Few deny this. More deny that it's predominantly man-made or that it's causatively linked to warming. More still think the increase and the source are irrelevant to what, if anything, we should actually do. And this is true even within climate science community. A number climate scientists assert that we would see a larger payoff and a much more effective near-term and possibly long term temperature drop if we focused on reducing methane concentrations and ignore CO2.
Which runs counter to some of the IPCC's assertions and, because of the 'tribal' or 'cargo cult' methods in which models are constructed, tested, and used in the climate community, there's no real way to know which particular parts of which models this runs against.
Sorry, I can't keep track of all the various flavors of 'consensus' and who subscribes to what. At least with Catholics, the faithful know what their stance should be. Certainly, several of the most vocal proponents of AGW theories have asserted or implied, if not out and out stated as much.
Again, one part of the "consensus' serious discussion" involves the sea levels potentially rising and making for some potentially uncomfortable real estate situations while other parts of the discussion make reference to turning the Earth into Venus in the next few centuries.
Some parts of our world have been screwed, crops and livestock-wise, since the beginning of civilization all the way up to present day. Some have been screwed right up until we gained the advanced technology and infrastructure that came along with the industrial revolution. This data actually suggests that some of those regions that have classically been screwed might benefit from the changing climate without the technology and infrastructure.
Sigh, I knew I was wrong.
Nothing will assuage all concerns. Once we get passed AGW, we'll worry about the climbing population or, since that's leveling off, the collapsing or aging population, or go back to worrying about the demise of the Y-chromosome...
What you asserted above, the fractionation of habitat with intolerable desert migrations, 1. doesn't agree with or isn't in any way asserted by 'consensus' and 2. is sorta wrong, historically, biologically and geographically. 3. We (and technically the ecosystem we brought with us) were far more destructive to species during our colonial/empirial days than we are today. Outside of Australia, on continental mainlands of the world, the number of species driven extinct since well before the industrial revolution is on par with the number of species we've saved and is well below the number we've saved, 're-introduced', and modified or created.
Lastly, I gotta ask again, what is the particular fear about fewer species?