Publications by John Lynch


Agriculture's contribution to climate change and role in mitigation is distinct from predominantly fossil CO2-emitting sectors

Frontiers in Sustainable Food Systems Frontiers Media 4 (2021) 518039

J Lynch, M Cain, D Frame, R Pierrehumbert

Agriculture is a significant contributor to anthropogenic global warming, and reducing agricultural emissions—largely methane and nitrous oxide—could play a significant role in climate change mitigation. However, there are important differences between carbon dioxide (CO2), which is a stock pollutant, and methane (CH4), which is predominantly a flow pollutant. These dynamics mean that conventional reporting of aggregated CO2-equivalent emission rates is highly ambiguous and does not straightforwardly reflect historical or anticipated contributions to global temperature change. As a result, the roles and responsibilities of different sectors emitting different gases are similarly obscured by the common means of communicating emission reduction scenarios using CO2-equivalence. We argue for a shift in how we report agricultural greenhouse gas emissions and think about their mitigation to better reflect the distinct roles of different greenhouse gases. Policy-makers, stakeholders, and society at large should also be reminded that the role of agriculture in climate mitigation is a much broader topic than climate science alone can inform, including considerations of economic and technical feasibility, preferences for food supply and land-use, and notions of fairness and justice. A more nuanced perspective on the impacts of different emissions could aid these conversations.


Global food system emissions could preclude achieving the 1.5° and 2°C climate change targets

Science American Association for the Advancement of Science 370 (2020) 705-708

M Clark, J Lynch, N Domingo, K Colgan, S Thakrar, J Hill, D Tilman, I Azevedo

The Paris Agreement’s goal of limiting the increase in global temperature to 1.5° or 2°C above preindustrial levels requires rapid reductions in greenhouse gas emissions. Although reducing emissions from fossil fuels is essential for meeting this goal, other sources of emissions may also preclude its attainment. We show that even if fossil fuel emissions were immediately halted, current trends in global food systems would prevent the achievement of the 1.5°C target and, by the end of the century, threaten the achievement of the 2°C target. Meeting the 1.5°C target requires rapid and ambitious changes to food systems as well as to all nonfood sectors. The 2°C target could be achieved with less-ambitious changes to food systems, but only if fossil fuel and other nonfood emissions are eliminated soon.


Global food system emissions could preclude achieving the 1.5° and 2°C climate change targets.

Science (New York, N.Y.) 370 (2020) 705-708

MA Clark, NGG Domingo, K Colgan, SK Thakrar, D Tilman, J Lynch, IL Azevedo, JD Hill

The Paris Agreement's goal of limiting the increase in global temperature to 1.5° or 2°C above preindustrial levels requires rapid reductions in greenhouse gas emissions. Although reducing emissions from fossil fuels is essential for meeting this goal, other sources of emissions may also preclude its attainment. We show that even if fossil fuel emissions were immediately halted, current trends in global food systems would prevent the achievement of the 1.5°C target and, by the end of the century, threaten the achievement of the 2°C target. Meeting the 1.5°C target requires rapid and ambitious changes to food systems as well as to all nonfood sectors. The 2°C target could be achieved with less-ambitious changes to food systems, but only if fossil fuel and other nonfood emissions are eliminated soon.


Establishing nationally representative benchmarks of farm-gate nitrogen and phosphorus balances and use efficiencies on Irish farms to encourage improvements

Science of the Total Environment 720 (2020)

IA Thomas, C Buckley, E Kelly, E Dillon, J Lynch, B Moran, T Hennessy, PNC Murphy

© 2020 Elsevier B.V. Agriculture faces considerable challenges of achieving more sustainable production that minimises nitrogen (N) and phosphorus (P) losses and meets international obligations for water quality and greenhouse gas emissions. This must involve reducing nutrient balance (NB) surpluses and increasing nutrient use efficiencies (NUEs), which could also improve farm profitability (a win-win). To set targets and motivate improvements in Ireland, nationally representative benchmarks were established for different farm categories (sector, soil group and production intensity). Annual farm-gate NBs (kg ha−1) and NUEs (%) for N and P were calculated for 1446 nationally representative farms from 2008 to 2015 using import and export data collected by the Teagasc National Farm Survey (part of the EU Farm Accountancy Data Network). Benchmarks for each category were established using quantile regression analysis and percentile rankings to identify farms with the lowest NB surplus per production intensity and highest gross margins (€ ha−1). Within all categories, large ranges in NBs and NUEs between benchmark farms and poorer performers show considerable room for nutrient management improvements. Results show that as agriculture intensifies, nutrient surpluses, use efficiencies and gross margins increase, but benchmark farms minimise surpluses to relatively low levels (i.e. are more sustainable). This is due to, per ha, lower fertiliser and feed imports, greater exports of agricultural products, and for dairy, sheep and suckler cattle, relatively high stocking rates. For the ambitious scenario of all non-benchmark farms reaching the optimal benchmark zone, moderate reductions in farm nutrient surpluses were found with great improvements in profitability, leading to a 31% and 9% decrease in N and P surplus nationally, predominantly from dairy and non-suckler cattle. The study also identifies excessive surpluses for each level of production intensity, which could be used by policy in setting upper limits to improve sustainability.


