The Cascade–Siskiyou National Monument is a national monument that protects 86,774 acres (35,116 ha) of forest and grasslands at the junction of the Cascade Range and the Siskiyou Mountains in southwestern Oregon and northwestern California, United States. The monument is managed by the Bureau of Land Management as part of the National Landscape Conservation System and was established in a presidential proclamation by President Bill Clinton on June 9, 2000.
On January 12, 2017, President Barack Obama expanded the monument by 48,000 acres (19,000 ha). The expansion contains 5,000 acres (2,000 ha) in Northern California, in addition to 43,000 acres (17,000 ha) in Oregon.
What you are seeing here is a time lapse video of annual image data recorded by Landsat Earth observing satellite from 1984 to 2016. The imagery is displayed as a false color composite to enhance the contrast between land cover types. Dark blue is mature conifer forest, light blue is young conifer forest possibly with some mix of deciduous vegetation, yellow is deciduous vegetation, orange/red is soil mixed with non-photosynthetic plant material, red/pink is barren rock/soil/sand, and pure blue is water.
In the video we see that much change has occurred in this region in 33 years. You’ll notice that more than half of the forested area experiences some change during this period. Forest harvesting and wildland fire are the major drivers of change throughout the series. Note the shielding effect the national monument designation has on the area within the white polygon after the year 2000 when it is largely protected from the intense harvesting happening on its eastern border.