Natural history collections as sources of long-term datasets.

In the otherwise excellent special issue of Trends in Ecology and Evolution on long-term ecological research (TREE 25(10), 2010), none of the contributors mentioned the importance of natural history collections (NHCs) as sources of data that can strongly complement past and ongoing survey data. Whereas very few field surveys have operated for more than a few decades, NHCs, conserved in museums and other institutions, comprise samples of the Earth's biota typically extending back well into the nineteenth century and, in some cases, before this time. They therefore span the period of accelerated anthropogenic habitat destruction, climate warming and ocean acidification, in many cases reflecting baseline conditions before the major impact of these factors.