Achieving ambitious climate targets: is it economical for New Zealand to invest in agricultural GHG mitigation?

Reducing agricultural greenhouse gas (GHG) emissions, which contribute approximately 24% of global emissions, is important to efficiently achieve the goals of the Paris Agreement; however, most mitigation options have focused on industrialized, not pastoral farming practices. New Zealand (NZ) has ambitious GHG reduction targets, but biogenic emissions from the agricultural sector are nearly half of total annual emissions and hence must be an integral part of the solution. We use a national-level economic land use model to estimate the benefits and costs of implementing land-based GHG emissions reduction practices that are currently available and/or under development. Results indicate the cost and effectiveness of modeled practices are highly variable, with individual practices capable of reducing gross GHGs by 2% to 62%. Methane inhibitors are estimated to be highly effective but costly, while targeted urine patch treatments are cheap but less effective. Afforestation and methane vaccines cost less than $50/tCO₂e and could reduce NZ's GHG emissions by at least 20%. Using a mix of current and emerging mitigation practices to achieve reduction targets ranging from 10% to 50% could cost an average of $14 to $76/tCO₂e, potentially much less than estimates for achieving similar targets from NZ's energy and transportation sectors. Sensitivity analysis indicates that commercialization of an effective methane vaccine at a cost that is typical of other livestock vaccines is critical to achieving a 50% gross emissions reduction target. Without it, a large portion of land could be left fallow. The practices and technologies evaluated in this paper are not unique to New Zealand and could be adopted globally, thereby helping other nations achieve their climate mitigation goals more cost-effectively. (letter)