The coast redwood (Sequoia sempervirens) is a mythical and iconic being, reaching the tallest height of any life form on the planet, with a maximum recorded height of 379-ft. The redwood is a shade-tolerant species with thick fire resistant bark, capable of reaching an ancient age of 2,200 years. Seedlings vigorously resprout from cut stumps, fallen trees, and root crowns, suggesting the possibility of root systems much older than the oldest known individuals. Fossil records reveal that this ancient tree’s presence on the planet dates back 200 million years, and was once widespread within the Northern Hemisphere.
Prior to European colonization, coastal redwood forests sustained a number of indigenous communities for generations upon generations. Nations including the Yurok, Tolowa, Wiyot, and Cahto used fallen redwoods for building materials, harvested tanoak acorns as a food source, managed forest stands through prescribed fire, and welcomed salmon home to their natal streams yearly. As European settlers in the turbulent gold rush era displaced local peoples from their ancestral lands, the coast redwood experienced similar devastation. Old-growth forests that historically covered an estimated 2 million acres were heavily logged, with less than 5% of the original old growth remaining today (120,000 acres). The vast majority of coast redwood is young, with 2% of their entire range (382,000 acres) protected and 77% (1,256,000 acres) privately owned.
The range of the coast redwood parallels the thickest regions of the California fog belt, extending inland in correspondence with coastal influences. This Mediterranean climate is characterized by mild rainy winters and cool dry summers, with rainfall typically exceeding 100-cm annually. With only 5% of the annual precipitation falling from June to September, coastal redwood forests depend on fog as a crucial water source in summertime. Fog may supply up to 45% of the total water used by redwoods annually (19% in summer months) and roughly 2/3 of total water used by understory species annually (up to 100% in summer months).
The ability of the coast redwood to harness immense quantities of water from both rainfall and fog, within such a mild climate, is fundamental to the diversity of life the forest type supports. Coast redwood forests hold serious implications for global climate mitigation; not only through their dynamic feedback cycle with the hydrological cycle, but also because they contain three times as much aboveground carbon as any other forest type. Their decay resistant wood, rich in volatile oils and tannins, can reach volumes of 700-1000m3, with total biomass (stem, foliage, branches) reaching 4000 tons/hectare, designating them as significant carbon sinks. Coast redwoods are considered among the most “structurally complex trees on Earth”, and the redwood ecoregion is regarded within the highest conservation priority class by the World Wildlife Fund based on biological uniqueness. From bay laurels, bryophytes, ferns, endangered marbled murrelets and threatened clouded salamanders whose lives are spent hundreds of feet up in redwood canopies to rare ephemeral orchids, fungi, and soil invertebrates that reside on the forest floor— the redwood forest is a refuge for unique diversity.
In order for these diverse coast redwood forests to effectively mitigate climate chaos, they must be able to withstand the climatic changes of their region. Home to active tectonics and heavy rainfall, the region is defined by low mountains, steep slopes and narrow canyons, and maintains one of the highest rates of natural erosion in the continental US. Evolving in a landscape prone to low intensity disturbances such as fire, wind, and flood, coast redwood forests are naturally comprised of uneven-aged stands and a multitude of diverse niches within their complex structure. The susceptibility of the landscape to erosion has been exacerbated in the past 150 years, with the destruction of the old-growth redwood forests that has accompanied human development. As natural weather-related disturbance is likely to increase within a changing climate, human-caused disturbance should be kept to a minimum in remaining old-growth redwood stands. Additionally, maximum diversity should be maintained and encouraged throughout the coast redwood region in order to harness the forest’s adaptive capability and resilience.
The coast redwood’s existence within a narrow coastal belt suggests significant genetic variation associated with latitude. Preserving genetic diversity of populations throughout the entire latitudinal range will give coast redwoods the best possible chance to adapt and migrate in response to changing climatic conditions. Although the redwood is the sentinel of the ecosystem it supports, the thousands of other species are not to be overlooked. The complex interactions between species are impossible to quantify, as new findings arise all the time. For example, a study examining understory species in old-growth versus logged redwood forests found that five plant species with known specialized fungal associations were completely absent from second-growth stands. This finding demonstrates the long lasting, and easily overlooked, effects logging has on plant and fungal diversity. Many understory species of the coastal redwood ecosystem, such as the heart-leaved twayblade (Listera cordata), are found only in old-growth stands, which are typically characterized by high vascular plant diversity. With such minimal old-growth forest remaining, the persistence of such species will require our specific attention in restoration projects.
The climate mitigating potential, biological wealth, and profound beauty of coast redwood forests are treasures to be cherished and sustained. Old-growth, as well as intact second-growth, stands should be permanently protected from future development and logging operations. Restoration efforts throughout the species’ historic range should work towards replanting whole ecological communities. From the coast redwood as the foundational pillar of the ecosystem to fungal webs weaving connections throughout the soil, the unique biodiversity of this rare and productive forest must be preserved and restored for future generations.