Spain has a "presumed consent" law, where individuals are automatically considered an organ donor unless they opt out, but Watson said that is not the only factor that explains the country's high level of organ donation.

CNN: Why transplants use 'imperfect' organs

According to Defra's chief scientist, Dr Bob Watson, we've consistently failed to factor-in the billions of pounds these ecosystem services are worth to our economy.

BBC: Putting a price on nature