Finding the biggest or oldest individual of a tree species, so called champion trees, is a pastime somewhat akin to a very slow version of train spotting. It could be easy to dismiss this activity, as I have tended to do without appreciating the scientific rigours involved, but reading these two books has completely changed my outlook. In fact, Elderflora by Jared Farmer, a Professor of History, emphasises a whole new dimension to tree conservation. Documenting the conservation status and reducing the extinction risk to individual tree species is one generally acknowledged conservation priority. Protecting assemblages of trees, especially those of species-rich forests, is another. Taking into account the age of trees and forests is yet another important factor emphasised by these two books. Farmer suggests that to become wise stewards of the planet, we must take greater account of the temporal component, recognizing the age of trees and emphasizing the value of old-growth forests. We should conserve trees, not only for their ecological value, but because they represent and record the very passage of time.

Individual ancient trees can be of great cultural and symbolic significance, revered for their connection with particular historical events, links with religious sites and their continuity through time in a local context. Collections of ancient trees in woodlands and forests may be valued for their strong sense of place. But the cultural and spiritual importance of forests has been widely overlooked during recent centuries of global forest exploitation. In the colonial era of settlement, the quest for land, building materials and profit has led to the clearance of vast areas of ancient trees without regard for the ecological consequences or the needs and beliefs of local people.

Old-growth forests are clearly of immense ecological importance for the habitats they provide and the biodiversity they support. In her relatively slender tome, Joan Maloof, a biologist and Director of the Old Growth Forest Network, sets out the importance of old trees for biodiversity. She points out that many species unique to old-growth sites disappear after timber management and that rare and threatened species are more likely to be found in old-growth forests. The chapters in her book Nature's Temples outline the support provided by these forests for different species groups and also document the value of old-growth forests for water and carbon, and for their sheer beauty. There are some odd gaps in her coverage, however. For example, the chapter on amphibians refers only to salamanders and frogs, without reference to other amphibian groups. The geographical scope is also somewhat limited: Maloof's book focuses mainly on the USA, with few references to ancient trees and forests in other parts of the world. The author points out that in the western USA, only 5% of forests remain unlogged and in the eastern part of the country, less than 1% of the land is covered by original, unlogged forest. She makes a strong case for leaving old-growth forests alone ‘for the species we share the planet with and for our human spirits’ (p. 147).

Farmer's fascinating—and much chunkier—book, on the other hand, provides a broad global and historical perspective. He highlights the interlinkages between people and trees throughout time and explains how the scientific value of dating trees can help understand the history of the Earth. ‘As a worldwide phenomenon, the modern cult of arboreal monuments could conceivably serve as a cross-cultural foundation for geotemporal thinking’ (p. 133).

And what of the oldest trees? Farmer notes there are c. 25 plants species that can, without human assistance, produce individuals that live for over a thousand years, and that these are mainly conifers of primeval lineage. He also draws our attention to the fact that the oldest individuals are not always the biggest. As noted in both books, a Great Basin bristlecone pine Pinus longaeva is acknowledged as the oldest recorded living tree. The story of ageing bristlecone pines as described by Farmer is as gripping as any novel. It was no small achievement for Edmund Schulman—who fought poverty and ill health to develop an academic career—to discover, in the late 1950s, living trees aged over 4,000 years old.

Bristlecone pines have not been major targets for their timber. The species is categorized as Least Concern on the IUCN Red List and is now protected within the Great Basin National Park thanks to the endeavours of Schulman and his successors. Other ancient trees such as the majestic Alerce Fitzroya cupressoides of Chile and Argentina or the Kauri Agathis australis of New Zealand have been depleted by logging and are under continuing threat of extinction. These two books highlight why we should record and care about all the world's ancient tree growth. As Farmer notes, ‘the demise of olden trees represents an ecological loss, a cultural impoverishment and a social problem’ (p. 305). The solutions are for us to remain engaged, network, do more where necessary and also learn to leave ancient forests alone without interference. Only if we do all this will the treasured and unique ancient trees and forests of this world be able to continue to play their crucial role in the intricate web of life.