduced deforestation while increasing forest regrowth. Our findings, thus, have a somewhat counter-intuitive policy implication: programs that increase financial resources for communities to invest in forestry operations could improve forest protection and restoration, with regional and global benefits for climate, biodiversity, and other ecosystem services.

Natural climate solutions (NCS) play a critical role in climate change mitigation. NCS can generate win–win co-benefits for biodiversity and human well-being, but they can also involve trade-offs (co-impacts). However, the massive evidence base on NCS co-benefits and possible trade-offs is poorly understood. We employ large language models to assess over 2 million published journal articles, primarily written in English, finding 257,266 relevant studies on NCS co-impacts. Using machine learning methods to extract data (for example, study location, species and other key variables), we create a global evidence map on NCS co-impacts. We find that global evidence on NCS co-impacts has grown approximately tenfold in three decades, and some of the most abundant evidence relates to NCS that have lower mitigation potential. Studies often examine multiple NCS, indicating some natural complementarities. Finally, we identify countries with high carbon mitigation potential but a relatively weak body of evidence on NCS co-impacts. Through effective methods and systematic and representative data on NCS co-impacts, we provide timely insights to inform NCS-related research and action globally. Rich evidence of the potential co-benefits and trade-offs of natural climate solutions is available but remains poorly understood. Assessing the literature with machine learning methods, this study maps and analyses the growing evidence of trade-offs in natural climate solutions globally.

Restoring tree cover changes albedo, which is the fraction of sunlight reflected from the Earth’s surface. In most locations, these changes in albedo offset or even negate the carbon removal benefits with the latter leading to global warming. Previous efforts to quantify the global climate mitigation benefit of restoring tree cover have not accounted robustly for albedo given a lack of spatially explicit data. Here we produce maps that show that carbon-only estimates may be up to 81% too high. While dryland and boreal settings have especially severe albedo offsets, it is possible to find places that provide net-positive climate mitigation benefits in all biomes. We further find that on-the-ground projects are concentrated in these more climate-positive locations, but that the majority still face at least a 20% albedo offset. Thus, strategically deploying restoration of tree cover for maximum climate benefit requires accounting for albedo change and we provide the tools to do so.

To estimate the potential and realized carbon emission reductions from implementation of reduced-impact logging (RIL) in Indonesia, we compiled logging emissions data from 15 concessions in Kalimantan and 10 from the Papuan provinces. Committed emissions data were collected for harvested timber as well as from collateral damage caused by felling, skidding, and clearing for haul roads and log yards. Emissions expressed as mean ± standard error per cubic meter of timber harvested, per area harvested, and per Mg of timber harvested (i.e., the ‘Carbon Impact Factor’) were 1.30 ± 0.15 Mg C m−3, 27.52 ± 4.44 Mg C ha−1, and 6.88 ± 0.84 Mg Mg−1, respectively. Among the sampled concessions, felling, hauling, and skidding caused 18–86%, 2–48%, and 6–75% of these emissions, respectively. Potential emission reductions calculated as the difference between observed emissions and those of the five best-performing concessions are 0.67 ± 0.15 Mg C m−3, 21.11 ± 4.38 Mg C ha−1, and 4.20 ± 0.83 Mg Mg−1, which represents reductions of 51%, 76%, and 61%, respectively. Extrapolating these estimates to all of Indonesia using average log production data from 2018 to 2021 results in an estimated annual emissions reduction of 14.47 Tg CO2 from full adoption of RIL, which is 2.9% of Indonesia’s nationally determined contribution (NDC) from the forestry sector.

Infestations of trees by woody climbing plants (i.e., lianas) are common and increasing in an estimated 250 Mha of the 1 billion hectares of mixed-species tropical and temperate forest subjected to selective logging. Cutting lianas that impede the growth of future crop trees (FCTs) in these forests would sequester carbon at low cost and increase timber yields. We estimate that application of this treatment to five liana-infested FCTs per hectare across the 250 Mha of selectively logged forest would result in 0.8 PgCO(2) of additional carbon removals by the liberated trees over 30 years at a direct cost of well less than $1.00 MgCO2-1. The same treatment could also be applied in forests not destined for logging where liana infestations were exacerbated by prior anthropogenic disturbances. If the numbers of trees liberated from lianas is kept small, undesired impacts on biodiversity will be minimized. One-Sentence Summary: Liberating future crop trees from lianas is a cost-effective way to increase rates of carbon sequestration, increase timber yields, and restore degraded forest.

