It's the dog that didn't bark, the issue that no one feels pressed to talk about. Where, in the election battle, is the environment? To judge by the manifestos of the three biggest parties, it's a long way down the list.

Even before you read what they have to say, you can see that it's hardly at the front of their minds. The environment section is three-quarters of the way down both the Labour and Conservative documents: third to last in Labour's; second to last in the Tories'. You'll find it three-fifths of the way down the Liberal Democrat manifesto, though in fairness it says more about the issue in the preceding sections than the other parties do. The environment has scarcely featured in the media debate, and I'm not holding my breath for the televised hustings tonight. They're all making vaguely appropriate noises, but it's obvious that the issue is off the agenda.

Labour's manifesto contains little that's new and less that's arresting. This is partly because the government has launched plenty of green initiatives in the last couple of years, but it's a sign of how little the environment counts in this contest that Labour didn't bother to save much up for the manifesto. Obliging landlords to ensure that the homes they rent are well insulated is a step forward; and I'm glad to see that Labour wants to encourage local communities to invest in windfarms and other co-operative projects. It will also start – only 20 years behind some other European nations – to separate public litter bins to encourage recycling. Like both the Conservatives and Lib Dems (the consensus on this issue is encouraging), it wants to ban the sale of illegally logged timber. But it's still committed to widening motorways and building a third runway at Heathrow. There's a sense throughout the manifesto that green concerns are being tacked on to other policies, rather than presenting a fundamental challenge to them.

Considering the predilections of most of their members, the Conservatives' manifesto could have been a lot worse. The party still supports the government's greenhouse gas targets. It wants to encourage offshore windfarms, but says nothing about onshore developments. It plans to give every household up to £6,500 of energy-improvement measures, but says nothing about making their uptake compulsory, even in rented homes. The Tories want to adopt the sensible Japanese system for improving the efficiency of household appliances. Like Labour, they hope to reform the common fisheries policy, though they emphasise their badger-killing credentials to keep the farmers happy. They wouldn't build a third runway and would protect disused railway lines from development in case they are needed in future. The party says it wants to give "the concerns of cyclists much greater priority", which is a dramatic change from its policy in the 1990s, but in the next paragraph says it wants to scrap speed cameras, which would put cyclists at greater risk.

The Lib Dems have some good ideas, such as refurbishing shipyards to manufacture wind turbines and the eco cashback scheme, which pays you to install double-glazing or replace your old boiler. They want to cut rail fares, introduce road pricing, tax freight planes and stop the third runway. Like Labour but unlike the Conservatives, they want compulsory water-metering in areas where supplies are short, and they want to restore rivers and wetlands to reduce the risk of flooding. But they want to use changes to the tax regime to deliver "the maximum long-term benefit to the UK economy of the remaining North Sea [oil and gas] reserves". This suggests that, like the other two parties, they haven't thought the issue of greenhouse gases through. They all want to reduce demand for fossil fuels while maximising supply.

It's partly because there's not a great deal that divides these parties that the environment has featured so little in the election campaigns. It's also because economic issues have distracted them, while Labour and the Conservatives are both desperate to prove that they are the party of big business. All three parties want to rescue the economy by increasing consumption, while crossing their fingers and hoping that this won't clash with their environmental aims.

So there's some truth in the claim made at the front of the manifesto launched this morning: "Only the Green party understands the need for a new economic and environmental settlement, in which our economy and our environment work with rather than against each other." Let's hope the Greens manage to stir the issue up a bit.