Can we describe all species on Earth before they disappear? We argue that this is possible only by endowing taxonomy with professional manpower and appropriate material resources as required by big science.

Contrary to Costello et al.’s (CMS) (1) statements, taxonomy is not an easy discipline accessible to all through a smartphone. It requires exhaustive training and long familiarity with field, specimens and literature (2).

CMS’s argument is framed in terms of species numbers, but different, non-overlapping species concepts apply to bacteria, brambles and birds (3,4,5): “the species” as common unit of biodiversity does not exist (6).

Even ignoring this conceptual and semantic issue, CMS’s estimates of undescribed biodiversity and extinction rates are based on insufficient evidence and poorly supported models. Biodiversity hotspots steadily emerge in geographic areas where diversity was long assumed to be largely described (7,8). The number of species, whatever species are, cannot be easily estimated because of the historical, rather than deterministic or teleological, nature of biological evolution (9,10).

Extinction rates are highly context-sensitive (11), lineage- and region-dependant, thus generally difficult to ascertain (12) without thorough analyses of data such as IUCN’s estimates of threats and extinctions (13). However, evidence being mainly restricted to vertebrates, the extinction risks in most other groups remain terra incognita. Furthermore, recent surveys (14,15) do not support CMS’s optimistic predictions regarding extinction rates.

CMS’s agenda emphasizes technology, voluntary work and recognition of subjective “morphospecies” (16). However, improvement of data storage and retrieval cannot substitute for the production of sound data. Serious taxonomists cannot describe two new species per week, as suggested by CMS’s calculations. Describing new species, even with the help of molecular data and especially in best-investigated groups, is increasingly demanding, following the “law of diminishing returns” (17). More than anything else, taxonomy requires professional manpower, unrestricted fieldwork and permanent collections.

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