Gillian Roy: Changing Timber Harvest on Private Land in California (1997-2019)


Gillian Roy, Christa Anderson, Chris Field


Over the past 20 years, timber harvest in California has continuously declined, including on privately-owned land. Beyond the decline in timber harvest over this time frame, there have also been other changes in forest management, including changes to the methods used for harvest. Understanding these trends in private forest management in California provides insight into the broader ways in which timberland management can effectively mitigate threats to forest health including fire and disease. In this project, we analyze Timber Harvest Plan (THP) data from CAL FIRE’s Forest Practice Timber Harvest Plan GIS database, which includes details about acreage, silvicultural management, region, and yard for every proposed THP, to understand private forest management changes in California from 1997 to 2019. We compare timber harvest practices over time including through analysis across regions, management types, and yard. These analyses identify a significant decrease in timber harvest from 1997 to 2019 while median harvest size has remained nearly constant. Harvest in all regions of California have sharply declined over the time frame, although this decline has been most pronounced in the Sierra region of California. Beyond declining trends in timber harvest, there have also been consistent declines across all regions in California in areas such as evenaged management, intermediate treatments, and the number of unique timber owners submitting THPs every year. Understanding these specific changes in private timber harvest in California over the last 20 years is essential for mitigating threats to fire and disease and promoting healthy and resilient forests. 



7 Comments on “Gillian Roy: Changing Timber Harvest on Private Land in California (1997-2019)

  1. Hi Gillian,

    Great presentation! Nice job presenting and sharing your work.

    You mentioned that timber harvests have decreased over time, and I was wondering if you have any hypotheses over why you might have seen these trends? Was this was you were expecting to see, or were your results surprising?

    Your presentation also made me think of the recent wildfires we’ve had in CA. How does these increasing wildlife events impact timber harvest, or individuals who might rely on them?

    • Hi Bianca,
      It is definitely hard to pinpoint exact reasons for a decline, although most papers that I have read (and I largely agree after this summer) point to the increasing regulations in CA compared to other states’ lower regulations as well as the subsequent rising costs of the timber plan/harvest. There are a few large companies like Sierra Pacific Industries in CA, but a lot of smaller, and sometimes even larger, companies are either shutting down or moving to a different state with less regulation.

      Wildfires are another interesting point, and it is something that I would like to consider further with this research. From what I have seen so far, the changes that we have seen in timber industry may be impacting wildfire behavior, especially as the forests have become more homogenous and dense. I am really interested in further looking into how wildfires and timber harvest interact and impact each other moving forward.

    • Hi Jenny!
      I learned a lot this summer about different methods and tools to use to understand large data sets like my own. I think the biggest challenge for me was the initial steps in data analysis, which was not something that I had done so in-depth before. For example, cleaning the data when there were no clear definitions of the different plan statuses and silvicultural managements took a fair amount of time and presented a large challenge upfront.

  2. Hi Gillian-

    Wow, it looks like you had a ton of data to work with, which can be challenging and fun, I bet! You did a great job pointing out the more interesting findings from all that data, nice work.

    I wonder what you think the next steps in the analysis could be? Are there specific questions that could be answered that might relate to current events like the wildfires? Conversion of forests to other land use seems concerning, did you have data about what type of land use the forests were converted to?

    • Hi Alison,
      Thank you so much! Right now, I am finishing up analysis of the CAL FIRE GIS THP dataset to make sure that I have not missed any trends in timber harvest before moving onto analysis of the CAL TREES dataset, which provides the full THP documents. In these next steps of analysis, I am going to ask questions about how timber harvesting trends over the last 20 years have been impacting wildfire and pest risk in the CA private timber logging areas. Unfortunately, there is not specific data about what the forests are converted to, although to qualify for that type of logging permit, the timberland must be being converted to a “non-timber use”.

  3. Hi Gillian,

    Your project on timber harvest was very insightful! I was wondering did you hit any roadblocks while researching? If so, how did you get past them?

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