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Meaningful protection of global oceans lags far behind that of land and has taken little consideration of climate mitigation potential to date (such as through assessment of blue carbon stocks and change). With the new emphasis on synergistic approaches to the identification and conservation of both carbon- and species- rich habitats, we need much better knowledge of the geography and status of blue carbon habitats beyond coastal wetlands. In subpolar and polar regions, some blue carbon habitats are still emerging and work as negative (mitigating) feedback on climate change, yet remain unprotected despite strong evidence of threat overlap. Scientific research expeditions are gradually increasing our understanding, but appropriate vessels are a limiting factor due to high costs and carbon footprints. Even when available such vessels cannot access all areas (e.g., remote fjords with sills) and may struggle to measure certain aspects of habitats (e.g., steep or vertical surfaces). New technologies and opportunities have advanced to aid some of these problems, and here, two of them are considered, mini-manned submersibles and autonomous underwater vehicles. These two platforms have both become much more available and affordable (through novel partnerships) while also being much more scientifically capable. This technology has the potential to reduce the carbon footprint of science and particularly aid in assessing biology and environment status and change on steep sides, such as fjord walls. LESS      Full article

This study aims to assess the additional Greenhouse gas (GHG) emissions affected by straw removal from the soil surface in sugarcane areas, including measurement of short-term soil CO₂-C emissions plus emissions associated with the recovery and transport operations of straw bales until to the industry gate (diesel emissions) and estimated soil N₂O emission, comparing with leaving all straw on the soil surface. Taking into account the main sources evaluated (soil CO₂, diesel and N₂O from straw), the total additional GHG emissions from the recovery of 6.9 Mg Dry Matter ha^-1 (27%) was estimated at 1423 kg CO₂eq ha^-1, resulting in a carbon footprint of 206.2 kg CO₂eq per megagram (Mg) of straw recovered. Applying the parameters cited in this study for electricity generation (GHG emission and offset potential), our results showed an additional GHG emission of (+) 860 kg CO₂eq ha^-1. Applying the same parameters for second generation (2G) ethanol production replacing gasoline, an avoided GHG emission of (-) 2316 kg CO₂eq ha^-1 could be achieved. The route of recovering 27% of sugarcane straw from the soil surface through bale system for bioelectricity production using the technical parameters and industrial efficiency rate of this case study resulted in a C footprint of 347 kg CO₂eq MWh^-1. Improving the efficiency rate for straw conversion in bioelectricity based on its lower heating value could reduce its C footprint to 62.26 kg CO₂eq MWh^-1 produced. For sugarcane straw recovery at the first cutting cycle in clay soil, the option of producing ethanol 2G could offset GHG emissions once replacing fossil gasoline, resulting in a C footprint of 0.86 kg CO₂eq L^-1 of 2G ethanol in the agricultural phase, an option to contribute to better sustainability of sugarcane straw recovery, supporting renewable and sustainable bioenergy systems, and reducing the impacts of Global Climate Change. LESS      Full article

Grasslands in the Southeast United States (SE US) cover 15.8 million ha and most of this area is dedicated to beef production systems. This region holds 6.3 million beef cows and 12.1 million cattle, including calves. Beef cattle systems in the SE US are mostly cow-calf based, and most of the greenhouse gas emission from cattle occurs during this phase (cow-calf) because of their forage-based diet. This review assessed the carbon footprint (C footprint) of beef cattle systems in the SE US and indicates possible ways to reduce it. Major emissions in beef cattle systems come from livestock enteric fermentation and greenhouse gases from excreta. Cow-calf systems in the SE US are typically low input, although they use some industrial fertilizers, machinery, and fossil fuel, which adds to the C footprint of the sector. There are opportunities to reduce the beef C footprint in the SE US by adopting climate-smart practices, including preservation of natural ecosystems that have potentially high carbon sequestration, afforestation, integration of forage legumes (and reduction of nitrogen fertilizer), use of slow-release fertilizers, and dietary interventions. In fact, depending on the level of adoption of some of these practices, it is possible to establish climate-neutral beef at the farm gate in the SE US. Beef is a key food for humans and has large economic effects. Development of climate-smart beef could create opportunities for a niche market that recognizes the environmental footprint of agricultural production and could incentivize producers to pursue those systems. LESS      Full article

