IPA: /ˌʌnˈfɔːrɪstɪd/
KK: /ʌnˈfɔrɪstɪd/
Not covered with trees or forested areas.
The region was largely unforested, making it vulnerable to erosion.
Unforested → It is formed from "un-" (meaning not) and "forested" (from the root "forest" which comes from Old French *forest*, meaning a large area covered chiefly with trees and undergrowth). The word "unforested" means not covered by forest or lacking trees.
Think of 'not' ('un-') having trees in a 'forest' — that's why 'unforested' means an area without trees.