National Tree Week is the UK’s largest annual tree celebration, we thought we’d start by celebrating the work of Dr Paul Smith, Author of Trees: From Root to Leaf. Dr Paul Smith has worked in conservation for over twenty-five years and joined Botanic Gardens Conservation International (BGCI) as its Secretary General in March 2015. He recently co-authored the ‘State of the World’s Trees’ report, published on 1 September 2021 as part of the IUCN World Conservation Congress, an event driving action on nature-based recovery, biodiversity and climate change.
He was previously Head of Kew Garden’s Millennium Seed Bank (MSB), London, where he oversaw its conservations of seeds from more than 25,000 species. We chatted to Dr Paul about his conservation work and beautiful book, Trees: From Root to Leaf.
Can you tell us about what you do at Botanic Gardens Conservation International (BGCI)?
We’re the largest plant conservation network in the world, and we coordinate about 700 member institutions around the world in plant conservation mainly. There are the large botanical institutions such as Kew and Missouri, but also a lot of small botanic gardens, universities, technical institutions, and forestry institutes in countries all around the world.
Our coordinating action, for example, includes carrying out and coordinating the Global Tree Assessment, to assess the conservation status of all 60,000 of the world’s tree species. That should be finished by the end of next year. We produced an interim report this time last year called State of the World’s Trees. That shows that 17,500 of those tree species are threatened with extinction at the moment under the International Union for Conservation of Nature (IUCN) categories, and about 440 species are down to fewer than 50 individuals. So we have a major issue with tree extinctions. But our partners are engaged in species recovery, working on in situ conservation and ex situ seed banks and so on. Our work at BGCI is about coordinating that network to make sure that no tree species becomes extinct.
You mentioned seed banks there, and you also worked on the Millennium Seed Bank. Could you tell us about that?
Yes, sure. I started out in 2000 when the Millennium Seed Bank first started. I was working at Kew before that and started as a coordinator for the seed collection programmes in southern Africa and Madagascar. In 2005, I took the role of Head of the Millennium Seed Bank for the next nine years and left that job in 2014. So I have a lot of seed banking experience behind me!
So the concept of seed banks is to prevent anything from going extinct?
Yes, also though to make material available for reintroductions and restoration. And for every seed collection that comes into the seed bank, we are, for example, learning how to germinate the seed. With wild species germinating the seeds is not something you take for granted, they have dormancy mechanisms and so on. It’s applying scientific methodologies to do that, so that we basically know how to turn the seeds into plants and into trees.
You have written this very beautiful book called Trees: From Root to Leaf. How did the idea of the book come about?
Thames & Hudson approached me because they wanted to write a book about trees. We had a chat about it, and it was wonderful actually because we came up with this idea of going through the life cycle of the tree and the different parts of a tree, and then linking that to other organisms, including ourselves and the dependencies and so on. Thinking about trees in the landscape, as they’re almost mother creatures. There are so many other organisms that rely on them as their keystone species, including ourselves, so we were thinking about it from that perspective, and therefore being able to bring in pollination biology, seed dispersal, and things like that.
Then there are human uses for trees, the practical uses like food and medicine and beverages and so on, but also art and architecture. Actually, it was serendipitous because I said to the editors that I’d love to tell the story of the Wayfarers Chapel in Palo Alto, California, which is really obscure. Nobody really knows about it, but it’s a Lloyd Wright building. It’s a kind of inside out cathedral built around redwoods, it’s the most beautiful church I’ve ever seen. And when I said I’d like to do something on that, Lucas, the Senior Editor, smiled and said, ‘I was married in that church.’ So it was it was meant to be, I think!
Thames & Hudson, because of their track record with architecture, art and design, were able to bring some really fantastic elements to this book, which is visually, I think, amazing.
What do you think the role of trees is in our world?
It’s fundamental. Because they’re the cornerstones of the ecology of this planet, there are cascade effects if we lose them. That’s something that is becoming clear to us here in the UK with Ash Dieback – everyone is noticing the dead trees; the councils are certainly noticing them because they have to clear up the mess and it’s costing them millions. But they [Common Ash trees] also have a really important role for wildlife, there’s a massive knock-on effect there. I think there are about fifty identified species that are obligate i.e. they only live with Common Ash. The role is that pivotal.
The book also explores how important trees were to us historically, but also today. Fruit trees, for example, are massive industries. Everyone has fruit from a fruit tree in their house at any given time, and beverages, and timber and so on. Trees are fundamental to us, and we take them for granted, I think.
