Geographers use the regional unit to map features of particular interest, and data can be compared between regions to help understand trends, identify patterns, or assist in explaining a particular phenomenon. Regions are traditionally defined by internal characteristics that provide a sense of place.
I think glass does. or maybe a glass prism.
The mongooses are very effective in controlling the snake populations, as is the case in Hawaii, but the problem is that they represent an invasive species. As an invasive species, they disrupt the whole ecosystem on the islands, the local fauna can not cope with them because they do not have the defense mechanisms needed, nor can reproduce as fast, and also head to head are out competed, so the local fauna is becoming endangered and in time will probably get exterminated by the invasive mongooses.
Ok that is not true at all it serves as a physical border between Mexico and the United States