About 3.5 billion or about 50 for each person. Yes, there’s some guesstimating but it can’t be far out.  Of course you can argue the toss about what counts as a tree and if you count tiny saplings you might get it up to 5 billion. Here’s the basis for this number - the UK is just over 60 million acres, of which about 14% is woodland.  That’s a big increase from 1900 when it was only about 5% and it’s far less than Europe where the average is almost 40%.  Anyway, suppose there are another 50% of trees outside woodlands - such as those in parks, field edges, urban trees, and on moorlands. That would be the equivalent of 12 million acres with tree cover.  How many trees per acre is a big question because large majestic trees can be so large that there can be only about 20 on each acre whereas for young saplings the number can be as high as 2,000. Conifers can be as many as 1,000 per acre but, as the tree crop is thinned, that reduces to the low hundreds. So a figure of just under 300 trees per acre looks typical and on 12 million acres that would give about 3.5 billion trees. They are not evenly distributed between different parts of the UK - for example Scotland has almost 20% tree cover and about 20M acres so of the UK’s trees, almost a third are in Scotland. That brings us onto what species these trees are. It turns out that in woodlands a quarter of the trees are Sitka spruce and half as much again are Scots pine.  Other conifers (Douglas fir, Norway spruce and Lodgepole pine) make up another 15% so over half our trees are conifers.  Of the deciduous trees English oak and Silver birch each make up another 10% or so with Beech and Hazel together making 15% of our trees. It’s a concentrated picture, with 87% of our trees being made up of the top 10 species. Whereas the British population is around a hundredth of the world’s population (1%) we are far less significant in tree terms. There are probably around 3 trillion trees worldwide so the UK has nearer to a thousandth of the trees in the world.  At least the UK is going in the right direction - whilst the world’s tree cover is reducing due to deforestation from fires, drought and agricultural expansion, the UK’s has been increasing, albeit gradually.  Since the start of the millennium we have probably increased tree cover by around 1%. [caption id="attachment_30295" align="aligncenter" width="650"] Chestnut coppice[/caption]

Several thousand years ago, Scotland was extensively forested.  As the Ice Age came to an end, so the glaciers retreated and Scots Pine, birch, rowan, aspen and juniper populated the land, forming the Caledonian* Forest.  Pollen records indicate that Scots Pine was present in southern England some 9000 years ago, it then moved into Scotland.  Scots Pine is one of the UK’s three native conifers; the other two being Yew and Juniper. As the climate warmed, Scots Pine was lost from most of England.  The pine woodland that formed in Scotland was the westernmost part of the boreal forest that extended across most of Northern Europe.  At its peak, (about seven thousand years ago), the forest covered some 1.5 million hectares in Scotland.  It was a ‘home’ to beavers, wild boar, brown bears, elk and wolves.  These have since been ‘lost’, though in recent times, the European Beaver has been re-introduced. However, with the arrival and establishment of neolithic farmers, areas of heath and woodland were burned to encourage fresh growth of heather for their cattle and goats. Some time later (about 3000 years ago), there was period of cold and wet weather, peat bogs spread and the tree line was lowered. In places, broad leaved trees replaced Scots pine.  Throughout historical times, the felling of trees for timber and fuel continued, as did the grazing of livestock.  Later came extensive sheep farming and this was followed in Victorian times by deer and grouse shooting.  All of these limited woodland regeneration.  So what was once an extensive forest was reduced to a fraction of its former size. Remnants of this once great forest can still be found and even today these woodlands offer a rich habitat that supports a diverse flora and fauna, where pine marten, capercaillie, red squirrel, Scottish crossbill and wildcat can be found.  Glenmore is a National Nature Reserve with many mature Scots Pine, Glen Tanar is another area of Caledonian* pine forest, set within the Cairngorms National Park.  The woodland floor provides a habitat for many plant species typical of the Caledonian Forest - twinflower, creeping lady's-tresses.    Rare and unusual insects are also to be found such as the bumblebee robber fly. According to a recent study by “Trees for life” many of the the remnants of the ancient pine forest are on a ‘knife edge’. Large numbers of deer have and are damaging the woodlands.  The deer eat pine saplings and damage bark. This can result in birch replacing pine. Whilst there have been efforts to exclude deer in some areas by putting fencing in place, the fenced areas were often not big enough or over time the deer were able to breach the fencing and continue to forage.  Pine trees need time to establish themselves free from the impact of grazing. Some areas of pinewood suffered from the planting (in the 1950s) on non-native conifers, such as Sitka Spruce.  As these grow they can crowd out Scots Pine.  Many others areas are small and ‘isolated’. This leads to a reduction in biodiversity, so it is more difficult for natural regeneration to occur.  It also means that resilience is lost in the face of threats like climate change.   * the roman name for the area now Scotland was Caledonia.   Scots Pine is sometimes described as an ‘honorary hardwood', as it grows slower than certain conifers and produces better quality timber. The loss of forest across the Earth is a cause for concern - see https://theconversation.com/how-forest-loss-has-changed-biodiversity-across-the-globe-over-the-last-150-years-140968    