Farming systems in Southern Africa are mostly maize mixed cropping, with some tree and/or root crop-based systems. Agroforestry systems (AFS), in particular, represent a model for ecological sustainability, with the potential of sequestering carbon (C) within soils and biomass. This review reveals that rotational woodlots sequester more C than other AFS types in the region. Additionally, C levels above and below ground range from 0.29 to 15.21 Mg ha^-1 yr^-1 and 30 to 300 Mg C ha^-1 in the first 100 cm soil depth, respectively. To measure C below- and aboveground biomass in different AFS, variable - and not easily adoptable - methodologies are being used in Southern Africa, which limits the standardization of C stock accounting. Since the magnitude of C sequestered in AFS is dependent on the species used, AF and farm management, and environmental conditions, we recommend the adoption of rigorous and replicable methodologies to account for C stocks in different AFS over time in Southern Africa. LESS      Full article

Biochar, a carbonaceous solid material obtained from the pyrolysis of biomass, has received considerable research attention because of its unique properties and potential to improve crop yields and soil carbon (C) sequestration while reducing environmental degradation and carbon footprints (CF). This paper summarizes the available results on several aspects of biochar research from numerous studies despite their short-term nature. The studies have shown that (1) biochar from the same source added at a given rate to different soils could have different effects, particularly on phosphorus (P) release/retention, based on the respective soil properties; (2) the elemental composition of a feedstock (the biomass source used for biochar production) is not an indication of plant-nutrient availability; (3) pyrolysis temperature has a significant influence on the properties of the biochar, but the optimal temperature depends on the desired qualities of the product such as P release, cation exchange capacity, and surface area; and (4) the risk of nutrient loss during biochar application depends on the nutrient release potential of the biochar as well as the nutrient retention properties of the soil. Some evidence from nature suggests that biochar can hold C in soils for thousands of years, but the mechanisms involved are not fully understood. In general, the available results on the effect of biochar application on field crops have been variable and site-specific so that general conclusions cannot be drawn on their applicability to a wide spectrum of situations and systems. A number of researchable priorities were identified, including CF under biochar. Similarly, although the land application of biochar to decrease CF sounds like a promising proposition, rigorous long-term studies under farm settings are required before recommending it for large-scale adoption. LESS      Full article

Forest conversion caused by subsistence or “basic needs populations” is difficult to track and measure. As the dynamics of these populations change over time, their carbon footprint impacts on natural resources also change. To reduce their potential negative impacts on forest resources, it is critical to understand what underlying causes influence their livelihoods practices. A systematic review was conducted to search for common basic needs livelihoods that result in forest loss and degradation, and thus in carbon footprint changes. Livelihood activities were grouped into seven themes (animal husbandry, crop production, fishing, illegal practices, non-timber forest products, and wood harvest). Under these themes, a non-comprehensive list of 25 activities was combined with “deforestation” and “forest degradation” as search terms in Scopus and Web of Science^TM. A two-level snowball sampling procedure was applied to the resulting screened publications. The review produced 2200 outputs, with a final sample of 101 articles and 161 basic needs communities described. The results show that wood harvesting and crop production were the most common livelihood activities engaged in by basic needs populations. Population pressure and alternative income sources were frequently mentioned as underlying causes influencing deforestation and forest degradation and likely affecting carbon footprints through land cover change. Often considered sustainable, livelihood activities by basic needs populations can become unsustainable in response to changes in contextual and socioeconomic factors. These factors are often interrelated, leading to environmental downward spirals, which increase carbon footprints through greater demands for natural resources resulting in deforestation and forest degradation. LESS      Full article

National-scale carbon footprints of livestock production are commonly computed from a set of production system characteristics that serve as inputs for greenhouse gas (GHG) emission models. We evaluated the feasibility of using such equations at a finer scale to derive a simple farm-scale indicator of emission intensity (milk yield per head). Using probabilistic simulations, we quantified the impact of input variable uncertainty on emission estimates for smallholder dairy farms in Kenya. We simulated emissions for farm-scale scenarios generated from a survey of 414 households and published or expert-estimated uncertainty bounds. We simulated the impacts of five interventions: changing breeds, retiring unproductive males, keeping fewer replacement males, feeding forage supplements, and balancing animal diets. Impacts were assessed against a true counterfactual and against a more realistic scenario affected by random effects. We estimated errors incurred in classifying farms into adopters and non-adopters of the innovations based on changes in milk yield per animal. Given the current uncertainty, such classification would either miss a large percentage of adopters or misclassify many non-adopters as adopters. As a critical uncertainty, we identified the milk yield of dairy cows. Added precision on this metric reduced but did not eliminate classification errors. We remain cautiously optimistic about using milk yield per head to proxy emission intensity, but its effective use will require further reduction of critical uncertainties. Replacing generic recommendations of parameter uncertainties with context-specific error estimates might lead to a more efficient quantification of the carbon footprint of milk production on smallholder farms. LESS      Full article