Abstract Restoring tree cover is a prominent natural climate solution1–3, but can decrease albedo and lead to global warming in some places4–10. Existing assessments of the mitigation potential from restoring tree cover 2,3,11,12 poorly account for albedo due to a lack of spatial data. Here we produce a global 500-m map that incorporates albedo and maximum carbon storage to quantify the net climate impact (CO2e) of restoring tree cover. We find that albedo offsets some of the carbon storage benefit across most of the globe. Contrary to prior work, albedo is not of greatest concern in boreal forests. Rather, arid biomes have a greater proportion of net negative climate areas (e.g., 61% in temperate savanna versus 10% in boreal forests). Accounting for albedo across previously published opportunity maps reduces total maximum CO2e by up to 37%. However, the magnitude of the offset varies substantially across the landscape, highlighting the importance of spatially refined estimates. Encouragingly, on-the-ground projects to restore tree cover are concentrated in climate-positive areas, but the majority (64%) still face a minimum 10% albedo offset. Thus, strategically deploying restoration of tree cover for maximum climate benefit requires accounting for albedo, and the maps herein facilitate this.

This repository contains spatial and tabular data central to the analysis reported by Walker et al. (2022) on the global potential for increased storage of carbon on land. All maps provided here are global (excluding Antarctica) in geographic scope at a spatial resolution of ca. 500 meters in the MODIS sinusoidal projection (SR-ORG:6842). Maps are stored individually as single-band GeoTIFFs. Grid cell units for carbon density maps are megagrams of carbon per hectare (MgC/ha). Water has been masked out as NoData (-32768). Associated computer code is available for download from https://github.com/whrc/Global-Potential-Carbon.

Significance Despite increased interest in land-based carbon storage as a climate solution, there are physical limits on how much additional carbon can be incorporated into terrestrial ecosystems. To effectively determine where and how to act, jurisdictions need robust data illustrating the magnitude and distribution of opportunities to increase carbon storage, as well as information on the actions available to achieve that storage. Here, we provide globally consistent maps for directing additional carbon storage under current and future climate, as well as a framework for determining how that storage could be gained through restoration, improved management, or maintenance of woody biomass and soil organic matter. Our estimates provide an upper bound on how improved land stewardship can mitigate the climate crisis.

Limited time and resources remain to constrain the climate crisis. Natural climate solutions represent promising options to protect, manage and restore natural lands for additional climate mitigation, but they differ in (1) the magnitude and (2) immediacy of mitigation potential, as well as (3) cost-effectiveness and (4) the co-benefits they offer. Counter to an emerging preference for restoration, we use these four criteria to propose a general rule of thumb to protect, manage and then restore lands, but also show how these criteria explain alternative prioritization and portfolio schemes. This hierarchy offers a decision-making framework for public and private sector actors to optimize the effectiveness of natural climate solutions in an environment in which resources are constrained, and time is short. Natural climate solutions, along with reduction in fossil fuel emissions, are critical to mitigating climate change and meeting climate goals. This Perspective outlines a hierarchy for decision-making regarding protecting, managing and then restoring natural systems for climate mitigation.

Restoration of forest cover can curtail the climate crisis and provide many co-benefits, or waste limited resources. To use restoration of forest cover to its highest potential, global dynamic monitoring is needed that combines existing restoration projects with control plots and remote-sensing technologies.

