Wild spices and their ecosystem service contributions in smallholder agroforestry systems of Aceh, Indonesia

Smallholder homegarden agroforestry systems are critical components of tropical landscapes, supporting agrobiodiversity and delivering multiple ecosystem services. Among their constituents, wild spices represent an underexplored plant group with high functional and cultural value. This study examines the species diversity, plant part utilization, functional roles, ecosystem service contributions, and conservation risks of wild spice species cultivated across elevation gradients in Aceh Province, Indonesia. A stratified sampling approach was applied across 120 home gardens distributed in lowland (0–300 m), mid-elevation (301–800 m), and upland (> 800 m) zones. Data collection involved semi-structured interviews, direct observations, and botanical identification, followed by statistical analyses including ANOVA, chi-square tests, and Spearman correlations. A total of 24 wild spice species from seven botanical families were documented, with Zingiberaceae comprising 41.7% of species richness. Species richness significantly declined with elevation (lowland: 16.2; mid-elevation: 11.4; upland: 9.5; F = 100.90, p < 0.001). The most commonly utilized plant parts were rhizomes (31.0%), leaves (27.6%), fruits (24.1%), and barks (10.3%). Culinary use dominated functional roles (74.3%), followed by medicinal (18.9%), aromatherapy (5.2%), and ritual (1.5%) applications (χ² = 245.86, p < 0.001). Trade-off analysis revealed a moderate negative correlation between provisioning and regulating services (ρ = –0.493, p = 0.014). Conservation risks were highest in mid- and upland gardens due to ecological marginality and socio-economic transitions. These findings highlight the ecological and socio-cultural multifunctionality of wild spices and their critical role in sustaining food systems and ecosystem resilience. Integrating wild spice conservation into smallholder development and agroecological landscape planning is essential to enhance biodiversity conservation and livelihood sustainability in tropical agroforestry systems.