Climate projections are not included here, but could be included in future analyses

Fragmentation and loss of farmland causes farmers to lose benefits associated with being part of a large farming community, such as sourcing inputs, accessing information, sharing equipment,and supporting processing and shipping operations . This is further exacerbated by loss of agricultural land near the Sacramento River, either due to future flooding or to mitigation of habitat for wild species. Also, by fragmenting the landscape and consuming more land area in the floodplain, urbanization in the A2 scenario could work against the provision of ecosystem services related to water quality, biodiversity conservation, open space and its aesthetic and recreational value . Strengthening the urban community’s interest and support of farmland preservation is a key challenge for mitigation of GHG emissions, and the long‐term viability of agriculture in Yolo County. Historically, urban and suburban development has covered many regions within California that were formerly leading agricultural producers, including the Los Angeles Basin and Orange County, much of the San Francisco Bay Area, and areas of the Central Valley near Fresno, Modesto, Merced, Sacramento, and Stockton. Between now and the year 2050 much additional urbanization is likely near these metropolitan areas, as well as in locations that are at a considerable distance from existing major cities, such as the Salinas Valley and Ventura County. Strategies to preserve agricultural land from urbanization are likely to dovetail with strategies to adapt to climate change and mitigate greenhouse gas emissions, reducing the state’s overall vulnerability to climate change. For example, maintaining a strong greenbelt of agricultural land around existing urban areas and adopting compact urban development policies can greatly reduce GHG emissions , while preserving agricultural production and potentially enhancing ecosystem services. This section considers urbanization implications related to agriculture and climate change,strawberry gutter system based on statewide modeling of 2050 urban growth scenarios, using existing datasets regarding agricultural production, land use, and soils.

The actual complexities of urban‐agriculture interactions require a great deal of monitoring and interdisciplinary synthesis that is beyond our scope, e.g., urban heat island or ozone effects may lead to additional vulnerabilities for agriculture with climate change. Our aim here is instead to present an initial overview of potential agricultural adaptation and vulnerability effects related to urbanization, and to suggest directions for further research. The strong policy framework in California for GHG mitigation under AB 32, the Global Warming Solutions Act of 2006, has drawn attention to the fact that California’s urban planning framework is in a state of uncertainty and potential transition. SB 375, the Sustainable Communities and Climate Protection Act of 2008, requires Metropolitan Planning Organizations within the state to prepare “sustainable communities strategies” that show how each region will meet GHG‐reduction targets through integrated land use, housing, and transportation planning. As of 2011, MPOs are just beginning to develop such plans. SB 375 is widely seen as having the potential to usher in a new era of land use planning in California, in which regional “blueprints” will be adopted to manage and reduce urban and suburban expansion . However, it is by no means clear how the California Air Resources Board or the legislature will react to ensure that such potential is in fact met. In addition, as of 2010 every county and municipality in the state must now consider GHG emissions within their General Plans and associated Environmental Impact Reports . Since 2007, the state Attorney General’s office has frequently threatened legal action against those jurisdictions that do not include planning alternatives to reduce GHG emissions . The California Air Resources Board is also strongly encouraging local governments and large institutions to prepare Climate Action Plans and GHG emissions inventories, and many have already done so.

These actions mean that local governments are now more actively exploring land use planning alternatives to mitigate GHG emissions and adapt to climate change. Although political resistance to growth management will certainly continue, such trends mean that in the future the state’s local governments are more likely to consider growth management scenarios that respond to the twin goals of preserving agricultural land and responding to climate change. This institutional and political environment affects our analysis below, and will be referred to when appropriate.To analyze the impact of future urbanization scenarios on agricultural landscapes within California within the context of climate change, we relied on modeling done by the UC Davis Information Center for the Environment using UPlan software under a separate portion of this Climate Change Vulnerability and Adaptation Study for California. We then performed additional analyses on the UPlan projections for 2050, using statewide data on agriculture, land use, and soils. UPlan is a geographic information system ‐based land use allocation model developed by ICE and used for urban planning purposes by more than 20 counties in California, including a number of rural counties in the San Joaquin Valley . It is particularly useful for large‐scale urban growth scenarios in rural areas, and has been used in a research context to analyze urbanization effects on natural resources , urbanization effects on wildfire risk , and the effect of land use policies on natural land conversion . Using UPlan, researchers first develop a base of GIS information related to geographical features such as roads, rivers and streams, floodplains, parkland, and existing urban areas. They then supply demographic inputs within future urban growth scenarios. Researchers also specify geographical features that are likely to attract urban growth , discourage growth , or prevent growth , and assign weightings to each. For example, freeway interchanges may attract development, since builders desire the locational advantages.

