The final paper of the Greenhouse Gases and Animal Agriculture (GGAA) Conference in 2010 posed the question ‘What place for livestock on a re-greening earth?’ and challenged researchers to look for new ways to incorporate livestock into ecosystems to maximise societal and ecological benefits while minimising harm (Janzen, Reference Janzen2011). Livestock farming faces substantial challenges of reducing its environmental effects while also responding to the growing demand for animal protein from an expanding and increasingly affluent population. At first sight, these objectives are contradictory, but ‘dilution of maintenance’ effects mean that more productive animals are usually more efficient, with reduced emissions of greenhouse gases (GHG) per unit product. Balancing the costs and benefits of a wide range of options from disparate activities is an important part of the inter-governmental negotiations on climate change and Muldowney et al. (Reference Muldowney, Mounsey and Kinsella2013) from the Department of Agriculture, Food and the Marine in Ireland provided some context for the position of agriculture in these negotiations.

Ruminants are an important potential source of growth in food protein supply, and are particularly important because of the ability to produce high-quality protein from forages and other feeds that cannot be used directly for human or monogastric consumption. However, livestock production makes a significant contribution to total anthropogenic GHG emissions, with around 12% coming directly from livestock and their manure and a further 6% associated with deforestation to produce grazing land (Clark, Reference Clark2013). It is estimated that livestock produced 5.4 Gt CO₂e in direct emissions (as methane or nitrous oxide) in the 2005 reference period. Dairy and beef cattle accounted for 3.3 Gt CO₂e of these emissions, with just over 70% as enteric methane (Gerber et al., Reference Gerber, Hristov, Henderson, Makkar, Oh, Lee, Meinen, Montes, Ott, Firkins, Rotz, Dell, Adesogan, Yang, Tricarico, Kebreab, Waghorn, Dijkstra and Oosting2013).

We are living in exciting times to be agricultural scientists – and particularly animal scientists! Research in traditional areas such as animal nutrition, breeding and health, soil science and farm wastes has renewed prominence in addressing these global challenges. It was with great vision that Professor Takahashi and colleagues organised the first Greenhouse Gases and Animal Agriculture (GGAA) conference in Japan in 2001. Subsequent meetings were held in Switzerland (2005), New Zealand (2007) and Canada (2010). The fifth meeting in the series was organised in Ireland jointly by University College Dublin and Teagasc, with the main sessions held in UCD's O'Reilly Hall in June 2013. The Local Organising Committee comprised Dr Frank O'Mara and Dr Richard Dewhurst from Teagasc, Dr Tommy Boland and Dr Karina Pierce from UCD, and Dale Crammond from the Department of Agriculture, Food and the Marine.

In addition to setting the scene for inter-governmental negotiations on climate change (Muldowney et al., Reference Muldowney, Mounsey and Kinsella2013), the opening session also surveyed the range of mitigation options with a focus on opportunities and constraints for implementation and exploitation in GHG inventories (Gerber et al., Reference Gerber, Hristov, Henderson, Makkar, Oh, Lee, Meinen, Montes, Ott, Firkins, Rotz, Dell, Adesogan, Yang, Tricarico, Kebreab, Waghorn, Dijkstra and Oosting2013). Life cycle analysis is increasingly used to quantify the total emissions associated with production systems, allowing the user to account for trade-offs between effects and incorporate the indirect emissions. Cederberg et al. (Reference Cederberg, Henriksson and Berglund2013) reviewed the recent development and standardisation of methodologies for life cycle analysis and identified gaps in information about soil C and N fluxes, as well as a lack of studies at the farm level, particularly in developing countries. These same information gaps were identified by del Prado et al. (Reference del Prado, Crosson, Olesen and Rotz2013) after reviewing farm-scale modelling work on GHG emissions. Although it is hoped that GGAA 2013 will fill some of these gaps, it is also evident from the range of papers submitted that there is still relatively more work on methane emissions and in developed countries and relatively less work on emissions from soils and manure and from developing countries. The large number of papers submitted from Brazilian researchers, only surpassed by the number of submissions from the UK, was a notable and encouraging aspect of the meeting. Berndt and Tomkins (Reference Berndt and Tomkins2013) reviewed techniques, challenges and some routes to solutions for tropical agriculture in both Australia and Brazil.

The meeting reviewed the state-of-the-art with a number of technologies relevant to components of GHG emissions. Leahy et al. (Reference Leahy, Kelly, Ronimus, Wedlock, Altermann and Attwood2013) reviewed progress with genome sequencing of rumen micro-organisms and discussed the potential to apply detailed understanding of genes and pathways in developing mitigation strategies based on vaccines, anti-methanogenic compounds and animal breeding. Each of these mitigation options was taken up in more detail in subsequent papers: while both vaccines (Wedlock et al., Reference Wedlock, Janssen, Leahy, Shu and Buddle2013) and anti-methanogenic plant components (Cieslak et al., Reference Cieslak, Szumacher-Strabel, Stochmal and Oleszek2013) show potential in mitigating methane production, there are serious challenges related to the resilience of the microbial community and progress towards implementation in vivo has been slow. This reinforces the need to understand the basis for the resilience of the microbial community in microbial genomics and metagenomics (Leahy et al., Reference Leahy, Kelly, Ronimus, Wedlock, Altermann and Attwood2013).

