Map of Tonga (click to view full-size)
FAO website contains information on ecological zones and soil erosion, forest cover and types. [http://www.fao.org/countryprofiles/selectiso.asp?lang=en] (requires javascript?)
Biodiversity interest: The Polynesian-Micronesian islands of the Pacific, of which Tonga is one group, are part of a Conservation International Biodiversity Hotspot, and Tonga also covers two secondary Endemic Bird Areas.
Further information about important species of Tonga can be found through this page
Further information about protected areas of Tonga can be found through this page