CO2 fluxes from three different temperate grazed pastures using Eddy covariance measurements

US grass-fed beef is as carbon intensive as industrial beef and ≈10-fold more intensive than common protein-dense alternatives

The high resource intensity of industrial beef in high-income economies has prompted growing interest in alternative, potentially lower environmental impact beef production pathways. Of those, grass feeding is promoted by some as one such alternative, but rigorous quantification of this claim is required. Motivated to bridge this knowledge gap, we integrate empirical evidence with a model based on authoritative equations governing beef cattle performance to quantify the greenhouse gas emissions of producing grass-fed beef. Because geographical specificity and dependence on agricultural intensity are key, we model widely varied herds, from extensive operations on semiarid, marginal rangelands to partially industrial, intensive ones in lusher, more accommodating settings. We find that emissions per kg protein of even the most efficient grass-fed beef are 10 to 25% higher than those of industrial US beef and 3- to over 40-fold higher than a wide range of plant and animal alternatives. Soil sequestration enhancement by rangeland grazing reduces these emissions from 280-390 to 180-290 kg CO2eq (kg protein)-1, still somewhat above industrial beef's 180 to 220 kg CO2eq (kg protein)-1, and well above nonbeef alternatives' 10 to 70 kg CO2eq (kg protein)-1. These differences prove robust across a broad set of combinations of grass-fed beef operation types, management practices, and ration qualities. Consequently, even with maximal credit for putative sequestration enhancement, grass-fed beef is still no less carbon intensive than industrial beef, and severalfold more intensive than nonbeef alternatives.

Feasibility of mitigation measures for agricultural greenhouse gas emissions in the UK. A systematic review

The UK Government has set an ambitious target of achieving a national "net-zero" greenhouse gas economy by 2050. Agriculture is arguably placed at the heart of achieving net zero, as it plays a unique role as both a producer of GHG emissions and a sector that has the capacity via land use to capture carbon (C) when managed appropriately, thus reducing the concentration of carbon dioxide (CO2) in the atmosphere. Agriculture's importance, particularly in a UK-specific perspective, which is also applicable to many other temperate climate nations globally, is that the majority of land use nationwide is allocated to farming. Here, we present a systematic review based on peer-reviewed literature and relevant "grey" reports to address the question "how can the agricultural sector in the UK reduce, or offset, its direct agricultural emissions at the farm level?" We considered the implications of mitigation measures in terms of food security and import reliance, energy, environmental degradation, and value for money. We identified 52 relevant studies covering major foods produced and consumed in the UK. Our findings indicate that many mitigation measures can indeed contribute to net zero through GHG emissions reduction, offsetting, and bioenergy production, pending their uptake by farmers. While the environmental impacts of mitigation measures were covered well within the reviewed literature, corresponding implications regarding energy, food security, and farmer attitudes towards adoption received scant attention. We also provide an open-access, informative, and comprehensive dataset for agri-environment stakeholders and policymakers to identify the most promising mitigation measures. This research is of critical value to researchers, land managers, and policymakers as an interim guideline resource while more quantitative evidence becomes available through the ongoing lab-, field-, and farm-scale trials which will improve the reliability of agricultural sustainability modelling in the future.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13593-023-00938-0.

Ecosystem carbon dioxide exchange and water use efficiency in a triple-cropping rice paddy in Southern India: A two-year field observation

The lowland tropical triple-cropping rice system has unique characteristics that affect the hydrological, nutrient, and atmospheric environments. To better understand the ecosystem carbon and water dynamics of a triple-cropping rice paddy from the perspective of sustainability, ecosystem-level CO2 flux and ecosystem water use efficiency (eWUE) were observed using eddy covariance over 2 years (2016-2018) at an experimental field site in southern India, and gross primary production (GPP) and ecosystem respiration (RE) were derived using the flux partitioning technique. Results showed that among the three crop seasons per year, GPP and RE were higher (887.2 and 570.2 g C m-2, respectively) in Thaladi (October-January: wet season) than in Kuruvai (June-September: dry season; 773.4 and 568.9 g C m-2, respectively) and summer rice (February-May; 694.0 and 499.7 g C m-2, respectively) owing to the longer growing season. Triple-cropping meant that the quasi-annual GPP of 2598 g C m-2 (i.e., the total value for the three consecutive seasons, including the corresponding fallow periods) was much greater than the quasi-annual RE of 1974 g C m-2. Consequently, the net ecosystem production value was positive (624 g C m-2). Evapotranspiration was also high on the annual scale (1681 mm); that is, 48 % greater than mean annual precipitation (1139 mm). Analysis revealed that Thaladi had higher eWUE (2.21 g C (kg H2O)-1) than that of Kuruvai (1.46 g C (kg H2O)-1) and summer rice (1.57 g C (kg H2O)-1) owing to decreased water loss in cloudy weather. Intense solar radiation is generally recognized as advantageous for crop growth in most regions, but not for Kuruvai and summer rice, when too strong solar radiation increases loss of water unused for photosynthesis. The findings indicate that water-saving techniques should be targeted on the Kuruvai and summer rice seasons.