Given the strong linkages between the agriculture sector and the other sectors of the economy, it is important to not only estimate the direct effects of pest damage but also the multiplier effects, because damage to crops by birds and rodents reduces the output of the agriculture sector and all other linked sectors. In general, the economic effects of a change in producer costs are usually broken down into three different categories: direct, indirect, and induced effects. The direct effect of a lower yield can be measured by the revenue lost that the grower would have earned from sale of that acre and the increase cost of pest control. For example, the direct effect of bird damage to an almond orchard would be the value of the damaged and eaten nuts and the farmer’s control costs. However, the revenue of individual growers supports other industries in the economy. Growers create jobs for shop owners, restaurant staff, police, fire, etc., which must also be measured when examining the total economic effect. These additional non-direct or multiplier effects are called secondary economic impacts and are composed of indirect and induced effects. Several studies exist that use IO models to estimate the total impact of California agriculture to the state economy , but no study exists using this model to analyze specifically the total impact of bird and rodent damage to these crops. This paper details the initial determination of the counties and crops that will be used in an IO model to estimate the total economic impact of a group of pests, birds and rodents, on California agriculture. The results of this study is a list of counties that will represent a segment of California’s agricultural production that has a high value and concentration of crops that are susceptible to bird and rodent damage. Ultimately, in subsequent phases of this study, IO modeling will determine the loss of employment and revenue to the regional economy created by birds and rodents.

Identification and accurate measurement of bird and rodent damage to crops has progressed; however, pest arrival, density,growing raspberries in containers and potential and real damage to crops is still an uncertain event at the farm level. Additionally, pesticide use and productivity varies across time and space . To more effectively limit pest dam- age, increased use of Integrated Pest Management tools in California agriculture suggest that California’s pesticide use levels for most crops are low relative to the rest of the United States . There are several important outcomes that emerge from this research on the economic impact of bird and rodent damage to California crops. A useful way to quantify the economic effects, which are likely to occur within the region as a result of change in agriculture expenditures resulting from increased costs and decreased yield due to bird and rodent damage, is through IO modeling. Many governments, agricultural associations, and others benefit from IO modeling but face limited budgets. The methodology presented in this paper is useful for the narrowing of an economic analysis, so that the regions or counties chosen for the analysis provide the most pertinent and valuable results for the stakeholder. Additionally, the results of this economic research can be used at the state level to advocate, in revenue and jobs lost terms, for additional and more effective pest control options. Fluvial suspended sediment fluxes from developed watersheds in semi-arid environments are influenced by natural and human induced changes to the land surface that interact with extremely variable climatic regimes. Environmental monitoring and sedimentary records indicate that fluvial sediment flux dynamics often exhibit temporal dependence over event to interdecadal time scales, particularly in arid to semi-arid climates . However, attributing changes in sediment regimes to a discrete cause is often complicated by the overprinting of many external drivers and internal dynamics that affect watershed scale sediment production and transport, which tend to obscure the effects of individual forcing factors . Furthermore, factors affecting watershed-scale sediment production operate over a wide range of time scales, with even seemingly discrete events generating legacy effects that may last for years or decades .

Semi-arid basins in particular have been found to display persistent dependence on climatically driven antecedent basin conditions, such as storm/flood and wildfire histories . The addition of human influences further complicates sediment flux controls in the highly developed portions of the world that are the most intensively studied . Thus, elucidation of temporal dependence in the suspended sediment dynamics of a highly developed, semi-arid basin is a forensic exercise of implicating and eliminating a host of potential controls. For this reason, when discrete controls on sediment dynamics are discovered in a given watershed it is often the result of scenarios where proportionally large areal disturbances have dominated the sediment response of relatively small watersheds. In this way, wildfire , urbanization , and agriculture have been found to exert significant control on fluvial sediment flux. However, understanding the fluvial sediment dynamics of most systems over inter-decadal time scales requires the disentanglement of multiple controls, particularly at larger spatial scales.The most important external driver controlling inter-decadal scale sediment flux is regional climate, which interacts with internal factors such as geological substrate and topography to influence internal processes such as geomorphic evolution, soil development, vegetation assemblages, and fire frequency . The interaction of vegetation, topography and interannual to decadal scale climatic expression also largely determines wildfire regimes . Sediment flux generally rises after wildfire due to increases in the erodibility of hillslope surfaces through the removal of vegetation and litter layers, destabilization of soil aggregates by organic matter combustion, and increases in soil mantle slides or overland flow due to the development of subsurface and surface soil hydrophobicity, respectively . In systems experiencing dry seasons, such as much of the Western U.S., this results in down-slopedry-ravel transport through gravity alone . Soil heating can also cause hydrophobicity increases in the soil surface that, along with decreases in interception and evapotranspiration, cause increases in surface runoff during the wet season . Increased surface runoff further exacerbates erosion from the destabilized hillslope. Indeed, the timing of high-intensity precipitation plays a large role in post-fire sediment flux augmentation .

