Andrew Ormerod’s personal view of the subject as little ‘snap shot’s’ exploring the importance of trees.
Part 1 Oldest, tallest and environmental benefits of trees
Courtesy of the Eden Project http://www.edenproject.com/eden-story/our-ethos/redwood-conservation-project
I have been interested in growing plants from seed – particularly trees since a mere sapling myself! My career ‘branched out’ into plant breeding, tissue culture and into economic botany research for exhibits at the Eden Project. While there I kept my hand in under my own steam raising populations of apple trees from seed. So I have always been interested in trees and although I appreciate the world of plant genetics, genomics and molecular biology think there is a role to play in demonstrating diversity in trees.
So to define a tree – Trees are plant having a permanently woody main stem or trunk, ordinarily growing to a considerable height, and usually developing branches at some distance from the ground – certain palms could be included in this particular definition too. Apologies for any licence taken for including any multi stem palms here!
So why are trees so remarkable?
A world with out their majestic presence would be hard to imagine. Scientists lead by Yale University in the USA reported in 2015 in Nature that there are just over 3 trillion trees on the planet. This is based on surveys in every continent except Antarctica – that is 422 for every person. In the UK 3 billion trees were estimated (47 for each inhabitant).
Ancient trees links from the past
They are a link to the past – through veteran trees that have witnessed history – older than generations of humanity forgotten in the mist of time. Among the oldest trees are the Bristlecomb Pine Pinus longaeva the oldest of which is around 5,000 years old and the Alerce Fitzroya cupressoides another conifer from Chile at around 3,800 years old.
Ancient trees are a fantastic habitat for a wide range of organisms (plants, animals, microbes). These are trees in Parque Nacional Alerce Andino near Puerto Montt in Chile
Also in the mix are ancient olives Olea europaea and yew trees Taxus baccata among others whose true age may be harder to ascertain due to their original trunks rotting away.
Relatively young olive tree display at the Eden Project at the Eden Project.
Even older are the root systems of clonal stands of trees such as those of Quaking Aspen Populus tremuloides in the USA – though the new trees are young the roots are estimated to be 80,000 or more years old. Among the amazing survivors of the tree world are the fossil trees from an age when creatures other than humans were the predominant species. Among those are Maidenhair tree Ginkgo biloba from China, once more widespread before the last ice age – the sole living link in its own category between lower and higher plants.
Ginkgo biloba has medical applications – here seen in the Crops for Health exhibit at the Eden Project. These trees are planted in an alley cropping format commonly associated with agroforestry.
Other anomalies include the Dawn Redwood Metasequoia glyptostroboides also from China that was the only living species in its genus of otherwise fossil trees – found as a few living specimens in 1944. Its ease of propagation and grace of habit have lead to its widespread ornamental planting in temperate parts of the world. Similarly but more recently – the Wollemi Pine Wollemia nobilis found in an isolated part of New South Wales, Australia has been propagated and spread around the world to help raise funds to protect its original habitat. Another more everyday species that we would find on an expedition to the local shops is the Avocado Persea americana native to South Central Mexico – its wild forms once the food of a now extinct giant ground sloth that would have aided distribution of its seeds. Sometimes missing links in more complex biology of trees can lead to their isolation. Another example of co-evolution and co-reliance is the fig tree and fig wasps – fig flowers relying on pollination and fig wasps rely on a few developing seeds as a food source for their larvae.
Biggest and tallest.
So we have touched on the oldest but what about the biggest and the tallest? – Well there can be an overlap. The giant sequoia (Sequoiadendron giganteum), known as ‘General Sherman’, is by volume the world’s largest single stem tree currently alive. There have been at least a couple of larger Coastal Redwoods, which were cut down in the 20th century. The tallest tree in the world is ‘Hyperion’ a coastal redwood (Sequoia sempervirens) at 380 feet tall – about 70 feet shorter than the top of the London eye or the equivalent of two and a bit Nelson Column’s! The Eden Project have recently teamed up with Archangel Tree Archive (https://www.ancienttreearchive.org) to grow a diversity of saplings of Coastal Redwood propagated from these ancient trees as an educational link for future generations of people interested in the marvels of tree biology. One of the biggest trees propagated had a trunk diameter of 35 feet at ground level. So you wouldn’t have much room for other plants eventually if you planted one in your garden!
Courtesy of the Eden Project http://www.edenproject.com/eden-story/our-ethos/redwood-conservation-project
However one of the world’s widest trees with a trunk 52 feet in diameter appears to have been the Glencoe baobab Adansonia digitata in South Africa until its trunk split in two.
Threats in literature reflecting reality here on earth.
