Combining Species Richness and Visual Preference Models

for the San Pedro River Basin Arizona, U.S.A. and Sonora, Mexico

Scott Bassett

Doctor of Design Thesis, GSD, June 2001

SUMMARY

The conservation of natural landscapes often follows two major ideals. The first, preservation of natural processes to ensure the long- term stability of the ecosystem, comes from the need to protect biodiversity for a host of reasons. The second, aesthetics, comes from a human ideal of what beauty is and what it may become. When mapped in space the highly valued lands representing the positive aspects of these ideals may overlap, but more often than not some controversy among them exists. To address this controversy and subsequent conflict in space new models have to be created which reflect aspects of both ideals. The objective and subsequent research summarized here reflects a single attempt at accommodating both ideals for a watershed, designated by identifying the contributing area around the San Pedro River, located on the U.S.-Mexican border in the states of Arizona and Sonora.

An integrated model illustrated how a visual model, aesthetic ideal, and a species richness model, biodiversity ideal, could be combined to accommodate locations based on their species diversity and visual beauty (Figure 1). The model allowed each factor to be represented equally in terms of total land area, yet allowed for preservation of the most visually pleasing viewsheds and the preservation of highly species diverse areas. As displayed in Figure 1 different paths existed for the species richness and visual value components of the integrated model. These paths were introduced to address the juxtaposition of previously selected reserves in relationship to the future reserve selection process. The most common path a reserve cell may take for the species richness and visual value component of the integrated model is shown in Figures 2 and 3.

Figure 1. Flow chart depicting the reserve selection methodology applied for the integrated species richness and visual value model. Two of the Paths under the species richness and visual value components of the integrated model are illustrated in Figures 2 and 3.

Figure 2. Reserve cell selection process for the species richness method when the next reserve cell was to be located on the edge of a reserve and redundancy factor of 3 separate reserves had not been met. This selection process is referred to as Path 1 of the species richness method

Figure 3. View-from reserve cell selection process used for the visual method when cells were adjacent to existing view-from reserve cells. This selection process is referred to as Path A of the visual method.

Once the model was run a series of evaluation techniques described the relative efficiency the integrated model had for conserving the species and visual resources present in the area. It was found that the integrated model provided improvements to the traditional method of placing reserves based on species richness and visual value. A second result indicated new reserve locations could be added to the already present reserve system to better accommodate the species and visual beauty of the region. The spatial locations identified by the integrated model indicated areas lacking adequate protection consisted of riparian and desert scrub communities in the North and grassland locations in the South. A total reserve system that would accommodate these locations and preserve 10% of the total area under a de novo scenario is presented in Figure 4. Figure 5 illustrates what happens when the existing reserve network is the starting point for 10% land area preservation.

The results presented by this research showed how a single modeling methodology could improve our decision process for placing reserves. The results also indicate a lack of consideration of some key locations important for the survival of species and maintenance of visual value. Inclusion of these key locations would add the necessary habitat and viewsheds to ensure the long time conservation of previously excluded natural landscapes.