Designation as prime farmland may discourage development, since local governments may take this factor into account within their zoning and growth management policy making, and farmers may participate in the Williamson Act or other programs designed to discourage urbanization. Acquisition of land as public open space will prevent urbanization altogether, thus making a “mask” designation appropriate within UPlan. Relying on the combined weightings for each 50‐meter grid cell, UPlan allocates the future population increase across four residential land use types , and several nonresidential land use types . The result is a spatial projection of future urbanization with designations for each land use type. ICE staff developed two main UPlan scenarios for statewide mapping within this project scenario of urban development. The other is a “smart growth” alternative that clusters development into nodes, specifies somewhat higher densities, and places more development within existing city borders. Such scenarios reflect growth management philosophies within the state during recent decades; many local and regional planning agencies have developed similar alternatives within their own planning processes. The ICE SG scenario is relatively conservative and does not assume any dramatic changes to current planning policies. In reality, over the past two decades,grow strawberry in containers development within the state near large metropolitan areas has become increasingly compact and focused on infill sites rather than greenfield locations. The California agricultural areas most affected by urbanization between now and 2050 will not necessarily be those with the greatest overall amount of new urban and suburban development. Rather, other factors will come into play. These include the amount of agricultural base remaining within the region, the extent to which urban development fragments agricultural landscapes, and the extent to which farmers benefit from increased access to urban markets. If there is relatively little agricultural base left, as is currently the case around some of the state’s large metropolitan areas, then it becomes more difficult for farmers to find suppliers, processors, and other agricultural support functions . This may affect farm operations on a crop‐by‐crop basis. For example, there is only one processor of apples left in Sonoma County, formerly home to extensive apple orchards, and if that facility closes, then production of classic varieties such as Gravensteins will become difficult . If urban development fragments agricultural land into isolated pockets separated by roads, subdivisions, office parks, and other urban facilities, then it becomes more difficult for farmers to move equipment from field to field, and conflicts may arise with new suburban residents over noise, odor, and potential spraydrift associated with farming operations. Fragmentation may also reduce the benefits farmers receive from being part of a large farming community, such as sourcing inputs, accessing information, sharing equipment, and supporting processing and shipping operations . Impacts on agriculture from urbanization will then be disproportionate to the land area covered. On the other hand, urbanization can benefit agriculture if it increases access to markets . This factor is likely to benefit some types of agriculture more than others. Specialty production of fruits, vegetables, meats, and dairy products for use by restaurants, distribution through high‐end grocery stores, and sale at farmers’ markets and through community‐ supported agriculture networks is likely to benefit. Conversely, production of grains and lower‐ value fruits and vegetables is not likely to see a boost from the presence of local markets, since farmers primarily sell these bulk commodities to large‐scale processing facilities for regional, national, or international distribution .Addressing climate change is a priority issue for Californians and involves individuals, businesses, and government.

