As in most parts of the world, the proportion of coastal lands (relative to non-coastal lands) varies immensely throughout the Asia-Pacific region. For example, in some of the most distant parts of this vast region such as the tropical Indian Ocean or Pacific Islands, every piece of land is coastal in the sense that it is affected directly by coastal processes. Yet for the largest land areas in the region, coasts by any definition comprise only a small proportion of the total land area. Such statements may be misleading, however, because, in terms of their importance to humans as locations for settlement, economic activities, and food production, coasts are generally more valuable than most other land areas of comparable size in the Asia-Pacific region. At the same time, coasts are more vulnerable to change than other land types, whose degree of natural resilience is commonly greater. As elsewhere in the world, the positions and the characters of Asia Pacific coasts have changed through time. These changes have sometimes brought about profound alterations to the lifestyles of coastal-dwelling humans in the region, yet also presented new opportunities for their descendants. In the same way, it is clear that changes within the past 100 years--a time of unprecedented increases in human population pressure on most parts of the Asia-Pacific coastal zone--have been more rapid than at most earlier times, causing widespread disruption to human lifestyles and posing significant challenges for the next hundred years; challenges this book is trying to help solve. Coastal changes can occur at a variety of scales, but it is useful, when assessing coastal history, to separate local from regional changes.