We investigated the recovery of vegetation and above-ground biomass in tropical secondary forests in Southeast Asia. We also evaluated the effects of a vegetational change from primary to secondary forests on biodiversity and an ecological network. As a result, in secondary forests in Sarawak, Malaysia, only about 60% of the biomass of their primary forests recovered, even though about 80 years had passed since the abandonment of the latter. In addition, it may be possible to predict to what degree vegetation recovery will be made in the future, if there is information on the age and soil texture of each secondary forest. The mammal fauna was greatly affected by hunting, and its species diversity in the secondary forests was lower than in primary forests. The polypore fauna did not recover to its level in primary forests, either, even when secondary forests were about 80 years of age. Also, the vegetational change may alter and destroy a system of ant-myrmecophyte interaction.