The Global Warming Solutions Act of 2006 seeks to reduce the emission of greenhouse gases to 1990 levels by 2020. This legislation goes into effect gradually, so that people will have time to implement the necessary actions to come into compliance by the 2020 deadline. Some businesses, however, are proactive on climate change mitigation, and are signing up through mechanisms such as the Climate Action Registry to become leaders and early adopters of GHG emission‐reduction programs. By making progress toward carbon neutrality ahead of deadlines, these companies may qualify for incentive programs and be recognized as environmental leaders. Among such leaders are a number of wine companies that are managing their vineyard lands and adjoining forests that maximize biomass on the landscape and balance the emissions generated in their production processes. This paper is a case study about one such company, Fetzer/Bonterra Vineyards, who has set their objectives to reduce their GHG emissions and use renewable sources to meet much of its energy demands. As an environmentally conscious business, and a major grower and producer of wines, Fetzer/Bonterra attempts to achieve a balance between habitat conservation, ecologically based organic production, production goals, and financial profit. When the company purchased ranches for growing grapes in Mendocino County, a decision was made to maintain a large fraction of that land in natural habitat without livestock grazing. This was based on an environmental ethic to combine wine production with conservation of the landscape’s natural integrity. This approach also included a series of sustainability measures . To learn more about the carbon storage and dynamics on its land, Fetzer/Bonterra collaborated with researchers at the University of California Davis to conduct an assessment of the distribution and magnitude of carbon stored across the vineyard‐woodland landscape. The main goal was to find a way to assess carbon stocks to determine the absolute and relative amounts of carbon stored in different vegetation and land use types. Fetzer/Bonterra’s rationale behind the assessment was to identify the relative value of the different vegetation types on their land in terms of contributing to the positive, or offset, side of their carbon budget. Because the study also collected data on the different woody plant species, information on the diversity of plant communities was obtained. The species and community diversity data make it possible to assess the relationship between carbon stocks and biodiversity, and to show how habitat type affects the magnitude of C stocks. This approach will allow vineyard managers to prioritize non‐vineyard land for carbon storage, biodiversity and habitat conservation, and eventually other types of ecosystem services, such as keeping steep slopes and stream corridors forested to protect against erosion and sediment loading in waterways. Greater carbon stocks in forests is to be expected, but it is significant to recognize that Fetzer/Bonterra uses a management approach for a combination of perennial woody crops and conserved habitat that maximizes the contribution of the heterogeneous landscape to total carbon stocks. Using this Fetzer/Bonterra case study experience as an example, this paper showcases the important role that California agricultural landscapes can play in climate change adaptation and mitigation strategies.

Juvenile salmon did not exhibit a habitat preference among these three choices

When cages were used, salmon were PIT tagged to track individual fish growth rates within a specific habitat. We consistently found that salmon growth rates in cages placed in flooded in rice fields were higher than growth rates for juvenile Chinook Salmon of comparative life stage in any of the adjacent riverine habitats and in other regions . Growth rates were also comparatively high when free-swimming salmon were introduced into larger-scale, 0.8-ha flooded agricultural fields. These studies were more representative than those using cages of how migrating salmon might use these habitats under natural flow events. For the multiple years that free-swimming salmon were used , they averaged a mean daily growth rate of 0.98mm d−1. Throughout all study years, caged salmon and free-swimming salmon showed very similar growth rates within the same experimental study units, despite the fact that they likely experienced different micro-habitat conditions . This observation suggests that our salmon growth results were not influenced by cage effects, a well-known issue in enclosure studies . To better understand managed floodplain processes across the region, in 2015, salmon were introduced in fields at a variety of locations in the Central Valley with various vegetative substrates: Sutter Bypass , three locations on the Yolo Bypass , and Dos Rios Ranch at the confluence of the Tuolumne and San Joaquin rivers . At all of the locations,strawberry gutter system juvenile Chinook Salmon grew at rates similar to those observed in experiments conducted at Knaggs Ranch in the Yolo Bypass during previous study years.

These results suggest that multiple geographical regions and substrate types can support high growth rates of juvenile Chinook Salmon. A key objective of our work in flooded fields was to determine whether substrate type has a measurable influence on growth and survival of juvenile Chinook Salmon. Substrate and vegetation can be an important micro-habitat feature for young Chinook Salmon , so we posited that there could potentially be some difference in salmon performance across treatments. In 2013, we examined this question across different substrate types in two ways: telemetry studies using PIT tags; and replicated fields. Both approaches indicated that juvenile salmon did not have a clear preference for different substrates, and grew at similar rates across substrates.We monitored the movements and use of PIT-tagged, hatchery-origin juvenile Chinook Salmon for approximately 1 month over fallowed, disced, and rice stubble substrates in two circular enclosures to determine if there was any preferential use. One enclosure included all three substrates, and one contained only disced substrate .Although growth rates were slightly higher in the enclosure that contained all three substrate types, juvenile salmon grew at very high rates, averaging 1.1mm/d regardless of enclosure. These growth rates were higher than other published growth rates for juvenile Chinook Salmon in the Yolo Bypass, and the region generally .Throughout the 2012–2016 study period, we consistently observed that juvenile Chinook Salmon were attracted to sources of inflow, and that this sometimes became the dominant factor in the distribution of salmon on experimental fields or in enclosures.

