I exported a section of the map as a GeoPDF around this reservoir near where I’m currently living up in the Willamette National Forest in Oregon’s Cascades. The areas identified as old growth are filled with purple. Everything else has been harvested at some point in the last 80 or so years, according to the NFS. I was particularly interested in verifying if the sections of the map classified as old growth forest were actually old growth, or if they contained sections of timber harvest that hadn’t been recorded as cut.

I don’t have any good way of verifying the accuracy of the dataset other than going out there and taking a look, so I drove up and walked some of the roads in this randomly chosen section marked as old growth above Hills Creek.

Incredibly, the map was actually pretty accurate. I found quite a few stands of really old growth douglas fir (at least 150-200 yro), intermixed with cedars and hemlocks. The oldest forest was especially concentrated around the four drainages along the road I walked.

There was one section on the road that had clearly been clearcut but was within the old growth boundaries. It looked to be maybe 50 or so years old, so should have been included in the dataset from the Forest Service. Not really sure how to handle these cases, will have to think about it more.

It’s encouraging though, will have to try a few more areas to get a sense for the accuracy. I imagine it will vary quite a bit by the National Forest, as the record keeping wouldn’t have been all the same quality for all.