Evaluating greenhouse gas mitigation and climate change adaptation in dairy production using farm simulation

Process-level modeling at the farm scale provides a tool for evaluating strategies for both mitigating greenhouse gas emissions and adapting to climate change. The Integrated Farm System Model (IFSM) simulates representative crop, beef, or dairy farms over many years of weather to predict performance, economics, and environmental impacts including various emissions and a farm-gate life cycle assessment of carbon, energy, water, and reactive nitrogen footprints of the feed, meat, or milk produced. To illustrate use of the model, a representative dairy farm in central New York was simulated over 25 years of recent historical weather to determine the environmental benefits and economic costs of alternative manure handling strategies. Use of an enclosed manure storage with a flare to burn the methane produced decreased the farm-gate carbon footprint of the milk produced by 20% at an increased annual cost of $42 cow^-1. Using an anaerobic digester to produce gas and electricity used on the farm reduced the carbon footprint by 19% and reduced profitability by $56 cow-1. The addition of subsurface injection of manure along with a reduction in N fertilizer use greatly reduced ammonia emission from the farm and increased annual profit by $9 cow^-1. Climate change is projected to affect many aspects of dairy production, including growing season length, crop growth processes, harvest timing and losses, cattle performance, nutrient emissions and losses, and ultimately farm profitability. Climate projections for high and low emission scenarios were downscaled from nine general circulation models. IFSM was then used to simulate the same New York dairy farm over 25-year periods using recent, mid-century, and late century climate projected by each of the climate models. Simulations were done without and with adaptation through modified crop varieties and planting and harvest dates. Forage production normally increased with projected climate change and corn grain yields decreased, and together feed production was maintained. Warmer temperatures increased volatile loss of ammonia N, and changes in precipitation patterns increased nutrient runoff losses in surface water. The reactive N footprint of the milk produced was increased by 2% to 11% with the change in climate, but other environmental footprints were relatively unaffected. With appropriate adaptation to climate change, annual farm profitability increased by about $100 cow^-1. However, for the high emission, late century projection, profit decreased by $10 cow^-1 and the risk or annual variance in profit increased by 34%, reflecting greater annual variation in crop and animal productivity. Whole-farm and climate models provide useful tools for studying the benefits and costs of greenhouse gas mitigation and the adaptation of farms to changing climate.