In the previously described PITtag observations in 2013, salmon in both enclosures positioned themselves nearest the inflow, regardless of surrounding habitat structure . This result is not surprising, given that juvenile stream salmonids commonly adopt and defend flow oriented positions in stream environments for acquisition of drifting food resources. On flooded agricultural fields, this orientation toward flow may not only be related to feeding behavior but may also serve to keep juvenile salmon in habitat areas that are hydrologically connected and have higher velocities. In fact, analyses of the environmental factors that predict movement of large groups of tagged juvenile Chinook Salmon in the Yolo Bypass found that drainage of flooded areas was a reliable predictor of fish emigration at downstream trapping stations . Although juvenile Chinook Salmon growth rates were consistently high across substrates and study years, we observed highly variable survival of salmon, and available evidence from the studies suggests that this was related, at least in part, to differences among years in drainage rates of the study fields and habitat availability on the floodplain at large. For example, survival in 2013 ranged from 0.0% to 29.3% in the replicated fields containing different agricultural substrates. This variability was likely unrelated to substrate type; instead, these low survival rates were most likely a result of very dry conditions across Yolo Bypass and the Central Valley, generally, when record drought conditions prevailed during 2012–2015, which affected water quantity and quality. In 2013, our replicated field study likely presented one of the only wetted floodplain areas for miles around, and thus presented a prime feeding opportunity for avian predators such as cormorants, herons, and egrets. However, when the same set of fields was used in 2016, survival was much higher . This was generally a wetter period, avian predation pressure was reduced, and we more efficiently opened the flash boards to facilitate faster drainage and fish emigration.

Note, however, there were some differences in methodology among years, which may have contributed to survival variability. Taken together, these observations of free swimming salmon survival suggest that field drainage rate, and overall floodplain habitat availability, are important factors for improving survival in managed agricultural floodplain habitats. Our observations of juvenile salmon orientation to flow, and the importance of efficient drainage on survival, reinforce observations from natural floodplains that connectivity between perennial channel habitat and seasonal floodplain habitat is an essential attribute of river-floodplain systems . Connectivity of managed floodplain habitats to unmanaged habitats in the river and floodplain is therefore a foundational condition needed to allow volitional migration of juvenile salmon. Further research is needed to identify how to provide sufficient connectivity to maximize rearing and migration opportunities for wild Chinook Salmon.Natural and managed floodplain habitat is subject to a variety of flow and environmental conditions. Variation in flow and temperature dictates when and where managed agricultural habitats may be accessible and suitable for rearing salmonids, with challenges during both wet and dry years, as well as during warm periods. As noted previously, survival in the replicated fields was variable but generally low. We associate these results with the effects of extreme drought conditions that prevailed during the core of our study from 2012 through 2015. Although our field studies were conducted during a time of year when wild salmon have historically used the Yolo Bypass floodplain , the extreme drought made for warm water temperatures, and resulted in our study site being one of the few inundated wetland locations in the region. As such, avian predators were attracted to the experimental fields, exacerbating salmon mortality during drainage. We observed high concentrations of cormorants, herons, and egrets on the experimental fields, and this concentration increased over the study period. As many as 51 wading birds and 23 cormorants were noted during a single survey. The small scale of our project could have further exacerbated predation issues. This situation highlights the importance of the weather dependent,fodder system for sale regional context of environmental conditions, which govern how and when managed floodplains can be beneficial rearing habitats for juvenile salmon. Under certain circumstances, flooded fields can generate high salmon growth but in other scenarios, these habitats can provide poor environmental conditions for salmonids and/or become predation hot spots. Even during wetter conditions, we found that management of agricultural floodplain habitat was challenging. For example, we had hoped to test the idea of using rice field infrastructure to extend the duration of Yolo Bypass inundation events in an attempt to approximate the longer-duration events of more natural floodplains; that is, through flood extension. As noted by Takata et al. , use of the Yolo Bypass by wild Chinook Salmon is strongly tied to hydrology, and salmon quickly leave river-inundated floodplains once drainage begins. We therefore reasoned that flooded rice fields might provide an opportunity to extend the duration of flooding beyond the typical Yolo Bypass hydrograph. In 2015, a flood extension study was planned but not conducted because drought conditions precluded Sacramento River inflow via Fremont Weir. To test the flood extension concept in 2016, we needed substantial landowner cooperation and assistance to install draining structures that allowed maintenance of local flooding after high flow events. Even then, we found it difficult to maintain water levels and field integrity during the tests. In our case, we were fortunate to have the cooperation of willing landowners. Partnership with landowners was key, and would be critical with any future efforts to test the concept of flood extension. We also planned a similar test in 2017, but high and long-duration flood flows prevented the study from occurring.

