Don’t miss the post Hanging about in the tree tops which is about the 2013 Explore: The Ancient Trees of Africa expedition.
So what do tree surgeons (or arborists to give them their official job title) do on their day off? Well, if you’re these tree surgeons you go climbing trees. Not just any old trees mind, very big ones! They are also not just doing it for fun, but to measure the accurate height of these very tall Karri gum (Eucalyptus diversicolor) trees, which were planted in 1926. This was done for the South African Champion Tree Project, part of which is to determine the heights of the largest trees in South Africa.
An edited quote from Leon Visser (on the right in the photograph below):
The grove at Brackenhill is phenomenal in its own right, and it was a great privilege to be able to climb and measure them.
This is the first ascent of these giant trees and whereas the previous height was given as 68m (223.1 feet), I measured them at 71.5m (234.5 feet).
This is the 3rd highest tree I have climbed, the tallest being the gums in Magoebaskloof which are 78.5 (257.5 feet) and 79m (259.1 feet) – the tallest measured trees in Africa and as far as we know the tallest PLANTED gums in the world.
[Click on photographs to enlarge them]
Can you see the climber sitting on a branch in the centre tree below?
To climb the trees, one needs mountain climbing gear, a very big catapult, lots of rope, a long tape measure and measuring stick or pole. Oh, and of course, people with serious climbing skills! [Note: this should only be done by professionals – do not try this at home!].
While there are more modern techniques of tree height measurement involving the use of electronic gadgets like tree height meters or hypsometers, these are not accurate enough when measuring trees which have a rounded crown, or trees which are leaning slightly. Hypsometers rely on the use of trigonometry and triangulation to calculate the height of the tree. So if you cannot accurately determine the highest point of the tree, the calculation will be inaccurate. To see how the measurements using a hypsometer are done click here. To read the guidelines of measuring a Champion (or Big) tree click here.
To begin with the climbers shoot the first rope up as high as they can using the big catapult. And then the climbing begins. In this case, the climbers could not secure the first rope on the tree they wanted to climb (because the lowest branches were too thin to take their weight), so one climber had to climb the adjacent tree, and then winch himself over to the “right” tree.
Once one of the climbers is as far up the tree as he can go, he uses a measuring rod to find the distance from his height on the tree, to the very top of the tree. Then a measuring tape is dropped to measure the height down to the ground. The two measurements are added to get the final and accurate tree height.
To give you some idea of just how high 71.5m (233 feet) is, take a look at the series of photos below. In the first photograph look at the little white spot below the red arrow. That is the top climber’s torso! The climbers are obviously not scared of heights.