He doesn t even define it, as if its meaning is obvious. We facilely apply it to native peoples, as though they, at least, lived a sustainable lifestyle. Only if we compare them with our profligate modern society, and if we only look at them over a short time period, do they appear to be living sustainably. Actually, wherever humans have moved, they have decimated the local species. To be honest, there is really no such thing as a sustainable lifestyle.
Trees drop leaves.
If the leaves accumulated, and weren t broken down by other members of the ecosystem, the trees would eventually bury themselves, be unable to reproduce, and die. The lifestyle of the tree can only approach sustainability by being part of an ecosystem that processes its wastes. Trees also produce oxygen. Humans, however lightly they live on the Earth, need to kill to eat. Every time you kill an organism, you risk destroying unique biodiversity.