Over the 6 years of study, except perhaps for 2013 when we focused on other study priorities, we never experienced ideal conditions to adequately test the flood extension concept. We were either in a severe drought, during which the Yolo Bypass did not flood from the river, or we experienced severe and sustained flooding, which made it impossible to contain flood waters within study fields. Based on these experiences, studying the concept of flood extension appears to depend on the occurrence of moderate flood events at the right time of year , provided fields are appropriately designed to hold water and allow efficient immigration and emigration of potentially large numbers of juvenile salmon. However, significant outreach and communication is necessary with landowners to maintain floodwaters on their fields during the natural drainage period. Because these events cannot be predicted well ahead of time, these communications—and availability of robust infrastructure—need to be constantly maintained even outside the flood extension period. As suggested in the previous section, such potential actions would need to be taken in a way that maintains hydrologic connectivity and salmon access, so that salmon can successfully locate potential managed habitats, use them for rearing, and then successfully emigrate from them at the appropriate time. Timing of such potential manipulations is critical because previous sampling has shown that salmon quickly emigrate from the floodplain during large scale drainage events , leaving relatively low densities of salmon in remaining ponded areas to potentially benefit from flood extension. Although our use of hatchery salmon gave us more experimental options during drought conditions, the use of these fish resulted in additional challenges. Our approach relied on a non-traditional use of hatchery salmon, which required a suite of permits and approvals to execute the project. As noted above, the project coincided with a major drought, so access to hatchery salmon was limited as a result of low salmon population levels. In addition, use of hatchery salmon affected the time-period when we could conduct experimental work. We were unable to test salmon response to early season flooding , because the hatchery salmon were too small to receive coded-wire tags as required under our permit conditions. Similarly, the timing of our work was affected by the availability of holding tanks at our partner hatchery , and by the availability of transport staff and vehicles to move salmon to our study site. While we were able to assess many important biological metrics in our study, direct measurement of the population-level effect of floodplain rearing on agricultural habitats proved elusive. A traditional approach to addressing this question involves inserting CWTs into very large numbers of experimental salmon and estimating the population response from expanded CWT recaptures in the ocean fisheries. Recoveries of CWTs in adult salmon from experimental releases made in the Yolo Bypass have generally been very low , making it difficult to get a high level of resolution with which to reliably compare survival rates, including with values in the literature. Although CWT recoveries could potentially be improved by increasing the number of tagged salmon, the effort required even to collect a single data point would be substantial and is limited by the availability of surplus hatchery salmon. A related issue is that it is difficult to design a survival experiment that provides a useful comparison to other management strategies or migration corridors. For example, it is challenging to assess the incremental survival value of flooded agricultural habitat versus adjacent perennial channels . Telemetry can partially address this issue, but current acoustic tagging technology does not allow estimates of survival once smolts emigrate from the estuary, and is also limited in the size of salmon that can be tagged.