This paper presents a case study in which the effects of agri-envirorimental policy on two Mediterranean-type farming systems, grazing dominant and cropping dominant, are contrasted. Two greenhouse gas abatement policies are examined; an emissions taxation policy and an emissions restrictions policy. The study seeks to determine firstly, how the policy impacts on the farming systems, and from that, how the nature of the farming systems impact on the effectiveness of the policy. It is shown that relative costs of abatement are higher for the grazing-dominant farming system. However, in the absence of technological change to aid abatement, the cost of substitution from high emitting enterprises, such as livestock, to low emitting enterprises, such as crop production, will determine the cost of abatement. For both farming systems the restriction policy is found to be more effective and economically efficient than the taxation policy. The analysis found that crediting trees as carbon sinks can significantly reduce the costs of abatement. At predicted emissions permit prices, trees would be adopted by both farming systems to offset farm greenhouse gas emissions. (c) 2005 Elsevier B.V. All rights reserved.