Large storms produce precipitation intensities and volumes sufficient to traverse runoff regimes, from sheet flow, to rill and gully erosion, and mass wasting, which can very effectively erode wildfire destabilized hillslopes . With increasing elapsed time between wildfire and high intensity precipitation events, hillslopes generally re-vegetate, re-stabilize, and yield less sediment for a given precipitation magnitude , although decadal scale legacies of individual fires have been reported . Humans have caused pre-historic to historic increases in global sediment flux due largely to agriculture and deforestation . This phenomenon has generally been followed by a rapid decrease in sediment flux during the 20th century, primarily from river impoundment, and to a lesser degree changes in agricultural practices and afforestation . Changes in agricultural practices over the last century have in many cases led to decreases in off-field sediment transport with the implementation of soil conservation practices, including changes to less erosive irrigation techniques . Flow regulation causes declines in basin scale sediment yield by trapping sediment in reservoirs and altering the natural flow regime, particularly through reduction of peak flood discharge magnitudes . After an initial spike during construction, urbanization can also lead to sediment load decreases with the increase in the cover of impervious surfaces . Conversely, extensive urbanization can act to increase sediment yield by altering basin scale precipitation – discharge characteristics ; for example shortening the time to peak flow,large plastic pots for plants decreasing total flow duration, increasing peak magnitude, and increasing total runoff volume .Due to the difficulty and expense of collecting samples, fluvial suspended sediment flux is usually estimated on the basis of infrequent sediment monitoring coupled with more frequent or even continuous discharge monitoring . The most common technique is to compute sediment concentration -discharge rating curves using log-linear regression or non-parametric localized regression methods such as LOESS . Anthropogenic disturbances and wildfire will alter CSS–Q relationships if they result in disproportionate changes in the magnitude and/or timing of the supply of sediment or water relative to one another . Thus, changes in sediment flux and CSS-Q relationships examined in relation to agriculture and wildfire activity over time can provide insight into these important controls onsediment dynamics in highly agricultural, semi-arid basins.

Determination of the dominance of a factor potentially controlling sediment production over other factors can be approached through the comparison of the temporal trends of control metrics with the metric describing sediment production. Correlation between control factors and sediment production metrics can then be analyzed and interpreted in light of the expected effects of a given control .The objective of this study was to examine how contemporary wildfire activity and land use change affected discharge normalized sediment delivery from highly agricultural, semi-arid mountainous watersheds in the context of additional hydrologic and climatic controls. The fundamental approach was to examine changes in suspended sediment – discharge relationships over time in light of temporal trends in wildfire and agricultural activities. Conversely, changes to less erosive agricultural technologies, such as increasing the proportional utilization of drip irrigation, would be expected to result in decreasing sediment production. Departure of sediment production trends from those expected on the basis of changes in a given control factor would be considered as evidence that the factor was not a dominant control on sediment production. Correlation of sediment production metrics with wildfire activities were then used to determine if wildfire disturbance also acted as a short term control on sediment production. Wildfire activity was expected to correlate positively with sediment production. Departure from this expected correlation between sediment production and wildfire would also indicate that wildfire was not a dominant control.The Salinas River drains 11,605 km2 of the Central Coast Ranges of California from a maximum relief of ~ 1,900 m with a mean discharge of 11.6 m3 /s from the lowest gauge in the basin for the periods of 1931- 2011 . The regional climate is dry-summer subtropical — most annual precipitation falls as rain originating from winter storms, the largest of which often occur during strong El Niño years . For this region ‘water years’ begin on 1 October of the previous calendar year and end on 30 September of the calendar year. A strong precipitation gradient extends from the wetter SW to drier NE region of the watershed due to predominant S-SW impingement of storms and orographical forcing . Geologic substrate is primarily Mesozoic sedimentary rock . The Salinas River valley consists of three lateral geomorphic zones – a riverbed, a bottomland, and flanking terraces, with one such terrace containing the major alluvial plain on the valley floor that is populated and used today. The bottomland is a broad bench situated lower than the surrounding plain and separated from it by well-defined side slopes. Though historically there was a well-defined, small, forested channel localized in the bottomland , today the channel is primarily a broad, destabilized active zone that is intermittently well-defined in space and time as either a meandering thread or braided channel. The modern channel is lightly vegetated, with the abundance depending on the duration of interannual dry periods between floods, as these times allow pioneer grasses and willow shrubs to emerge though not necessarily persist. The Salinas valley has been influenced by humans and animals throughout its recorded history and likely thousands of years before the arrival of Europeans. Pre-historically, the Ohlone natives of the region used fire to maintain an open terrain on the main valley floor and to promote their food supply, whereas the hills and mountains around the valley were forested and home to large predators . The moist bottomlands were well vegetated with cottonwoods, sycamores, live oaks, willows, and some pines and white oaks . Archival records and drawings from the Spanish and Mexican era indicate that the bottomlands were deforested in support of the development of the rancho economy prior to American conquest. Further, beaver were likely abundant in the river and important in its morphology and sediment dynamics, yet are now demonstrated to have been extirpated from the landscape as part of the maritime California fur trade during the Spanish and Mexican era . Meanwhile, the higher plains adjacent to the bottomlands were grazed by some millions of free-ranging cattle during this era , until the devastating drought of 1861-1865 ended California’s cattle-based economy.