Tanzania, Aug. 3 -- Iringa/Njombe. A few years ago, when his three children were still in primary school, Wanging'ombe farmer Mr Alphonse Chengula made a bold prediction.

"The three children you see have all the school fees they need to complete their education, even up to PhD level. I already have the money," he said.

His confidence was rooted not in a bank account but in pine trees.

Each year after selling maize, Mr Chengula invested part of the proceeds in tree plantations. At the time, buying an acre of land planted with young pine trees cost between Sh2 million and Sh3 million. The trees were only knee-high, but he knew patience would pay off.

Pine plantations typically take seven to 10 years to mature. By then, their value incre...