The reasons people opt for a ‘natural’ or ‘green’ burial varies greatly. The movement to more sustainable and planet-friendly choices in all aspects of life has meant many people choose something more aligned to these ethics in death.
Cremation is still viewed by many as being the most environmentally sound choice (‘we should save the land for the living’), but if a burial site is creating a woodland or wild-flower meadow that benefits flora and fauna, then this is no longer the case and the carbon footprint is very different. Green burial in this case is the most environmentally sound choice.
For more information please see this study by Leedam.