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Despite increasing attention for relationships between species richness and ecosystem services, for tropical forests such relationships are still under discussion. Contradicting relationships have been reported concerning carbon stock, while little is known about relationships concerning timber stock and the abundance of non-timber forest product producing plant species (NTFP abundance). Using 151 1-ha plots, we related tree and arborescent palm species richness to carbon stock, timber stock and NTFP abundance across the Guiana Shield, and using 283 1-ha plots, to carbon stock across all of Amazonia. We analysed how environmental heterogeneity influenced these relationships, assessing differences across and within multiple forest types, biogeographic regions and subregions. Species richness showed significant relationships with all three ecosystem services, but relationships differed between forest types and among biogeographical strata. We found that species richness was positively associated to carbon stock in all biogeographical strata. This association became obscured by variation across biogeographical regions at the scale of Amazonia, resembling a Simpson’s paradox. By contrast, species richness was weakly or not significantly related to timber stock and NTFP abundance, suggesting that species richness is not a good predictor for these ecosystem services. Our findings illustrate the importance of environmental stratification in analysing biodiversity-ecosystem services relationships., G.S. was supported by grant 022.006.011 from the Dutch Research Council (‘NWO’) for the Graduate Programme ‘Nature Conservation, Management and Restoration’. D.S. & J-F.M. benefited from an “Investissement d’Avenir” grant managed by the Agence Nationale de la Recherche (CEBA: ANR-10-LABX-25-01).

Despite the importance of non-timber forest products (NTFPs) for local livelihoods in tropical countries and the increasing attention for biodiversity-ecosystem services relationships, it remained unclear how the ecosystem service of NTFP provisioning is related to plant diversity. Although it is generally assumed that plant diversity is positively related to ecosystem services, this had not been assessed for NTFP provisioning. We applied bivariate and multiple regression models to explore the relationships between the abundance of 58 commercially relevant NTFP species and woody plant diversity across 287 plots of tropical forests in Northern Suriname. We found that NTFP abundance showed both positive and negative relationships to plant diversity indicators. In contrast to expectations, NTFP abundance was negatively related to woody species richness. In addition, across the plots disproportionately few (2–6) NTFP species determined >50% of NTFP abundance. The occurrence and the identity of these ‘NTFP oligarchs’ was associated to specific floristic compositions. Overall, more than half, i.e. 55.9%, of the observed variation in NTFP abundance could be explained by a combination of taxonomic and structural plant diversity indicators. Our case study findings are relevant for conservation policies in general. In most countries NTFPs are not on the agenda of governments and current tropical conservation policies often focus on forests with high species richness and/or carbon stocks. Our findings indicate that current policies may not cover valuable forests in terms of high NTFP abundance. To support sustainable NTFP provisioning, additional conservation efforts would need to include those vegetation types with high NTFP abundance.