They provide important respite, social connection, and stress reduction to urban residents, often particularly in need of peaceful spaces. In the words of one farmer, “Urban farms can be havens of peace, health, and community, but it requires heavy involvement and advocacy from those communities for the long term in order to be successful” . Agroecology calls for responsible and effective governance to support the transition to just, equitable and sustainable food and farming systems. In an urban environment, this requires the creation of enabling policies that ensure equitable land access and producer control over access to land, especially among the more vulnerable and historically marginalized populations. Land access is expressed most frequently as an obstacle to scaling urban food production by survey respondents, and it is certainly more of a challenge for lower income and minority groups interested in cultivating their own “commons” . There are examples among ourEast Bay survey respondents of collective governance at the farm and community level, such as one farm site which is owned cooperatively by three non profit organizations that collectively serve minority and formerly incarcerated populations, aspiring beginning farmers, and the local community through a cooperative goat dairy, fruit tree nursery, and annual vegetable production plots. City and county governance bodies have an opportunity to strengthen the resilience of urban agriculture operations and opportunities for farmer collaboration by providing subsidies and incentives for social and ecosystem services. City level efforts to compensate or recognize farmers for ecosystem services such as soil remediation and carbon sequestration, for example,vertical indoor hydroponic system are not yet realized. Further examples of responsible governance from our data include recommendations for public procurement programs to source food from aggregated urban produce .

Our respondents are engaged in circular and solidarity economies, key features of agroecology, including bartering, sharing, and exchanging resources and produce with those in their social networks. They are also interested in collaborating in a localized effort to strengthen the link between producers and consumers by aggregating produce and sharing distribution . As cities work to fulfill their role in providing basic services to citizens, farmers are pointing out an important opportunity to provide refrigerated transportation, storage, and organizational infrastructure to transfer all possible produce grown on urban farms to the best distribution sites. Communication platforms, transport systems, and streamlined procurement in this arena following from other regional “food hub” models could improve the landscape for urban food distribution dramatically . All urban farm respondents are also engaged in closed loop waste cycles: through composting all farm waste onsite and collecting food scraps from local businesses, farms are involved in a process of regeneration, from food debris to soil.Through extending the UAE framework from farms to urban policy and planning conversations, more efficient pathways for addressing food insecurity in part through strategic centers of urban production and distribution can emerge in cities of the East Bay and elsewhere in the United States. Finally, agroecology relies on the co creation and sharing of knowledge. Top down models of food system transformation have had little success. Urban planners have an opportunity to address food insecurity and other urban food system challenges including production, consumption, waste management and recycling by co creating solutions with urban farmers through participatory processes and investing in community led solutions.

In our systematic review of the literature on whether urban agriculture improves urban food security, we found three key factors mediating the effect of UA on food security: the economic realities of achieving an economically viable urban farm, the role of city policy and planning, and the importance of civic engagement in the urban food system . A radical transformation toward a more equitable, sustainable and just urban food system will require more responsible governance and investment in UA as a public good, that is driven by active community engagement and advocacy. Coastal salt marshes are a vital interface between terrestrial and marine ecosystems, providing erosion protection, secure nurseries, runoff filtration, and critical habitat for threatened species . Despite the value of these ecological services, most salt marshes have been lost or degraded by human activities . In fact, 91% of the wetlands in California have been drained and reclaimed for other uses, and the few that remain exist in altered states . To restore ecosystem services lost to these changes requires re establishment of healthy salt marsh vegetation . Tidal inundation regimes create salinity and moisture gradients that covary with elevation, driving variations in abiotic conditions that can restrict plants to specific zones within the ecotone . An ecotone is a transition between two ecological systems with a steep environmental gradient, such as salinity and moisture levels . At lower elevation in the ecotone, frequent inundation ensures regular soil saturation and salinity values close to that of seawater, and species intolerant of these conditions are restricted to higher elevations . In the upper ecotone tides are infrequent, and in the absence of rainfall, salts are concentrated in the soil via evaporation. In Atlantic coastal salt marsh, year round rainfall prevents buildup of salts, creating relatively benign growing conditions in the upper ecotone . In contrast, the dry summers of Mediterranean climates drive high evaporation rates that concentrate salts in the soil, making conditions at higher elevations more stringent during warmer parts of the year .

