Libraries are the repositories for the world's knowledge. Unfortunately, even well bound books printed using quality paper exhibit a tendency to decay over time. While some knowledge preservation advocates are pressing for a move to digital storage formats, there is a danger in this form of library preservation as well. Electronic media is subject to system and power failures where data can be corrupted or lost. Although keeping bound books is a less efficient storage system, properly equipped libraries can play a vital role in the prevention from corrosion damage of books.
The main problem with library preservation that has to be overcome is the damage done to paper when exposed to air, especially the moisture generally present in air. Even small amounts of humidity will damage paper over time, causing it to degrade and the words printed upon it to be lost forever. Vacuum storage is used in the case of rare, unreproducible documents, but this is cost prohibitive and beyond the means of most libraries. Sealed rooms with dehumidifiers placed throughout are a far better means of system preservation, and limiting access also has the added benefit of keeping the air relatively insulated from external contaminants.
Library preservation can benefit from a supplementary digitization project, although relying solely on digital documents can be dangerous. Some documents cannot be scanned due to their age and advanced state of deterioration, and others aren't conducive to scanning, but in general most books can be scanned into a computerized database as a sort of digital back up to be used in case of a physical world accident or contamination damaging the library. In truth, even the best physical protection schemes and storage systems sometimes fail, and the contents protected by them are not immune to degradation - the rate is merely slowed. Digitization serves as a useful adjunct to physical library preservation.
As with any preservation effort, library preservation benefits from a scaled, multi-faceted approach. Putting documents in an already advanced state of decay into a vacuum sealed container and then placing that container in an atmosphere controlled vault will keep items deserving of this treatment preserved. Maintaining an archive that is climate controlled, dehumidified, and kept under restricted access protocols will serve for valuable documents that are not too badly degraded. And utilizing digital storage systems will help enhance library preservation and back up the contents of a library for later reproduction if needed.