Taxonomy, in the biological sense, is the science of the definition, recognition, and naming of groups of biological individuals. It defines species and infraspecific groups as well as a higher-level classification (usually on the basis of evolutionary relationships). It is an essential biological discipline, allowing us to generalize the knowledge we have obtained from a few individuals and apply it to a large set of other individuals.
To my knowledge, there was never any principal doubt that scientific taxonomy needs to take all available information about organisms into account: morphology, anatomy, behavior, physiology, genetics, etc. If we talk about biological, genetic, phylogenetic, or morphological species concepts, the discussion is primarily related to the practicality of science.
In its history, taxonomy originally recorded all available relevant information in publications. However, it soon appeared that as science was constantly learning more and more about, e.g., a species, the published information was often insufficient.
Often, older concepts had to be split into two concepts, or it was ambiguous whether two species had to be merged into a single one or not.
Taxonomists, therefore, started to require the preservation and explicit definition of “type specimens”. A type specimen, preserved in a private or institutional biological collection, can be used to study properties overlooked by earlier scientists. If a taxonomic concept is split, the type specimen defines with which concept the older name remains, and which concept requires a new name. Since in most groups dry storage were the most practical and affordable preservations techniques, properties that survived this treatment (outer morphology, skeletal features) became dominant in taxonomy.
However, times have changed. We can record and globally share excellent digital representations of appearance, physiology, behavior and genetic properties. Physical type specimens were never an ideal solution since they can be studied only locally, are often fragile, often deteriorate when being studied, and in many cases, the preserved morphology is insufficient for the taxonomic question (i.e., features are missing or two species have identical outer morphology). In many organism groups (e.g., virology, bacteriology, mycology, protozoology, microalgae), morphology is no longer sufficient to base taxonomy or identification on morphology alone. This does not mean morphology is useless: Just like other properties, it remains relevant for our understanding of evolution, function, or ecology (“functional traits”), as well as useful for organizing selective sampling in the field.
In my analysis, I consider it likely that over time all morphological type concepts will be phased out and replaced with sufficiently complete, long-term stable and globally sharable nucleotide sequences (“molecular barcodes”). I also consider it the best use of the limited resources available, to establish the connection between barcode-based and classical taxonomical names only for well-known species. For the remaining species, as far as they have been described at all, science should simply start fresh. The synonymization process of the remaining historical names and the study of the history of science can then easily be deferred one or several hundred years. For this, the type specimens should be safely stored, but need not necessarily be accessible for several decades.
With respect to the type specimens in natural history collections, I believe that it is our responsibility to preserve them. Wherever a genetic barcode sequence can be obtained cost-efficiently from old type specimens, it should be done. Otherwise, such work can wait. In all groups, where the specimens preserved in natural history collections are significantly different from how citizen scientists observe living organisms in nature, we should probably not even invest into photographing the type specimens. Obtaining and sharing excellent, life-like photographs, audio-video recording and 3D models of well-identified species would be much more effective for using morphology in field identification (where possible), preselection (including the use of citizen scientists or “parataxonomists”), and engaging the general population with nature.