Natural Diversity Act - Authorizes the Secretary of the Interior to provide grants to the States for implementing State programs for maintaining landscape and other natural diversity with supporting biological data management systems. Requires each State to prepare a plan identifying, classifying, maintaining, and monitoring elements of natural diversity occurring within its boundaries in order to renew its grants.

Directs each State to submit to the Secretary a priority list of sites which contain important elements of the State's natural diversity and which can be best protected through acquisition. Directs the Secretary to make matching grants for acquisition upon a finding that the site will contribute to the goals of this Act.

States that the sites acquired by such grants shall be known as Diversity Preserves and that a registry of sites shall be maintained by the Secretary.

Requires each Federal land management agency to establish a natural diversity program and biological data management system and to designate sites on Federal lands for entry on the registry.

Directs the Secretary to prepare an annual summary assessment of the status of the nation's national diversity.

Establishes the Federal Natural Diversity Office in the Department of the Interior and a technical advisory committee.