Simplify the following text for a Grade 16 native English-speaking person.
Original: Natural capital is described in the book Natural Capitalism as a metaphor for the mineral , plant , and animal formations of the Earth 's biosphere when viewed as a means of production of oxygen , water filter , erosion preventer , or provider of other ecosystem services .
Simplified: Natural capital is a metaphor for the mineral , plant , and animal formations of the Earth 's biosphere when viewed as a means of production of oxygen , water filter , erosion preventer , or provider of other ecosystem services .