The UK's parks, lakes, forests and wildlife are worth billions of pounds to the economy, says a major report.
The health benefits of merely living close to a green space are worth up to £300 per person per year, it concludes.
"Urban green space, for example, is unbelievably important - if affects the value of houses, it affects our mental wellbeing.
"This report is saying 'this has got incredible value, so before you start converting green space into building, think through what the economic value is of maintaining that green space' - or the blue space, the ponds and the rivers."
On the global stage, several countries have previously evaluated the economic worth of specific factors such as forests or fisheries.
And two international studies - the Millennium Ecosystem Assessment (MEA) and The Economics of Ecosystems and Biodiversity (Teeb) - have given broader views of society's environmental trajectory, and the costs and benefits.
But the UK is the first nation to produce such a detailed assessment across the piece.