Hiking is generally a very safe and healthy activity, but as with many outdoor persuits you need to respect the environment. Weather, particularly in the mountain environment, is not always predictable; factors such as fire, erosion and natural weathering can cause known paths to change or even be destroyed; landmarks such as trees can dissappear and places where you expected to find water can suddenly become dry or be polluted. There are a number of safety rules that should be followed – these are usually common sense – but are often ignored.