Population Increase

Let's look in detail at trends in human population increases, first on a regional basis, then by state and area, and later in terms of the changing balance between rural and urban areas.

In the Sonoran Desert Bioregion, population nearly doubled (+98%) between 1970 and 1990 to a total population of 6.9 million (Table 3). The greatest increases in population occurred mostly in coastal resort areas, state capitals, and along the U.S. - Mexico border (Figure 2). The municipio of the popular Gulf of California resort area, Puerto Penasco, ballooned a walloping 188%. Maricopa County, home of Phoenix, grew 118% and the Sonoran capital, Hermosillo, grew by 116%. Within individual biotic communities, population more than doubled in three of the seven major communities (Arizona Upland/Lower Colorado River Valley, Plains of Sonora, and Magdalena Plain). Population in all of the other subregions grew by half or more, to population densities of up to 25 people/km2 except for Viscaino, which witnessed growth of 16% to a population density of only 2 people/km2 (Table 3, Figures 2 and 3).

However, striking population increases are not the rule for all areas, and population densities remain relatively low in some subregions. In forty-two percent of the counties and municipios, population increased by less than 30% or even decreased in some Sonora municipios. However, these counties and municipios represent only 14% of the land area while 68% of the land area is occupied by counties whose population increased by over 60% (Figure 2). Even though population increased by over 85% in Central Gulf Coast and Magdalena Plain, 1990 population densities were only 1 and 5 people/km2 (Table 3, Figure 3).

Currently, there is no sign that human population growth rates in the region will taper off during the next few decades. The Arizona Department of Economic Security estimates that Maricopa County will have nearly 2.5 times its 1995 population in 2045. While Maricopa County's current population is already well beyond carrying-capacity, other so-called underpopulated counties and municipios are also expected to grow well beyond their current resource base and infrastructure in the next few decades. By 2045, Yuma County is projected to harbor nearly 2.7 times its 1995 population. By 2010, the municipios of Mexicali and Ensenada in Baja California Norte are projected to be 40 and 124% more populous than they were in 1990 (Baja California 1992).

From:
Nabhan, Gary Paul and Andrew R. Holdsworth. 1998. State of the Sonoran Desert Biome: Uniqueness, Biodiversity, Threats and the Adequacy of Protection in the Sonoran Bioregion. p.24-25. Tucson, Ariz.: The Wildlands Project.