Climate‐change effects and adaptation options for temperate pasture‐based dairy farming systems: a review

Abstract

Temperate pasture‐based dairy farming systems with low input of supplementary feed are vulnerable to changes in climate through alterations in feed supply and nutritive value. Although current systems in New Zealand (NZ) and southeast Australia have been successful in adapting to variable weather conditions, they will need to undergo further changes to continue to profit in the future. This review describes predicted changes in climate in NZ and southeast Australia, likely effects on the feedbase used in the pasture‐based dairy industry and the flow‐on effect on milk‐solids production and profitability. Potential adaptation options that will allow farmers to take advantage of new opportunities and minimize any negative impacts of climate change are also identified. For example, in many regions, annual pasture production is predicted to increase due to carbon dioxide fertilization and warmer temperatures during winter/spring. Production may decline, however, in regions with either reduced rainfall or severe flooding. Should this occur, farmers could strategically use supplementary feed, reduce stocking rates, irrigate or sow alternative plant species with greater drought tolerance. Pasture‐based dairy systems have high levels of adaptive capacity, and there are opportunities to continue to improve production efficiencies particularly where rainfall change is small. Further investigation into possible adaptation options is required to determine their impact on milk‐solids production and profitability, as well as to identify additional options.

Predicted Yield and Nutritive Value of an Alfalfa–Timothy Mixture under Climate Change and Elevated Atmospheric Carbon Dioxide

“…Elevated temperature and changes in precipitation might offset the positive crop response to elevated [CO 2 ] (Morgan et al, 2004b;Hatfield et al, 2011;Izaurralde et al, 2011;Lee et al, 2013;Piva et al, 2013).…”

“…Increased temperature was shown to reduce forage or pasture nutritive value (Thorvaldsson, 1992;Wan et al, 2005;Thorvaldsson et al, 2007;Lee et al, 2013), and specifically to reduce the in vitro neutral detergent fiber (NDF) digestibility in timothy (Bertrand et al, 2008;Jing et al, 2013b) and in vitro dry matter digestibility in alfalfa (Sanz-Sáez et al, 2012). Elevated atmospheric [CO 2 ] has been found to decrease the crude protein (CP) concentration of several species (Milchunas et al, 2005;Soussana and Lüscher 2007;Sanz-Sáez et al, 2012;Baslam et al, 2014;Irigoyen et al, 2014;Dumont et al, 2015), including alfalfa (Bertrand et al, 2007b), and to reduce the digestibility of grasses (Morgan et al, 2004a) but not that of alfalfa (Irigoyen et al, 2014).…”

“…Previous studies have shown that rising temperatures may have a positive or negative effect on yield, depending on the current climatic conditions at a given location, the species-specific critical temperature range for growth and photosynthesis, and soil resources (Hunt et al, 1991;Riedo et al, 1999;Hatfield et al, 2011;Lee et al, 2013). This conclusion is supported by the results of the present simulations, in which rising temperatures along with small changes in precipitation caused reductions in annual forage DM yields of pure timothy, pure alfalfa, and alfalfa-timothy mixture in the warmer area (QSW), compared to increases in the colder area (QE), except in the more drastic scenario, DF8.5 (Fig.…”

“…The positive effect of increased [CO 2 ] on legume crops, which has been demonstrated in experiments and modeling studies, appears to be due to the favorable effect of elevated atmospheric [CO 2 ] on biological N 2 fixation, although the exact mechanism is not clearly understood (Zanetti et al, 1996;Lazzarotto et al, 2010). Moreover, N 2 -fixing species have been found to show a greater positive response than non-fixing species to increased atmospheric [CO 2 ], possibly because N 2 -fixing species are able to meet the higher N requirements associated with elevated [CO 2 ] (Lee et al, 2003). Growth chamber studies have produced divergent results concerning the effect of elevated [CO 2 ] on timothy yield.…”

“…Assessing the eff ects of future climate conditions (elevated temperature and precipitation changes) on forage crop production is diffi cult because they depend on the current climatic conditions at a given location, the species-specifi c critical temperature range for growth and photosynthesis, and soil resources (Hunt et al, 1991;Riedo et al, 1999;Hatfi eld et al, 2011;Lee et al, 2013). In growth chamber experiments, increased temperature reduced DM yield of timothy (Bertrand et al, 2008;Piva et al, 2013).…”