Next year is the centenary of Vaughan Williams' much-loved tribute to the skylark: The Lark Ascending. He evoked the song of the skylark to illustrate the green and pleasant land that British troops were leaving to go and fight in the first world war. Now, the skylark is a threatened bird and its song, that provides the soundtrack to our summers, is growing quieter.

The skylark's future, like many other species, is now partially dependent on how ministers across the UK implement the latest round of the much-maligned and technocratic common agriculture policy (CAP).

At the end of November, Defra concluded a "landmark" consultation seeking the public's views on how their money should be spent supporting farmers through the CAP. Some may wonder why the public needs a view on CAP. But this was a colossal opportunity for the public to make their voice heard on a policy that will cost them over £20bn in the UK alone over the next seven years. The CAP matters. Not only does it direct subsidies to farmers, it also rewards them for maintaining our landscapes, providing opportunities for outdoor recreation and, critically, providing a home for much of our wildlife, including Vaughan Williams' skylark.

Defra's consultation revealed strong public support for shifting some of the funding for subsidies to rewarding those farmers who help protect landscapes and wildlife. Under European rules, Owen Paterson, environment secretary, can direct 15% of English farmers' direct subsidies towards those farmers wanting to do the most for the environment. Previously, Paterson has indicated to parliament that he feels this is where the money should be spent, and we couldn't agree more.

Last week, though, the environment food and rural affairs select committee published a disappointingly "regressive" report, which made depressing reading. In contrast to Defra's stance on CAP, it pandered to the farming unions at the expense of getting value for money for you, me and other taxpayers.

Contrary to the evidence, the Efra report cites the risk of British agriculture losing competiveness by switching funding away from direct subsidies. In contrast, government figures make it clear this claim is based on nothing more than smoke and mirrors, and shows the net benefit to society from such a switch is up to 33 times greater than the costs associated with a decline in revenue.

Such a viewpoint betrays all those farmers and citizens wanting a countryside richer in wildlife while achieving better value for the public's multibillion investment in British agriculture.

Farming, of one form or another, covers three-quarters of our countryside. Many species, including the corn bunting, the turtle dove, the corn flower and the marsh fritillary butterfly rely on wildlife-friendly farmers for their survival, but many of these species are struggling and they need help now more than ever if they are to remain part of "our" countryside. Thousands of respondents, including me, believe rewarding farmers for providing that help is a priceless use of public money.

The wildlife imperative is clear. Recent figures suggest that for every 10 turtle doves we had in 1995 we're now down to two. And the Bird Atlas, published two weeks ago by the British Trust for Ornithology, reveals many tales of woe, including the plight of the corn bunting, which has been lost from over a third of the areas where it occurred just two decades before. The State of Nature report – launched by Sir David Attenborough in May – revealed that 60% of the species reliant on farmland are declining and half of these are declining seriously. Our threatened wildlife hasn't got time to wait, and we hope the government will recognise the imperative for action.

Owen Paterson criticised the recently published Naturecheck report implying that the coalition of wildlife groups who produced it were being unfair about the scale of the environmental problems we're facing. However, the government's own England Biodiversity Strategy report – produced at the end of October – highlighted many of the same issues. Wildlife is in crisis and we need a credible plan to stem the loss.

We know Paterson's in-tray is bulging and we recognise that public funds are tight. However, transferring funding from direct payments to wildlife-friendly farming is a fiscally neutral measure that will go a long way to buffering our threatened wildlife from potential extinction. These payments are the only way to make wildlife-friendly farming pay.

We trust that Owen Paterson and David Cameron know this, and will make the right decisions for wildlife and the public purse. We couldn't think of a better way for the prime minister to burnish his green credentials, and maybe, just maybe, give Vaughan Williams' skylark a brighter future.

• Martin Harper is conservation director at the RSPB