Understanding the environmental impact of global dairy production

Abstract

Some popular press articles and social media discussions continue to cite the erroneous data presented in the “Livestock’s Long Shadow” publication (FAO, 2006). While this data has subsequently been shown to be incorrect (Pitesky et al, 2009), on-going discussions about the high level of impact of livestock on global GHG emissions continue to be shared as fact nearly 15 years later. There is inherent complexity in studying the biology of livestock for meat and milk production. Efforts to make this complexity more understandable can lead to incorrect assumptions and create an unfavorable and incorrect view of dairy and livestock production for the general public. An unfavorable image of animal production creates added challenge for dairy and livestock producers. If the general public is to believe information about the environmental impact of livestock production, it is critical that that information is both accurate and easily understood. The following paper that highlights sustainable animal science and practices by Capper and Cady (2020) provides a review using modeling techniques for more recent updates (2007–2017), GHG emissions and overall impact of dairy production on environmental sustainability. Additionally, the contribution of ruminants to overall GHG emissions has also been more recently been summarized by Mitloehner (2018.)

Introduction

Past estimates of the contribution of global livestock production to GHG emissions were 14.5% with dairy production accounting for 2.9% of that total (FAO, 2013). Since the time of those estimates, the dairy industry in both the US as well as worldwide has undergone significant changes. The removal of milk quotas from dairies in the European Union in 2015–2017 as well as shifts in milk production in China and other areas of the world mean that these estimates may be outdated and more current research is needed to assess the impact of the dairy industry on GHG emissions and overall environmental impacts. This current paper by Capper and Cady (2020), used a modeling approach to show that from 2007 to 2017 global production of ECM increased by 13.6% with increases in milk fat and protein percentages of 12.1% and 10.3%, respectively at the same time that the total dairy cattle population required to produce 1 MMT of ECM was reduced. Furthermore, modeling results showed that efficiency of feed use across the dairy production system was positively impacted by lower somatic cell counts, calving interval and length of dry period. Of concern is the decrease in number of lifetime lactations shown in the model, but this trend did not outweigh the increases in ECM. Also reported was a reduction in the land use for milk production, which would have a positive impact on overall sustainability. Capper and Cady (2019) modeling results showed that despite a nearly 14% increase in ECM the GHG emissions increased by only 1% over the same time period. However, there are several other studies that could be utilized to increase the robustness of the current modeling results. Work by Hristov et al. (2013a) indicated a more moderate impact of feed efficiency on enteric methane emissions compared to the current paper. Inclusion of feed ingredients or additives that mitigate methane production often depress feed intake and thus have the potential to decrease overall productivity. Additionally, Hristov et al. (2013b) reported that there was not enough evidence linking low residual feed intake to lower methane production per unit of feed. The authors of the current paper agree with findings of Hristov et al. (2013a, 2013b) that the sources of methane, enteric or manure, must continue to be evaluated in order to provide more accurate data. Since feed production is closely associated with animal productivity in many dairy farming systems, the impact of land use with integrated crop/livestock systems can also be a key influencer to GHG emissions and fossil fuel usage. Malcolm et al. (2015) reported similar GHG emissions from dairy farm systems that had the same level of milk production, but with different system characteristics like amount of fossil fuel used and imported or grown grains. Animal production systems are complex, and modeling offers a way to evaluate the impact of the whole system in a cost-effective manner. However, it is imperative that all available data be utilized in order to make the best use of the models. With regard specifically to methane emissions, a review by Hristov et al. (2018) reported that due to the complexity of biological processes involving livestock production, measurements are best done with large data sets and global collaboration.

Sustainable production of milk and meat to feed a growing world population has been critically discussed in recent years. In order to continue to be sustainable, a production system will need to make incremental improvements in efficiency at the individual farm level that keep businesses economically and environmentally viable. The complexity of not only the biology of the animal, but also the various parts of the production systems can benefit from the use of large datasets and a sound modeling approach to better understand the interrelated aspects of changes in the system. Further research to study the impact of livestock and dairy production on a more global scale in order to determine the true contributions of these production systems not only for GHG emissions but also for water use, land use, social acceptability and other factors will continue to improve modeling estimates and information for the public in the future.