Scope of Preservation Needs
Virtually every medium used to record information is threatened by the natural forces of deterioration. The magnitude of preservation needs in a library is determined by the interplay of many factors; chief among them are the age, scope, and composition of the collections. Research library collections include a multiplicity of formats (e.g., monographs, journals, newspapers, maps, manuscripts, photographs, digital images) and media (e.g., paper, vellum, photographs, films, magnetic tapes, various types of disks). Among these diverse resources there is tremendous variation in life expectancy. Paper made from cotton fiber has lasted for more than a thousand years, preservation microfilm can have a life expectancy of hundreds of years, woodpulp newspaper pages deteriorate within decades, and some types of computer disks show loss of information after a few years.
While the durability and longevity of library collections are determined in part by inherent characteristics of the media, libraries and users also play a role. Many media deteriorate much more quickly when housed under hot, humid, or otherwise poor storage conditions; when adequate collection maintenance is lacking; or when the media are improperly handled by users.
Among the variety of media, paper-based materials compose the largest portion of research collections and are at the center of the preservation crisis. A series of assessments of the condition of research collections describe in alarming detail the magnitude of the preservation needs in research libraries. The most comprehensive survey was undertaken at Yale University Library in 1982 with funding from the National Endowment for the Humanities. This large-scale study assessed the physical condition and extent of deterioration of books in a random sample of 36,500 volumes; the results brought the size of the problem into sharp focus. In the Yale University collections, which numbered more than 7.7 million volumes at that time, 82.6% of the books were printed on acidic paper, 37.1% were already brittle, and 12.8% needed immediate repair.6 More recently, a survey of 40,000 volumes in the Western European Local History Collection in the Harvard University Library revealed that 44% were damaged.7 Overall these studies indicate that about one-fourth to one-third of larger research collections show significant signs of disintegration, that embrittlement is an ongoing process and threatens millions of books in the nation's research libraries. One estimate based on a Library of Congress study shows that 77,000 volumes in that library's collection become "brittle" each year.8
While the brittle books problem has dominated the preservation discourse, research libraries also hold vast collections of manuscripts, archives, and rare books printed on alkaline paper that require conservation treatments to restore them to usable condition. In addition, there are aging problems with motion picture films, sound recordings, and videotapes, all of which have limited life spans and require substantial preservation investment.
Electronic information and communications technologies are reshaping research libraries. At present, digital resources are a small percentage of total collections, but this situation will change dramatically. The amount of information that is created on computers is increasing exponentially, and the number of electronic collections is already huge. Not only will this upward trend continue, it is certain to accelerate. Information created in electronic form is presenting libraries with yet a new set of preservation challenges. The traditional preservation strategies used in the past to ensure the longevity of intellectual resources are no longer appropriate in the digital environment. Not only are digital media short-lived, there are no warning signals when they are becoming unreadable. Long-term retention of digital resources requires systematic maintenance and monitoring of data integrity, with continued upgrading of system components. Migration to newer technologies will eventually occur, and new information technology standards will be implemented as they are developed.9 Ensuring long-term survival of digital information is a complex technical and economic problem that will consume an increasing portion of preservation investments in the twenty-first century.