Digitisation is a concept that, depending on the person, context or situation, may have different meanings (see also p. 3 in Cobb et al. 2019). Generally, digitisation is the process of creating a virtual representation of physical objects. When considering collection digitisation, however, this can relate to the electronic registration of the basic information of an entire collection, it may relate to registering information about the storage units (box, container, jar) or species present in a collection or it can mean electronically storing the label data of individual specimens. Using the term digitisation in some cases explicitly refers to making digital images whereas in others it is restricted solely to data. When using digitisation in combination with registering data, it may include all the data linked to a specimen or only part of the data (Saarenmaa et al. 2019). By using the term ‘digitisation’ one also cannot assume that this also includes validation or georeferencing. In some cases this may apply but in many others it may not. For communication purposes it is crucial that both the sender of a message with the term ‘digitisation’ and the receiver of that message attach exactly the same meaning to the term ‘digitisation’. If there is a mismatch between sender and receiver this may result in a misunderstanding which may lead to frustration, resistance and ultimately result in unwillingness to undertake digitisation tasks together from both sides.

• In the current study the term “digitisation” refers to the electronic registration of data and information from individual specimens or samples, possibly but not necessarily including imaging, validation, georeferencing, etc.

The current study carried out as part of the ICEDIG project, originally was aimed at natural history collections of private collectors, amateur societies, and smaller museums and herbaria. This was in line with a precursor study also carried out in the ICEDIG project which was formulated as follows: ”Inventory of content and incentives for digitisation of small and private collections.” However, straight from the onset of the implementation of this precursor study it was decided to exclude “small” collections as a separate entity and restrict the target group to private collections only. The main argument for this adjustment is that a distinction based on size is rather artificial and “small” collections are therefore difficult to address as an entity. As privately owned collections outnumber collections of amateur societies and smaller museums and herbaria many times and by their very nature form an easily distinguishable group, a distinction based on ownership therefore offers a clearer and more practical boundary than collection size. The distinction made for the precursor study in ICEDIG has also been adopted for the current study.

The current study was therefore aimed at those collections that are privately owned, usually kept in a residential building and managed and cared for by a private person who does not receive any funding for this. Private collections on average are relatively small. Results from a survey carried out across Europe in 2018 as part of the ICEDIG project and presented as deliverable D2.2 of this project (van Egmond et al. 2019) showed that most private collections hold less than 10,000 specimens, some 25% having more than 10,000 specimens. Private collections with more than 100,000 objects are exceptional but still form some 5% of the totalof private collections around. The 2018 European survey showed that the total number of specimens owned by private collectors, who responded(!) to the questionnaire lies between 9 and 31 million. This is only the tip of the iceberg, the overall total number of specimens in all European private collections is many times higher, as not all the collectors were reached, only a small percentage that were reached responded and there were big differences on how the various countries were covered. Based on the survey results it is not possible to make a reliable guesstimate of the total number but quite likely this surpasses 100 million or more. In comparison, institutional natural history collections in Europe hold 1.5 billion specimens.

65% of the respondents of the survey said that they manage their collection data fully or partly electronically. Over 90% are interested in sharing their data some way, preferably through a public website, and by listing metadata of their collection in some kind of public register. Most private collection owners (55%) indicated they need tools, such as a dataset template or a web based digitisation platform, followed by guidelines (36%) and physical equipment (27%). The report concludes that future efforts to help private collection owners to digitise their collections should focus on providing appropriate online tools and information on how to get started with digitisation. In particular, there is a large interest in a new European-wide website where private collection owners can register and subsequently share collection-level data.

Results of this study were written as a formal deliverable (D5.4) of the ICEDIG Project and were previously made available on Zenodo (Willemse et al. 2020) and submitted to the European Commision as a report. While the differences between these versions are minor the authors consider this the definitive version of the report.

The main goal was to reach out to the private collection owners, present them the idea of collection digitisation along with the different strategies and means of digitisation. As a mediator, ideally, a collection owners association was to be approached. After the first contact with this association, testing would start where collection owners would digitise their collections through the PlutoF workbench and publish the data to GBIF. This process would be documented and analysed and finally presented as a best practice case for a workflow of private collection digitisation and publishing of collection data and metadata to GBIF.

UTARTU collaborated with the Estonian Lepidopterists’ Society (ELS) to promote the concept of private collection digitisation and data sharing. The contract was signed between UTARTU and ELS for organising a public workshop and publishing an article in the ELS yearly magazine for promoting digitisation and giving guidelines to ELS members and the wider public. The Workshop was held and the article published in winter 2019 with twelve ELS members and other public participants.

