Conservationists have established land reserves to preserve the last remaining habitat for certain species whose surv...

Max-Youngquist on September 1, 2018

@smilde11 the passage establishes that conservationists established the reserves "to preserve the LAST remaining habitat" for certain species. It goes on to say that if global warming occurs as predicted, that the areas where certain types of vegetation will be able to grow will shift to areas that "are currently cooler." In other words, types of vegetation will shift locations, changing habitats in the process.

There will therefore be new habitats that can support certain species in locations that are cooler today, meaning the location the reserves were set up will likely NOT be the last remaining habitat for those species in the future. SInce the purpose of setting up the reserves were to preserve the last remaining habitats, the reserves would no longer be serving their purpose when new habitats spring up due to global warming. I hope that helps!