Lower-middle-income countries disproportionately face the burden of the Open Access publication model

While the Open Access (OA) publishing model may promote equity in the readership of scientific publications, its implications for global research authorship remain poorly quantified. We analysed 504,723 publications over the past decade from 350 Scopus-indexed ecology and evolution journals to compare publication rates and institutional diversity a) between Subscription-Based (SB) and OA publishing models, and b) before and after journals transitioned to fully OA, across country income groups. We found that both publication rates and institutional diversity were lower in the OA publishing model, but with variable differences across country groups. These differences were weaker (by ∼140%) in low-income countries (where full waivers on Article Publishing Charges (APCs) are automatically provided) compared to middle-income countries (where only discounts on APCs are provided). For journals transitioning to a fully OA publication model, publication diversity decreased in middle-income countries and increased significantly in low-income countries. Therefore, OA disproportionately concentrates publishing potential within a few institutions, undermining authorship equity. The OA model, despite its egalitarian philosophy, risks amplifying geographic and institutional disparities in ecology and conservation science. Incorporating models that account for individual and institutional-level variations in funding availability, or providing alternative pathways for publishing, may help reduce this disparity.