[jerf]

In the next 200-300 years, I consider it highly likely that either A: humankind's population will shrink enough to satisfy all but the wildest econaut's dreams or B: biodiversity will incomprehensibly explode as we start tinkering with genes directly. We may fancy ourselves masters of the process and ecologists may decry it as being "unnatural", but in the end it really won't be. Evolution will be as functional as ever, even if the link between genes and reproduction becomes more complicated. Indeed if anything it threatens to become far too functional for our likings.

In the grand scheme of things, the idea that setting aside "half the planet" will somehow fix, well, anything is really quite a parochial viewpoint. We either won't need to because biodiversity will be getting along just fine, or we'll be setting aside a great deal more than "half"....