Some people sit under trees, others barely notice them. But there's a bunch who is obsessed with them, climbing them armed with measuring tapes in a quest to find "champion" trees. Fearless tree climber Leon Visser and protege Cameron Brand, together with their ground crew, Brian Bredenkamp, professor emeritus in forest management at Stellenbosch University, and government forestry scientist Izak van der Merwe, are on the hunt for this extraordinary class of tree.Champion trees are trees or groves of trees of extraordinary height, beauty, size or heritage value which are protected by South Africa's National Forests Act.People who are aware of any such trees, whether in their gardens or in the wild, are asked to contact them.Van der Merwe, mastermind of the champion trees project, said they received between 12 and 20 nominations each year."We need people to monitor trees for us and submit a tree if it seems significant," he said.mini_story_image_hleft1Unlike most tree enthusiasts, he prefers to keep his feet on the ground - although he did once climb the 19m-high Sunland baobab, a tree in Modjadjiskloof, Limpopo, with a pub built inside its trunk.The biggest indigenous tree in South Africa - in terms of height, stem diameter and crown size - is the Sagole baobab in Limpopo.This extraordinary tree is home to a colony of rare swallows.The Western Cape is the province with the most champion trees.But this month two ancient yellowwood trees in Limpopo were officially noted as the tallest measured indigenous trees in South Africa.Visser and Brand - both addicted to scaling trees and exploring a realm most people will never see - discovered them while searching for champion trees in the forests of Blouberg."Trees are big living organisms. We climbed past orchids in flower to the canopy and could feel their age," said Brand.The Outeniqua yellowwoods were measured at 40m and 40.15m - just centimetres taller than the Tsitsikamma "Big Tree", which is 39.6m and estimated to be 600 to 800 years old.Louis "Nipper" Thompson, 59, first saw the Blouberg yellowwoods when he was 10.He said the memory of the trees kept his father alive when he flew a bomber for the Royal Air Force during World War 2.For decades Thompson and his wife, who live in the misty Magoebaskloof forests, have struggled to conserve the yellowwoods.The barefoot Thompson even joined Visser and Brand when they ascended into the trees to measure their height.Thompson, a geologist-turned-organic cheese farmer, is concerned that plans to mine in Blouberg could harm the forest.Roughly a third of South Africa's champion trees are clumped together on less than 5% of the country's land.The climate and soil as well as the role played by tree-planting pioneers have contributed to this distribution.full_story_image_hleft2Bredenkamp has identified many champion trees in Stellenbosch and its surrounding areas and sits on the project's panel of experts ."I walk around looking up at trees all the time," he said."Most champion trees are completely unmarked and one thus understands that damage can occur."For example, there is a river red gum [an Australian species] in Stellenbosch [which is] the largest living organism in the town and is known to only a few tree huggers," he said.The tree's roots were severely damaged last month when a trench was dug next to it.Exotic trees planted in South Africa centuries ago do qualify as champions provided they are not invasive.They are the tallest trees or often have heritage value like the Post Office Tree, a milkwood, in Mossel Bay, where Portuguese sailors are thought to have left letters centuries ago.The Dendrological Society of South Africa manages a national register of big indigenous trees."Our indigenous trees are older and more bulky but the exotics grow twice as tall."The gums actually grow faster here than in Australia. They are the tallest trees in Africa," said Van der Merwe.full_story_image_hright3Tall claims need evidence to back them up and that is where Visser and Brand, also from Stellenbosch, come in with their measuring tapes.In 2013, Visser was part of an international tree climbing expedition, Explore: The Ancient trees of Africa, guiding five overseas climbers in the Magoebaskloof plantations near Tzaneen.That is where the Sunday Times met up with him and Brand, in the 101-year-old Commonwealth plantation.High up in the canopy of the second-tallest measured tree in South Africa, at 81.1m, we witnessed their excitement and efficiency.The pair were unperturbed when the trunks of two tallowwood trees bent as we traversed a rope suspended between them, about 25 storeys off the forest floor.Branches can break, so it is critical to be sure what you anchor to, said Visser, who got into a spot of bother while learning the ropes years ago.On that day his rope was not long enough to reach the ground and his safety line was not long enough to lock him around the tree, yet he got down safely."That was the dodgiest tree experience," he said."I think there's a difference between being fearful and frightened, and I'm not frightened." Listen to the Story-Behind-The-Story here:nbsp;For details, visit daff.gov.za and search for champion trees; Izak van der Merwe can be e-mailed at izakvdm@daff.gov.za..