Projected impact of future climate conditions on the agronomic and environmental performance of Canadian dairy farms

Highlights

• Future climate conditions will favor perennial forage crops and warm-season crops.

• The yield of small-grain cereals is expected to decrease slightly.

• Ammonia emissions from manure storage and handling are expected to increase.

• Methane emissions from manure storage are expected to increase.

• Greater change is expected in N than C footprint: farm N-use efficiency is crucial.

Abstract

Climate change is expected to increase agricultural productivity in Canada and in other northern countries but this increase will likely affect the environmental performance of dairy farms, one of the most important agricultural sectors in Canada. The objective of this study was to project the impact of climate change on the agronomic and environmental performance of a virtual dairy farm in each of three climatically contrasting areas of Canada through near future (2020–2049) and distant future (2050–2079) periods, using the Integrated Farm System Model (IFSM) and three climate models (CanESM2, CanRCM4, and HadGEM2). Under future climate conditions and relative to a reference period (1971–2000), projected yields of perennial forages and warm-season crops increased, whereas those of small-grain cereals decreased slightly. Projected ammonia emissions increased on virtual farms of the three areas and in all future scenarios (+ 18% to + 54%). Methane emissions from manure storage increased (+ 26% to + 120%), whereas those from enteric fermentation and field manure application decreased. Projected farm N₂O emissions changed only slightly relative to the reference period. Fossil fuel CO₂ emissions related to field operations increased slightly, due to a larger number of forage cuts per year in future scenarios, but CO₂ emissions related to grain drying decreased substantially. Projected losses of P increased on virtual farms of the three areas. The projected reactive N footprint of dairy farms in future scenarios varied more (− 15% to + 46%) relative to the reference period than the C footprint (− 5% to + 9%). Although greenhouse gas mitigation should be a priority for dairy farms under future climate conditions, it should not overshadow the need for strategies to reduce reactive N losses.

Introduction

Dairying in Canada and elsewhere is known to have significant environmental impacts. Total greenhouse gas (GHG) emissions from Canadian milk production, based on annual milk production of 81.8 million hL in 2015 (Canadian Dairy Information Centre, 2015), can be estimated at 8.4 Mt CO₂ equivalent (CO₂eq) (Quantis Canada et al., 2012). Nevertheless, the environmental impact of dairy farms is not limited to GHG emissions, as the dairy sector also generates NH₃ emissions (Sheppard et al., 2011b) and contributes to water pollution through nitrate and P losses (Paul and Zebarth, 1997, Simard et al., 1995), as has been demonstrated in Canadian studies.

Although a number of recent studies proposed mitigation measures for reducing the environmental impact of Canadian dairy farms (Hawkins et al., 2015, Chai et al., 2016, Jayasundara et al., 2016), little research has sought to project how climate change will affect the environmental performance of Canadian dairy farms in the future. Based on projections derived for many northern regions in the world (Tatsumi et al., 2011), climate change can be expected to have a positive impact on crop productivity in Canada given the expected increased CO₂ concentration, warmer temperature, and longer growing season (Qian et al., 2016a, Qian et al., 2016b, Smith et al., 2013, Wang et al., 2012). However, Canadian studies using simulation models have projected an increase in N₂O emissions from crop production systems as a consequence of higher N rates required to support expected greater crop yield (Smith et al., 2013), as well as an increase in annual NO₃ losses from an agricultural watershed due to expected increase in precipitation (Dayyani et al., 2012). Climate change can reasonably be expected to affect other environmental emissions as well, since it is known, for example, that higher temperatures increase NH₃ and CH₄ emissions from manure (Sheppard et al., 2011b, Jayasundara et al., 2016) and that an increase in precipitation intensity leads to higher P losses (Messing et al., 2015). A better understanding of the overall agronomic and environmental effects of changes in temperature, precipitation, and atmospheric CO₂ concentrations on dairy farming through modelling would enable the identification of the best suited mitigation measures and adaptation strategies for sustainable production in the future (Rotz et al., 2016).

A dairy farm is a complex system, and comprehensive whole-farm simulations are required to describe the internal cycling of nutrients on the farm and the nutrient exchange that occurs between the farm and its environment (Schils et al., 2007). Several farm-scale models have been developed in recent years, such as DairyWise in the Netherlands (Schils et al., 2007), WFM (Whole-Farm Model) in New Zealand (Beukes et al., 2008, Wastney et al., 2002), GAMEDE (Global Activity Model for Evaluating the sustainability of Dairy Enterprises) in France (Vayssières et al., 2009a, Vayssières et al., 2009b), and the Integrated Farm System Model (IFSM) in the United States (Rotz et al., 2015). The IFSM is the only process-based farm-scale model that has been developed to represent dairy, beef, and cash-crop farms in the temperate regions of the northern United States and southern Canada. The model provides an assessment of the economic and environmental sustainability of dairy farms (Rotz et al., 2014). The model's components include crops and soils, harvest and storage, animal feeding, manure storage and handling, and economic analysis (Rotz et al., 2015). Jégo et al. (2015) previously showed that IFSM can be used to simulate the current yield and nutritive value of perennial forage crops and annual crops in eastern Canada. Thivierge et al. (2016) used IFSM to simulate the future yield and nutritive value of an alfalfa (Medicago sativa L.) and timothy (Phleum pratense L.) mixture in eastern Canada. Environmental losses simulated by IFSM (e.g. NH₃ and GHG emissions; N and P losses to water) have been compared with reports in the literature and with farm measurements and have been found to be in the realistic range (Chianese et al., 2009a, Chianese et al., 2009b, Chianese et al., 2008, Rotz et al., 2014, Rotz et al., 2011).

The objective of this study was to examine the projected impact of climate conditions in the near (2020–2049) and distant (2050–2079) future on the agronomic and environmental performance of one virtual dairy farm in each of three climatically contrasting areas of Canada, by using IFSM with three climate models and under two representative concentration pathways (RCP 4.5 and 8.5). The main hypotheses were that under future climate conditions, (1) yield would increase for most crops except for small-grain cereals, (2) emissions of N₂O, CH₄, and NH₃ in the atmosphere as well as losses of N and P in water through runoff and leaching would increase, and (3) N and C footprints would increase, particularly in the distant future.