Alongside the steep reductions needed in fossil fuel emissions, natural climate solutions (NCS) represent readily deployable options that can contribute to Canada’s goals for emission reductions. We estimate the mitigation potential of 24 NCS related to the protection, management, and restoration of natural systems that can also deliver numerous co-benefits, such as enhanced soil productivity, clean air and water, and biodiversity conservation. NCS can provide up to 78.2 (41.0 to 115.1) Tg CO2e/year (95% CI) of mitigation annually in 2030 and 394.4 (173.2 to 612.4) Tg CO2e cumulatively between 2021 and 2030, with 34% available at ≤CAD 50/Mg CO2e. Avoided conversion of grassland, avoided peatland disturbance, cover crops, and improved forest management offer the largest mitigation opportunities. The mitigation identified here represents an important potential contribution to the Paris Agreement, such that NCS combined with existing mitigation plans could help Canada to meet or exceed its climate goals.

CORRECTION article Front. For. Glob. Change, 28 April 2021 | https://doi.org/10.3389/ffgc.2021.658469

While enthusiasm grows for reforestation as a tool for combatting climate change, we lacked information about how fast or slow new forests across the globe could capture carbon dioxide. So we created a first-of-its-kind map of potential carbon capture from natural forest regrowth for every square kilometer of the planet. - submission by Susan C. Cook-Patton, Sara M. Leavitt, Peter W. Ellis

To constrain global warming, we must strongly curtail greenhouse gas emissions and capture excess atmospheric carbon dioxide1,2. Regrowing natural forests is a prominent strategy for capturing additional carbon3, but accurate assessments of its potential are limited by uncertainty and variability in carbon accumulation rates2,3. To assess why and where rates differ, here we compile 13,112 georeferenced measurements of carbon accumulation. Climatic factors explain variation in rates better than land-use history, so we combine the field measurements with 66 environmental covariate layers to create a global, one-kilometre-resolution map of potential aboveground carbon accumulation rates for the first 30 years of natural forest regrowth. This map shows over 100-fold variation in rates across the globe, and indicates that default rates from the Intergovernmental Panel on Climate Change (IPCC)4,5 may underestimate aboveground carbon accumulation rates by 32 per cent on average and do not capture eight-fold variation within ecozones. Conversely, we conclude that maximum climate mitigation potential from natural forest regrowth is 11 per cent lower than previously reported3 owing to the use of overly high rates for the location of potential new forest. Although our data compilation includes more studies and sites than previous efforts, our results depend on data availability, which is concentrated in ten countries, and data quality, which varies across studies. However, the plots cover most of the environmental conditions across the areas for which we predicted carbon accumulation rates (except for northern Africa and northeast Asia). We therefore provide a robust and globally consistent tool for assessing natural forest regrowth as a climate mitigation strategy. A one-kilometre-resolution map of aboveground carbon accumulation rates of forest regrowth shows 100-fold variation across the globe, with rates 32% higher on average than IPCC estimates.

Farmers, food supply companies, and policymakers need practical yet scientifically robust methods to quantify how improved nitrogen (N) fertilizer management can reduce nitrous oxide (N2 O) emissions. To meet this need, we developed an empirical model based on published field data for predicting N2 O emission from rainfed maize (Zea mays L.) fields managed with inorganic N fertilizer in the United States and Canada. Nitrous oxide emissions ranged widely on an area basis (0.03-32.9 kg N ha-1 yr-1 ) and a yield-scaled basis (0.006-4.8 kg N Mg-1 grain yr-1 ). We evaluated multiple modeling approaches and variables using three metrics of model fit (Akaike information criteria corrected for small sample sizes [AICc], RMSE, and R2 ). Our model explains 32.8% of the total observed variation and 50% of observed site-level variation. Soil clay content was very important for predicting N2 O emission and predicting the change in N2 O emission due to a change in N balance, with the addition of a clay fixed effect explaining 37% of site-level variation. Sites with higher clay content showed greater reductions in N2 O emission for a given reduction in N balance. Therefore, high-clay sites are particularly important targets for reducing N2 O emissions. Our linear mixed model is more suitable for predicting the effect of improved N management on N2 O emission in maize fields than other published models because it (a) requires only input data readily available on working farms, (b) is derived from field observations, (c) correctly represents differences among sites using a mixed modeling approach, and (d) includes soil texture because it strongly influences N2 O emissions.

