An old-growth forest – also known as a primary forest or primeval forest – refers to a forest that has reached a significant age without significant disturbance, such as a devastating wildfire or logging. With a variety of tree species that range in heights and diameters, old-growth forests have multi-layered canopies that provide diverse habitats for a variety of species. In some cases, these specific ecological formations in the forests offer unique habitats for rare or at-risk animals, like the marbled murrelet.
In the San Juan Islands, there are few old-growth forests left, but those that remain offer a rare environment. Due to the drier location, these island forests tend to have an open canopy with little underbrush as oppose to the wetter, main-land forests typical in the Pacific Northwest. Within these pockets of the San Juans' old-growth, some trees are estimated to be over 300 years old. Douglas firs, Sitka spruce, big leaf maple, and western red cedar are the most common species in the islands’ forests, with the occasional native trees such as western hemlock, grand fir, Pacific yew, and shore pine.
Like many old-growth forests, the San Juan region lost many of its virgin growths due to industry expansion. Many trees were used during the height of the lime kiln industry in the early 20th century, especially on San Juan Island. Due to their drier nature, the island's trees were ideal for burning in lime kilns which lead to quick deforestation. Trees not used for kiln fuel were then used for barrels to ship the lime in. Logging also contributed to deforestation, but at a lower rate than what was seen on the mainland.
Today, most of the old-growth forests in this region are found on Orcas Island. The forest surrounding Mountain Lake in Moran State Park is one particular example. Several other old-growth forests also exist in small, scattered pockets on San Juan Island. As our understanding of their importance grows, it becomes more and more apparent that these remaining forests must be protected. Fortunately, with wise logging practices and growing awareness, the old-growth forests of the San Juans may have a reasonable chance for survival.