Woodlands and savannas are biomes that cover 20% of the world's land surface and are highly concentrated between the equatorial rain forests and the mid-latitude deserts and semi-deserts. Woodlands are typically easy to distinguish from forests; however, the grade between woodland and savanna is often complicated. The term "savanna" is derived from the Amerindian word for "treeless grassland" in the West Indies, but has come to mean any grassland, or continuous grass stratum, with trees and/or shrubs. The distinction between woodland and savanna is amorphous at best and for this reason we combine the two into one biome category. For this website, woodlands and savannas are considered open stands of trees with crowns not usually touching (generally forming 25-60% cover). Canopy tree cover may be less than 25% in cases where it exceeds shrub, herb, and nonvascular cover, respectively.