Private collection owners who showed interest in the digitisation of their collections were assisted with their digitisation efforts. To this end, a specialist assistant was contracted by UTARTU. For some collection owners, access to the digital photography facilities in UTARTU were enabled to image the collection specimens.

Early 2017, a questionnaire about the composition of collections and their digitisation status was sent to members of the Dutch Entomological Society (Nederlanse Entomologische Vereniging 2017). As part current study, a number of private collection owners who responded to the 2017 survey and had not yet started digitising their collections were approached and subsequently visited at their home address where the collection was kept. During this meeting the collection was viewed, motivation probed and digitisation (specimen data registration only) of their collection discussed in terms of what was needed to get started.

Starting early 2019 nine collection owners joined the pilot. Out of the nine collection owners five indicated they preferred to do the digitisation themselves whereas four collection owners indicated they lacked the time but agreed to let volunteers do the work. For the latter group three collections would be digitised at an institute (instead of the home address) while in one instance the collection owner agreed to let a volunteer come and do the work at his home address. For collection owners doing the work themselves, all required items (manual, template file for data entry, registration codes) were prepared and handed out during an introductory session. Collection owners were then very much left alone, having been given contact details in case of questions.

Volunteers with no or hardly any experience in entomology were recruited using social media and were given a short instruction session. Each volunteer, as a rule, only worked for a single day per week. Altogether seven volunteers were deployed, one working at the home address of a collection owner and six volunteers working at the institute. For the latter group using 1-2 workplaces, collections were brought to the institute, digitised and returned to the owner.

Table 1 summarises the results in numbers of specimens digitised per collection. Results clearly indicate that the output in terms of number of specimens digitised tend to be larger when volunteers are involved.

In addition to the digitisation efforts, a one day meeting was organised for members of the Dutch Entomological Society. Among other reasons, this was organised to inform participants about the pilot that had taken place, the lessons learned, remaining questions, future plans and feedback. During the day a hands-on training on specimen digitisation was included and several aspects (imaging, online portals, management tools) demonstrated. Around 25 participants attended the meeting.

The diversity of private collections, their owners and the cultural aspects linked to private collections across Europe is enormous. In this respect the two approaches to get private collection owners involved in digitisation carried out in Estonia and the Netherlands only scraped the surface of a multitude of possible approaches. This diversity makes a comparison between approaches in terms of effectiveness difficult. An approach that works very well for amateur entomologists with private collections in Estonia or the Netherlands may not work at all in other countries. Advocating an approach that works very well for most entomological collections across Europe may turn out to be a complete failure when applied to malacological collections.

During the pilot in Estonia, a workflow was set up and tested for managing and publishing the digitised collection data, using PlutoF biodiversity data platform, GBIF IPT and GBIF API. The workflow proved to be suitable for intended use as a tool for private collection digitisation. However, the willingness of private collection owners to share the data was quite low and only a small number of them actually published the data. There are no clear explanations for this, but as indicated during meetings with the lepidopterologists society, collectors consider digitisation a time consuming activity which is not seen as something they are interested in in the first place.

The approach used in the Netherlands including nine participants showed that conviction of the importance of digitisation and having been given the tools to start digitising do not always provide enough impetus to get and keep collection owners going in the medium and long-term. Lack of time or rather making choices on how to spend your time hampers the start and/or continuation of digitisation related activities. Within the Dutch cultural setting the use of volunteers provided a workable solution to overcome time constraints. Along the way various remarks were made or questions raised about specific aspects of digitisation which were not taken into account at the start but have been incorporated in this publication. Such questions and comments very much helped in realising that making digitisation of private collections a success can only be brought about by a strong commitment and a joint effort from all stakeholders involved.

Private collection owners are at the heart of their collection digitisation. They are at the same time customer and supplier.

Rights: Private collection owners are the primary data owners who decide about digitisation in the first place and whether - and if so in which way - or not are shared.

Responsibilities: Digitisation of private collections is impossible without the initial consent or action of private collection owners. However, their actions are based on voluntarism and cannot be forced.

Revenues (benefits): By having their collection digitised, private collection owners can much more easily manage their collections or share information with other collection holders for instance for specimen exchange. Digitisation is also required in order to publish data online and opening the collection up to the global research community. This makes collections a lot more meaningful not only for the community at large but also for the owners.

Relationships: Depending on the national context, Private collection owners are most closely linked to non-governmental organisations or citizen science associations. Private collection owners can be members of those associations and share information about their collections through the membership network. Depending on country and cultural aspects, private collection owners may be in contact with collection holding institutes as regular visitors or even as external specialists.

