It’s late and I rushed this post a bit, but I hope it all made sense. Thanks for the reply.
It still makes sense, no worries and I think we agree on a lot of things, but not on all
Well, yes and no. Two decades of research has shown a strong link, but most of it studying simple systems and a single function. Linking biodiversity to complex, multi-functional ecosystems is still very much in its infancy.
Though it is still a young science indeed, there is a lot of interesting work being done by multiple groups, there are already enough interesting results for a fruitful discussion, see for starters:
https://www.nature.com/articles/ncomms11109 on biodiversity and multifunctionality in European forests, from whom I stole the "jack of all trades"
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I basically agree. Again, though, our understanding of which taxa are functionally redundant and the ramifications of a given action on a given ecosystem is usually poor to non-existent.
I’m the opposite. For me, the core purpose of conservation is to protect ecosystem functioning (and, by extension, services). We may be able to live in a world where 50% of biodiversity went extinct, but we can’t safely eliminate 50% of biodiversity without knowing which half we need. It’s therefore imperative to protect as much as we can, especially in the most diverse regions.
I think we can predict relatively well which species we need if we want to conserve ecosystems to deliver particular ecosystem services, even though exact knowledge is not there.
Take for example the East Usambara mountains in Tanzania. Which is a small mountain range with an incredibly high biodiversity with lots of endemics. For Tanzanians it fulfills 4 major services, 1) it is the source of water for the large coastal city of Tanga, 2) the forests on the steep slopes act agains soil erosion, 3) it is an important area for spice production (cloves, cinnamon, cardamom, black pepper), which are partly grown in an agro-forestry set-up and 4) the forests are used as a source for fire wood by the local people.
For services 1,2 and 4 it does not matter too much whether the trees growing there are of a rare endemic species or if they are Maesopsis eminii, an exotic tree. As long as there is forest there and Maesopsis does not need many additional species to keep it flourishing, as it's seeds are easily spread by sykes's monkeys and hornbills (trumpeter and silvery-cheeked), all species of no particular conservation interest. Such a degraded system may have a lower resilience to adapt to any change, but as we are talking about generalist species.
The 3rd services is a provisioning one, though it increases the overall landscape heterogeneity and landscape biodiversity might increase, for species of conservation interest it is not that interest, as they are mainly confined to the forests (see e.g. the land sparing vs. land sharing debate and research done by the group of Andrew Balmford, Cambridge).
There is however also a 5th important ecosystem service in the Usambara system, which is (eco-)tourism. Though most tourists will be happy enough with seeing the monkeys, hornbills and chameleons that are present in the Maesopsis dominated forests (which also holds palm civets, servaline genets & dwarf galago to keep mammalogists happy), there is however a smaller group, to which we both belong
, that is more interested in olive ibises and tailorbirds and other rarities. This particular group is probably the only for which it is really important to conserve a high biodiversity system. But when we add all the services and compare them in monetary terms, they only have a very small contribution.
What may be more important is the pride Tanzanians (both local and national) get from having such biodiversity hotspots, which may lead to efforts to conserve such ecosystems, which is also something that looks good to the outside world, as conserving biodiversity is good for your image nowadays....
Apart from this you could off course still easily argue that an Amazon rainforest yields overall much more ecosystem services, than the cattle farm by which it is replaced, which is true, but do you need that insanely high biodiversity to deliver these services at an "acceptable" level, no probably not...
he trouble with the “ethical argument” is that it’s not really an argument. The assumption that species have a right to exist is a predicate, but never really proven. That strikes me as bizarre, since it goes against everything we know about the history of life (
You can turn the argument around and say "what right do we have to let such high levels of biodiversity go extinct?". This indeed does not make sense in an purely evolutionary sense, as humans have become the best adapted species in different way, especially in transforming landscapes to our own (short-term) benefits.
Humans are however ethical beings, which is part of why we have become so successful. It is generally considered unethical to kill another human being, so why should it be ethical to kill a chimpanzee or an elephant for example, as they are only different by degrees and are fundamentally similar to us, they also know what death is, have emotions and their own ethics. Humans have come as far as they have come, not because they are killing machines without ethics, but because they are very social animals with ethics.
