Why is the species-area effect important in efforts to conserve species?

A species area effect deals with the relationship between the area of a habitat or a portion thereof and the quantity of species the occur within that area. Also the number of species tend to increase with the size of the area. Therefore, to preserve species it is important to preserve their territory from encroachment by industry etc where possible and this knowledge spurs the development of provincial and federal parks and protected areas, in Canada for example.