What do you think is the biggest threat to trees?
Human activities. The State of the World’s Trees report shows that it’s primarily land use change. Cutting trees down for agriculture, mainly. Ironically, tree planting is a big threat now because we’ve got hundreds of millions of hectares pledged for tree planting, for carbon sequestration. We’re seeing fast growing exotics like eucalyptus and pine going into landscapes, even here in Wales, and displacing biodiversity.
Just to let you know, that’s not how we do things at all at The Future Forest Company!
No, I know. I’ve been looking at your website.
What are your thoughts on reforestation – done right! – considering that the UK has one of the lowest levels of woodland cover in Europe?
We’re working actively on that at BGCI. We are in the process of developing a standard that will provide assurance that biodiversity is not being harmed and wherever possible being enhanced. PlantLife are working on something similar, so I think that regulation of reforestation will be covered ultimately. But we’re primarily working in developing, high biodiversity countries, and there are a lot of cowboys out there selling eucalyptus at the cheapest possible price and not caring too much about whether they survive or where they’re put.
So land use change is a threat, and also climate change has a knock-on effect for pests and diseases, and changing climatic patterns which are putting trees under stress. Cutting down trees for firewood, and charcoal making are also threats.
Another concern is there are more rare tree species than there are common tree species, and the Global Tree Assessment shows us that 58% of tree species are endemic to a single country. It’s amazing to me that it was only in 2017 that we had our first global checklist of tree species, given how important they are.
What would you like to see happening with trees and forests across the UK, and across the world?
I’d like to see a shift towards exactly what The Future Forest Company doing, a shift to towards putting in native species where there are genetic advantages in terms of resilience. There are massive knock-ons for biodiversity as a whole. If you plant an oak tree, it’s documented that 2,300 other species rely on that oak for their life cycle, so the additional benefits of biodiversity are enormous.
If you put spruce in, you don’t get anything like that, and that’s true across the world where commercial forestry is set up to deal with a few hundred species at most. What we tend to see is the fast-growing exotics – Acacia decurrens, Eucalyptus, Grevillea robusta, Pinus patula – species that do very little for biodiversity and create other problems, including water table issues, fire risk and so on. We need a much bigger portfolio of tree species in seed systems, seedling systems, nursery systems and so on.
We’re lucky in this country as we have relatively few native tree species – 36 maybe, depends who you talk to – and we have plenty of capacity for managing those species. But elsewhere around the world – well, to give you an idea, we keep the database of all the plant species grown in the world’s botanic gardens. All of the world’s botanic gardens together grow about 18,000 different tree species, about a third of the total, whereas foresters grow maybe 100, 150 species. So we need to be expanding and sharing that knowledge. Our role at BGCI is to mobilise botanical expertise and knowledge. Sharing the information we have in botanic gardens is an excellent start to broadening out the tree portfolio so that we can cultivate, manage, and secure many more tree species, and all the knock-on effects for biodiversity they have.
Did you learn anything about trees that you didn’t know before whilst writing your book?
Yes, lots! You have to check your facts and do your research. I have a daughter and gone are the days when dads could make stuff up, because the kids have all got Google and they say, ‘Are you sure about that, Dad? No, I don’t think so.’
One of the things that’s covered in the book is trying to calculate how many leaves there are in the world. The figure I came up with is about 200,000 per person. Also, the weight of the largest tree in the world is six times the weight of a blue whale.
Do you have a favourite tree species?
Yes I do, it’s a bit of an obscure one as far as people in the UK are concerned because it’s an African tree called mopane. It’s the best firewood in Africa because it’s very dense, in fact it’s sold to go into fish tanks because it’s heavier than water and it sits on the bottom of your fish tank. It burns like a low-grade coal with a lovely scent. More importantly, it’s an important wildlife species. It produces beautiful colours in the autumn and looks a bit like a beech forest, because it tends to grow almost as a monoculture. It’s called cathedral mopane when you get the tall form of the tree, which gives you an idea of the pillars, and the colours are amazing. It’s a legume and it produces little pods that smell of nutmeg. It’s a beautiful, lovely tree, with butterfly-shaped leaves.
Help us to plant UK woodlands today. With our range of subscription plans and one-off gifts, you can contribute towards tree planting, conserving and restoring biodiversity on our UK sites and have a positive impact on reversing the nature crisis.