The evolution of swidden fallow secondary forests in Asia W. de Jong, U. Chokkalingam Center for International Forestry Research. P.O. Box 6596 JKPWB, Jakarta 10065, Indonesia, w.de-jong@cgiar.org D. Perera Department of Botany, University of Peradeniya, Peradeniya, Sri Lanka Journal for Tropical Forest Science, 13 (4) 800-815 DE JONG, W. , CHOKKALINGAM, U. , PERERA, D. 2001. The evolution of swidden fallow secondary forests in Asia. Swidden agriculture in tropical Asia is a diverse practice, making it difficult to draw general conclusions on trends of the evolution of swidden fallow secondary forests (SFSF). There is, however sufficient evidence to recognise trends of a gradual endogenous intensification, often through incorporation extensive tree production in SFSF. These, however, are not the only changes that can be observed in SFSF dominated landscapes. Exogenous factors have also lead to change, including emerging markets for cash crops or timber and pulp-wood production. Although swidden fallow land use has often been stigmatised as leading to forest decline and related decline in the environmental functions that forests provide, there is sufficient evidence that conversion of a SFSF dominated landscape to more intensive tree crop land use does have a negative environmental impact.