I know I'll be labeled a Malthusian by James and his ilk but the reality is we are unlikely to avoid the extinction of all wild animals and all wild spaces. The projection I remember reading went like this.
If the current rate of bringing land into development and conserving land as wild, as has been practiced over the last 20 years, were projected forward the two lines would never intersect, meaning development will always out pace conservation until 100% of the landmass is consumed.
If we cut development by 25% and increase conservation by 33% of those same rates the point of intersection is a negative number. Meaning that intersection would not theoretically take place until 100% of the of the landmass were consumed.
If we cut development 50% and increase conservation 66% of those same rates the point of intersection occurs at a positive number near 90%. This means 90% of all the landmass has been developed. Since the Himalayas, Rimo Muztagh, Rocky's, Alp's, Carpathian's, and parts of other mountain ranges are really unsuited for any real development 90% development means 99% habitat and wildlife loss. The loss of everything below tree-line is a fairly complete loss.
If we cut development by 75% and increase conservation by 100% of those rates then we can avert the extinction of all wildlife on the planet. We'll still lose much more than we currently have but we won't lose it all and a substantial amount of biodiversity will remain.
Now some will argue that this won't happen and some will argue it doesn't matter. If you believe it doesn't matter then that is your choice but to believe it won't happen is hard to swallow. The numbers speak for themselves. While the extinction isn't inevitable I have a hard time believing we will, in the extremely near future, cut the losses to wildlife habitat that are a product of human development enough to prevent this. If you believe the change will be this dramatic and this fast you have a much more Panglossian outlook than I do.
Incidentally wildlife means not just a tiger but a tiger living in its natural habitat. A tiger in a zoo is not wildlife but rather an animal in captivity.
John Thornton