Douglas Adams so often captured the fragility of the human condition and its impact on the environment. In answer to Ford Prefect’s observation when returning to a prehistoric earth in the ‘Restaurant at the End of the Universe’; “How can you have money, if none of you actually produces anything? It doesn’t grow on trees you know.” A management consultant talking about fiscal policy said “Since we decided a few weeks ago to adopt the leaf as legal tender, we have, of course, all become immensely rich. But we have also run into a small inflation problem on account of the high level of leaf availability. The current going rate has something like three deciduous forests buying one ship’s peanut. So in order to obviate this problem and effectively revalue the leaf, we are about to embark on a massive defoliation campaign, and…er, burn down all the forests. I think you’ll all agree that’s a sensible move under the circumstances.” In reality trees are disappearing fast – a cause for concern – 15 billion are disappearing annually, according to the Yale University led project data, due to deforestation and land use change for farming, settlements or mineral extraction. Unfortunately the movie Avatar (2009) though relating the plight of mining exploitation of lush forests on the planet Pandora to solve the earth’s looming energy crisis is fictional – it relates to similar situations occurring here on earth in various parts of the world, affecting the forests biodiversity and indigenous people. Some trees, in common with other plant life forms, prefer to grow on mineral rich land and may provide a signal for prospectors. In addition influence of minerals on growth characteristics of trees such as leaf colour and tree habit were recorded as long ago as 1556 in ‘De Re Metalica’ one of the earliest comprehensive books on mining by “the father of mineralogy”, Georg Bauer, (pen name Georgius Agricola). The subject of the earths mineral interaction with plants later evolved into the discipline of Geobotany.
Changing climatic and pest and disease conditions.
While it is important to conserve locally adapted ecotypes of trees it is important to consider the impact of climate change. Evidence from reciprocal planting of ash trees from sites from the South of France to the North of Scotland – indicated a northerly flow of adaptation with warming climates – ash trees from the South of France flourished in Aberdeen for example. With changing weather patterns and globalization there appear to be increasing levels of threats from spreading pests and diseases. I recall photos from an aerial survey on a late autumns afternoon in 1946 in the Fowey Valley in Cornwall where I live. The long shadows of elm trees in the photos are now just a memory in most of the UK’s landscapes. One of the latest threats is to ash trees from Ash Die Back. There appears to be a change in policy to deal with tree diseases depending on the type of disease. When Chestnut Blight decimated the American chestnut the approach was to clear fell trees – changing the North American landscape and removing any potentially resistant trees as well as the disease susceptible trees. In the UK I think the approach with Ash Die Back is to look out for the few resistant trees, which may be needed to rebuild future populations of trees in the countryside.
Elm traditionally used for building, farm vehicles, furniture and ship building for its water resistent properties. Elm sculptures at the Eden Project were originally part of the ‘Rosebud’ the trawler that took a petition to parliament to stop parts of Newlyn being demolished in the 1930’s.
Environmental benefits of trees
So what about the environmental benefits of trees? Well forests can have a significant effect on rainfall patterns. There are literary precedents such as Jean Giono’s book ‘The Man Who Planted Trees’ where the fictional shepherd Elzéard Bouffier brought moisture and life back to villages in a previously parched and treeless Provencal landscape by planting oak seeds and establishing woods over many years. There has been scientifically controversial suggestions made by Russian physicists in the mid 2000’s that rather than temperature differences, vapour pressure differences from condensing moisture produced by forests acted as a ‘Biotic Pump’ drawing in water vapour from surround oceans and the forests. This can act as a foci for ‘aerial rivers’ that water surrounding land. In the case of the Amazon rain forest according to Cornish based scientist Dr. Peter Bunyard loss of forest would affect the aerial rivers that channel rain south and north to the grain baskets of North America. Similarly it has been suggested loss of forest in Kenya has led to the disruption of the ‘water tower effect’ and drying of the surrounding farmland.
Influencing water quality and soil nutrients
In addition trees and forest prevent flooding and the run off excess nutrients from agricultural land that would otherwise contaminate waterways. They can act as windbreaks and reduce the impact of snowfall. Trees can be used as ‘Fertiliser Trees’ – particularly legumes – in tropical countries where the branches are cut off and break down to provide nutrients to field crops below. It isn’t just legumes that capture nitrogen – other species have beneficial effects too. Alder species for example – It has been suggested planting trees including the nitrogen fixing Andean Alder Alnus acuminata was one of a group of practices adopted (along with terracing and irrigation that helped revive agriculture and the fortunes of a collapsed pre Inca civilization. What ever the true impact was I have seen the impressive effect that Italian Alder Alnus cordata and the Russian olive Eleagnus angustifolia as nurse crops have in relation to the growth of Walnuts at two comparable trials in Oxfordshire. With the nurse crop the walnuts Juglans regia are over 20 feet tall – without the nurse crop the walnut trees barely reached 6’ tall in about 16 years. Subsequent planting of E. angustifolia appears to be improving the growth of the trees that did not benefit from these first time round.
