Old trees are in big trouble.
Entire forests with giant sequoias fire-resistant up to 3,000 years old have recently caught fire. Entire stands of drought-tolerant Great Basin bristlecone pines, a species that can be up to 5,000 years old, have been sucked in by bark beetles. Monumental baobabs, the longest-lived flowering plants, are giving way under drought stress in southern Africa. Mount Lebanon’s iconic cedars, ancient symbols of longevity, are struggling in hotter, drier conditions. Thousand-year-old kauri trees in New Zealand and century-old olive trees in Italy are succumbing to invasive diseases.
Cumulatively, it’s more than cyclical revenue. That’s a big decrease: less megaflora (massive trees), less elderberry flora (ancient trees), less old-growth forests, less old-growth species, less species in general.
Although the Earth’s “tree cover” – three trillion plants covering about 30% of all land – has expanded recently, the canopy is increasingly made up of trees planted for wood, pulp and paper. cooking oil and for services such as soil protection against wind erosion and compensation. carbon dioxide emission. It’s young. Ancient communities are rare and becoming rare.
Ancient trees also provide services, but in reality they are gift givers. Of all their gifts, the greatest are temporal and ethical. They inspire long-term thinking and encourage us to be aware. They appeal to our deepest faculties: to venerate, analyze and meditate. If we can recognize how they appeal to our ethical imperative to care for them, then we should slow climate change now and pay for the people who will need a future planet with chronodiversity as well as biodiversity.
Old trees are needed to support the rich communities of species in forests. They deposit on the ground seeds and litter eaten and used by the animals; in height, they shelter epiphytes and birds. In conservationist Meg Lowman’s formulation, there is an animated “eighth continent” in the canopy.
The underground ecosystem could just as easily be the ninth. Trees share nutrients through mycorrhizae, the symbiotic association between fungi and plants at the root level. Preliminary research into these webs, called the “Wood-Wide Web,” demonstrates that large, ancient trees are outsized, serving as hubs for hundreds of other trees.
These centers redistribute vital nutrients of nitrogen and carbon – first to their own species, then to unrelated plants, sometimes even to competing plants. For a seedling, the help of a great old tree can be the difference between death and a long, long life. Suzanne Simard of the University of British Columbia, a leading ecologist in this field, calls well-connected donors “mother trees.” The destruction of old-growth forests not only destroys standing trees, but also the underground connections between them.
Each secular tree is also a precious genetic deposit. According to the models, a quarter of the trees in an old-growth forest will be triple or quadruple the median age, and a hundredth will be 10 or 20 times the median age. Each plant in this latter group appeared at a specific time in the past when favorable conditions allowed their establishment—conditions that may not recur for centuries. As bridges between pasts and possible futures, these plants contribute to the genetic resilience of the population.
The oldest are irreplaceable for science too. Only about 25 plant species can, without human help, live beyond a millennium, and these are mostly primitive-lined conifers. Their genetic code, the product of hundreds of millions of years of evolution, contains information that scientists are only just beginning to analyze. As genetic sequencing technology advances, people may find new applications for DNA from ancient trees.
Some thousand-year-old conifers such as bristlecone pines have a distinct utility. Their tree rings are living data – indicators of temperatures, winter snows, summer droughts and supervolcanic eruptions. Dendrochronologists use them to reconstruct past climates and model future climates. As climate recorders, tree rings are comparable to layers of ice, but more sensitive.
On a purely utilitarian level, ancient tree populations temporarily absorb some of the excess carbon in the atmosphere. The slower tall old trees grow, the greater their potential for negative emissions; the longer they delay death and decay, the more they can sequester greenhouse gases inside their wood.
For this reason, some organizations and companies struggling to offset their emissions have resolutely pursued tree planting. But these initiatives have an uneven track record. The protection of existing old-growth forests should take priority over the creation of new tree cover.
The challenges and scale of forest management have changed with the climate crisis. Large-scale habitat preservation is no longer enough; it must be accompanied by a rapid decarbonization of the economy. Otherwise, the future of old stands is in ashes.
Can we care enough about it in time? History suggests we can. Stories of sacred plants – and their keepers and defilers – are some of the oldest living stories, from Gilgamesh in the cedar forest to the Buddha under the Bodhi tree.
All over the world, in shrines, temples and cemeteries, locals protect trees planted centuries ago – or quite recently – the latest in a long, unbroken line of consecrated plantings. Sacred groves are traditional features of many cultures and religions. And state-protected areas with tall, ancient trees – centuries-old sacred groves – can be found from the Alishan National Forest Recreation Area in Taiwan to Waipoua Forest in New Zealand to the National Park of Alerce Costero in Chile.
Among plants there are ephemera, annuals, biennials, perennials – and beyond all a category that I call “perennials”. Perseverance is resilience over time. Humans can recultivate this attribute by caring for old trees and future elders. Cultivating long-term relationships with long-lived plants is a rejection of The End, an affirmation that there will be—must be—tomorrow. It’s a gift.
The New York Times