Climate change is a major global threat affecting food security and sustainability. Land use systems involving trees have the potential to positively impact climate change by reducing atmospheric carbon dioxide (CO₂) and providing long-term carbon (C) storage. This review evaluated the C sequestration potential of two major land use systems of the United States (US) involving trees, forests and agroforests, which can also provide other ecosystem services.The estimated total forest C stock on forest land in the US in 1990 was 50,913 Tg and another 1885 Tg remained in harvested wood and discarded wood products. From 1990 to 1995, total C stock rose by 2%, and from 2000 to 2005, it rose by 1.7%. The US forests collectively lose (flux) about 200 Mg C y^-1 from disturbance and harvesting. Currently, about 12% of the conterminous US forest land is at high or very high risk of wildfire. Annually, insects and diseases could transfer ~ 21 Tg of live aboveground biomass to litter and woody debris pools. A scenario that targets an afforestation policy for rural landowners in the eastern US and a reforestation policy targeting understocked federal forest lands in the western would improve US annual sequestration compared to the baseline of 323 Tg CO₂ eq yr^-1 in 2015 to 469 Tg CO₂ eq yr^-1 in 2050.Agroforestry offers greater potential to increase C sequestration of predominantly agriculture-dominated landscapes than monocrop agriculture by storing C in above- and belowground biomass, soil, and living and dead organisms and further extending the duration of C in soils. The estimated total C sequestration of current alley cropping (211,938 ha), riparian buffers (640,732 ha), silvopasture (34 Mha), and windbreak (2.37 Mha) practices is 219 Tg C yr^-1. The total C sequestration would be 240 Tg C yr^-1 with 5% of the US cropland converted to alley cropping (3.7 Tg yr^-1), 15-m wide riparian buffers on both sides of 5% of the total stream length (4.75 Tg yr^-1), 34 Mha converted to silvopasture (207 Tg yr^-1), and windbreaks on 5% (7.45 Mha) of the cropland (25 Tg yr^-1). Despite many limitations including uncertainty of land areas under agroforestry, lack of standardized estimation protocols, and lack of accountability on various C stocks (source-sink services, detritus C, insect/pest damages, etc.), we believe these new accrual rates and the land areas under each practice are much more realistic as new information became available over the last decade.The total C sequestration by forests (776) and agroforests (219) is 995 Tg yr^-1 and represents approximately 15% of the US CO₂ emissions. This review highlights the importance of sustainable management of forests and integration of agroforestry on agricultural lands to mitigate climate challenges further while meeting society’s need for food and a healthy environment. LESS      Full article

Stabilizing greenhouse gas (GHG) emissions from croplands as agricultural demand grows is a critical climate change mitigation strategy. Depending on management, the Agriculture, Forestry, and Other Land Use (AFOLU) sector can be both a source as well as a net sink for carbon. Currently, it contributes 25% of the global anthropogenic carbon emissions. Although India’s emissions from this sector are around 8% of the total national GHG emissions, it can contribute significantly to the country’s aspirations of reaching net-zero emissions by 2070. In this review, we explain the carbon footprints of the AFOLU sector in India, focusing on enteric fermentation, fertilizer and manure management, rice paddies, burning of crop residues, forest fires, shifting cultivation, and food wastage. Furthermore, using the standard autoregressive integrated moving average method, we project India’s AFOLU sector emission routes for 2070 under four scenarios: business as usual (BAU) and three emission reduction levels, viz., 10%, 20%, and 40% below BAU. The article focuses on how the AFOLU sector can be leveraged proactively to reach the net-zero emission goals. Increasing forest cover, agroforestry, and other tree-based land-use systems; improving soil health through soil management, better crop residue, and livestock feed management; emission avoidance from rice ecosystems; and reducing food waste are all important strategies for lowering India’s AFOLU sector carbon footprints. LESS      Full article