Jonathan Drori loves trees. So much so that he has spent a career working with them as a documentary film maker at the BBC, and on the boards of Kew Gardens in London, and the Eden Project in Cornwall. On a very wet afternoon yesterday in a full auditorium at The Piano for WORD Christchurch Festival an audience of enthralled drendrophiles (tree lovers) and nemophilists (woodland enthusiasts) got to hear Drori tell us about his passion for trees, and recount some enlightening stories from his recent book Around the World in 80 Trees.
Jonathan was first introduced to the wonderful world of plants by his father, a Russian emigre to the UK, who would take him to botanic gardens where he took a very unorthodox approach to botanical education. His father would feed him small pieces of the plants on show, some of which were psychoactive (like the opium poppy his dad suggested he lick), or even poisonous, like the unfortunate plant known as the dumb cane. The story behind this particular plant is deeply unpleasant as the name comes from that fact that slave owners fed it to their slaves as a punishment as it was extremely distasteful and could cause the mouth and tongue to swell up until the slave could no longer speak.
There is much talk these days, Drori said, about what people need, but he is more interested in what trees need, and this provided the structure for much of his talk. Firstly, trees need water, and it seems that this sets a fundamental limit on how tall they can grow of about 120 meters, above which they are physically unable to bring water up from the ground to the leaves, flowers, and fruits in their uppermost reaches. For this reason, none of the tallest tree species ever exceed this height, and they never will, despite any evolutionary pressure that might otherwise drive them to do so.
The second thing that trees need is food, which they get not from the soil, or even sunlight (although that does drive the process), but in fact the mass of a fully-grown tree has almost entirely come from carbon dioxide in the air, a fact that is of obvious significance in the context of climate change.
A perhaps less known requirement of trees is for particular species of fungi, called mycorrhizae, that live in the soil and form close associations with tree roots. In many cases, the trees can’t survive without them. These associations are often very specific, for example the fungi that birch trees need form the familiar red mushrooms with white spots known as fly agaric, which are very poisonous. (Drori had some entertaining stories about these mushrooms, but I’ll let you discover them for yourself in his book, see p.21). The mushrooms themselves are only a temporary, and very small part of the fungus as a whole, necessary only for its reproduction, but the vast bulk of the fungus is in the form of thin threads, hidden from view in the soil, which wrap around and interact with the roots of trees and other plants. Drori painted a picture of a vast information super-highway of fungal threads that allow trees to communicate. For example, when one tree is attacked by insects it can use these fungal threads to warn others around it, so that they can activate their defenses.
Defense was the next need that Drori told us about, and he spent quite a long time on it, telling us several amazing stories. He told us how caffeine is used by plants to defend themselves from attack by plant-eating insects. We learned that the alder tree, which lives in boggy ground and is highly resistant to rot, was used extensively for building in water-logged renaissance Venice, and apparently its charcoal makes the best gunpowder, still favoured by the military.
We heard about the whistling thorn, which whistles in the wind because of small holes made by ants that live inside the tree and protect it from other insects. A particularly gruesome story in this section was about how certain Buddhist monks used a tea made from the sap of the lacquer tree to mummify themselves while still alive, becoming ‘whole-body relics’, a truly horrific form of suicide by dehydration that is now thankfully no longer practiced.
Drori then moved on to talk about sex and seed dispersal, as trees need to make more trees. We heard that the laxative properties of many fruits are an evolutionary adaptation to make them pass through the gut quickly before the seeds are digested so that they can be deposited elsewhere in their own little pile of fertilizing dung. We heard about the extraordinary, and provocatively-shaped coco da mer, the heaviest seed in the world, once highly revered, which exchanged hands for extraordinary sums of money. We also heard about the traveller's tree of Madagascar, the blue seeds of which can only be dispersed by lemurs as they are the only animals strong enough to break open their seed pods. This means that the fate of the tree is tied to that of these endangered lemurs, emphasizing the connectedness of trees with the other organisms in their environments, and the extent to which species rely on each other in fragile ecosystems.
This brought Drori to his final, and perhaps most important point; trees need love. To make this point he talked briefly about his involvement with the Eden Project, “the largest rainforest in captivity”, and mentioned the possibility of an Eden Project coming to Christchurch’s red zone, although in a rather different form much more suited to the needs of the local community, and in keeping with our own native flora. What we need, he said, is “a mycorrhizal network of people” dedicated to caring for, and looking after, the interests of trees. Inspirational stuff!
Drori finished his talk by pre-empting a question he had been asked before; if you could be any tree, which one would you be? The Quiver tree, the national tree of Namibia, he said. Why? Because whenever anyone sees one they smile, and then they want to stroke it – a lovely end to a delightfully entertaining and informative tour of the fascinating world of trees.
Drori’s talk was accompanied throughout by beautiful illustrations from his book drawn by Lucille Clerc. They are truly stunning, and this is one of the most beautiful books I have seen this year. It is full of many more amazing stories about trees like those we heard in this wonderful talk and I can’t recommend it highly enough!