Thank you. Biodiversity is of course not the same as nature. I'll  write a follow-up post discussing Maier's proposal to finding unique value in nature (nothing to do with biodiversity).

"Ecosystem services" is not a useful frame and does not support biodiversity maintenance (read my summary or the relevant section in Maier's book). Biodiversity comes with many disservices (think of pollinators of noxious weeds, crop pests, diseases...) and its conservation can stand in the way of services. Any unbiased assessment of the question whether biodiversity is valuable on ecosystem grounds must include those disservices and the context of non-ecosystem services. More importantly, it is not diversity  (of species, functions or other categories) that performs valuable services, but particular species or populations. It is a category mistake to confuse biodiversity with individual species.

There are hundreds of bee species and most of them contribute very little to crop pollination, see here. So pollination is not a good argument to support bee diversity conservation.

Option value does not inherently favor biodiversity conservation. Conservation without apparent or rationally expected benefits is a costly gamble that can be won but also lost (if it turns out that conserving had less value than not conserving). Imagine you spend resources on conserving a species that will never turn out to be beneficial, or at least less beneficial than having spent the resources on other, more valuable things.