Our second most abundant category was Braconidae which was dominated by Aphidiinae, parasitoids of aphids commonly found on crop plants at our research sites. This research supports the enemies hypothesis in UA and empowers urban farmers to adopt on-farm management practices that increase agroecosystem function and increase ecosystem services. However, we did find conflicting results, floral provisioning is an important predictor of increased abundance of natural enemies, including PH, and increased biological control services in many urban specific and rural farm diversification research. Our findings indicated that floral richness was a strong predictor, across many PH taxa, of reduced abundance. Two factors presented by Heimpel and Jervis in 2009 may be important factors in this observed reduction; 1. In areas of high floral occurrence, parasitoids may be seeking hosts away from concentrations of food sources as these areas may increase the opportunity for hyper-parasitism. Hyperparastioids, specifically the cynipds, were a large proportion of our collected wasps. Many of these cynipoids, specifically the subfamily Alloxystinae are known secondary parasitoids of baraconid aphid parasitoids. In both chapters 3&4, these PH were found in high abundance,plastic planters bulk indicating that there may be significant pressure from secondary parasitoids in areas of high floral nectar. Secondly, floral nectar may not be in great demand in urban areas.
Landscaping with flowering plants is common and may be introducing an important confounding variable. Given these findings, floral provisioning may not be promoting biological control services in urban farms. A second salient explanatory variable that had a positive impact on PH abundance across measured farms was on-farm non-crop areas. Many previous research efforts regarding ecosystem function in fragmented landscapes have focused on matrix and patch quality as explanatory variables for species occurrence or resulting ecosystem services in fragmented landscapes. While these factors continue to be compelling, recent meta-analysis call into question on-farm spatial composition as an important determinant of ecosystem function . These non-crop areas differed greatly during sampling, but were often distributed throughout the farm. Future research on agroecosystem function should pay closer attention to the composition and evenness of these often overlooked ruderal patches within urban farms. A note on other important natural enemy taxa: Our research explicitly looked at aphids and parasitic Hymenoptera in urban agroecosystems. Both PH and aphids have been shown to be resilient in the context of urbanization and fragmentation in agroecosystems. Less mobile taxa, such as ground beetles and spiders have shown significant declines with habitat fragmentation. Overall ecological function of cities should be an important topic in future discussions regarding urban planning and growth. Important ecosystem services, linked with declines in diversity of terrestrial invertebrates should not be overlooked in the context of this research.
Two competing legends dominate the telling of California’s agricultural history. According to the first legend, California farmers are progressive, highly educated, early adopters of modern machinery, and unusually well organized. Through irrigation, they made a “desert” bloom. Through cooperation, they prospered as their high-quality products captured markets around the globe. This farmers-do-no-wrong legend is the mainstay of the state’s powerful marketing cooperatives, government agencies, and agricultural research establishment. According to the opposing legend, the California agricultural system was founded by land-grabbers who continue to this day to exploit impoverished migrant workers and abuse the Golden State’s natural environment.Although the contest between these competing interpretations of the nature of California’s farm system has raged for the past one and-a-half centuries, neither account has engaged in a systematic accumulation and dispassionate analysis of the available data, and both have generally lacked the comparative perspective needed to assess why California agriculture developed as it did.This chapter analyzes major developments in California’s agricultural history to provide a better understanding of how and why the state’s current agricultural structure and institutions emerged. We will focus on major structural transformations: the growth and demise of the extensive wheat economy of the nineteenth century; the shift to intensive orchard, vine, and row crops; and the emergence of modern livestock operations. Intertwined with our discussion of sectional shifts will be an analysis of some of the special institutional and structural features of California’s agricultural development.
Here we offer a brief look at the subjects of farm power and mechanization, irrigation, the labor market, and farmer co-operatives. In all of these areas, California’s farmers responded aggressively to their particular economic and environmental constraints to create their own institutional settings. The results have been remarkable. In recent years, this one state alone has accounted for one-tenth of the value of the nation’s agricultural output. What distinguishes California from other regions more than the volume of output, however, is the wide diversity of crops, the capital intensity, the high yields, and the special nature of the state’s agricultural institutions.When disgruntled miners left the gold fields, they found an ideal environment for raising wheat: great expanses of fertile soil and flat terrain combined with a climate of rainy winters and hot, dry summers. By the mid-1850s, the state’s wheat output exceeded local consumption, and California’s grain operations began to evolve into a form of agriculture quite different from the family farms of the American North. The image of lore is of vast tracts of grain, nothing but grain, grown on huge bonanza ranches in a countryside virtually uninhabited except at harvest and plowing time. While this picture is clearly overdrawn, it contains many elements of truth. California grain operations were quite large by contemporary standards and extensively employed labor-saving, scale-intensive technologies. As examples, they pioneered the adoption of labor-saving gang plows, large headers, and combined harvesters.Most of the wheat and barley was shipped to European markets, setting a pattern of integration into world markets that has characterized California agriculture to the present. Large-scale operations, mechanization, and a reliance on hired labor would also become hallmarks of the state’s farm sector. Not only were California wheat farms typically larger and more reliant on laborsaving machinery and animal power than mid-western and eastern wheat farms, Californians grew fundamentally different varieties of wheat and employed different cultural techniques than