The Santa Cruz cypress (''Hesperocyparis abramsiana''; formerly classified as ''Cupressus abramsiana'') is a species of North American tree within the

Cypress Cypress is a common name for various coniferous trees or shrubs of northern temperate regions that belong to the family Cupressaceae. The word ''cypress'' is derived from Old French ''cipres'', which was imported from Latin ''cypressus'', the ...

family. The species is endemic to the

Santa Cruz Mountains The Santa Cruz Mountains, part of the Pacific Coast Ranges, are a mountain range in central and Northern California, United States. They form a ridge down the San Francisco Peninsula, south of San Francisco. They separate the Pacific Ocean from ...

within the Santa Cruz and San Mateo counties of west-central

California California is a U.S. state, state in the Western United States, located along the West Coast of the United States, Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the List of states and territori ...

.Wolf, Carl B. (1948) Taxonomic And Distributional Studies Of The New World Cypresses, Aliso: A Journal of Systematic and Evolutionary Botany: Vol. 1: Iss. 1, Article 2. p. 206. The U.S. Fish and Wildlife Service listed the species on the

Endangered Species Act The Endangered Species Act of 1973 (ESA or "The Act"; 16 U.S.C. § 1531 et seq.) is the primary law in the United States for protecting imperiled species. Designed to protect critically imperiled species from extinction as a "consequence of ec ...

in 1987 due to increasing threats from habitat loss and disruption of natural forest fire regimes.U.S. Fish and Wildlife Service. 1987. Endangered and threatened wildlife and plants; Determination of endangered status for ''Cupressus abramsiana'' (Santa Cruz cypress). Federal Register 52: 675-679. https://ecos.fws.gov/docs/federal_register/fr1017.pdf In 2016, the conservation status of the Santa Cruz cypress changed to Threatened. The cited reasoning was a decrease in threats against their habitat.U.S. Fish and Wildlife Service. 2016. Endangered and Threatened Wildlife and Plants; Reclassifying ''Hesperocyparis abramsiana'' (=''Cupressus abramsiana'') as Threatened. Federal Register Vol. 81. No. 33. https://www.govinfo.gov/link/fr/81/8408?link-type=pdf

Physical description

Cupressus abramsiana (Santa Cruz Cypress) (31149531532)

Individuals can grow 10 to 25 meters tall with branches 5–10 cm in diameter covering the trunk to nearly the ground. The shape of the tree is pyramidal, with branches longer toward the base.Peattie, Donald Culross. A Natural History of Western Trees; Illustrated by Paul Landacre. Boston: Houghton Mifflin, 1953. p . 246-247. Print. The tree’s leaves are light green and scale-like and can grow up to 15mm in length, persisting on branches for many years. The bark of the trunk is fibrous with thin grey vertical stripes. Individuals begin to produce cones at 11 years in age. Pollen cones can grow up to 4mm long and produce large amounts of pollen that spread in the wind. Female seed cones are produced annually on the tree and grow up to 20 to 30mm in diameter. They remain on the tree until the supporting branches die, typically as a result of natural fires. Individuals can live beyond 100 years, with one of the oldest individuals identified as being between 127 and 162 years old.U.S. Fish and Wildlife Service. 2009. Cupressus abramsiana 5-Year Review: Summary and Evaluation. Federal Register 81: 8408-8418.

Reproduction and phenology

Close_up_of_Santa_Cruz_cypress_seeds_(24486756544)

The reproductive age of the Santa Cruz cypress is on average 11 years of age. Seed viability falls to 10 percent by the time a tree is 30 years old. Like some other

conifer Conifers are a group of conifer cone, cone-bearing Spermatophyte, seed plants, a subset of gymnosperms. Scientifically, they make up the phylum, division Pinophyta (), also known as Coniferophyta () or Coniferae. The division contains a single ...

ous trees, the seed-bearing cones of the Santa Cruz cypress depend on fire to heat open the cone and release the seeds. The fires burn the vegetation in the area, including the parent tree. The seeds of the cypress are then able to germinate without the competition of other plants in the area.

Ecology

The habitat of the Santa Cruz cypress consists of the

chaparral Chaparral ( ) is a shrubland plant community and geographical feature found primarily in the U.S. state of California, in southern Oregon, and in the northern portion of the Baja California Peninsula in Mexico. It is shaped by a Mediterranean c ...

and

closed-cone pine forest Closed-cone pine forest is a plant community of coastal California and several offshore islands. The plant community is often mono-dominant and single-aged, but dense with ladder fuels. Closed Cone forests grow in low nutrient and/or stressed soils, ...

communities in the

. The habitat ranges from 300 to 750m in elevation, consisting of poorly developed sandstone or granitic soils.IUCN 2020. The IUCN Red List of Threatened Species. Version 2020-1. https://www.iucnredlist.org. The climate of this area produces cool, wet winters and hot, dry summers, and natural fire regimes periodically destroy the vegetation in the area. The Santa Cruz cypress have evolved to be dependent on these fires for reproduction. The trees are obligate seeders, meaning they do not regenerate after burning up in a fire. Instead, the seeds germinate after the fire to minimal competition. They are then able to regenerate and grow the population. If fires are too frequent, seedlings will not be able to reach reproductive age. If fires are too infrequent, the trees do not reproduce often enough to maintain population size.

Distribution

This species grows only in a 16 km² (6.2 mi² or 356 acres) stretch of land in

. Within this range are five different localities with stands of the trees. The range covers parts of the

and the Santa Cruz and San Mateo counties. Historically, the populations had a much larger range, covering at least 76 km² (30 mi² or 19,200 acres). The estimated total population is less than 300 individuals, but abundance varies between localities. Some stands of the cypress only have a few individuals left.Farjon, A. 2013. Cupressus goveniana var. abramsiana. The IUCN Red List of Threatened Species 2013: e.T34000A2839959. https://dx.doi.org/10.2305/IUCN.UK.2013-1.RLTS.T34000A2839959.en. One exceedingly rare type, the Butano cypress, exists in only one grove, of about 10 acres. This grove was described by William Dudley in the early 1900s. All of the adult trees died during the CZU Lightning Complex fires in 2020. Thousands of young Butano cypress seedlings were found growing in the grove in 2022.

