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?

Coast Redwood Communities

Coast Redwood Communities

Photo by Jessica Weinberg/NPS


Old-growth coast redwood forest communities are doing well, but second-growth redwood forests, which make up the majority of the redwood forests on Mt. Tam are in Fair condition with an overall Declining trend.

Coast redwood forest condition and trend in the One Tam area of focus

Invasive Species

Due to the generally low understory light levels, non-native, invasive plant species are a minor problem for this community.


Assessment of the avian community associated with redwood forests indicates that all expected species are present and Northern Spotted Owls (Strix occidentalis caurina) are doing well across the region in this habitat type.

Habitat Structure

The major stressor to this habitat is Sudden Oak Death and its impact on tanoaks (Notholithocarpus densiflorus) that are common understory associates within redwood forests. Second-growth forests are in cautionary condition due to a lack of forest structure and age diversity. In many stands within the Mt. Tam area of focus, nearly 100% of the tanoaks have been impacted. These trees are stuck in a cycle of stem death, followed by root crown stem regeneration, followed by stem death. This turns them from mid-canopy redwood forest components to lower canopy and shrub layer components. It also adds a great deal of potential fire fuel to the forest floor.