Restoring forest cover is a prominent option for climate mitigation. Effective deployment requires knowing where opportunities are and how they vary in carbon capture, costs, co-benefits, and feasibility. Here, we combined spatial, economic, and feasibility analyses to examine 10 different opportunity classes for restoration of forest cover across the contiguous United States. These include non-stocked forests, shrublands, protected areas, post-burn landscapes, pasture lands, croplands with challenging soils, urban areas, floodplains, streamsides, and biodiversity corridors. We found 51.6 Mha of total opportunity, which could capture 314.2 million tons of carbon dioxide each year, equivalent to 15% of the United States' 2016 commitment to the Paris Agreement. Half of this mitigation is possible at $20 tCO2−1. However, the highest-ranked opportunity class with respect to carbon capture, costs, co-benefits, and feasibility changed depending on location. Our maps are publicly available to guide policy and implementation efforts at local, state, and national levels.

Disposal of coal fly ash in soil-capped landfills has raised questions regarding the presence of potentially toxic elements in the ash and their future disposition in the local ecosystem. Experiments were carried out on the uptake of chemical elements by cultivated and indigenous plants grown on a coal fly ash landfill and on control sites. Selenium was found to concentrate in amounts more than 50 times higher in landfill-grown plants than in control plants, and was the element of greatest interest and concern. Other elements, such as Mo and B, were often higher in the tissues of control plants, but the degree of uptake was usually less than two-fold. Rutabaga (Brassica napus L., Cruciferae), birdsfoot trefoil (Lotus corniculatus L., Leguminoseae), and alfalfa (Medicago sativa L., Leguminoseae) absorbed more Se than other species such as carrot (Daucus carota L., Umbelliferae), corn (Zea mays L., Graminae), timothy (Phleum pratense L., Graminae), bromegrass (Bromus inermis Leyss, Graminae), red clover (Trifolium pratense L., Leguminoseae), or milkweed (Asclepias syriaca L., Asclepiadaceae). Cauline leaves of wild carrot and bitterweed (Picris hieracioides L., Compositeae) contained more Se than older rosette leaves. In sweet and field corn cultivars, greater amounts of Se were found in leaves and kernels than in stems, cobs, or roots. Coal flue gas desulfurization will result in the production of CaSO3 as a byproduct, from which gypsum (CaSO4) can be made easily. Research by others indicated that application of gypsum to Se-containing soils often resulted in reduced Se uptake in plants. In the studies described here, application of gypsum at the rate of 2 metric tons/ha reduced the uptake of Se in both rutabaga and carrot shoots and roots. We conclude that gypsum application offers a possible management tool to control uptake and cycling of Se through plants to other biota.

Tropical forests contain approximately 40% of the carbon accumulated in terrestrial biomass. However, the loss and degradation of forests worldwide liberates this carbon and contributes 11% of total global emissions. Forest degradation is an increasing source of carbon emissions, contributing 25% in tropical forest environments; and selective logging is among the principal causes. The central objective of this study was to evaluate biomass impacts and committed carbon emissions from selective logging in two forestry communities (ejidos with common forest use and rights) in the southern Yucatan Peninsula, Mexico. We compared emissions performance from logging operations in both ejidos, one of them certified as sustainably managed by the Forest Stewardship Council (FSC). The species of roundwood extracted as well as the number of impacted trees from harvesting were recorded and the type of collateral damage from felling, skidding, and transport of timber was quantified. Biomass of harvested timber and impacted vegetation was estimated to calculate carbon emissions using allometric equations. Results indicated that selective logging generated 1.2 Mg m -3 1.5 Mg m -3 of total carbon emissions in the Caobas and 20 de Noviembre ejidos, with 5% and 12% corresponding to collateral damage during felling, respectively. Overall lower committed emissions and collateral damage from felling and skidding were present in Caobas, the FSC certified ejido. We discuss how forest certification, through implementation of reduced impact logging (RIL) practices can significantly reduce carbon emissions from selective logging in the region.