A tropical forest of trees characterized by buttress roots, long, straight, lower trunks, and leathery leaves (see I. Turner 2001). The vegetation shows distinct layering: the canopy, or upper layer, at around 30 m; the intermediate layer at 20–25 m; and the lower layer at around 10–15 m. Undergrowth is poorly developed but epiphytes and lianas are common. Davidar et al. (2005) J. Biogeog. 32, 3 indicate that seasonality, and not annual rainfall, is the variable that drives tropical rain forest tree diversity. The range of plant and animal species is immense. Hill and Hill (2001) PPG 25, 3 evaluate the following theories explaining the species richness of tropical rain forests: cumulative evolution, productivity, genetic drift and isolation, pleistocene refugia, intermediate disturbance, niche packing, habitat heterogeneity, seedling and foliar herbivore, recruitment limitation, and temporal resource partitioning.

The felling of the rain forest causes soil erosion and the destruction of potentially useful species (Voeks in D. S. Edwards et al. 1996), and the reduction of oxygen from photosynthesis, while smoke from burning logs increases the quantity of aerosols and carbon dioxide in the atmosphere (Stein (1982) GeoJ. 6, 2). Clark et al. (2003) PNAS 100, 10 report strong reductions in tree growth and large inferred tropical releases of CO₂ to the atmosphere during the record-hot 1997–8 El Niño; ‘these and other recent findings are consistent with decreased net primary production in tropical forests in the warmer years of the last two decades.’ Lettau et al. (1979) Monthly Weather Rev. 107, 3 find that modest deforestation in the Amazon basin will bring slightly warmer, moister weather with drier soils, but that more radical deforestation will result in a drier, cooler climate. See E. Guhardja, ed. (2000) on human impacts on tropical rain forest in Kalimantan.