Bristlecone pine  (Pinus longaeva)

The bristlecone pine is classified as Least Concern (LC) on the IUCN Red List (1).

The bristlecone pines are one of the world’s oldest living organisms (3); the oldest known living tree is called ‘Methuselah’ and has been dated at a mighty 4,789 years of age (2). These ancient trees have a fittingly gnarled and stunted appearance, especially those found at high altitudes (4), and have reddish-brown bark with deep fissures (2). The green pine needles give the twisted branches a bottle-brush appearance. The name bristlecone pine refers to the dark purple female cones that bear incurved prickles on their surface (5).

Pinus longaeva is found in the mountains of California, Nevada and Utah; the oldest trees are located in the Ancient Bristlecone Pine Forest in the White Mountains of California (5).

Bristlecone pines inhabit harsh mountainous environments where there is generally very little moisture (4) (5). They are found in the upper tree line at 1,700 to 3,400 metres above sea level (2), on dolomite outcrops (5).

Bristlecone pines have an extremely slow rate of growth. The summer months are very short-lived; new cones and twigs must be formed at this time and reserves stored for the long over-wintering phase. If trees are damaged by fire or drought, their living tissues will die back retaining only what can be sustained by the tree, thus much of the tree appears dead but it is still able to produce cones with viable seeds in the summer months (5).

Tree growth rings reveal the age of an individual tree but can also provide insights into past climates. Pines produce wide growth rings in generally good conditions, that is, sufficient moisture and good soil, and narrow growth rings form in poor conditions: little moisture and poor soil. By studying these growth rings, light can be shed on past climatic events (5). Because bristlecone pines are such old organisms, and because their timber persists for an incredibly long period after death (3), the study of the wood of these ancient trees has revealed environmental conditions stretching back to almost 9,000 years ago (4) (5).

The bristlecone pine has an intrinsically low rate of reproduction and regeneration, and it is thought that under present climatic and environmental conditions the rate of regeneration may be insufficient to sustain its population (1). In addition, an introduced fungal disease known as white pine blister rust (Cronartium ribicola) is believed to affect some individuals (5), while other insect and disease agents such as the mountain pine beetle (Dendroctonus ponderosae) and dwarf mistletoe (Arceuthobium spp.) are detrimental to this species’ survival. Fires in lowland populations of bristlecone pine within mixed forests are also a danger, as the thin bark is only able to withstand low-severity fires (1). Vandalism is a new threat that these ancients face and the location of ‘Methuselah’ is unmarked in order to protect its identity (5). Climate change may potentially pose a threat to the bristlecone pine in the future, but its impacts are not yet certain. 

Bristlecone pines are protected in a number of national parks, such as the Ancient Bristlecone Pine Forest in the White Mountains of California and the Great Basin National Park in Nevada (3) (5), where cutting or gathering wood is prohibited (3). Some populations are within areas which have been protected purely for the monitoring and conservation of this ancient tree species (1). Ex-situ conservation measures for the bristlecone pine include the collection of its seeds and pollen. Identification, propagating and planting of individuals resistant to white pine blister rust may be an appropriate regeneration method. More research into the effects of climate change on the diseases and insect pests affecting this species could also help with its long term conservation (1). The sheer age of these trees, which were seedlings at the time of the pharaohs, inspires awe and protection.

For more information on the bristlecone pine and its conservation see:

• Global Trees Campaign:
  www.globaltrees.org
• BBC Wildlife Finder:
  http://www.bbc.co.uk/nature/species/Pinus_longaeva