We'd carve a place out of the wilderness—" "But there is no wilderness, Mane said. "Even without war, even if you found a space not already cultivate… - Stephen Baxter

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We'd carve a place out of the wilderness—"
"But there is no wilderness, Mane said. "Even without war, even if you found a space not already cultivated, you would be forced to occupy a region, delineated in space, time, and energy flow, already exploited by another portion of the ecology."
It took some time for Emma to figure that out. "Yes," she said. "There is bound to be some environmental impact. But—"
"Other species would find reduced living space. Diversity would fall. And so it would go on. Soon the world would be covered from pole to pole by humans, fighting over the diminishing resources.