From the Forest & Bird website:
Coal is the dirtiest fuel – burning coal is the single largest global source of greenhouse gases, which are causing climate change. Burning coal also causes air pollution which has a direct effect on people’s health.
As well as the carbon released when coal is burnt, trapped methane (another greenhouse gas) is also released when coal is mined. For example Pike River Coal’s planned coal mining over the next 20 years will release trapped methane equivalent to more than all the dairy cows on the West Coast.
Maybe Forest & Bird want to now use a different example.