Future change for the region was simulated using the State of California’s regional population projections and the complete implementation, or "build-out," of the area’s current plans. The projections based on current plans indicate a future urbanization of all currently unbuilt land in the region (Figure 4).

In addition, a Fall 1995 graduate-level studio simulated and compared five alternative scenarios reflecting different development and conservation policies. Alternative #1 illustrated the implications of a continuation of the current spread of extensive single-family and rural-residential growth, with an assumed disregard of the regional plan (Figure 5). Alternative #2 also followed spread development, but it introduced a major conservation effort in the year 2010 (Figure 6). Alternative #3 proposed private conservation by encouraging large lot ownership adjacent to and within important habitat areas (Figure 7). Alternative #4 employed a multi-centers approach based on cluster development and new communities (Figure 8). Finally, Alternative #5 concentrated growth in a new city (Figure 9). All of the alternatives accommodated the projected population forecast and were then extended to build-out. The following are some probable impacts of the changes between the 1990s baseline and the build-out of existing plans.

With the exception of land on Camp Pendleton, there will be a nearly complete loss of agriculturally productive soil to urban development.

The landscape ecological pattern will transform from a well-connected, natural landscape with urban areas into an urban landscape with fragmented natural areas.

With the exception of those species that live on the biologically well-managed Camp Pendleton and the Cleveland National Forest, several important species, including some that are threatened and endangered, will have significantly smaller areas of habitat.

Species richness of the region’s 375 vertebrate species will decline. Approximately 20 species could become regionally extinct; most at risk are birds dependent upon riparian habitats.

Vegetation will change due to the suppression of fire that accompanies urbanization. Fuel build-up in areas of fire suppression will place houses located in fire-prone areas at greater risk. When the several regional alternatives were developed to build-out and their impacts compared, each exhibited a similar pattern caused by the transformation of a "natural" regional landscape into a predominantly "urbanized" one. The most beneficial and least damaging alternatives from the perspective of biodiversity are those which combine low-density private conservation and the more concentrated new city and multiple-centers approaches; the worst are the existing plans of the region’s many jurisdictions and their consequent spread development.

This first comparison of alternative futures had three dominant conclusions. First, there are several key areas where the currently linked natural landscape is vulnerable to fragmentation from future development. Second, the alternative that delayed conservation until the year 2010 demonstrated that by that time it would be too late; there would be little left worth conserving for the maintenance of biodiversity. The third major conclusion was that one of the major hydrological consequences of upstream change would be an increase in storm runoff as areas of higher infiltration potential are paved, causing an increase in flooding in all the major rivers and particularly in the Santa Margarita River Basin; flood peaks would double where the river passes Camp Pendleton’s air base.

These three related findings shaped the problem that was posed to the fall 1996 graduate student studio: "What is the best, most feasible alternative for the study area that accommodates at least 40 years’ population growth, maintains biodiversity, and minimizes hydrological damage?"