Due to the elevation gradient, tidal regimes, and variable rainfall, salt marsh ecotones develop salinity and moisture zones that can intersect in ways that impact species differently. Change within these zones can be driven by environmental factors as well as human influence, and impose short or long term effects; for example,vertical farming tower for sale heavy rain can temporarily dilute the salinity gradient, while the breaching of a dike can restore a salinity gradient where it has long been absent . Salt marsh systems therefore have dynamic abiotic gradients that can be further modified through restoration activities. Removal of non native species creates large bare soil patches, where higher evaporation rates concentrate salts in the soil . Restoration activities can thereby intensify naturally occurring moisture and salinity gradients present, affecting success of salt marsh revegetation efforts. If the relative influence of these stressors varies across species, planting strategies that account for these differences could improve restoration outcomes. This knowledge would facilitate planting species into zones where stress levels are tolerable. For instance, Distichlis spicata can tolerate a wide range in salinity, but little is known about its sensitivity to drought . Intelligent placement of D. spicata might therefore depend on its water requirement rather than salinity limitation. Salinity affects water uptake, transport, and transpiration, requiring plants to have adaptations to survive in saline soils . Salt secretion via salt glands is the most common method of salt removal for non succulent plants; however, salt can also be removed via salt hairs. Both methods require the plant to take up salt and eliminate it through specialized organelles . Another common strategy is succulence, which dilutes ions to non lethal levels, allowing plants to survive in high salinity environments Salinity exclusion in the roots is a third method, though it is much less common . Soil moisture also affects plant performance, because water uptake, photosynthesis, and turgor pressure can be reduced under dry or high salinity conditions . Both low soil moisture and high soil salinity can decrease plant water potential, which is measured as the negative pressure required to move water through the plant. The lower the value, the more difficult it is to take up and move water through the plant , possibly affecting growth and survival . For this reason, water potential is often used as an indicator of stress. Here, we applied watering treatments varying in salinity and volume to determine the relative influence of each on halophyte plant performance. We expected to observe a more negative water potential for plants in drought or high salinity treatments compared to plants in saturation or freshwater treatments. In addition, salinity and drought stress should exhibit interactive effects, such that combinations of moderate salinity and drought also reduce performance. We predicted that plant tissue water potential would reflect stress caused by drought and/or salinity, and that more negative values would correlate with reduced survival and growth. Because the natural distribution of salt marsh species differs within the ecotone, where moisture and salinity covary with elevation, we expect treatment effects to vary across species. To test these hypotheses, we subjected five native perennials to eight different watering treatments in the greenhouse.

Plant tissue and soil water potential were measured to assess physiological and abiotic effects of treatments, and growth and survival were tracked to assess treatment effects on plant performance. To create a gradient of moisture and salinity stress in the greenhouse, we conducted three preliminary experiments. The first and second identified watering volumes that would induce drought stress but avoid total mortality. The first identified a range of possible watering volumes through soil moisture retention while the second identified final watering volumes using D. spicata and S. macrotheca. The third preliminary experiment developed treatments that imposed a gradient of salinity stress while avoiding mortality . To do so, we applied five watering treatments to D. spicata and J. carnosa, allowing us to observe the effects of different watering volumes and salinity concentrations on plants. Soil water potential was affected by treatment, leading to significantly more negative water potentials in the drought treatment, and in treatments of increasing salinity . There was also a significant interaction between drought and salinity , with the effects of salinity intensifying in the drought treatment . Patterns for tissue water potential were similar with water potential generally declining as salinity increased across all five species . Although plants in the drought treatment received less than half of the water than the saturation treatment, tissue water potential remained similar across watering volume for most species. Nonetheless, drought had a significant effect on tissue water potential for all five species . The effect of salinity and its interaction with drought differed across species; E. californica showed a significant response to salinity and the interaction between drought and salinity. F. salina and J. carnosa showed a significant response to salinity, but not the interaction between drought and salinity. Finally, D. spicata and S. macrotheca did not respond to either salinity or the interaction between drought and salinity. The range of measured tissue water potential varied greatly among species, with D. spicata reaching as low as 12 MPa. In contrast, J. carnosa and S. macrotheca stayed within 1.5 to 3 MPa, and E. californica and F. salina had intermediate values.Our experiment simulated two stressors – drought and salinity – that are important determinants of plant distribution in California coastal wetlands. The treatments resulted in distinct water potential patterns for both soil and plant tissue across species. Soil water potential in particular showed a striking response to treatment, with measurements ranging from ~ 0.5 MPa to 6 MPa – low enough to expect impacts on plant performance. The soil water potential at which plants are unable to take up sufficient water to compensate stomatal water loss is known as the permanent wilting point; it is often the soil water potential where the plant irreversibly wilts and dies . 1.5 MPa is commonly accepted as the permanent wilting point for glycophytes ; however, Warrick notes that due to the substantial variation in plant species tolerance, some can survive well past the 1.5 MPa permanent wilting point threshold. At the moment, very little research has been done to identify soil water potential thresholds affecting halophyte performance or permanent wilting points. Treatments here clearly affected plant tissue water potential, with readings ranging from 1.5 MPa to 12 MPa; most species remained above 7.5 MPa. For glycophytes, plant tissue water potential of 1.5 MPa generally reduces cell expansion, cell wall synthesis, and protein synthesis. As water potential continues to drop, photosynthesis and stomatal conductance dramatically decrease, while solute and abscisic acid accumulation increases . Hsiao and Acevedo briefly discuss halophytes, but there is insufficient research to draw firm conclusions on halophyte physiological response to decreasing plant tissue water potential. Although the patterns were similar for plant tissue and soil, the magnitude of change was different, so soil water potential cannot be used as a direct indicator of plant tissue water potential.