Measuring the health of Mt. Tam

Maintaining a healthy, vibrant and diverse Mt. Tam begins with understanding how key ecological resources are faring, and how we can better care for this iconic and beloved place.

One Tam partners and Bay Area scientists have come together to try to answer the question: How healthy are Mt. Tam's natural resources?

Shrubland Communities

Shrubland Communities

Photo by Brian Washburn


Coastal scrub and chaparral communities are in Good condition with No Change in their overall trend. They have been stable and show no major negative signs from the impacts of ecological stressors that are affecting many of Mt. Tam’s other plant communities such as invasive species, or Douglas-fir (Pseudotsuga menziesii) encroachment. Their extent has remained fairly stable and the have a full complement of associated bird species.

Coastal scrub and chaparral condition and trend in the One Tam area of focus

Rare Plants

Numbers and demographics of rare maritime chaparral species are a concern, and the extent of other rare scrub and chaparral species is an outstanding information gap.

Plant Disease

It is not currently known to what extent Phytophthera species, such as the one that causes Sudden Oak Death, have affected these plant communities on Mt. Tam.

Climate Change Considerations

A recent analysis of projected future vegetation changes forecasted increases in shrublands, especially chamise-dominated chaparral (Cornwell et al., 2012). However, even chaparral species that are adapted to or tolerant of very dry conditions are not immune to drought stress, and may suffer under hotter, drier climate scenarios (Jacobsen et al., 2007; Paddock et al., 2013).

Learn More


Cornwell, W. K., Stuart, S., Ramirez, A., Dolanc, C. R., Thorne, J. H., & Ackerly, D. D. (2012). Climate change impacts on California vegetation: Physiology, life history, and ecosystem change (White Paper from California Energy Commission’s California Climate Change Center). Publication number: CEC-500-2012-023. Berkeley, CA: University of California, Berkeley. Available from:

Jacobsen, A. L., Pratt, R. B., Ewers, F. W., & Davis, S. D. (2007). Cavitation resistance among 26 chaparral species of southern California. Ecological Monographs, 77(1), 99-115. Available from:

Paddock, W. A. S. III, Davis, S. D., Pratt, R. B., Jacobsen, A. L., Tobin, M. F., López-Portillo, J., & Ewers, F. W. (2013). Factors determining mortality of adult chaparral shrubs in an extreme drought year in California. Aliso: A Journal of Systematic and Evolutionary Botany, 31(1), 49-57. Available from: