Report to the California Biodiversity Council
October 9, 1997
Bill Stewart, Chief
Fire and Resource Assessment Program
California Department of Forestry and Fire Protection
PO Box 944246, Sacramento, CA 94244
(916) 327-3939 FAX (916) 327-1180
Over the past 50 years, California has always been a major magnet for people looking for new opportunities. Consequently, it has had one of the fastest rates of population growth in United States. Population growth will continue to present a major challenge to the protection of California’s unique and varied biodiversity.
California is a magnet for people looking for new opportunities and has experienced one of the fastest rates of population growth and land use change in the United States. The scale and pattern of population growth will continue to present a major challenge to the protection of California's unique and varied biodiversity. To assess the potential impacts of future population, FRAP reviewed existing regional and local population patterns and used some simple rules to allocate new residents across the landscape.
County population patterns and future estimates from the Demographic Research Unit of the California State Department of Finance are aggregated into 10 different regions to illustrate recent trends and the potential long-term population changes. The economic recession during the mid-1990s and the subsequent rebound demonstrates the close relationship between employment prospects and migration.
Regional growth rates vary widely across the state. The San Joaquin Valley and other inland regions with relatively good transportation access to major metropolitan areas are growing faster than the state as a whole. The Sacramento Valley is the only bioregion following the projected path for the whole state. The population growth for the four coastal regions was slower than the state during the mid-1990s, and these regions are projected to continue to grow at a slower rate for a number of different reasons. The San Francisco Bay Area and Southern California, the two most densely populated regions in the state, have relatively little land left in which to expand. The Central Coast and the North Coast have considerable potentially developable land but have few existing urban centers or strong transportation networks to support rapid regional economic growth compared to the total size of the regions.
The land use impacts of these increases in population will be accommodated by the expansion of existing residential areas according to what is allowed by zoning and what is economically feasible. Without any major changes in land use economics or policies, a reasonable hypothesis is that the distribution of the new population will closely follow existing patterns. In terms of land use, 14 million acres in the state is occupied with widely scattered residences on 1 to 10 acre parcels while only 4 million acres are covered with subdivisions or urban areas. The remaining 82 million acres has little to no residential land use on it. At the county level, California counties can be grouped into four distinct development patterns.
Land use impacts related to future population growth will probably follow these distinct patterns.
The following information focuses on what we know about the first two questions – how many people are projected to move into California by bioregion and what are some of the patterns of residential land use that we can expect. One of the main conclusions is that there is not a "California pattern" for population impacts. We should not expect that there will be a "California solution" to this issue. Each bioregion exhibits its own set of population related changes that most probably will have a strong influence on future biodiversity related policies.
Population forecasts are developed and updated by the Demographic Research Unit of the California State Department of Finance. A single estimate for the state, counties, and major cities is developed based on an extrapolation of the most recent available data and a specific package of methodologies and assumptions. The economic recession during the mid 1990s produced a number of unexpected changes in the domestic migration that required a significant lowering in future population projections in the most recent estimates. Since counties are the smallest unit for standard population projections, county boundaries rather than the bioregional boundaries are used to define populations of the bioregions. The following table compares population of bioregions defined by county boundaries and the smaller census blocks. The most significant difference is the shift in residents out of the true South Coast bioregion to the Mojave (San Bernadino and Riverside counties) and the Central Coast (Ventura). The San Joaquin Valley population also increases with the inclusion of portions of the Delta and the Sierra Nevada.
Bioregion |
By County |
By Census Block |
Difference |
County over/ |
California |
29,363,156 |
29,428,496 |
-65,340 |
0 |
South Coast |
13,647,766 |
16,092,094 |
-2,444,328 |
-15 |
Bay Area - Delta |
5,891,240 |
6,593,315 |
-702,075 |
-11 |
San Joaquin Valley |
2,700,652 |
2,009,534 |
+691,118 |
+34 |
Mojave |
2,561,101 |
595,015 |
+1,966,086 |
+330 |
Central Coast |
1,856,648 |
1,203,879 |
+652,769 |
+54 |
Sacramento Valley |
1,700,429 |
1,496,266 |
+204,163 |
+14 |
Sierra |
541,159 |
614,038 |
-72,879 |
-12 |
North Coast/Klamath |
321,223 |
388,294 |
-67,071 |
-17 |
Colorado Desert |
106,784 |
362,112 |
-255,328 |
-71 |
Modoc |
36,154 |
73,949 |
-37,795 |
-51 |
Source: FRAP analysis of 1990 Census data. 1990 Census and 1990 DOF populations are slightly different due to different base month.
Bioregions |
July 1990 |
July 1996 |
July 2000 |
July 2010 |
July 2020 |
California |
29,944,045 |
32,383,000 |
34,704,000 |
40,939,000 |
47,507,000 |
South Coast |
13,831,000 |
14,741,100 |
15,540,600 |
17,682,800 |
19,928,500 |
Bay Area/Delta |
6,052,000 |
6,502,800 |
6,809,500 |
7,488,900 |
8,031,100 |
San Joaquin Valley |
2,768,200 |
3,123,500 |
3,526,300 |
4,607,800 |
5,838,400 |
Mojave |
2,631,300 |
2,985,900 |
3,371,400 |
4,597,400 |
6,010,500 |
Central Coast |
1,883,900 |
1,987,000 |
2,110,900 |
2,459,900 |
2,829,000 |
Sacramento Valley |
1,737,200 |
1,877,250 |
2,054,500 |
2,502,400 |
2,967,800 |
Sierra |
559,920 |
631,960 |
717,400 |
918,400 |
1,110,200 |
Klamath North Coast |
332,300 |
349,650 |
376,500 |
445,400 |
512,600 |
Colorado Desert |
110,800 |
141,200 |
152,300 |
185,200 |
222,600 |
Modoc |
37,425 |
42,650 |
45,000 |
51,100 |
56,700 |
Source: Department of Finance, April 1997
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There is a wide range of growth rates across the different regions. The following figure illustrates the projected populations indexed to 1990 populations. Diversity is the key. The Sacramento Valley is the only bioregion following the projected path for the state as a whole. Areas with large irrigated agriculture are projected to experience the greatest rates of growth and the coastal areas are projected to have considerably lower rates of growth.
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Of the four main components of population change (births, deaths, foreign immigration, and domestic migration), the sudden reversal of domestic migration of people moving in and out of the coastal counties explains why overall population forecasts were revised. As the following figures for California illustrate, there are no significant changes in terms of the birth and death rates (the two components of natural increase) or any significant changes in international immigration. The major change was the significant movement of people out of the coastal counties to Sierra Nevada counties or other states. Research at the Federal Reserve (Gabriel, S.A., Mattey, J.P. and Wascher, W.L. The demise of California reconsidered: interstate migration over the economic cycle. Economic Review No. 2. Federal Reserve Bank of San Francisco, 1995. p.30-48) analyzed trends in domestic migration from California and concluded that nearly all the variation was driven by the loss of jobs in those counties during the recession. They predicted that resurgent economies would reverse the trend and lead once again to significant rates of overall population growth in areas that had experienced net domestic out migration during the mid 1990s. The figures for the nine other bioregions (on pages 5-7) illustrate many bioregion-specific patterns for the components that make up overall population change. All regions experienced significant drops in the rate of domestic in-migration but the Sierra Nevada was the only region that experienced a positive flow of domestic migration throughout the 1990 to 1996 period.
SEE Average Annual Population Change 1990-1996
The preceding analysis suggests that population growth rates will vary considerably throughout the state and from year to year. The impacts of changing populations to land use and biodiversity can not be predicted simply from population projections. Increases in population will be accommodated by the expansion of existing residential areas according to what is allowed by zoning and what is economically feasible. Without any major changes in land use economics or policies, a reasonable hypothesis is that the distribution of the new population will closely follow existing patterns.
The following figures and tables (Patterns of Settlement Density) illustrate some of the prevalent patterns of residential land use across the state. Using housing data from the 1990 Census, land within each county is classified into eight density classes ranging from no permanent residents to high-density urban areas. The graphs show what proportion of land is in each density class and allows counties of different sizes to be compared on the same scale. The four figures use a number of counties to illustrate how increased population growth has been accommodated in different land use patterns.
Orange County represents a case where most land is either in subdivisions or in unpopulated or very lightly populated wildlands. Sacramento County illustrates the pattern of a major metropolitan area growing onto a residential landscape with many scattered residences that developed around an agriculturally based economy. Sonoma, Santa Cruz, and El Dorado counties represent a third pattern where a large fraction of the total landscape already has many homes scattered among wildlands and in the intermix area between urban areas and the wildlands. Each pattern has a very different implication about where biodiversity is now and who will own and manage the land in the future.
The final table classifies all counties in California into four land use types. The classification rules are:
- Wildland and Agricultural - over 70 percent wildland and agriculture AND less than 3 percent developed
- Agricultural/Metro - less than 30 percent AND more than 3 percent developed
- Small Parcel - more than 30 percent intermix and limited agricultural area
- Suburban - less than 30 percent intermix, limited agricultural acreage AND a high percentage of developed land
The combination of the population projections and settlement patterns suggests a wide range of challenges and takes us back to the final two population related questions raised at the beginning of this paper. Significant institutional challenges will need to be addressed in different ways across the state to ensure that demographic trends do not endanger the quality of life in California.
SEE Patterns of Settlement Density
California Department of Forestry
and Fire Protection
Fire and Resource Assessment Program
(frap.cdf.ca.gov)
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