Pinus torreyana Parry ex Carrière

Pinaceae

Distributed in California, USA with two subspecies, one on the mainland and one on Santa Rosa Island. Both have very restricted distributions and small population sizes. On the mainland, outside of the main protected area of Torrey Pines State Park it is threatened by urbanisation.

Distribution

USA: southern California (San Diego and Santa Barbara Co.). Two subpopulations are recognized, one as subsp. torreyana north of San Diego; and the second as subsp. insularis on Santa Rosa Island. Records from Sanat Catalina Island represent introduced trees.

There are an estimated 4000–4500 mature trees in two populations (two subspecies).

Habitat and Ecology

Pinus torreyana is a relict species now confined to littoral habitat on the coast (up to 1.6km inland) and on a small island off the coast of southern California. It grows from immediately above the high tide mark to about 180 metres above sea-level. on rocky or sandy slopes. On these sites it seems dependent on the daily fog that comes in from the ocean in the afternoon, mitigating the heat of the sun and the resulting excessive evapo-transpiration. It grows with a sparse chaparral and few other trees; in ravines sometimes accompanied by a few oaks (Quercus spp.) and Arbutus menziesii

Human Uses

Torrey pine is not used as a timber tree; at present the two disjunct populations are protected by law. It is in cultivation in California in gardens and some arboreta, but rare elsewhere. In the better growing conditions of gardens it can grow to a large tree; a specimen in New Zealand was 45 m tall with a girth of 1.5m in 1982 (Grimshaw & Bayton, 2009). Although its conservation seems more or less assured at present, growing this species more widely as an ex situ backup is to be recommended; it is also an interesting species to grow and requires a mild climate with warm, sunny summers and (near) absence of frost in winter.

Conservation Status

Global status and rationale

Critically Endangered B2ab(ii,iii,v)

Urbanisation is encroaching on the mainland population (subsp. torreyana) with the effect that trees outside the Torrey Pines State Park are still disappearing. There is also an acute risk of a major fire wiping out a large part of the population, a risk that is known to increase for various reasons where housing developments are near the population in a potentially fire-prone area. The present decline is probably slow, but ongoing in one of the two subspecies (mainland population). The actual area of occupancy is very small for the two subspecies combined, less than 1km². Critically Endangered is the correct assessment for this species, even through the island subspecies has been assessed as only Vulnerable.

Global threats

The small population on the mainland that constitutes the typical subspecies is in part (southern subpopulation) legally protected in the Torrey Pines State Park. However, the small overall size, fewer than 3500 mature trees covering ca. 320ha in two subpopulations, and close proximity to major urban development, put the subspecies highly at risk of destructive events such as fires, pest epidemics and diseases. Trees outside the reserve are often not protected from development; they are sometimes incorporated in urban landscaping and sometimes felled (personal obs., 1992). Urbanisation outside the reserve is ongoing, with expanding housing projects encroaching on the population of Torrey pines. It is expected that this will result in continuous, slow loss of mature trees unless all are incorporated in a protected area.

The even smaller population on Santa Rosa Island, with ca. 1000 mature trees, is not under pressure from encroaching urbanization and is not declining. It is at high potential risk from destructive fires

Conservation Actions

One of two subpopulations on the mainland is protected within a specially created reserve (Torrey Pines State Park), where collecting and other activities detrimental to the pines are strictly prohibited and enforced. It is strongly recommended to create a reserve for as many trees as possible in the second subpopulation. The population of subsp. insularis is legally protected.