Can Attributional Life Cycle Assessment Tell us How to Farm and Eat Sustainably?

Integrated Environmental Assessment and Management Wiley 16 (2020) 400-402

J Lynch, T Garnett


Demonstrating GWP*: a means of reporting warming-equivalent emissions that captures the contrasting impacts of short- and long-lived climate pollutants

Environmental Research Letters IOP Publishing 15 (2020) 044023

JM Lynch, M Cain, RT Pierrehumbert, M Allen

The atmospheric lifetime and radiative impacts of different climate pollutants can both differ markedly, so metrics that equate emissions using a single scaling factor, such as the 100-year Global Warming Potential (GWP100), can be misleading. An alternative approach is to report emissions as 'warming-equivalents' that result in similar warming impacts without requiring a like-for-like weighting per emission. GWP*, an alternative application of GWPs where the CO2-equivalence of short-lived climate pollutant (SLCP) emissions is predominantly determined by changes in their emission rate, provides a straightforward means of generating warming-equivalent emissions. In this letter we illustrate the contrasting climate impacts resulting from emissions of methane, a short-lived greenhouse gas, and CO2, and compare GWP100 and GWP* CO2-equivalents for a number of simple emissions scenarios. We demonstrate that GWP* provides a useful indication of warming, while conventional application of GWP100 falls short in many scenarios and particularly when methane emissions are stable or declining, with important implications for how we consider 'zero emission' or 'climate neutral' targets for sectors emitting different compositions of gases. We then illustrate how GWP* can provide an improved means of assessing alternative mitigation strategies. GWP* allows warming-equivalent emissions to be calculated directly from CO2-equivalent emissions reported using GWP100, consistent with the "Paris Rulebook" agreed by the UNFCCC. It provides a direct link between emissions and anticipated warming impacts, supporting stocktakes of progress towards a long-term temperature goal and compatible with cumulative emissions budgets.


Can technology help achieve sustainable intensification? Evidence from milk recording on Irish dairy farms

Land Use Policy 92 (2020) 104437

L Balaine, EJ Dillon, D Läpple, J Lynch

This article explores the potential of a farm technology to simultaneously improve farm efficiency and provide wider environmental and social benefits. Identifying these ‘win-win-win’ strategies and encouraging their widespread adoption is critical to achieve sustainable intensification. Using a nationally representative sample of 296 Irish dairy farms from 2015, propensity score matching is applied to measure the impact of milk recording on a broad set of farm sustainability indicators. The findings reveal that the technology enhances economic sustainability by increasing dairy gross margin and milk yield per cow. Furthermore, social sustainability is improved through a reduction in milk bulk tank somatic cell count (an indicator of animal health and welfare status). Conversely, milk recording (as it is currently implemented) does not impact farm environmental sustainability, represented by greenhouse gas emission efficiency. While the study shows that milk recording is a ‘win-win’ strategy, ways of improving current levels of utilisation are discussed so that milk recording achieves its ‘win-win-win’ potential in the future.


Improved calculation of warming-equivalent emissions for short-lived climate pollutants

npj Climate and Atmospheric Science Springer Science and Business Media LLC 2 (2019) 29

M Cain, J Lynch, MR Allen, JS Fuglestvedt, DJ Frame, AH Macey


Availability of disaggregated greenhouse gas emissions from beef cattle production: A systematic review

