Terrific Scientific is BBC Learning’s science project for 2017.
In May, UBoC and LEAF hosted the Trees experiment, in which children from the UK’s 25,000+ primary schools found out why trees are important for the climate, oxygen, biodiversity, flood prevention, air quality and more – and then surveyed the trees that grow in or around their school.
Learning about climate change can be quite worrying, so UBoC also arranged for nearly 45,000 Terrific Tropical Trees to be planted in Africa, where trees work harder for the climate than in the UK. So about 20 trees per tree surveyed, or nearly two trees per school in the UK, will soon be working to capture and store damaging carbon dioxide.
The pupils counted, identified and measured the trees in and around their school grounds by lining up the whole tree against a 30cm ruler, marking a line on the trunk equivalent to the 3cm mark on the ruler, measuring the the height of the line, and multiplying that height by 10. Then, using our calculator, they estimated the amount of carbon stored in their trees, and therefore how much these are helping to tackle climate change.
How many trees?
Over 6,000 trees were counted during the investigation and more than 2,000 of them were measured and identified.
The average (median) number of trees per school was 30 – we were surprised to find that this was exactly the same for both urban and rural schools! Schools that described themselves as suburban (somewhere in between urban and rural) had the most trees, with a median average of 35 per school.
4% of schools unfortunately had no trees at all, but nearly 90% of schools had more than 10 trees on their grounds – read on to find out what type of trees they were!
What kind of trees did the pupils find?
For schools in the countryside, birch was by far the most common type of tree to be found (11% of the total), followed by oak, cherry and willow. Whilst birch trees were also the most popular in urban schools (8% of the total), pupils in towns and cities found that sycamore and lime trees were the second and third most popular. The most common type of tree in suburban schools were cherry trees (12%), closely followed by field maples.
The children were able to identify 87% of the trees they surveyed. A further 11% were classified as having broad, flat leaves (broadleaf) or thin, needle-like leaves (needleleaf), only 2% of the trees surveyed could not be identified.
Across the UK, more than nine out of ten of the surveyed trees were broadleaf and less than 10% were needleleaf trees. In Scotland however, needleleaf trees were more common, making up 16% of all surveyed trees.
Whilst the most common trees across England were birch, most of the trees surveyed in Scotland were willow, and in Wales the most common trees were oak. In Northern Ireland, oaks, beech and elm were the most common trees.
How big were the trees?
The trees found on the school grounds came in a variety of shapes and sizes. Most of the trees surveyed were shorter than 10 metres. Two out of every five trees surveyed were taller than 10 metres, but only one in every 50 trees were taller than 20 metres.
The tallest tree was estimated to be 30 metres tall – that’s more than 3 times the height of an average house! But that’s small compared to the tallest tree in the UK, a mighty 60 metre tall fir tree!
The widest or thickest tree surveyed was over 5 metres in circumference – you would have to join hands with several of your friends to be able to hug that one!
We found that on average, trees measured in urban schools were slightly wider than those found in rural schools – this will be partly due to dominance of birch trees in rural schools which tend to be quite thin. What would this mean for the amount of carbon they store?
How much carbon do the trees store?
In total, the children estimated that the trees they surveyed contained around 550 tonnes of carbon (1 tonne = 1000 kilograms) – that’s over 2,000 tonnes of carbon dioxide. This is equivalent to the annual carbon footprint of 275 people living in the UK added together.
We found that on average the rural trees surveyed here were slightly smaller and therefore contained less carbon than those measured in towns and cities.
If we use the data collected by pupils during the Trees Investigation and extend this to all 25,000 primary schools in the UK, we would estimate that trees in UK primary schools have removed around 400,000 tonnes of carbon dioxide from the atmosphere over their lifetimes. That’s equivalent to the annual carbon footprint for around 55,000 people in the UK (the same amount of people who live in Kettering, Macclesfield, Loughborough or Canterbury).
Unfortunately, this is only 0.1% of the amount of carbon dioxide that is emitted by human activities in the UK every year [about 500 000 000 tonnes of carbon dioxide] – so we are emitting much more carbon dioxide into the air than our school trees can soak up.