The country's slowed economic growth has contributed extremely to the preservation of its environment and ecosystems. Forests, including dense tropical growth and valuable teak in lower Burma, cover over 49% of the country, including the areas of acacia, bamboo, ironwood and michelia champaca. Coconut, betel palm and rubber have been introduced. In the highlands of the north, oak, pine and various rhododendrons cover much of the land. Since 1995 forestry law went into effect has seriously reduced forest acreage and wildlife habitat. The lands along the coast support all varieties of tropical fruits and once had large areas of mangroves although much of the protective mangroves have disappeared. Most of central Myanmar (the Dry Zone), vegetation is sparse and stunted.