The rain forest canopy consists of the treetop region or, more precisely, of the aggregate of every tree crown in the rain forest, including foliage, twigs, fine branches, and epiphytes. The upper canopy represents the interface between the uppermost layer of leaves and the atmosphere, and, for practical purposes, many researchers consider this layer to be only a few meters deep. Most of the biological activity in and biodiversity within tropical rain forests appears to be concentrated in the upper canopy.

Many abiotic and biotic characteristics of the canopy are different from the understory beneath. Its higher illumination levels promote more rapid rates of photosynthesis, which, in turn, promote higher vegetal production, and consequently sustain a more abundant and diverse community of animals than in the understory. In a much publicized article in 1983, Terry Erwin termed the canopy of tropical forests "the last biotic...