Environmental Impact Assessment Review Elsevier 76 (2019) 69-78

J Lynch

Agriculture is a significant source of anthropogenic greenhouse gas (GHG) emissions, and beef cattle are particularly emissions intensive. GHG emissions are typically expressed as a carbon dioxide equivalent (CO2e) ‘carbon footprint’ per unit output. The 100-year Global Warming Potential (GWP100) is the most commonly used CO2e metric, but others have also been proposed, and there is no universal reason to prefer GWP100 over alternative metrics. The weightings assigned to non-CO2 GHGs can differ significantly depending on the metric used, and relying upon a single metric can obscure important differences in the climate impacts of different GHGs. This loss of detail is especially relevant to beef production systems, as the majority of GHG emissions (as conventionally reported) are in the form of methane (CH4) and nitrous oxide (N2O), rather than CO2. This paper presents a systematic literature review of harmonised cradle to farm-gate beef carbon footprints from bottom-up studies on individual or representative systems, collecting the emissions data for each separate GHG, rather than a single CO2e value. Disaggregated GHG emissions could not be obtained for the majority of studies, highlighting the loss of information resulting from the standard reporting of total GWP100 CO2e alone. Where individual GHG compositions were available, significant variation was found for all gases. A comparison of grass fed and non-grass fed beef production systems was used to illustrate dynamics that are not sufficiently captured through a single CO2e footprint. Few clear trends emerged between the two dietary groups, but there was a non-significant indication that under GWP100 non-grass fed systems generally appear more emissions efficient, but under an alternative metric, the 100-year global temperature potential (GTP100), grass-fed beef had lower footprints. Despite recent focus on agricultural emissions, this review concludes there are insufficient data available to fully address important questions regarding the climate impacts of agricultural production, and calls for researchers to include separate GHG emissions in addition to aggregated CO2e footprints.


Climate impacts of cultured meat and beef cattle

Frontiers in Sustainable Food Systems Frontiers Media 3 (2019) 5

J Lynch, R Pierrehumbert

Improved greenhouse gas (GHG) emission efficiency of production has been proposed as one of the biggest potential advantages of cultured meat over conventional livestock production systems. Comparisons with beef are typically highlighted, as it is a highly emissions intensive food product. In this study, we present a more rigorous comparison of the potential climate impacts of cultured meat and cattle production than has previously been made. Warming impacts are evaluated using a simple climate model that simulates the different behaviors of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O), rather than relying on carbon dioxide equivalent (CO2e) metrics. We compare the temperature impact of beef cattle and cultured meat production at all times to 1,000 years in the future, using four synthetic meat GHG footprints currently available in the literature and three different beef production systems studied in an earlier climate modeling paper. Cattle systems are associated with the production of all three GHGs above, including significant emissions of CH4, while cultured meat emissions are almost entirely CO2 from energy generation. Under continuous high global consumption, cultured meat results in less warming than cattle initially, but this gap narrows in the long term and in some cases cattle production causes far less warming, as CH4 emissions do not accumulate, unlike CO2. We then model a decline in meat consumption to more sustainable levels following high consumption, and show that although cattle systems generally result in greater peak warming than cultured meat, the warming effect declines and stabilizes under the new emission rates of cattle systems, while the CO2 based warming from cultured meat persists and accumulates even under reduced consumption, again overtaking cattle production in some scenarios. We conclude that cultured meat is not prima facie climatically superior to cattle; its relative impact instead depends on the availability of decarbonized energy generation and the specific production systems that are realized.


Potential development of Irish agricultural sustainability indicators for current and future policy evaluation needs

Journal of Environmental Management Elsevier 230 (2018) 434-445

J Lynch, T Donnellan, JA Finn, E Dillon, M Ryan

There is a significant and detailed range of sustainability indicators for Irish agri-food production, but there remain areas where further indicator development or new indicators could prove valuable. This review provides an outline of potential developments in Irish assessment of agricultural sustainability following the latest research and in order to meet policy demands. Recent research findings have suggested means of improved quantitative modelling of greenhouse gas emissions, but additional dietary and soil data may be important for this, especially for the potential inclusion of any soil sequestration. This information could also benefit more detailed modelling of nutrient losses to water. Specific concerns over pesticide and antibiotic use may require additional survey work on the particular locations or types of farms of interest. Biodiversity monitoring could be improved by expanding the range of results-oriented agri-environment schemes or employing remote-sensing habitat monitoring, likely supplemented with targeted field surveys for specific objectives. Farm-level economic sustainability is largely well-covered, but additional data collection may be of benefit to address specific issues such as labour costs. Recent additional surveys on farm-level social sustainability have addressed important social indicators of isolation and access to local services, and could be rolled out on a larger number of farms in the future. Wider societal concerns such as animal welfare, genetically modified materials in foodstuffs and antibiotic resistance have limited indicators currently available, and could also benefit from additional surveys. The breadth and detail required in agri-food sustainability indicators present a significant challenge to survey design and implementation, but many developments can be achieved without additional surveys through the use of remote sensing and geospatial technologies and integration of existing datasets. Despite the important benefits of further developments in Irish sustainability indicators, consideration must also be given to farmer confidentiality and survey fatigue.


