sentences:  He performed this job well, training the existing marksmen to comply with new regulations that had come into force and that were designed to make the forest sustainable.This early exposure to the practical side of sawmilling and forest management would become very valuable years later, when he had his own sawmilling business.In an era of indiscriminate felling of trees, he stressed the risks inherent in upsetting the balance of nature by felling one or two species of tree only, pointing out that such selective fellings would undermine the principle of removing mature growth to improve conditions for young growth in the forest.