Does absence from natural history collections mean not present in the landscape?

Résumé

Herbaria are excellent sources of data for addressing questions about biogeography, including determining a species’ distribution, tracking species’ range changes over time, and identifying the timing of introduction of non-native species. However, if a species is absent from a collection or botanists fail to find it in the field, we cannot be certain that means it is not present. Climate change, urbanisation, and population growth are causing a decrease in biodiversity. Thus, records of the presence or absence of a species are important in assessing changes in biodiversity. The Canadian Arctic Archipelago is remote and herbarium specimens have been sparsely collected temporally and spatially, thus limiting researchers’ ability to determine changes in biodiversity. At Alexandra Fiord, Ellesmere Island, Nunavut, researchers have conducted ecological research since the early 1980s. The first comprehensive survey of the vascular flora was undertaken in 1980–1983, a second was completed in 2007–2008, and a third in 2019. In all three surveys, the goal was to document all species present in the Twin Glacier valley, Alexandra Fiord. The 2019 survey recorded 80 species, fewer than the earlier ones, which recorded 91 and 90 species, with no indication of new species migrating into the Twin Glacier valley. I explore possible explanations for the differences in the number of species collected during each survey and discuss whether this represents a loss of species diversity or extirpation and the possible implications.