By Richard Black
BBC News environment correspondent
The environment has rarely been a significant issue in a British general election.
Cleaner alternative fuel cars would cut pollution
In 2001, the Labour manifesto included a list of 'Ten Goals for 2010'; the environment, in the form of a pledge to 'tackle climate change', was tenth and last.
So far, it looks as though this year's election will follow previous form, with little debate about environmental issues.
Of the three main parties, the Liberal Democrats have made an early bid for the environmental vote with their 'Ten Reasons to Vote Liberal Democrat', the fifth reason being "cleaner energy, cleaner transport".
Labour has come up with 'six pledges', none of which has any environmental content; these were followed by six campaign policy documents, in which again, the environment does not figure.
The Conservative manifesto, meanwhile, unveiled on 11th April, avoids any mention of environmental issues.
IS IT DEVOLVED?
Scotland: Partly Devolved
Wales: Partly Devolved
NI: Partly Devolved
Devolved issues are the responsibility of the Scottish Parliament, Welsh Assembly, or NI Assembly. Climate change is negotiated by the UK government
Of the remaining parties, the Greens, naturally, feature the environment heavily; but rather than treating it as a separate issue, it is the central philosophical underpinning for most of its policies.
On climate change, arguably the key issue, they would go much faster than the three main parties towards a low-carbon economy, pledging a 20% cut in greenhouse gas emissions by 2010.
The commitments in Labour's 2001 manifesto included ambitious plans to make transport greener by increasing the passenger capacity on Britain's railways by 50%, scrapping environmentally-damaging road schemes, cutting road tax for smaller, cleaner cars, lowering duty on greener fuels, and encouraging walking and cycling.
Labour also promised to cut greenhouse gas emissions as agreed under the Kyoto Protocol and to become the first country to introduce greenhouse gas trading.
It said it would make progress towards a target of recycling 35% of household waste by 2015.
Labour's performance against these targets has been patchy.
The 'passenger patronage' on Britain's trains - i.e. use rather than capacity - increased by just 5% between 2001 and 2004. And the campaign group Transport 2000 gave the government an amber light for its Local Transport Plan in 2004, with ten new road schemes approved and five turned down.
Tax differentials have been introduced for smaller and less polluting cars but they have been criticised for being too small.
Following the 2005 budget, the lowest band of road tax - for a car emitting less than 100 grams of carbon dioxide per hundred kilometres and running on 'alternative' fuels - is £55 per year - while the highest band is £170.
According to the charity Sustrans, use of the National Cycle Network - which includes both on and off road routes - nearly doubled between 2001 and 2003.
Meanwhile, greenhouse gas emissions have fallen by around 5% since Labour came to power in 1997, but have remained roughly constant since the 2001 election.
Britain is however on target to meet its Kyoto Protocol target, and a UK emissions trading scheme was launched in 2002. A more ambitious, unilateral target to reduce carbon dioxide emissions by 20% from 1990 levels by 2010 will probably not be met.
Government statistics say 17% of household waste was recycled during 2003/4 - an increase of 3% on 2002/3. So if this rate of progress is sustained, the 35% target will be met.
Conservatives: Improve Energy Efficiency
All the main parties have put forward new plans for tackling environmental issues.
The Conservatives want to transform the existing Energy Efficiency Commitment (the obligation on energy suppliers to improve energy efficiency) into a market-based mechanism.
They want to set the objective that all new buildings produce zero carbon emissions, and that every vehicle procured by government departments to be the most fuel efficient, or use alternative fuel.
They also want aviation to be included in European Emissions Trading Scheme.
They would increase differentials in Vehicle Excise Duty so the least polluting cars pay nothing; tax discs would be colour-coded according to emissions.
Liberal Democrats: Green Thread
The Liberal Democrats, who say that a "green thread" runs through all their policy deliberations, want to set mandatory energy efficiency standards for all buildings, machinery and vehicles.
And they have ambitious targets for climate change, setting a target of 20% of UK electricity generated from renewable sources by 2020 and aiming for a global goal of 60% reduction in carbon dioxide emissions by 2050, using the concept of 'contraction and convergence' as successor to the Kyoto Protocol
They want to promote road charging to replace vehicle excise duty and would replace Airport Departure Tax (levied per passenger) with an emissions tax on each aircraft.
They also aim at 60% of all household waste recycled within 7 years.
Labour's own targets are slightly less ambitious.
They want to recycle 25% of household waste by 2006 and 35% by 2015.
They also want to raise the average efficiency of homes by 20% by 2010.
The government says it wants 10% of new cars sold in the UK to be 'low carbon' by 2012 and wants to pilot a scheme to offset the carbon dioxide produced through air travel by government officials.
On Kyoto, it says that by 2010 it will move towards a 20% reduction in carbon dioxide emissions below 1990 levels, through measures including energy efficiency and renewables.
It has a target of 10% of electricity to be generated by renewables by 2010 - double the current level - with an 'aspiration' to 20% by 2020.
Scotland and Wales
Although key issues like climate change, taxation, energy policy are determined at the UK level, environment is also an intensely local issue.
In Scotland, which has traditionally produced more energy than it has consumed, half of it from nuclear power, there is resistance to replacing the ageing nuclear reactors, led by the Greens and the SNP.
Some progress has been made on developing renewable sources of energy like wind farms - but they has encountered opposition in many local areas where they are considered a blight on the landscape.
The Welsh Assembly has given its policy a green tinge by ensuring in law that sustainability is considered for every piece of legislation. The siting of wind farms and their effect on the rural landscape is also an issue in Wales.
Whichever party wins the election, achieving real change on environmental issues will require the kind of political commitment which has not always been forthcoming on the British political scene.