Plant biodiversity, vegetation structure and provisioning services in rainforest, traditional and industrial oil palm cultivation systems in Liberia, West Africa

Abstract

Societal Impact Statement: Oil palm is native to the west African forest, where industrial production is expanding. We assessed differences in plant biodiversity, vegetation structure and provisioning services across 54 forest, community agriculture and oil palm plots in Sinoe County, Liberia. Traditional cultivation systems have lower ecological impacts in terms of species richness, composition, canopy height and structural complexity compared with industrial production, though yields per hectare are likely to be lower. Traditional systems can inspire improved management of industrial plantations, including choice of cover crop, intercropping with locally valued species and reduced clearance and pesticide regimes, increasing biodiversity and local food security. Summary: Tropical agriculture contributes to national and global food security, but the conversion of natural habitats to agriculture has severe consequences for biodiversity, ecosystem functioning and society. Significant research efforts have focussed on improving the sustainability of palm oil production in Asia, but less research has been conducted in the African forest zone, where oil palm is native and production is expanding. Working within the Sustainable Oil Palm in West Africa (SOPWA) Project (Sinoe County, Liberia), we surveyed canopy trees and understorey plants in 54 plots distributed equally across three ecological systems - rainforest, traditionally-cultivated oil palm (“country palm”) and industrially-managed oil palm - to assess differences in plant biodiversity, vegetation structure and provisioning services. Traditionally-cultivated oil palm systems had intermediate plant biodiversity (species richness, weighted endemism) and structure (canopy height, complexity) compared with industrial production or rainforest. Provisioning services (proportion of species supplying non-timber forest products) did not differ by the system on average, though the absolute number of useful species recorded was highest for the forest. Of surveyed plant species, 81% had a local name (Sapo or Kru); a smaller proportion of forest species were named compared with either traditional or industrial oil palm systems. Our study emphasises the higher ecological value per hectare of traditional oil palm production compared with industrial production methods, though yields are likely to be lower, leading to implications for industrial management such as growing alternative cover crop species, intercropping with non-timber forest products or locally valued crops and implementing reduced clearance and pesticide regimes.