Why was the cascade siskyou national monument designated to be a national monument?

Answer 1

According to the presidential proclamation (national monuments are done this way; national parks are done by congressional legislation), it became a national monument "in recognition of its remarkable ecology and to protect a diverse range of biological, geological, aquatic, archeological, and historic objects. The Cascade-Siskiyou National Monument is the first monument set aside solely for the preservation of biodiversity. Due to several complex biological and geological factors and processes operating simultaneously, the monument contains an unusually high variety of species in a geographically small area."