I’ve had a quick glance through of the deal between the Conservatives and the Liberal Democrats available from the BBC and other places:
It has this to say on the enviroment:
The parties agree to implement a full programme of measures to fulfil our joint ambitions for a low carbon and eco-friendly economy, including:
The establishment of a high-speed rail network.
The building phase of High Speed Rail will emit large quanities of CO2: the current proposal is not part of a low carbon economy.