Conservation status

The

International Union for Conservation of Nature The International Union for Conservation of Nature (IUCN; officially International Union for Conservation of Nature and Natural Resources) is an international organization working in the field of nature conservation and sustainable use of natu ...

(IUCN) added the Santa Cruz cypress to the Red List in 1998 as

endangered An endangered species is a species that is very likely to become extinct in the near future, either worldwide or in a particular political jurisdiction. Endangered species may be at risk due to factors such as habitat loss, poaching and inva ...

. In 2011, the IUCN updated the listing to critically endangered. The U.S. Fish and Wildlife Service added the Santa Cruz cypress to the United States'

(ESA) in 1987, listing it as endangered. In 2009, a 5-year review recommended the status lower from endangered to

threatened Threatened species are any species (including animals, plants and fungi) which are vulnerable to endangerment in the near future. Species that are threatened are sometimes characterised by the population dynamics measure of ''critical depensat ...

. Following petitions from local cattle and agricultural organizations and reconsideration of the review, the U.S. Fish and Wildlife Service reclassified the tree as threatened in 2016.

Current population threats

Alteration of fire regimes

The modern habitat of the Santa Cruz cypress no longer experiences fires at its natural frequency. Without disturbances like fire, the trees undergo little population growth and decreasing reproduction. Existing trees become post-reproductive and no longer produce viable seeds. Human-created fires can occur too often, destroying immature trees before reaching reproductive age. The U.S. Fishing and Wildlife Service cited the altered fire regime as one of the most important threats to the populations.

Nonnative species

Nonnative species serve as competition and habitat modifiers that can limit cypress success. Acacia dealbata and Genista monspessulana impact Santa Cruz populations by blocking sunlight and by competing for soil space to germinate. More nonnative invasions are possible in the future due to the cypress’ closeness to residential areas. The foot travel and human activities in these areas can bring more invasive species.

Genetic Introgression

In 2016, the conservation status of the Santa Cruz cypress was reduced to threatened. The cited reasoning was a decrease in threats against their habitat.U.S. Fish and Wildlife Service. 2016. Endangered and Threatened Wildlife and Plants; Reclassifying ''Hesperocyparis abramsiana'' (=''Cupressus abramsiana'') as Threatened. Federal Register Vol. 81. No. 33. https://www.govinfo.gov/link/fr/81/8408?link-type=pdf However, a lengthy section of the 2016 federal report titled "Genetic introgression" (also known as

introgressive hybridization Introgression, also known as introgressive hybridization, in genetics is the transfer of genetic material from one species into the gene pool of another by the repeated backcrossing of an interspecific hybrid with one of its parent species. Introg ...

) explains how the integrity of this species is also threatened by nearby horticultural plantings of a sister species, Monterey cypress, whose historically native range is nearby: on the opposite side of Monterey Bay. Hybridization is known to occur between the two endemics — as well as with a widely planted sister species native to Arizona: Arizona cypress. The ease of hybridization of cypress species in the American southwest has fostered a parallel history of

taxonomic Taxonomy is the practice and science of categorization or classification. A taxonomy (or taxonomical classification) is a scheme of classification, especially a hierarchical classification, in which things are organized into groups or types. ...

disagreements of where genus and species distinctions should apply. It thus provides a case study of neoendemism in conifers. As well, it illustrates an element of ongoing human impact — wind-dispersed pollen contamination from horticultural plantings — that cannot easily be corrected to meet conservation goals.

Additional threats

Another major human-derived threat to the species is

climate change In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to E ...

. Rising temperatures may push populations northwards, as well as further alter the fire regime. The species is also damaged by vandalism and unauthorized recreational activities. Actions like carving into bark damage the trees, encouraging infections and disease. In the past, the conversion of habitat into agricultural lands and residential areas was a major threat. But as populations became protected and preserved, the threat has since decreased.

Current conservation efforts

The U.S. Fish and Wildlife Service released the first recovery plan for the Santa Cruz cypress in 1998. In 2009, the updated recovery plan recommended the reclassification of the species to

when protection for all five populations and their habitat is secured. Downlisting from endangered to threatened was authorized in the 2016 update of the recovery plan. The listed primary threats to control are

logging Logging is the process of cutting, processing, and moving trees to a location for transport. It may include skidding, on-site processing, and loading of trees or logs onto trucks or skeleton cars. Logging is the beginning of a supply chain ...

, agricultural conversion, and development. The U.S. Fish and Wildlife Service lists all 356 acres of habitat as a necessary/critical habitat in conserving the species. The plan also recommends delisting the species if all five populations experience long-term reproductive success. They provide insurance against failure by the availability of stored seeds. The plan also classified the Recovery Priority Number to a 6. This is the lowest priority and represents a species with low impact on human activities. Updated resource-use plans and ordinances from the Santa Cruz and San Mateo counties currently protect some populations. More than half of all the individuals in the species occur on private lands owned by conservationists. State and county parks protect the remaining individuals. Watershed management plans have begun for some of these areas to aid in protections.

References

External links

IUCN

Calflora

ECOS Profile
{{Taxonbar, from1=Q5194570, from2=Q32856048 abramsiana Endemic flora of California Natural history of the California Coast Ranges Natural history of Santa Cruz County, California Natural history of San Mateo County, California ~ Trees of the Southwestern United States Plants described in 1948