A recent question and answer item in BMC Biology focused on human-induced extinctions, featuring expert Baron Robert May  (Open access). It is a useful piece, and here's a short excerpt about how the workforce in biology is misconstructed to fully understand biodiversity:
The workforce of systematists and taxonomists is estimated to be apportioned roughly equally among vertebrate animals, invertebrate animals and plants (with microorganisms an order of magnitude smaller). Yet the known number of vertebrate species is smaller than those of plant species and invertebrate species by one and two orders of magnitude, respectively. Things get worse as we move to research literature on conservation biology: a recent study of 2,700 papers published over 15 years in the two top conservation research journals shows 69% on vertebrates (four-fifths of the 69% on birds and mammals), 20% on plants, and 11% on invertebrates (one-third of the 11% on Lepidoptera).
- . Q&A: Extinctions and the impact of Homo sapiens. BMC Biology. 2012;10(1):106.