'Cut another branch, Zelao,' she cries out. Brandishing telescopic pruning clippers, 42-year-old Jose Raimundo Ferreira, known as Zelao, expertly manipulates the tool and a branch of the itauba, whose wood is prized for use in making boats, falls at the scientist's feet. Botanist Marta Pereira, who is delighted to have secured his services, says there are only about 20 people who can do what he does. These tree climbers are even more important in an area where scientists believe they know only about 30 percent of the biodiversity. Dressed in just a T-shirt and Bermuda shorts, Zelao climbs five or six times a day up trees that can reach 50 meters (some 164 feet) in height. He also installs cameras on tree tops to film birds and monkeys. For security he has a harness, a rope and thick rubber-soled boots. Sometimes he clambers from one tree to another. Even so, he has no intention of slowing down. Even though his profession is highly sought after, these tree climbers have no job security. 'Their work should be regularized as field technicians and they should get training,' said Pereira.