We've signed up to cut our greenhouse gas emissions by 40% over the next ten years. At the same time, the number of cows in the country is growing annually. As part of RTÉ's Climate week, Fran McNulty and Aisling Moloney explain the difficult decision policy makers have to make - it seems we can hit our targets, or we can continue to allow the national herd to increase, but we can't do both.