Jeez. A few years ago, urbanization was labeled as the primary factor for extinction. So, yet another global warming claim that is unprovable, but will touted as gospel by the global warming fanatics.
What is interesting is that in his review, Gore cites as a problem that global warming is making the Earth too wet. In the past, periods of wetness has increased biodiversity because more precipitation has increased the carrying capacity of many regions. For instance, compare North Africa 10,000 years ago with North Africa today. So there is, in reality, no historical precedent for an overall decline in biodiversity.
I would point out, though, that the end of the Medieval warming period was marked by cooler temperatures and increased precipitation in Europe, which destroyed crops and reduced crop yields, causing severe famines.
(Update 2/12/2014--correction and citation to specific percentage of warming models that are wrong).