Natural Regeneration of Forest Ecosystems through Seed Dispersal and Pollination Mediated by Faunal Diversity: A Review

Abstract

Natural regeneration is increasingly central to forest restoration because it can rebuild vegetation without the costs and ecological simplification associated with universal tree planting. Its success, however, depends on more than the presence of remnant vegetation or favourable soils. Animal-mediated pollination and seed dispersal determine whether reproductive propagules are produced, moved across landscapes and delivered to sites where recruitment can proceed. This critical narrative review examines how faunal diversity influences these sequential stages of forest regeneration, with emphasis on tropical and subtropical forests where biotic mutualisms are especially prominent. Literature published from 1990 to 19 July 2026 was selected through searches of multidisciplinary, ecological and agricultural scholarly sources and evaluated for methodological quality, ecological realism and evidence-claim alignment. The synthesis shows that species richness alone is an incomplete predictor of regenerative function. Functional traits, interaction complementarity, movement behaviour, body size, dietary specialisation and spatial connectivity often determine whether pollination and dispersal remain effective after disturbance. Birds and bats can move propagules across open or degraded habitats, large-bodied frugivores disproportionately contribute to the dispersal of large-seeded and late-successional plants, and rodents can either destroy or secondarily disperse seeds depending on context. Pollination is similarly sensitive to the loss of mobile or specialised taxa, yet network-level apparent robustness may mask deterioration in pollen quality, gene flow or reproductive success. Defaunation, fragmentation and hunting can therefore generate regeneration debt even where canopy cover is recovering. Recent chronosequence and network studies further indicate that vegetation structure can recover faster than the interaction networks and functional seed rain required for mature-forest composition. Restoration should consequently treat faunal communities and landscape connectivity as components of regenerative infrastructure, while recognising that perches, nuclei and corridor interventions are conditional tools rather than universal solutions. The strongest inference is that natural regeneration is most resilient when multiple, functionally distinct animal partners connect reproductive stages across space; confidence is weaker where studies stop at visitation, seed removal or short-term seed rain rather than following recruitment.