Declining rates of species description call for improved taxonomic strategies: insights from a megadiverse insect order

Classifying organisms is fundamental in biodiversity research, but time-consuming. Although technological advances in species discovery and phylogenetic analysis have marked the early 21st century, we are far from achieving a comprehensive inventory of species diversity, as many taxa remain largely undocumented. Discovering or classifying lineages without formally describing and naming them leaves biodiversity knowledge incomplete and non-interoperable, as such units cannot be consistently referenced or validated across datasets and disciplines. Accelerating formal species description therefore requires a strategic, data-driven plan to maximize efforts with finite resources. Using a uniquely complete dataset, we explored past, current and projected trends in the description of the megadiverse yet largely understudied true flies (Insecta: Diptera). We found evidence of a persistent global decline in Diptera species descriptions since the late 1990s. At current rates, it will take centuries to describe even the well-studied groups, which represent only a fraction of Diptera diversity. We argue that many other insect orders are in the same conditions, given the misalignment of research priorities, under-utilization of emerging tools, the overall shortage of taxonomic expertise and the limited availability of curated data for neglected groups. To address these challenges, we propose five strategic priorities for a renewed, data-integrative taxonomy aimed at accelerating the formal description of species, with potential applications across much of the remaining undocumented animal diversity.