What is generally considered to be theodore roosevelt's greatest contribution to the reform movement of the early 20th century?

One of President Theodore Roosevelt's most lasting and significant contributions to the world was the permanent preservation of the some of the most unique natural resources of the United States. According to the National Geographic, the area of the United States placed under public protection by Theodore Roosevelt, as National Parks, National Forests, game and bird preserves, and other federal reservations, comes to a total of approximately 230,000,000 acres or about 84,000 acres per day!