Let me start with some considerations, and I promise I'll provide a more direct answer later.
There are different definitions for conservation-related concepts.
Some people confuse "conservation" with "preservation". The latter is often used to define the practice of keeping a portion of natural environment 'just as it is', which is quite difficult, except maybe for very remote, very sparsely inhabited regions.
Conservation involves much more, because human populations are considered in the context of the ecosystems they belong to, and thus, human use/exploitation of living and non-living resources is contemplated.
That's where the concept of 'sustainable use' comes in. Resource management must take into account ecological, economic and social aspects; this means accepting input from different disciplines (biology, sociology, economics, anthropology...). And like you said, there's an ethical value to biodiversity, as well as more tangible ecological/economical values to consider.
Now, there are 2 basic approaches for maintenance of stocks of living organisms: 'ex situ' (=out of place), for instance: zoos, botanical gardens, seed banks, cell and tissue cultures, etc), and 'in situ' (=in place), namely protected areas of diverse kind.
These two basic types encompass the methods we have to conserve biodiversity. Both have advantages and drawbacks.
Thus, my view is that we should use all the tools for conservation that already exist, as well as keep developing new ones, to achieve a balance between preservation and the rational, long-term use of natural resources, because the fact is that human populations cannot subsist without exploiting other species.
I don't trust apparently simple 'solutions'; for instance, it's easy to say that Area So-and-So should be preserved, or that Species X must not be hunted... but the local people from So-and-So will need food and money, and illegal commerce will drive Species X to extinction if the local authorities don't have the means to act.
Long-term conservation requires lots of research, both basic and applied, and research requires money. So the best we can do is learn and stay informed, and let our politicians and decision-makers know that we care and we're watching, and that we want them to make intelligent decisions, even if they seem unpopular.
