Tropical forests offer many more products than the category for which they are best known, viz. wood products. They can supply a host of raw materials, such as resins, oils, fibres and fruits, which collectively represent a commercial value far higher than is generally recognized. In addition they provide an exceptional abundance and variety of genetic resources, which make substantial contributions to modern agriculture, medicine, industry and energy. On top of these materials, tropical forests supply significant environmental benefits, such as protection of the soil and safeguards for watershed systems. While it is sometimes difficult to quantify the economic values of these diverse goods and services, they are often to be reckoned as equal to, if not higher than, the marketplace values represented by the commercial hardwood timber. Yet when the forests are exploited for their hardwood timber, the process is usually so disruptive to forest ecosystems that the other outputs are severely reduced. By contrast, one may exploit the forests for their other outputs with virtually no disruption to forest ecosystems. The paper describes the main categories of non-wood products available from tropical forests, analyses their relative worth, and offers summarized proposals for an expanded approach to forest development in order to take integrative account of the full range of forest benefits.

An attempt was made to evaluate the consequences of applying a strict definition (Brokaw 1982a) to the delimitation of forest gaps in the field. The northernmost Neotropical rain forest, at Los Tuxtlas, Mexico, was searched for young (1–2 years old) single-event gaps that would meet the criteria of the definition. In 60 ha of rain forest, only 12 such gaps containing pioneer species could be found. Thirty-three pioneer species (shrubs and trees) were used as indicator species for gap conditions. Gap size, measured as projected canopy opening (sensu Brokaw 1982a), underestimated from 44 to 515% the size of the area colonized by pioneer species. On average the size of the colonized area was 3.4 times larger than the size of the projected canopy opening. The majority of the pioneer species showed a relative preference for gap borders, an area generally not included in the projected canopy opening. Pioneer plant abundance and density, and species richness and density, did not differ significantly between gap centres and gap borders. Floristical variation was not related to gap size or location in the gap. These findings can be explained if gap environment (to which pioneer plants respond) is seen as the result of many interacting factors, of which size of the canopy opening is only one. It is concluded that the definition for delimiting gaps in the field as proposed by Brokaw (1982a) cannot be regarded a generally applicable definition, and that its value as a comparative standard is doubtful.