Forestry policy and ecology
Forestry policy, poverty and availability of other fuel sources can have a marked effect on countries boarders when seen from space, For example the border between Haiti and the Dominican Republic and South and North Korea are marked by the lack of trees in Haiti and North Korea where lack of fuel has lead to excessive use of trees. On the border between North and South Korea the Demilitarized Zone (DMZ) has recovered without human intervention and has thriving woodlands and wildlife habitats. In addition since the Korean War ceased successive governments in South Korea have run an aggressive forestry campaign to reafforest the country, rebuilding their natural capital.
Pockets of forests may not be enough to support biodiversity, however, in the ecologically diverse Atlantic Rainforest, which is found on the west coast of Brazil and Argentina – corridors are being recreated to assist the movement of wildlife. Similar corridors are helping to protect wildlife in parts of Africa as well.
Different tree survival tactics
Let’s take another example where tree species adopt different survival strategies under contrasting climatic conditions. Let’s consider oak trees. Species of oaks have proved to be of significant source of carbohydrates for human hunter gathers populations during the autumn. Oaks were according to Gordon Hillman (retired Archaeobotanist from University College London) – one of the most significant families of plants ‘never domesticated’. In Great Britain there are some fine ancient specimens of oak trees such as the ‘Major Oak’ (Quercus robur) in Sherwood Forest but these Northern species have got a different survival strategy compared to some of evergreen oaks found around the Mediterranean. Some such as the Holm Oak Quercus ilex and the Kermes Oak Q. coccifera from the Mediterranean region have underground storage organs that allow them to survive and re grow after fire. They send out many new shoots that mop up phosphates that would otherwise be washed away – almost like putting these reserves into a bank account to prevent them being lost. Over the years many of the shoots die off as the main trunk of the tree regrows. This approach for dealing with fire is completely different to that of the Cork Oak Quercus suber. They develop ‘fireproof coats’ better known to wine and Champaign lovers as the source of bottle corks. This amazing natural fireproof layer also provides cork for the automotive and aerospace industries, among other uses. that is capable of withstanding extremes of cold and heat without breaking down.
Woodlands – naturally
When planting forest parkland appropriate management has to be considered. Left to nature land would either revert to forest or to grassland depending on the ecological and climatic conditions. There are very few areas of the British countryside, which are truly natural – one however is the ancient dwarf oak woodland found on Dartmoor, for example Wistman’s Wood– stunted by harsh conditions.
Eden Project – Atlantic temperate rainforest in the “Wild Cornwall’ exhibit. Lead sculptures of ancient oak trees dwarfed by harsh environmental conditions were used to represent the types of trees found in Wistman’s Wood – while the real things got established.
So what would happen if humans disappeared and environmental conditions favoured trees? In the Tamar Valley in Cornwall you can see the effect of abandoned cultivated market gardens and strawberry and daffodil fields now covered by woodland. The tell tale signs that the woods were not always present are the thicker bands of trees – where the hedges were – and the abandoned packing sheds in the woods. Finally the few daffodils in the woods – including the late flowering ‘Tamar double white’ once grown as a crop now add a bit of light to the woodland in early springtime.
Trees in open park or farm land
Forest parkland is unstable and is a result of the presence of a dominant species of herbivore/browser or human intervention that maintains this habitat. In the UK open fields and parkland are home to some amazing veteran trees – it isn’t clear yet if they have survived purely on happenstance or if the trees genetic make up has helped them to survive so long. They may have been planted and maintained by farmers who care about them for their majesty and as a legacy for the future. So could these trees play a role in farming or forestry?
Farming, forestry and ecology are there ways of finding areas of common ground?
Too often there appears to have been a cultural and educational disjunction commonly between farmers, policy makers and foresters which has not encourage more widespread adoption of mixed ecology farming involving trees and perennial and annual crops. A joke may sum up the risk of specialisation – apologies for any sweeping generalization! “If you take a bus load of farmers and foresters to see an agroforestry system they will never see eye to eye; as the farmers will be looking at the plants near ground level and the foresters will be looking at the crowns of trees!” These systems however have had historic precedence in parts of Europe. Farmer’s may be happy to have trees on the boarders of their fields – but are often concerned about the presence of new trees within their fields (unless they are planting an orchard). There appear to be cultural differences in terms of the boundaries of the productive landscape – commonly in the UK this ends at the hedge, whereas in parts of France it includes the hedge where trees may be harvested as a resource – for fuel or fodder for example.
Policies over payments to farmers have played a role in changing landscapes – in the last quarter of the twentieth century incentives to farmers led to the loss of traditional orchards. There appear to have been some conflicting incentives for trees on farmland between the EU’s conservation and production policies. In some European countries there are disincentives for farmers to plant trees on their farmland – because of changing status and levels of payments for long-term tree planting, which can lead to reclassifying agricultural land as woodland. On a positive note I was interested after the launch of the Satoyama Initiative in Japan (which aims to promote agricultural production and contribute to conservation of ecosystems and biological diversity) to hear Pablo Eyzaguirre from Bioversity International say on a youtube interview – agriculture and the environment are ‘now friends’. Hopefully heralding closer collaboration towards common objectives.
Andrew Ormerod copyright @ 2017