their eastern brethren. These biological differences, although not generally appreciated, were critical to the success of the early California wheat industry. In fact, when eastern farmers migrated to California they had to relearn how to grow the crop. In the eastern U.S. , grain growers planted either winter-habit varieties in the fall to allow the seedlings to emerge before winter or spring-habit varieties in the spring shortly before the last freeze. The difference was that winter-habit wheat required prolonged exposure to cold temperatures and an accompanying period of dormancy to shift into its reproductive stage. Spring-habit wheat, by contrast,good drainage pots grew continuously without a period of vernalization, but generally could not survive extreme cold. With the mild winters of California, farmers learned it was advantageous to sow spring-habit wheat in the fall . California’s wheat experience exemplifies what happens in the absence of continual biological innovation. After learning to cultivate Sonora and Club wheats in the 1850s, 1860s, and 1870s, California grain growers focused most of their innovative efforts on mechanization, and purportedly did little to improve cultural practices, introduce new varieties, or even maintain the quality of their seed stock. According to contemporary accounts, decades of monocrop grain farming, involving little use of crop rotation, fallowing, fertilizer, or deep plowing, mined the soil of nutrients and promoted the growth of weeds. Complaints that the land no longer yielded paying wheat crops became common from the 1890s. The grain also deteriorated in quality, becoming starchy and less glutinous. It is interesting to note these unsustainable “soil mining” practices may well have been “economically rational” under the high interest rates prevailing in the state in the mid-nineteenth century.The result was such sharply declining yields in many areas that wheat, formerly the state’s leading staple, ceased to be a paying crop and was virtually abandoned .2Between 1890 and 1914, the California farm economy fundamentally and swiftly shifted from large-scale ranching and grain-growing operations to smaller-scale, intensive fruit cultivation. By 1910, the value of intensive crops equaled that of extensive crops, as California emerged as one of the world’s principal producers of grapes, citrus, and various deciduous fruits.
Tied to this dramatic transformation was the growth of allied industries, including canning, packing, food machinery, and transportation services. A vantage point on the state’s transformation is offered in Table 1, which provides key statistics on the evolution of California agriculture between 1859 and 1997.Almost every aspect of the state’s development after 1880 reflected the ongoing process of intensification. Between 1859 and 1929, the number of farms increased about 700 percent. The average size of farms fell from roughly 475 acres per farm in 1869 to about 220 acres in 1929, and improved land per farm dropped from 260 acres to about 84 acres over the same period. Movements in cropland harvested per worker also point to increased intensity of cultivation after the turn of the century. The land-to-labor ratio fell from about 43 acres harvested per worker in 1899 to 20 acres per worker in 1929.Between 1869 and 1889, the share of California farmland receiving water through artificial means increased from less than one percent to five percent. Growth was relatively slow in the 1890s, but expansion resumed over the 1900s and 1910s. By 1929, irrigated land accounted for nearly 16 percent of the farmland.Data on the value and composition of crop output put California’s agricultural transformation into sharper relief. Between 1859 and 1929, the real value of the state’s crop output increased over 25 times. Growth was especially rapid during the grain boom of the 1860s and 1870s, associated primarily with the expansion of the state’s agricultural land base. Subsequent growth in crop production was mainly due to increasing output per acre and was closely tied to a dramatic shift in the state’s crop mix. After falling in the 1860s and 1870s, the share of intensive crops in the value of total output climbed from less than 4 percent in 1879 to over 20 percent in 1889. By 1909, the intensive share reached nearly one-half, and by 1929, it was almost four fifths of the total.Figure 1 provides further documentation of the transformation of California’s crop mix over the late 19th and early 20th centuries. The Figure shows how cropland harvested in California was distributed across selected major crops over the 1879-1997 period. The acreage data reveal that in 1879, wheat and barley were grown on over 75 percent of the state’s cropland whereas the combined total for the intensive crops was around five percent. By 1929, the picture had changed dramatically. Wheat and barley then accounted for about 26 percent of the cropland harvested and the intensive crop share stood around 35 percent.In absolute terms, the acreage in the intensive crops expanded over ten times over this half century while that for wheat and barley fell by more than one-third.4Data on shipments of California fresh, dried, and canned fruits and nuts reveal the sector’s spectacular expansion over this period. During the 1870s and 1880s, growth rates exceeded 25 percent per year . Shipments continued to grow at robust rates of about eight percent per annum over the 1890s and 1900s. By 1919, California produced 57 percent of the oranges, 70 percent of the prunes and plums, over 80 percent of the grapes and figs, and virtually all of the apricots, almonds, walnuts, olives, and lemons grown in the United States. In addition, California produced significant quantities of apples, pears, cherries, peaches, and other lesser crops. The spectacular growth in California production of specialty crops had important international consequences as traditional Mediterranean exporters of many crops were first driven from the lucrative U.S. market and then faced stiff competition from the upstart Californians in their own backyard of northern Europe. California production significantly affected the markets and incomes of raisin growers in Málaga and Alicante, prune growers in Serbia and Bosnia, and citrus growers in Sicily.Explanations for the causes and timing of California’s structural transformation have long puzzled scholars. The traditional literature yields numerous causal factors, including: increases in demand for income-elastic fruit products in eastern urban markets; improvements in transportation, especially the completion of the transcontinental railroad; reductions in the profitability of wheat due to slumping world grain prices and falling local yields; the spread of irrigation and the accompanying breakup of large land holdings; the increased availability of “cheap” labor; and the accumulation of knowledge about California’s environment and suitable agricultural practices.