How many trees are there in the world? When Thomas Crowther and Henry Glick used geospatial data in 2015 to estimate the number of trees in the whole world there was good news and bad news. Good news that there were several times as many trees as anyone had previously realised (total is about 3 trillion) and bad news that the number was declining faster than expected.  The calculation was done partly to establish a baseline so that tree-planting efforts could be put into perspective - the UN's Billion Tree Campaign managed to plant about 15 billion trees over 10 years in virtually all countries across the world (193).  But whilst these numbers sound large this has only added 0.5% of trees so much more needs to be done if we want to reduce the damage humans have done to tree numbers - before humans emerged there were about twice as many trees as there are now.  Perhaps that's why the Trillion Tree Campaign was launched in 2018 in Monaco - a principality covering only two square kilometres and almost bereft of trees. More locally, the UK has a tree count of about 3 billion trees - about 45 trees per person - calculated by analysing aerial photos and estimating tree numbers as was done under the UN's Plant for the Planet project.  There is some flexibility on the definition of what counts as a tree - and this assumes you don't count all the self-sown seedlings or bushes, which some might consider as trees.  This number is dominated by a few species - of the commercially grown plantations in Scotland, for example, 60% of the trees are Sitka Spruce so they don't add as much to biodiversity as a wider species mix would do.  And those 45 trees per person is a bit misleading in that there may be nearer to  400 trees per person in Scotland  - it is more sparsely populated with less than a tenth of the UK's population but almost half the trees. The UK's tree-planting is put into perspective by comparing the relative numbers - the UK's 3 billion trees amounts to one thousandth of the global total whereas nearer to 1% of the world's population is British - so by comparison with the world's average, on a per-person-basis a Briton has a tenth as many trees as the average citizen of the world.  The most densely tree-ed parts of the world are the tropics where 43% of the world's trees are growing. At a recent general election (2019) the political parties were competing to promise how many new trees they would ensure were planted - the Liberals and SNP each promised 60 million a year, whereas Labour said they would do 100 million every year.  A more realistic Conservative party promised 30 million trees every year which would equate to about 15,000 hectares (or 6,000 acres).  Despite this lower manifesto promise, the government is really struggling to achieve even that amount - but if they did reach that target every year for 10 years it would add 10% to the UK's tree cover. There is ample scope for more trees with the UK having only 13% tree cover, but are there are other ways to increase the numbers beyond tree planting? Trees will naturally establish themselves if they are not cut or grazed - perhaps one thing the government could do would be to reduce the number of wild grazers - mostly deer and sheep.  

Scottish moorlands often stretch uninterrupted towards the horizon, a mosaic of greens and browns. The tallest plants growing only ankle high. but even so, walking may require careful attention. There are hummocks covered in heather (Calluna vulgaris) and / or cotton grass (Eriophorum spp.) but inbetween, there may be somewhat soggy patches of sphagnum moss.  Lying beneath the moss, heather and sedge is peat – this is a nutrient-poor, but carbon rich mass of partly decayed organic matter.   Plants growing in the bogs are rooted in the peat, but are also contributing to ‘new peat’ as they grow. As their leaves wither and die, they drop into the acidic and watery surroundings – a process that has been going on for possibly for millennia . Read more...

Checking through my emails, I came across a link sent by a friend to one of the winter talks in the program offered by the Botanical Society of Scotland - specifically “The Scottish Uplands: how to revive a degraded landscape” by Dr Helen Armstrong.  The talk was live-streamed but was also recorded and is available here.   Dr Armstrong spent 24 years at the Nature Conservancy Council, the Macaulay Land Use Research Institute, Scottish Natural Heritage and Forest Research carrying out research and advisory work. The following is an attempt to summarise some of the key features of her informative and enlightening talk. Read more...

Having put in place the basic infrastructure so that I can store tools, equipment and firewood and have somewhere for shelter and to work, my attention turned to the top two priorities on my ‘to do’ list – well actually, numbers 2 and 3, number one will always remain ‘relax, do nothing and just enjoy it’. Firstly there is a semi-circular clearing near the eastern side of what is essentially a triangular plot. I have planted a ‘family copse’ Read more...

There is a plan to create a massive northern forest in the UK.  There is a logic behind this in that the UK has only some 13% woodland / forest cover.  This is low as compared to the european average.   More trees will result in more carbon dioxide being absorbed from the atmosphere, helping with global warming, and also helping the Government meet its 2050 carbon emissions targets.  The trees will also hopefully enhance the environment, providing habitats and niches for many plants and animals; including us, offering places to walk and unwind. The plan is to dramatically increase the woodlands and tree cover along the M62 corridor Read more...

Making woods resilient has become the latest fashion in forestry as illustrated by the RFS conference being organised with the Woodland Trust in Birmingham at the start of October.ˇ Resilience in this context means resilient both to diseases and to climate change effects.  Much of the thinking is based on the 2015 British Woodlands Resilience Survey which has been organised by the Sylva Foundation and sponsored by Oxford University, the RFS and the Woodland Trust.ˇ There have also been useful presentations on the subject such as the one given at the CONFOR Show (Confederation of Forest industries) show at Longleat, Wiltshire in early September 2015. Read more...