In addition to those many islands that are surrounded by water, other "islands" also exist. For example, "islands" in the desert (oases), populated islands in otherwise unpopulated tropical or boreal forests, populations clusters in high closed mountain valleys or isolated mountains or hills that are located on extensive plains. Students might see if they can locate at least one example of each of these types. Then have students work in teams to list all of the advantages and disadvantages they can for each type of "island" they have identified.