Thousands of people marched to Whitehall on Saturday to demand the government invests in wildlife-friendly policies and swiftly reverses the decline of British ecosystems.

Protesters including Billy Bragg delivered a radical manifesto, co-edited by the broadcaster Chris Packham, to the Department for Environment, Food and Rural Affairs. The manifesto called for an end to the “war on wildlife” following the decline of more than half of British species in recent decades.

The manifesto made a series of recommendations, including twinning primary schools with farms to help children understand how food is produced, banning driven grouse shooting, making it illegal to dredge for scallops and stopping Scottish seal culling.

“It’s time to wake up,” said Packham. “We are presiding over an ecological apocalypse and precipitating a mass extinction in our own backyard. But – vitally – it is not too late. There is hope we can hold to, and there is action we can take.”

In what organisers called a natural revolution, the People’s Walk for Wildlife began in Hyde Park under light showers as Bragg, Grace Petrie and others entertained the crowd with songs addressing environmental issues.

“Its hard to ignore the politics of the environment given the way that the climate is changing,” said Bragg, the singer and activist, describing how storms on the coast where he lived had noticeably intensified during his life. “We need genuine green policies at the forefront [of political debate], and a bit of people pressure on that is quite positive.”

As the rain began to ease, the demonstrators – some of whom were dressed as foxes, doves and badgers – departed for Westminster to the tune of digital birdsong reverberating through the streets of London from hundreds of smartphones.

Farmland birds declined by more than half between 1970 and 2015, and people in attendance were anxious to highlight their loss.

“Nature has been decimated over the decades,” said Sally Whitman, from Stroud, Gloucestershire. “We’ve lost over 40 million birds and it is such a huge loss. Most people will never again hear a nightingale or see a turtle dove, while the skylarks are disappearing. We’re losing magical parts of our landscape.”

Others echoed the concerns of animal rights activists that trail hunting is being used as cover for bloodsport.