By Nick Assinder
Political correspondent, BBC News website
There was a time, not so long ago, when the UK had just the one Green Party - and it struggled to be heard.
Today there isn't a single political party in the land that doesn't claim to be the greenest of them all.
Political parties are trying to prove who is greenest
Gordon Brown and David Cameron are currently giving us a glimpse of future election battles by delivering rival speeches on the environment and climate change.
Mr Brown is doing the prime ministerial thing by suggesting the way forward is for leaders like him to broker big international agreements to affect real, significant changes in global behaviour.
That is being underlined by the prime minister who is pointing to the recent EU deal for targets on renewable energy as a clear example of how successful international deals are the way to go.
Bike-riding Mr Cameron is suggesting increased taxes on air travel to penalise bad environmental behaviour - a symbol of just how serious he wants to be seen on the issue.
But he is insisting such taxes should not be used to increase the overall tax burden.
The Lib Dems, meanwhile, can point to their past policies to claim they were there first with their suggestion of green taxes, counter-balanced by reductions in other taxes.
Sir Menzies Campbell's party will be keen not to lose their advantage in the battle for green supremacy, just as the issue appears to grow in importance among the electorate.
Mr Gore has led concerns on climate change
And of course it remains to be seen how the main parties' focus on the environment will impact on the Green Party in future elections.
Will voters forget about them among all the environmental talk, or will the focus on the subject raise awareness of them and persuade more people to back them.
It certainly seems that it is no longer seen as a fringe issue - anyone who claims climate change may actually have more to do with natural, rather than man-made conditions, is almost universally dismissed, ridiculed or ignored.
Tory John Redwood was attacked for even daring to suggest he took a "sceptical view" of the consensus on climate change.
And ex-US vice president Al Gore, the Oscar winning environmental film-maker, is being courted by both the Labour and Conservative parties.
With the three big parties battling to occupy more or less the same political middle ground, they are all now keen to claim the environment - a subject that shows a party has heart - as their own.
Anyone examining all this - and some opinion polls suggest the environment has rocketed up voters' agenda - might be forgiven for thinking the next general election will be fought on the single issue of the environment.
But, even if it has little chance of replacing the economy at the top of people's election priorities, few doubt that climate change will play a part in the next election.
And with signs that next time around the election outcome will be a lot closer than we have become accustomed to, it is easy to see why none of the main parties want to hand over such a feelgood issue to their opponents.