Endangered Species Act:

It authorized the Secretary of the Interior to list endangered domestic fish and wildlife and allowed the United States Fish and Wildlife Service to spend up to $15 million per year to buy habitats for listed species. It also directed federal land agencies to preserve habitat on their lands. The Act also consolidated and even expanded authority for the Secretary of the Interior to manage and administer the National Wildlife Refuge System. Other public agencies were encouraged, but not required, to protect species. The act did not address the commerce in endangered species and parts.

Please answer a question about this article. If the question is unanswerable, say "unanswerable". What did the National Wildlife Refuge System preserve?
unanswerable