“All human beings should plant one tree for every year that they live on earth and experience the joy and pride of embracing their massive trunks and sitting under their shady canopies.”
The New Sylva, Bloomsbury Publishing, 2014

Young people planting a tree
Young people planting a pine tree. Photo Gabriel Hemery.
The New Sylva book
The New Sylva book

I wrote these words in The New Sylva but have never explained the detail behind my thinking for this ‘call to the spade’. If we did adopt such a personal life mission, what might we achieve?

Most people with a modicum of environmental consciousness will recognise the importance of trees to life on Earth, and the devastation we are causing to the world’s biodiversity hotspots and the planet’s lungs; namely the destruction of tropical forests. Few may stop to think how over-consumerism in the Developed world is driving this destruction, and how, by our failure to plant trees for their utility and protection in our own countries, we are exporting our harmful impacts elsewhere.

The UK is one of the least wooded countries in Europe, with 13 per cent woodland cover compared to around 37 per cent for European Union countries and global forest cover of around 30 per cent. You might think this would make it a good model for assessing the potential for my suggested life mission. I wrote about forest cover of the UK in 2011 and I’ve now updated my graph to feature the latest statistics from the Global Forest Resources Assessment 2015 (FAO, 2015). Move your mouse over the graph below as it is interactive.

Our lack of trees in the UK is now well recognised. For example the Woodland Trust aims to plant 64 million trees in the next ten years (by 2025). English government has set a target to plant 11 million trees, although one industry group says it will be seven years behind the target, just one year after establishing it.

So, why do I suggest we should plant a tree for every year of our lives? After all, this would equate to meeting the Woodland Trust target every single year. Is it just a convenient sound bite or has it more substance? If we met such a target what would that actually mean in terms of trees planted and forest area created, in the context of our current tree cover?

If we assume 80 years life expectancy (see Official Statistics) and no change in population size (currently 64 million), then between 2017 and 2097:

  • Each individual would plant on average 80 trees during their lifetime.
  • 25,600 ha (63,237 acres) of new forest would be planted in the UK every year.
  • Over 80 years this would create a forest of 2,048,000 ha (5,058,560 acres).
  • Ultimately containing 204,800,000 mature trees.
  • UK forest area would increase by 8%, from 13% to 21%
  • As a result the UK would remain well below the average area forested among European countries (29.6%).

So, even adopting such an ambitious collective societal approach would still leave the UK towards the bottom of the European forest league! It just goes to show how insignificant our current planting targets are.

But take heart, it’s never to late to catch up in your personal tally. It only takes a couple of minutes to plant a tree, so even at 80-years-old you can plant (perhaps with a little help) your full contribution in an hour or two.

Maths and Assumptions

population × years = (number of trees × area per tree m2 )/10,000 = forest area (ha)

64,000,000 × 80 = (5,120,000,000 × 4)/10,000 = 2,048,000 ha

  • UK human population = 64 million
  • Life expectancy = average 80 years (assuming no change)
  • Trees planted at 2×2m spacing = 4m2 per tree (or 2,500 trees per hectare)
  • Area of trees planted = 256,000,000 m2
  • Convert this area to hectares (/ 10,000) = 25,600 ha
  • A thinning rate of 25 to 1 (i.e. removal of trees to allow others to grow to full size)
  • Mature tree (e.g. oak) area = 100m(or 100 trees per hectare)
  • UK land area 24,361,000 ha

Interested in use of maths in forestry? Read these other articles:

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