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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

The global soil carbon pool has been estimated to exceed the amount of carbon stored in the atmosphere and vegetation, though uncertainties to quantify below-ground carbon and soil carbon fluxes accurately still exist. Modeling soil carbon using artificial intelligence (AI) - machine learning (ML) and deep learning (DL) algorithms - has emerged as a powerful force in the carbon science community. These AI soil carbon models have shown improved performance to predict soil organic carbon (SOC) storage, soil respiration (R_s), and other properties of the global carbon cycle when compared to other modeling approaches. AI systems have advanced abilities to optimize fits between inputs (geospatial environmental covariates) and outputs (e.g., SOC or R_s) through advanced pattern recognition, learning algorithms, latent variables, hyperparameters, hyperplanes, weighting factors, or multiple stacked processing (e.g., convolution and pooling). These machine-oriented applications have shifted focus from knowledge discovery and understanding of ecosystem processes, carbon pools and cycling toward data-driven applications that compute digital soil carbon outputs. The purpose of this review paper is to explore the emergence, applications, and progress of AI-ML and AI-DL algorithms to model soil carbon storage and R_s at regional and global scales. A critical discussion of the power, potentials, and perils of AI soil carbon modeling is provided. The paradigm shift toward AI modeling raises questions how we study soil carbon dynamics and what conclusions we draw which impacts carbon science research and education, carbon management, carbon policies, carbon markets and economies, and soil health. LESS      Full article

Brazil is one of the main producers in the agricultural and forestry sector worldwide, with production systems based on high consumption of inputs that contribute to high levels of greenhouse gas (GHG) emissions. This paper presents an analysis of the scenario of national GHG emissions and carbon footprints in the major production systems of agriculture, including livestock production and forestry, and the potential for soil carbon storage as a mitigation strategy under these systems. The main sources of national GHG emissions are beef cattle due to enteric fermentation and the management of agricultural soils through the use of nitrogen fertilizers. The increasing adoption of low-carbon agriculture has led to a reduction in the carbon footprint through no-till technologies, agrosilvopastoral systems, N₂ fixation, and tree plantations. These technologies deserve to be increasingly disseminated to generate economic opportunities leading to financial gains from the commercialization of carbon credits and payment for environmental services. LESS      Full article

The urgent global reduction of greenhouse gas emissions depends on political commitments to common but differentiated responsibility. Carbon footprints as a metric of attributable emissions reflect individually determined contributions within, and aggregated national contributions between, countries. Footprints per unit product (e.g., of food, feed, fuel, or fiber) require a lifecycle analysis and support individual decisions on consumption and lifestyles. This perspective presents a framework for analysis that connects the various operationalizations and their use in informing consumer and policy decisions. Footprints show geographical variation and are changing as part of political-economic and social-ecological systems. Articulation of footprints may trigger further change. Carbon footprints partially correlate with water and biodiversity footprints as related ecological footprint concepts. The multifunctionality of land use, as a solution pathway, can be reflected in aggregated footprint metrics. Credible footprint metrics can contribute to change but only if political commitments and social-cultural values and responsibilities align. LESS      Full article

Increase in global populations of humans and domesticated livestock are impacting the resource use and have a large ecological footprint (EFP). The ever-increasing EFP of humanity is accelerating climate change, increasing water scarcity and contamination, aggravating soil degradation, and dwindling above and below-ground biodiversity. Several sub-components of EFP include resource footprint (RFP) which comprises land (LFP), water (WFP), nitrogen (NFP), biodiversity (BFP) power (PFP), carbon (CFP), etc. Agricultural practices (e.g., tillage, fertilizer and pesticide use, farm operations such as irrigation, harvesting, baling, etc.) also cause the emission of greenhouse gases (GHGs) such as CO₂, CH₄, and N₂O, and these gasses equivalent in their global warming potential (GWP). In general, CFP is reported as CO_2eq by converting CH₄ and N₂O into CO₂. The Human diet, consisting of plant and/or animal-based products and grown diversely with or without chemicals, irrigation, and modern innovations, has a wide range of EFP. The latter, is the widely used measure of resource consumption and humanity’s impact on the planet. EFP encompasses the cumulative GHG emissions by an individual, community, organization, institution, nation for a specific service or product. It can vary widely because of using different reference systems of the studies and differences in system boundaries. Therefore, standardization of the methodologies may require a better understanding of the various ways related CFP concepts are relevant for decisions at individual to global levels. There is no one size that fits all. It is also widely recognized that the global average per capita CFP of humanity, estimated at 4.47 Mg CO_2eq in 2020 is not sustainable, and must be reduced to < 2 Mg CO_2eqif the global warming is to be limited to 2 ⁰C. Therefore, understanding the magnitude of CFP of agriculture and food systems (FSs), and factors affecting it, can lead to identification of technological options which can enhance the use efficiency of inputs, reduce wastage, and decrease the CFP. Different FSs affect CFP through diverse components of production and supply chains, and in the manner in which food is stored and cooked and the waste is disposed or recycled. There is need to adopt international standard (ISO) protocol. Therefore, this review identifies and deliberates technological options which may be needed for reducing CFP of humanity in general but that of agriculture and FSs in particular, while also advancing Sustainable Development Goals of the Agenda 2030 of the United Nations. CFP of diverse agro-ecosystems, land use and management systems are also discussed. Specific examples of CFP include type of farming systems (organic vs.. conventional, dietary preferences, and food waste). There are several options for the humanity to change lifestyle and make it more sustainable. Food waste, about one-third of all, is an important factor impacting CFP while also accelerating global warming. The impact of avoidable food waste on gaseous emissions, estimated at 2.0 to 3.6 Mg CO_2eq per Mg of food waste on dry weight basis, must be minimized. LESS      Full article

Carbon Footprint (CFP) refers to the emission of all greenhouse gases (GHGs) during a given period by any activity or entity. The standard unit for measuring it is the carbon dioxide equivalent (CO_2eq), such that the impact of each GHG is expressed in terms of the amount of CO₂ that would create the same amount of warming. It is widely recognized that the 2020 global value for average per capita CFP (estimated as 4.47 Mg CO_2eq) is not sustainable and that it must be reduced to < 2 Mg CO_2eq if global warming is to be limited to 2⁰C. Recent estimates show that 31% of human-caused GHG emissions originate from the world’s agri-food systems, the major sources being deforestation, livestock production (from enteric fermentation and manure), food waste disposal, and fossil fuel use (by farms and the food-retail sector). Land application of chemicals such as fertilizers, weedicides, and insecticides is the most significant factor in the AFOLU (agriculture, forestry, and other land-use) sector. Enhancement of the natural process of terrestrial C sequestration in soil and vegetation is a widely recognized approach to reducing the AFOLU sector CFP. The adoption of multispecies agroforestry systems with nitrogen-fixing trees is a promising strategy for accomplishing this goal. Another is integrated silvopastoral systems that combine animal production with deep-rooted grass and trees that could counteract the GHG emission through enteric fermentation in animals with enhanced soil C sequestration. LESS      Full article