While I appreciate the intent of trying to establish a baseline ecological state of the world prior to the discovery of the Americas, I think the "Pre-Columbian reference is unnecessary and American and Eurocentric. We would achieve the same effect if we referred to "the state of the land when occupied by the "first nations" or first known inhabitants to a particular region." This would work for different regions which have different timelines in terms of human development, from ancient Greece to the aborigines in Australia.