The following is an excerpt from a paper submitted by RECON Enviromental,
Inc. Titled "Land Cover Data Assessment in Pima County"

Organ Pipe Cactus National Monument

The National Park Service conducted a parkwide survey of existing vegetation between
1977 and 1981, as part of a proposal for managing the monument's natural resources.
The survey encompassed the entire 517-square-mile monument and was conducted
using both remote sensing and field techniques. Vegetation boundaries were interpreted
from and delineated on 1:24,000 color aerial photographs, then checked and attributed
with vegetation type information in the field. Representative examples of each vegetation
association were sampled in order to classify types. Vegetation classification was based
on Brown, Lowe, and Pase (1979) with new associations named below the existing BLP
legend. This detailed study recognized 29 vegetation associations and subassociations
named and described in CPSU Technical Report No. 8 (Warren et al. 1981).

Organ Pipe Cactus National Monument vegetation mapping represents the most detailed
study in the county. A GIS coverage exists for this mapping and includes attributes
containing BLP code and association name for all polygons. BLP codes include an "R"
where the polygon contains riparian vegetation. The Organ Pipe coverage used in the
composite map is shown in Figure 3. Series-level colors are differentiated on the map;
additional polygon boundaries show classification detail at the association and
subassociation levels. There were some questionable attributes in this database which
were corrected based on a discussion with Peter Warren. These corrections are briefly
discussed in Section IV.A. of this report.