Assessing the performance of commercial farms in England and Wales: Lessons for supporting the sustainable intensification of agriculture

Food and Energy Security Wiley 7 (2018) e00150

L Firbank, J Elliott, RH Field, J Lynch, WJ Peach, S Ramsden, C Turner

Understanding the trade‐offs between yield, ecosystem services, and other societal benefits is a fundamental prerequisite for the sustainable intensification of agriculture. Here, we develop and test an holistic approach to assessing farm performance across production, social, financial, and environmental dimensions. A longlist of potential indicators was reduced to a smaller subset of Headline Indicators, covering financial performance, levels of food production (standardized in terms of energy content), social characteristics of the farmer (including age, level of education, and degree of business cooperation), hours worked on the farm and provision of public access, and environmental quality (including impacts on climate regulation and water quality). A new index for biodiversity was created and validated, based on land use and management. Data were collected from 59 English and Welsh farms, using a questionnaire structured to be similar to the UK Farm Business Survey. Data were analyzed per farm and per unit area. The main overall variation in Headline Indicators was due to positive relationships between production, profitability and predicted levels of nitrate and GHG emissions, while social variables and biodiversity were generally unrelated to production. Cereal production was associated with relatively low levels of GHG emissions per unit of food production. There were strong differences in indicator profiles between farm types. Such metrics have value in helping understand how best to drive sustainable intensification, especially as it should involve reducing the pollution footprint of food production.


Grand challenges in sustainable intensification and ecosystem services

Frontiers in Sustainable Food Systems Frontiers Media 2 (2018) 7-

LG Firbank, S Attwood, V Eory, Y Gadanakis, JM Lynch, R Sonnino, T Takahashi

Arguably the greatest grand challenge for humankind is to keep the biosphere within its safe and just operating space, providing sufficient resources to meet people’s needs without exceeding the Earth’s capacity to supply them (Raworth, 2012). “Safe” is defined in terms of keeping planetary environmental processes, through mechanisms such as climate regulation and improved nutrient cycles, within limits over the long term (Rockstrom et al., 2009). “Just” is increasingly being interpreted in terms of meeting the UN Sustainable Development Goals, with targets addressing various forms of equity as well as biophysical needs (Griggs et al., 2013). Keeping the biosphere within the operating space requires that we produce the food we need, along with the ecosystem and socioeconomic goods and services we require (Garnett et al., 2013). By definition, achieving this challenge also means achieving the sustainable intensification (SI) of agriculture, whereby more food is produced from the same area of land (or water), with reduced or reversed negative environmental impacts accompanied by a range of positive societal and environmental co-benefits. SI is variously considered as a goal (Royal Society, 2009), a process (Firbank et al., 2013), a trade-off between economic production activity and ecological performance (Gadanakis et al., 2015), or a suite of interventions (Godfray and Garnett, 2014).


Integrating the economic and environmental performance of agricultural systems: a demonstration using farm business survey data and Farmscoper

Science of the Total Environment Elsevier 628–629 (2018) 938-946

J Lynch, D Skirvin, P Wilson, S Ramsden

There is a continued need to monitor the environmental impacts of agricultural systems while also ensuring sufficient agricultural production. However, it can be difficult to collect relevant environmental data on a large enough number of farms and studies that do so often neglect to consider the financial drivers that ultimately determine many aspects of farm management and performance. This paper outlines a methodology for generating environmental indicators from the Farm Business Survey (FBS), an extensive annual economic survey of representative farms in England and Wales. Data were extracted from the FBS for a sample of East Anglian cereal farms and south western dairy farms and converted where necessary to use as inputs in ‘Farmscoper’; farm-level estimates of nitrate, phosphorus and sediment loadings and ammonia and greenhouse gas emissions were generated using the Farmscoper model. Nitrate losses to water, ammonia and greenhouse gas emissions were positively correlated with food energy production per unit area for both farm types; phosphorus loading was also correlated with food energy on the dairy farms. Environmental efficiency indicators, as measured by either total food energy or financial output per unit of negative environmental effect, were calculated; greenhouse gas emission efficiency (using either measure of agricultural output) and nitrate loading efficiency (using financial output) were positively correlated with profitability on cereal farms. No other environmental efficiency measures were significantly associated with farm profitability and none were significant on the dairy farms. These findings suggest that an improvement in economic performance can also improve environmental efficiency, but that this depends on the farm type and negative environmental externality in question. In a wider context, the augmentation of FBS-type data to generate additional environmental indicators can provide useful insights into ongoing research and policy issues around sustainable agricultural production.