I definitely agree with your statement that there aren’t substitutes for biodiversity. It’s easy to become wrapped up in the thought that all species are here for human gain and the only reason to manage them and preserve them is so that humans can continue benefitting from harvesting. However, it’s equally important to consider the ecological importance of a species. They may be the species that an entire ecosystem hinges on, and by removing them, a whole ecosystem may collapse. Human gain is not the only thing that should be considered when thinking about sustainability.