How Four Agencies Measured the Ecological Health of Mt. Tam

Before anyone could say whether Mount Tamalpais was healthy, the mountain's four public land managers had to agree what healthy means. Each works under different missions, policies and regulations, so the definition had to cover all of them and still make sense to the public. Michelle O'Herron, an independent consultant in science communication and landscape partnerships, describes in Park Science how they did it.

One mountain, four managers

Mount Tamalpais, known locally as Mt. Tam, stands just north of the Golden Gate Bridge and runs from the Pacific shore up to 2,500 feet and back down to the shores of San Francisco Bay. A marine upwelling zone on one side and a large estuary on the other, plus its folded topography, create many microclimates. Its soils have let diverse plant communities form, including several species found nowhere else in the world. It is home to threatened and endangered wildlife, among them the northern spotted owl, the California red-legged frog, and coho salmon and steelhead trout, and it is a stopover for migrant birds on the Pacific Flyway. Its reservoirs supply drinking water to almost 200,000 nearby residents.

Its 36,000 acres (14,569 ha) of open space were protected at different times and for different purposes, so four agencies manage them: the National Park Service, California State Parks, Marin County Parks and the Marin Municipal Water District. The plants and wildlife face climate change, invasive species, habitat fragmentation, altered fire regimes, diseases such as sudden oak death, and noise, light and air pollution, and the stressors interact. The mountain has more than 200 miles (322 km) of trails and receives about five million visitors a year.

The agencies had worked together before but largely operated independently, without a shared strategic approach. In 2014 they joined the nonprofit Golden Gate National Parks Conservancy to form the Tamalpais Lands Collaborative (TLC), which focuses on priority conservation and restoration projects, coordinated education and volunteer programs, and stewardship. One Tam is its public engagement initiative.

Building the assessment

The partners concluded that they needed a baseline understanding of the mountain's overall ecological health to guide their shared priorities and make a clear case for public support. A small, scientifically diverse advisory committee of staff from the partner organizations, along with Point Blue Conservation Science, took the job; keeping it small made it efficient and eased the burden on agency resources. The committee asked groups elsewhere that had made similar assessments, including the National Park Service and the San Francisco Estuary Partnership. Four lessons stood out:

• Choose indicators that are ecologically meaningful and measurable, and weigh those the public values.
• Use a structured framework to engage the right experts while keeping the project's scope and scale in check.
• Base the first report on existing data, because collecting new data can cost too much in time and money; gaps then point to future study.
• Share the findings in clear, scientifically sound and engaging communications.

The committee followed a method like that of the National Park Service's Natural Resource Condition Assessments: existing information to judge trends and conditions, confidence levels, stressors and threats, and critical data gaps, with expert observation and opinion added. The report was not meant to be a management document, though it includes research, monitoring and management considerations for each indicator. The author says the last lesson mattered more than expected. Early on the committee defined the report's purpose and audience, which was to distill the best available knowledge about the mountain's resources so that managers find it useful and the public finds it clear and compelling, and returning to that purpose helped the team through later complications.

What "healthy" means here

Each agency is tasked with preserving natural processes and biodiversity, but under different rules. The committee chose parameters of ecological function, biodiversity, species richness, resiliency and natural processes. In its definition a healthy Mt. Tam has:

• the full range of plants, animals and other life-forms present, able to reproduce and to find food, shelter and water for as long as climate conditions allow them to persist there;
• natural processes occurring as often and in the way considered normal, judged from historical evidence or from whether the processes can maintain ecological functions and adapt as the climate changes; and
• resilient ecosystems, able to function or recover despite disturbances, changes or shocks.

Choosing what to measure

The committee first listed 37 potential indicators (species, taxonomic groups, communities and ecological processes) and was reluctant to cut the list early. An indicator made the cut for one or more reasons: it occurs in the One Tam area of focus; it measures an important aspect of the mountain's health; information or expert opinion exists to judge its condition or trend; it is a federally or state threatened, endangered or rare species whose loss would affect the mountain's health; or it is iconic or charismatic enough to build public interest.

Using existing data was a big job: each partner had kept its own monitoring, inventories and research at different levels of detail, over different timescales, with different protocols and formats, so a new team member gathered it all into combined databases and bibliographies. For each indicator the committee then wrote a summary worksheet, borrowing from the Park Service's condition assessments: a preliminary condition and trend, the confidence in them, the reason for choosing the indicator, a description of the resource, current and desired conditions, goals and metrics, key stressors, information sources, known gaps and planned management.

Of the 37, 24 were the basis for a one-day workshop with approximately 40 natural resource scientists from the partner agencies, the Conservancy, Point Blue, the National Park Service Inventory and Monitoring Program and Point Reyes National Seashore. Two more workshops brought in 60 local academic and agency scientists. Where data were scarce or missing, participants used their best professional judgment and named the research or monitoring needed to fill the gap. Everyone understood that the product was a decision-support and public-engagement tool rather than a research paper, and that they would have to state conditions and trends without full certainty. Everyone who took part could also give technical review of the final report.

How each indicator is rated

What came out of it

Seven wildlife species, three wildlife groups and seven plant communities were chosen as indicators because there was enough information or expert agreement to set metrics and assess condition and trend. Broad landscape-level themes were also evaluated, using a species-traits database of plant community associations, climate vulnerability and sensitivity to stressors. Important indicators without enough information or opinion became needs statements for future research or monitoring.

The report, Measuring the Health of a Mountain: A Report on Mount Tamalpais's Natural Resources, was completed in the fall of 2016. Managers use it to focus monitoring and research, implement shared data collection and align planning and budgets to common needs. A summary video, a brochure and an interactive web dashboard present its findings, and hundreds of members of the public, along with local scientists and conservationists, have attended two annual symposia on the results.

Sources

• Michelle O'Herron (independent science communication and landscape partnerships consultant), The ascent to peak health: Measuring the state of a mountain's natural resources, Park Science 34(1), National Park Service, 2018; rewritten in hubnx's own words.