There has been growing interest in the potential to breed ruminants for reduced GHG emissions and the conference considered the two distinct approaches that are in progress. Pinares-Patiño et al. (Reference Pinares-Patiño, Hickey, Young, Dodds, MacLean, Molano, Sandoval, Kjestrup, Harland, Pickering and McEwan2013) present the first substantive data on genetic parameters for methane production from sheep. Individual methane measurements are costly and laborious, so progress has been slow, but the authors now have data from 1225 animals in their analysis. The indirect approach to reducing methane production per unit product is to select for factors such as feed conversion efficiency and longevity and Basarab et al. (Reference Basarab, Beauchemin, Baron, Ominski, Guan and Miller2013) discussed this in relation to their extensive work with the residual feed intake trait.

Excreta contribute around 25% of direct GHG emissions from cattle (Gerber et al., Reference Gerber, Hristov, Henderson, Makkar, Oh, Lee, Meinen, Montes, Ott, Firkins, Rotz, Dell, Adesogan, Yang, Tricarico, Kebreab, Waghorn, Dijkstra and Oosting2013). Dijkstra et al. (Reference Dijkstra, Oenema, van Groenigen, Spek, van Vuuren and Bannink2013) provided an overview of the effects of diet on the level and form of Nitrogen in urine and explored implications for nitrous oxide emissions. Petersen et al. (Reference Petersen, Blanchard, Chadwick, del Prado, Edouard, Mosquera and Sommer2013) provided an update on techniques for mitigating GHG emissions from manures – both during storage, as well as during and after application. Two papers in the soil/manure sessions covered technologies outside the usual range of animal, manure and soil managements. There is increasing use of livestock manures and forages in anaerobic digestion systems and Pucker et al. (Reference Pucker, Jungmeier, Siegl and Pötsch2013) considered some of the implications of agricultural managements on these systems. There was much interest at previous GGAA meetings about the use of nitrification inhibitors such as dicyandiamide applied to soil to reduce nitrate leaching and nitrous oxide emissions (e.g. de Klein et al., Reference de Klein, Cameron, Di, Rys, Monaghan and Sherlock2011). Subbarao et al. (Reference Subbarao, Rao, Nakahara, Sahrawat, Ando and Kawashima2013) introduced the production of biological nitrification inhibitors in the rhizosphere of certain plants, most notably the tropical grasses of Brachiaria spp.

Previous GGAA conferences have focused on mitigation of GHG, with little mention of adaptation issues. We were able to include two papers on adaptation through the support of the EU Framework Programme 7 project ‘AnimalChange’. Hoffmann (Reference Hoffmann2013) used FAO information about a wide range of locally adapted breeds to identify potential to respond to changing climate and urge further effort in characterising these important resources. Skuce et al. (Reference Skuce, Morgan, van Dijk and Mitchell2013) reviewed some of the health issues associated with climate change, with a focus on parasites that would be affected both by increasing stocking rates and changes in temperature and rainfall patterns.

This Special Issue also contains papers relating to a series of workshop presentation on developments in techniques for GHG research. The strengths and weakness of the respiration chamber and sulphur hexafluoride (SF₆) techniques for estimating methane emissions are well recognised and were discussed at previous GGAA meetings (e.g. Pinares-Patiño et al., Reference Pinares-Patiño and Clark2008). This session focused on alternative techniques: micrometeorological methods (McGinn, Reference McGinn2013), the laser methane detector (Chagunda, Reference Chagunda2013), chemical markers including methanogen-specific lipids (McCartney et al., Reference McCartney, Bull and Dewhurst2013) and an increasing array of approaches using spot samples of breath (Hegarty, Reference Hegarty2013). Clough et al. (Reference Clough, Müller and Laughlin2013) outlined and reviewed the increasing range of stable isotope methods used to track Nitrogen in the soil and atmosphere.

Having started off by considering the ‘big picture’ and moving through a series of technical options relating to various components of animal, microbial, soil or atmospheric processes, the meeting concluded with papers on models designed to synthesise this information, particularly at the farm scale. del Prado et al. (Reference del Prado, Crosson, Olesen and Rotz2013) provided an overview of modelling in the GHG area and provided new insights by making comparisons between models and considering potential to make links between different GHG models and other physical and economic models. Wheeler et al. (Reference Wheeler, Ledgard and Boyes2013) described the use of the OVERSEER model to produce farm-specific estimates of emissions per unit product for New Zealand individual farms, while Murphy et al. (Reference Murphy, Crosson, O'Brien and Schulte2013) described the development of the CARBON NAVIGATOR as a knowledge transfer tool to guide farmers and advisers in reducing emissions from Irish dairy and beef herds.

A special word of thanks is due to the Scientific Committee who in addition to guest editing the papers in this Special Issue, also chaired the scientific sessions at the meeting and reviewed over 350 offered contributions that are published as one-page summaries in Advances in Animal Biosciences volume 4, part 2. These are Dr Gary Lanigan, Professor Nick Holden, Professor Dominic Moran, Professor Dave Chadwick, Dr David Kenny, Dr Ed Charmley, Dr Tianhai Yan, Professor Jamie Newbold and Dr Padraig O'Kiely.