London residents share space with 13,000 wildlife species, 3,000 parks, and 8.3 million trees.

The city was officially declared an urban forest in 2002. Now London could become a national park — sort of.

Advocates of the idea handed out their ambitious proposal to Londoners in July. Their bid is part of a larger campaign urging lawmakers to officially declare London the world's first National Park City, and it's gaining steam — the movement has drawn support from London's Assembly members, four London Councils and at least 100 organizations.

If you can't wrap your head around the idea of London as a national park, it might help to imagine a city where a self-governing body is responsible for looking after and increasing the amount of green space in the city. That's not too different from how a national park runs.

Geographer Daniel Raven-Ellison founded the Greater London National Park City initiative. Image courtesy of Daniel Raven-Ellison

The United Kingdom already has 15 of those — protected areas of mountains, meadows, woods and wetlands stretching out in rural areas where locals bodies shape the landscape.

It was a trip to these national parks in 2013 that got geographer Daniel Raven-Ellison — founder of the Greater London National Park City initiative and one of National Geographic's emerging explorers — thinking.

"Considering that 10% of England and 7% of the UK is urban, I began to wonder why this very distinct and important kind of landscape wasn’t represented within our family of national parks," he tells Tech Insider. "We go to national parks because we know they’re special places where people care more for nature and enjoy the great outdoors. What if we applied exactly the same idea to the urban environment?"

For the past 18 months, Raven-Ellison has been trying to bring the national park model to the London landscape, which is home to 8.3 million people.

His movement aims to make green spaces easily accessible, connect kids with nature, clean up the city's air and water, and build affordable green homes.

Raven-Ellison imagines that city-dwellers could play a part, re-planting their paved-over front gardens and giving green makeovers to vast unused open spaces.

A map of London's green spaces Greater London National Park City

The bare bones

Turning London into an urban national park won't be easy.

The first problem: Campaigners are asking the government to officially declare London a National Park City. That would only be possible if at least two-thirds of London's 649 electoral wards — the smallest political unit — and the mayor give the nod.

London Mayor Boris Johnson is unlikely to do that. He's reportedly said that while "the idea of a national park is an engaging way of sparking debate ... [he] does not have the powers to create a new class of urban national park."

But that hasn't stopped the activists from soldiering on. Even withou the official go-ahead, they can create a non-profit body that cares for the National Park City.

Another issue: To become a national park in in the U.K., a landscape has to be an "extensive tract of country" — which London isn't.

Instead, the idea is to create a new kind of national park that sits outside of legislation. "Because it doesn’t exist at the moment, we’re in a privileged position to define it for ourselves," said Raven-Ellison.

For now, the campaigners have come up with a working definition of a National Park City:

"A large urban area that is managed and semi-protected through both formal and informal means to enhance the natural capital of its living landscape. A defining feature is the widespread and significant commitment of residents, visitors and decision-makers to allow natural processes to provide a foundation for a better quality of life for wildlife and people."

Is it realistic?

The costs won't be too hefty compared to designated national parks in the U.K., which get grants of more than $6 million annually from the government. In its early years, a National Park City will only need an estimated $900,000 each year to spend on staffing and project development.

The projects will run on philanthropic donations and private sector aid, according to the proposal.

Raven-Ellison believes businesses will also have reason to sponsor new innovations in the National Park City. For example, an insurance company might want to fund a project that aims to reduce flood risk in an area, since fewer people dying in floods would mean fewer insurance claims. Similarly, greening pavements would result in business opportunities for horticulturalists.

Some businesses seem to be taking note. The movement already counts architectural design heavyweights Aecom and Farrells among its advisors and backers.

And the most daunting part of the challenge — the fact that London is a city with millions of people in it, not an empty green space — hardly bothers Raven-Ellison.

"I see people as an opportunity, not a challenge," he says. "Think about it this way. A child born four years [from now] could be born in a National Park City, where everyone is connected to nature."