Final answer:
The 20th-century environmental reform was driven by the recognition of industrial impacts on nature, with a post-WWII shift to global issues and diverse participation.
Step-by-step explanation:
Calls for environmental reform in the 20th century were prompted by a growing awareness of the negative impacts of industrialization on the natural world, which became particularly evident after World War II. During this time, the environmental movement saw a shift in concerns from conservation and protection of wilderness to broader issues such as global warming, pollution, and sustainable development. The movement became characterized by more scientific legitimacy through figures like Rachel Carson, a broadening of its participant base to include a more diverse range of voices, and increasingly sophisticated methods of advocacy and activism. Post-WWII environmentalism differed from earlier movements as it addressed emerging global challenges such as climate change, employing both local and international strategies, and engaging in efforts to enact policy changes, such as the Clean Air Act of 1963 and international treaties like the Montreal Protocol and the Paris Agreement.