Too Long for a Tweet, Too Short for a Blog Post

Here's an excerpt from a book I am reading now, The Plundered Planet by Paul Collier:

"Environmentalists are right that each generation has responsibilities for natural assets that it does not have toward other assets. But economists are right that nature is an asset, to be used for the benefit of mankind. We are not curators of the natural world, preserving nature as an end in itself. We are not ethically obliged to preserve every tiger, or every tree. We are custodians of the value of natural assets. We are ethically obliged to pass on to future generations the equivalent value of the natural assets that we are bequeathed by the past. The natural world indeed presents us with distinct obligations, but those obligations are essentially economic."