and spread of new diseases (Carlson 2020) are some of the most visible facets of this crisis. Because of its global scale, it is generating new momentum in international negotiations (e.g. Convention on Biological Diversity, United Nations Framework Convention on Climate Change), although it has not yet led to a significant shift toward a production and consumption model that can limit its effects.
This situation creates a significant demand for the scientific community to produce measurements and indicators to assess the causes, magnitude and the evolution trends of this crisis (IPCC 2018; IPBES 2019; Díaz et al. 2020; Rounsevell et al. 2020). It is in this context that bodies such as the IPCC (Intergovernmental Panel on Climate Change) and the IPBES (Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services) at the international level have been created. At the national level in France, numerous structures have also been created to analyze problems and implement appropriate solutions1. This context has led to the emergence of new scientific themes. For example, assessing the global state and trends of biological and cultural diversity and the environment requires a large amount of data and the organization of these data into temporal or geographical series. Natural history collections are an extraordinary resource in this context. In addition to their original function as repositories for systematics, they are now becoming a colossal source of information, contributing to the exploration of this problem. The economic benefits of their contribution, even if they are still little evaluated, could be of the order of several billion dollars (Suarez and Tsutsui 2004).
1.1. Collections in early 21st century science
Research on collections is gaining unprecedented scientific importance because of its potential to answer the major questions of our time. Collection specimens contain information that allows us to reconstruct the puzzle of the history of life, humankind and the universe, as well as provide clues for understanding environmental transformations. This broadens the scope of research on the collections. Collections remain indispensable for systematics. In turn, systematics contributes more than ever to the enrichment of collections because of the unprecedented development of identification methods and to phylogenetic and evolutionary inferences. The result is an increase in the number of identifications and the availability of new datasets that facilitate the study of living organisms as a whole. Systematics creates new forms of association between specimens and information that are increasingly numerous. Its role is essential and indispensable for any further use of the specimens.
Collections are increasingly used in two new areas: the research of new information on specimens and global analyses on large datasets of specimens. The principle of open science, on which systematics was built and which has always been the basis of collection data exchange, is thus shaping new forms of data provision. A wide range of tools has been developed to access information residing in collections. For example, new techniques are available to identify parasites and commensals (viruses, bacteria, protozoa, etc.) or to measure the chemical content (carbon content, heavy metals, stable isotopes, etc.) of collection specimens. New computer approaches allow the availability of all collection data from single portals called “aggregators”.
1.2. New explorations because of the magnitude and diversity of the collections’ data
The magnitude of the taxonomic, spatial and temporal diversity of the data housed in the thousands of natural history collections is colossal. The collections host not only the name-bearing types that allow the use of scientific names but also, very often, numerous specimens presumed to belong to the same species. The richness of this content not only allows us to study questions of genetic diversity and species limits but also to understand global phenomena for which a large number of specimens are essential. The numerous specimens of the same species constitute genetic, spatial and temporal replicas that allow us to test many hypotheses.
The magnitude of the collections is also reflected in their gigantic spatial coverage. Most of the world’s environments have been sampled and have corresponding specimens in the collections. For many localities, there is a wealth of data. Millions of specimens trace the history of thousands of institutional or individual missions that have allowed us to access the most diverse and challenging environments (Figure 1.1). They also tell the story of the explorations and many scientific questions asked during the last centuries. In fact, the collections allow us to have a global view of the distribution of life on the planet. No global expedition would be able to collect again these millions of pieces of information, especially since most of the places have been transformed and the natural environments of the past have been replaced by cities or cultivated areas.
Another important aspect of the collections is the fact that they contain specimens collected at various times in the past, even in very remote times. The most extraordinary examples mentioned in this volume are the remains of flower garlands found on the royal mummy of Ramses II (Chapter 12 by Quiles et al.), or the collection of mummies dated between the 2nd millennium BCE and the 19th century CE (Chapter 4 by Thomas et al.). In European institutions, it is not uncommon to have diverse collections on most of the biomes of the five continents dating from the 17th century. Some very old objects provide information on the way of life of the populations, their physical characteristics, their environment or their culture.
Figure 1.1. Examples of environments that are difficult to sample. (a) The Canopy Raft in French Guiana, a device to collect and study tropical canopies (in the foreground is an entomologist’s net to collect insects; inset, a general view of the device). (b) Mission to Spitsbergen, marine ecology and study of Carboniferous and Devonian rock outcrops. © R. Garrouste, ISYEB
However, the main interest of large time series is to provide what is commonly called “zero points”, that is, reference points on the state of populations or environments before certain human actions, for example, at the beginning of the industrial era. The distribution of organisms can thus be known before the destruction of natural habitats, and certain effects of climate change on biodiversity can be measured (see Chapter 15 by Robuchon et al. and Chapter 16 by Muller et al.). This knowledge is essential for refining proposals for the conservation of organisms, or even their reintroduction, as is the case with the germination of seeds of extinct plants from herbariums (see Chapter 10 by Muller et al.).
1.3. Research using and driving the constitution of natural history collections
Such a high number of positive results might lead one to imagine that the collection data speak for themselves. But nothing could be further from the truth. Extracting information is a scientific process that requires expertise, inventiveness, knowledge of tools and methods, as well as background knowledge of the issues being addressed. For this reason, very often, this research is inter- or trans-disciplinary and carried out in the framework of inter-institutional collaborations, where each party brings complementary expertise. These approaches benefit from international collaborative strategies, such as the creation of aggregators that bring together the databases and data used (e.g. GBIF), the creation of taxonomic repositories that make nomenclature and taxonomy available, the development of collaborative analysis systems (R Core Team) (see Chapter 18 by Monnet et al.), the creation of reference libraries for studies of ancient DNA (see Chapter 13 by Gagnevin et al.), and so on. The development or adaptation of methods, inherent