The citizen science associations are networks of institutions and/or individuals who utilise citizen science methods, crowd-sourcing or are representing citizen scientists.

Rights: Citizen science associations have no specific rights regarding data originating from digitised private collections.

Responsibilities: Citizen science associations do not carry an active role in collection data digitisation itself. However they could play an important role in communication, not only to encourage their members to list their collections in public catalogues but also to inform them about ongoing developments and activities.

Revenues (benefits): The main aim of citizen science associations is to promote knowledge of and stimulate interest in the subject of the association. Digitising and publishing data from private collections may contribute significantly to that.

Relationships: Citizen science associations carry a networking value for collectors. They can play an important role as “middleman” between more formal structures (governmental agencies, institutes, universities) and individual citizen scientists.

Non-governmental organisations represent research communities linked to - or whose daily activities center on - specific topics or tasks (e.g. Estonian Naturalist’s Society, Estonian Ornithological Society or the Vlinderstichting, EIS and Floron in the Netherlands) including citizen scientists who for instance submit observational data.

Rights: Non-governmental organisations do not usually have the rights to access digitised data from private collections. In some countries, however, natural history associations can act as a non-governmental organisation by representing private collectors or observers can obtain rights to the data they are submitting.

Responsibilities: Non-governmental organisations can support private collectors in their digitisation efforts, collection management or taxonomic expertise.

Revenues (benefits): If private collectors share data with Non-governmental organisations, this can be leveraged to form partnerships with other institutions, government agencies, etc. In some cases the non-governmental organisations have exclusive rights to the data being submitted and raise revenue by providing consultation services for the public administrations based on these data. This sometimes results in data not being shared openly.

Relationships: These specialised interests groups can bring in expertise to governmental projects or serve public interests.

Collection-holding institutions comprise all the smaller and larger regional and national museums, institutes, universities, etc. holding a natural history collection.

Rights: When there is an agreement on the future donation of a private collection to a biodiversity repository, the data use rights as a rule are transferred as well but sometimes the timing can coincide with the physical transition.

Responsibilities: As a rule of thumb, digitisation of donated collections is the responsibility of the recipient collection-holding institute. Prime goal of the current study was to ensure that in the future more and more collections that are being donated to a collection-holding institute have already been digitised according to the standards and protocol used by that same institute and to ensure that the effort to migrate data into the local management system can be kept to a minimum. Moreover, digitisation by collection owners allows for a more accurate and complete dataset as they consciously or unconsciously include their knowledge and information in the process. Chapter 4 describes a number of tasks that can be undertaken by collection holding institutes in order to facilitate the digitisation of collections prior to the donation.

Revenues (benefits): There are two important benefits for collection-holding institutes to be gained from digitising privately owned collections. First, it saves time to digitise the collection once it has been donated. Secondly, curators or research staff working at the collection-holding institute may directly use the data for their research.

Relationships: Collection-holding institutes are often the most qualified agents for digitising natural history collections, having access to technology, human resources, knowledge and expertise. Private collection owners may have direct contact with researchers, curators or collection managers working at collection-holding institutes either to receive help or to assist with taxonomic expertise. The institutes also are often organised nationally or internationally in gremia that include other stakeholders.

The research community can be considered both as the collection of all the individual researchers whose research is linked to data residing in natural history collections, and as the fora in which researchers are organised to represent their common interest.

Rights: As long as collections have not been digitised (or published in a paper), data and information residing in a collection is only available to the collection owner. Once collection specimens have been digitised, publication online generally implies that data become available to everyone without restrictions.

Responsibilities: If private collection data are used for research, it is crucial to acknowledge this in the resulting paper so as to stress the value of private collections for research and emphasising the importance of their digitisation. Consortia like CETAF and other bodies focussing on research and formed by researchers can play an important role in removing obstacles that prevent or impede private collection owners in the digitisation of their collection. Possible ways in which the research community can assist collection owners are mentioned in Chapter 4.

Revenues (benefits): Researchers are the main end-users of digitised collection data and therefore benefit most from any improvements in the process of making data from privately owned collections available online .

Relationships: The research community communicates through scientific papers and by visiting (inter-)national gatherings. The main objective behind creating a private collection may differ between collectors (“stamp” collector versus the scientific collector). The scientific collector will be part of the research community, the “stamp” collector not.

Public administration in this context includes environmental agencies, ministries, etc. that act in public interests, regulating nature protection, land use, etc.

Rights: No direct rights.

