Happy almost-Friday everyone! Oh my goodness, where is the week going? I've been pairing up some repeat photos of Lassen Volcanic National Park in CA in the lab and I think it's really cool...so I am going to teach you about it!
Repeat photography is one of the tools we use to visualize vegetation change in a specific location. It's exactly what it sounds like; we take an old picture of a national park taken in the 20's, 30's or 40's back when the parks were being established and advertised, then go back out and find the EXACT SAME SPOT where the photographer took the picture and take the exact picture again. Almost as soon as national parks were established, an enormous fire suppression policy took effect because wildfires are bad and we should put them out, right? (wronnnng) We are now realizing that fires were an important part of lots of forests and ecosystems because they cleared out underbrush and allowed big trees to grow without competition for resources, among gazillions of other reasons. Fire suppression has resulted in the growth of LOTS of little trees that would have been wiped out otherwise. Fast forward 80 years and these little trees are getting pretty big, which creates MORE fuel for future fires to burn, thus creating a bigger risk for high intensity fires that aren't natural (aka BAD).
Comparing photographs of the same site reveals how forests have changed from fewer bigger trees to many smaller trees, which also blocks the dramatic vistas that characterize the national parks.
Here's an example of my favorite from Yosemite. The picture on the top is from the early 1900's and the one on the bottom is from the 1990s.
WAAAA! If you go there today, you would have no clue that what you're seeing is not natural at all!
Forest and park managers are working to restore natural conditions by using prescribed fire, and researchers help by determining what "natural" or reference conditions were. And that is part of what I do at grad school!