Complex sentence: Some of these plants are of great value to local peoples in many ways; others, such as water hyacinth, are a major problem in some tropical valleys, and water buffaloes may help to keep waterways clear.
Split into simpler sentences: Some of these plants are of great value to local peoples. Others, such as water hyacinth, are a major problem in some tropical valleys, and water buffaloes may help to keep waterways clear.