Responsibilities: They play a very important role not only in making policies, regulating laws and cash flows but also in raising general awareness about nature and nature conservation. As law makers, they can play an important role together with the collection holding institutes in tackling specific obstacles, like an approach for illegally collected specimens or species residing in private collections. Overall, by acknowledging the importance of private collections as part of natural history heritage they can stimulate the digitisation process.

Revenues (benefits): To make informed decisions when enacting policies or laws, public administration makes use of reports and data from the research community either based on specific publications or on assignments carried out by NGOs. The more data are available to support results presented in publications or reports, the better.

Relationships: Direct links between private collections and the public administration are weak. However there is a network of contacts between the public administration and other relevant stakeholders.

Data aggregators integrate data originating from different data sources into a coherent data pool. They also act as a data publisher, thus making data publicly accessible. One of the well known data aggregators and publishers in earth and life sciences is the Global Biodiversity Information Facility (GBIF).

Rights: They obtain (some of the) rights to digitised private collection data if shared by collection owners in the process of data publication.

Responsibilities: An important task is to provide information about standards and workflows for registering private collections and also for uploading the data. Offering a multitude of tools and applications (spreadsheet upload, data management workbenches, IPTs, etc.) will help collection owners with variable data skill levels to find appropriate data management tools.

Revenues (benefits): Including private collection data in publicly available data repositories will help to fill the taxonomic, geographic and temporal gaps. Hence, it will also raise the value of these repositories for research.

Relationships: Traditionally the biodiversity data aggregators and publishers are not directly connected to private collectors. Data facilities are usually tailored for institutional use and access for private individuals is limited. However, if a private collector is associated with a natural history society or other academically accepted NGOs, this may help to facilitate access to data aggregators and publishers.

Data originating from natural history collections can be used for various purposes in industries. Examples can be found in creative industries, tourism, the food and health industries, agriculture or forestry. Another small but important industry is the digitisation industry that provides equipment, software, and services for digitisation!

Rights: There are no inherited rights for the industry sector. The collection data can only be used by the industry when a commercial license is bought or issued by the original data holder.

Responsibilities: The sustainable use of biodiversity data in industrial applications can be beneficial for society as a whole.

Revenues (benefits): Industry can generate revenue, using biodiversity data for creating certain products or building services.

Relationships: Providing biodiversity data to the industry may be an economically one-sided relationship but it may help society to understand and appreciate the value of data in general.

Regardless of concrete steps to be taken to enhance or start digitisation, a private collection owner can at any time:

• contemplate and ideally decide as early as possible about the person, museum or institute that he or she wishes to donate the collection to in the future,
• ensure that the collection has an acceptable curation standard i.e. specimen/samples mounted or prepared, labeled, identified and stored in adequate containers,
• if applicable, retrospectively look up coordinates for sampling sites visited in the past for which coordinates on specimen labels are still missing and add these either in the field books, in a separate electronic file or directly in records for specimens that have been digitised.

Looking at collection owners with private collections and considering the aspect of ‘registration/digitisation’ of their collection, roughly three scenarios can be distinguished:

1. not yet started (0% registered or digitised),
2. partly or completely registered in some form of paper archive,
3. electronically digitised either partly or completely with or without the use of unique identifiers attached to the specimens/samples.

Below, the three scenarios are briefly introduced and although their starting situation is very different, the roadmap of actions is by and large identical.

One aim of citizen science associations in this context is to generate interest and enthusiasm in the study of specific nature related themes or groups. Citizen science associations represent the interests of their members and as such can play a key role in connecting private collection owners to other stakeholders, in particular collection-holding institutes. When it comes to the digitisation of private collections citizen science associations can facilitate this process by spreading awareness and information among its members and beyond through mailings, workshops or meetings. In particular, a roadmap for citizen science associations should include:

• searching for and making available relevant information as well as being familiar with (inter-)national programs linked to digitisation,
• informing members,
• looking for ways to have an up-to-date inventory of collections kept by members,
• if feasible looking for means to stimulate digitisation of private collections,
• contacting collection holding institutes to discuss common strategies.

Like citizen science associations, non-governmental organisations are organised around expertise and studies of specific groups of organisms. Contrary to citizen science associations, non-governmental organisations (rather than representing the citizens’ interests and facilitating them) use data gathered by citizens, whether observation or collection based. It is in the interest of non-governmental organisations to ensure that citizen scientists keep publishing data online and that these data are accurate and verifiable. A roadmap for non-governmental organisations regarding the digitisation and online publication of private collections could comprise:

• together with citizen associations and collection holding institutes create and keep up to date an overview of specialists, national or international, that can be approached,
• to stress the importance of digitisation and properly identified specimens/samples at meetings, workshops, etc. attended by private collection owners,
• to contact collection holding institutes to discuss common strategies, for instance to include (the digitisation of) private collections in atlas projects.

