1. Hunting and land use change modify herbivore abundances and cause cascading effects in natural ecosystems. The outcomes for vegetation depend on changes to specific plant-animal interactions, such as seed dispersal or predation, or physical disturbances. 2. We experimentally manipulated wildlife populations in a primary lowland forest in Malaysia over an 18-yr period (1996-2014) to understand how artificially high or low densities of terrestrial wildlife affects tree and liana regeneration. Our study site retains a diverse wildlife community and artificially high densities of native wild pigs (Sus scrofa) that are sustained by crop-raiding in distant oil palm plantations. We used fencing that excluded terrestrial animals >1kg to experimentally simulate conditions in defaunated forests. These two treatments - abnormally high pig abundances in habitat edges and megafauna loss from hunting - represent common outcomes in disturbed Southeast Asian forests and are characteristic of many forests globally. 3. We focus on trees and lianas because they are the two dominant woody lifeforms in tropical forests and crucial determinants of forest structure and function. 4. We found that liana sapling abundances (30-100 cm height) increased by 86% in unfenced control plots with wildlife but were stable in exclosures. In contrast, tree abundances did not change in unfenced control plots but increased by 83% in exclosures without wildlife. Evidence of scaring on surviving stems suggested that these inverted outcomes were driven by selective use of tree saplings for wild pig nests. Lianas may also have greater tolerance to wildlife disturbances. By the end of the study, lianas comprised 38% of all saplings in unfenced controls but just 14% in exclosures. 5. We conclude that abundant wildlife such as wild pigs may shift understory woody communities towards lianas while defaunation may shift it towards trees. These results highlight that ecological cascades from hunting or land use change can alter plant functional types and reshape to long-term patterns of forest succession and change. Managing unnatural wild boar populations may be required to conserve native plant communities in both their native and exotic ranges, including in South America.