Rare roots
April is World Habitat Awareness Month, so today we look at Torrey pines, the rarest native pine in the U.S.
The Torrey pine could be the rarest pine in the world. It only grows naturally in two places. One is on Santa Rosa Island (one of the eight Channel Islands) and the other is in San Diego. Scientists think that it never was a very abundant pine, probably always needing to be near the coast, but they do believe that in the past it occurred in more places along the coast. Unfortunately, specific places cannot be identified because of lack of fossil records. It is not known which Torrey pine forest (Santa Rosa Island or San Diego) is the oldest.
It’s known for its gray-green needles in clusters of five, large woody cones with edible seeds, and a characteristic open, spreading crown, though it can grow much larger in cultivation than in its harsh native habitat. Conservation efforts have helped its population recover from critically low numbers, and it’s a popular landscape tree despite being endangered.Conservation Status: Declared rare and endangered by the California Native Plant Society and critically endangered by the International Union for Conservation of Nature.
Population: Wild populations were once as low as 100 trees but have recovered to around 3,000 through conservation.
According to the National Park Service, there is much debate on how and when the Torrey pine arrived on Santa Rosa Island. To date, researchers have yet to agree on an arrival date. Some have suggested several million years ago while others have suggested between 5,000 and 43,000 years ago. The seeds were most likely transported from the mainland by birds, possibly jays that are known to transport seeds a long distance, or possibly by cones floating across the ocean. The other possible explanation is that the Chumash or their ancestors brought them over. The Chumash were excellent seamen and traders and they did use Torrey pines. If that is true, the trees couldn’t be much more than 13,000 years old (since this is the oldest human date from the islands). However, until it can be established by either fossil evidence or genetic variation that the trees were here before the Chumash, this possibility cannot be discounted.
The reserve
California has 280 state park units and contains the largest and most diverse recreational, natural and cultural heritage holdings of any state agency in the nation. Only 16 have the “reserve status.” A natural reserve status is assigned to an area of importance, and typically is one that contains threatened plants, animals, habitats or unique geological formations. Torrey Pines State Natural Reserve is a wilderness island in an urban sea. The park preserves not only the trees, but also one of the last salt marshes and waterfowl refuges in Southern California. The reserve features high, broken cliffs and deep ravines on headlands overlooking the ocean. Hikers can follow trails through stands of wind-sculpted pines. A picturesque, pueblo-style structure that served as a restaurant when it was built in 1923 houses the visitor center, featuring interpretive displays. The reserve’s rich plant community features wildflowers in the spring and visitors can see the California quail gathered in coveys in the early mornings of fall and winter. For a deep dive on the history and ecology of the reserve, visit the Torrey Pines Docent Society Nature Center and Reserve History pages.Picnicking and camping are prohibited in the reserve.
The Torrey pine used to be known as the Soledad pine (Solitary pine). The name, given by Spanish explorers, remained until 1850. That year—the year that California became the 31st state—a botanist for the Mexican Boundary Survey, Dr. Charles C. Parry, first described the tree botanically and named it for Dr. John Torrey, his mentor and one of the leading botanists of his time.
You can learn more about the reserve here.
The island trees
Thousands of years of isolation on Santa Rosa made this island version of the Torrey pine distinct. It is genetically different enough from the mainland trees that it is considered a separate subspecies and given its own common name-the Santa Rosa Island Torrey pine (subspecies differ from each other in various ways but if crossed will produce fertile offspring). This island tree grows shorter, broader and bushier than the mainland one. Also, its bark is thicker and scalier and its cones are rounder.
Most scientists agree that the climate changed to a hotter and drier environment between 3,000 and 8,000 years ago, which may have caused a decrease in the number of Torrey pine forests, particularly on the mainland. The pines most likely survived here because of the cool, moist air from the persistent island fog and because of the limited competition from other plants-due to the island’s isolation, a smaller number of plant species exist on the island as compared to the mainland.
In 1888, when the island Torrey pine was first described, the population of the grove was heavily impacted by sheep and was estimated to be about 100 mature, reproductive trees. With the removal of the sheep by 1910, the grove expanded to 1,500 trees by the mid-1990s and by 2015, the population increased to 3,500 trees and over 8,500 seedlings. Some of the oldest trees are in the heart of the grove and have been dated to over 250 years old.
You can learn more about the Channel Islands here.
Sources: National Park Service, Torrey Pines State Park, Torreypine.org, UCSD, Conifers.org