For regional and national institutes, digitisation of private collections is or will become part of their core business. This statement is based on the fact that most if not all private collections one day will be offered as endowments to publicly owned collections. If private collections at the moment of transition are not digitised, they will add to the total backlog of digitisation of the institute receiving the collection. More importantly, information may become lost if private collections are digitised at a far later stage when the original owner is no longer available or capable to provide additional information related to the collection. In order to guarantee the highest possible data quality (accuracy, precision and completeness), and ensuring that datasets are standardized in such a way that they can be migrated easily, institutions should actively promote the digitisation of private collections at the earliest possible opportunity. Therefore, it is of utmost importance that collection-holding institutes facilitate and participate in activities linked to the digitisation of private collections - which in the future will become their collections. A roadmap for collection holding institutes regarding the digitisation and online publication of private collections could comprise:

• contacting citizen science associations and non-governmental organisations to discuss common strategies, like a common communication strategy,
• preparing an up-to-date list of private collections that could be donated in the future with the help of citizen science associations,
• actively approaching private collection owners to discuss their plans regarding bestowal and linked to that the state and or plans regarding digitisation,
• preparing policies and protocols required to streamline various aspects linked to digitisation of private collections, for instance the use of unique identifiers,
• deciding on resources to be made available for digitisation of private collections; if necessary this could lead to efforts to find funding.

The biodiversity research community at large has a vested interest in online data. Whether data is derived from specimens kept in larger museums or small private collections is much less important than the certainty of high data quality and reliable identifications. The already mentioned survey carried out in the ICEDIG project(van Egmond et al. 2019) in 2018 showed that the overall size of private collections and the data they contain is impressive and for specific groups or geographic areas unique. The research community is organised in a multitude of programs, platforms and projects both at the national and international level. These platforms (e.g. CETAF, DiSSCo) should be made aware of the importance of private collections as a potential source for biodiversity data. Not only is more communication required but an online tool providing access to high level information of private collections would also be a great asset to raise awareness and to facilitate searching these collections. Once the research community is aware of the (importance of) private collections they may actually be able to contribute to digitisation and online publication for instance by allocating funding, facilities or manpower. More in particular, the roadmap for the research community regarding the digitisation and online publication of private collections could comprise:

• to create an online access portal with information about individual private collections,
• where (inter-)nationally feasible, to look for opportunities to organise stakeholders into setting up a joint approach for aspects related to the digitisation of private collections,
• to develop a communication strategy together with other stakeholders.

Public administration plays a very important role not only in making policies, regulating laws and cash flows but also in raising general awareness about nature and nature conservation. When it comes to a roadmap linked to the digitisation and online publication of private collections, public administrations could tackle:

• as law makers they can play an important role together with the collection holding institutes in tackling specific obstacles like an approach for illegally collected specimens or protected species residing in private collections which are donated to a publicly funded institute.
• overall, by acknowledging the importance of private collections as part of natural history heritage they can stimulate the digitisation process.

Online access to collection data is provided in a myriad of ways by institutes as well as (inter-)national initiatives in Europe and the world. Each of these portals differ in the metadata they publish, the source of data (observations and/or collections), accessibility and possibilities to add or change data and technical solutions to accomplish this, quality checks, etc. An additional complicating factor is the rights management when private collections, become incorporated in larger regional or national collections. What happens to online data when a physical collection changes address and ownership? Considering the temporary nature of private collections in combinations with the many portals available to choose from, working toward an internationally standardised solution for publishing data from private collections becomes quite a challenge. A pragmatic approach would be to start looking at national levels for solutions to make (meta)data from private collections accessible online. Nevertheless, one should strive for streamlining national initiatives across countries, to anticipate an international solution. When it comes to a roadmap linked to the digitisation and online publication of private collections, data aggregators and online publishers could focus their attention on:

• streamlining efforts to standardise the online publication at a national level,
• notwithstanding national efforts, looking into ways to streamline the online publication of collection data at an international level,
• together with other stakeholders putting effort into optimising messages and channels of communication directed toward all stakeholders involved but particularly the private collection owners regarding the online publication of collection data,
• develop protocols with other stakeholders aimed at keeping virtual data and information synchronised with data and information in the physical collection.

Except for companies directly supplying products and services linked to digitisation, industries are not directly involved in digitising or publishing data. Overall, they use data that are directly or indirectly linked to collections. Industry here has a very wide range from food industry to creative industries with no concrete common interests or responsibilities. Therefore despite their vested interests, a roadmap with concrete combined actions has not been drawn up.