When we talk about longevity, our minds rush to think about giant tortoises and crocodiles, elephants and other animals.

Indeed, crocodiles can live as much as human beings and elephants also reach the sixties. Giant tortoises are proved to live more than 200 years. And some ravens and parrots are indeed, more long-lived than other birds the same size (but reject those crap information about 100 years and so on!).

But we tend to oversee that, in fact, for trees a secular age is something quite common. Oaks and beeches easily reach three-four centuries; and with them, many species of broad-leaved trees. Baobabs are reputed to live till 3,000 years, but as this tree does not produce growth rings, this cannot be proven. Instead, coniferous trees - that produce growth rings - are proven as the champions of lifespan on Earth. Their slow metabolism, efficient resins against pathogens and dry-resistant adaptations seem to have brought them success.

If common spruces and firs can live till eight centuries, they are far away from being the champions. Sequoia (redwoods), which are the largest trees in the world, are at the same time amongst the most long-lived. But, the oldest still living individuals were found to belong to two pine species from the mountains of southwestern USA (Utah, Nevada, Eastern California, Colorado, Northern New Mexico, Arizona): Great Basin Bristlecone Pine (Pinus longaeva) (photo) and Rocky Mountains Bristlecone Pine (Pinus arista).

The oldest individual of Pinus longaeva was found to have 4,900 years!

When the Egyptian civilization was emerging, these pines were seedlings!

Paradoxically, we are not talking about towering trees: they hardly reach 15 m (45 feet); 3.6 (11 feet) in diameter. Their growth is very slow: 2,5 cm (one inch) per century! And their leaves are the most longevous known leaves: till 45 years!

The wood of these trees is currently half dead, but it does not decompose due to the dry, cold climate in which they live, at 2,500-3,700 m (7,500-11,100 feet) altitude. In fact, the climate and the durability of their wood can preserve them long after death, with dead trees as old as 7,000 years persisting next to living ones. The area where these trees grow is now totally protected.

Trees growth rings can record the climate of a year (wet years produce thicker rings, dry years thinner ones). The rings of these pines counted us the climate of the last five millennia in southwestern US: after a warm and a wet period, following the glaciations, 2500 years temperatures decreased and so did the rainfalls. 1000 years ago, a warm and dry period, which still persists, installed.