There are many ways to value the natural world.
We may argue it has intrinsic value and needs assigning no other. Its beauty suggests an inherent aesthetic value. And we rely on the natural world to live, meaning it has an immense, perhaps encompassing, practical value.
However, despite the significant value many of us place on the natural world, much of it is disappearing; habitats and species are being degraded and lost.
In recent years, scientists have therefore started to investigate the financial value of nature. They do so to inform us, and how scant conservation funds might be best spent, and to broaden the debate about how and why nature should be conserved.
It is widely acknowledged that the natural world should not just be reduced to a series of financial values, which are necessarily estimates.
However, in a world that often focuses on money, it can be a useful tool to help remind us that nature does have a value, and what might be lost if aspects of it disappear.
The Costing the Earth interactive game is based on the following sources.