Urban agroecology enhances agrobiodiversity and resilient, biocultural food systems. The case of the semi-dryland and medium-sized Querétaro City, Mexico

Small-scale agroecological practices in the urban areas of Querétaro, México, as in other mid-sized cities, could maintain agrobiodiversity pools and sufficient productivity for a food sovereignty baseline. The application of agroecological principles fosters agrobiodiversity and socio-ecological resilience in urban food production. Emerging urban gardens result from an immediate necessity for food that does not appear in local statistics, nor is there any account of them in any cadastral source or land register of Querétaro City. Based on studies of 28 urban gardens, we survey and analyze farming practices using socio-ecological resilience methodologies and the Diagnostic Survey of Agroecological Practices. We find that the agroecological management of urban gardens results in significantly more species richness than in conventionally managed plots, likely due to the multifunctional purposes associated with biocultural memory. The number of social actors participating in agroecological management is increasing. It represents an urban strategy of resilience that contributes to enhancing the microclimate and nutrient cycling, as well as to improving water management and biodiversity. Results also indicate that gardens of approximately 200 m2 harbor the highest levels of agrobiodiversity. This area size for home vegetable production appears optimal for user-friendly management practices in urban settings and could represent the minimum benchmark for a family and a goal for urban planning and policy recommendations. Urban gardens contribute to the adaptive capacities of city dwellers to enhance their food security and sovereignty. Therefore, given that 70% of the national population face some level of food insecurity, we argue that, along with the protection of land-use rights, the promotion of a diverse urban landscape could improve long-term socio-ecological and food supply resilience. Additionally, urban gardens promote neighborhood social inclusion and affordable access to food. The empirical results and insights from this study in Querétaro can inform land-use policies for urban agriculture more broadly, especially in Latin American metropolitan areas

Fog interception by Ball moss (<i>Tillandsia recurvata</i>)

Interception losses are a major influence in the water yield of vegetated areas. For most storms, rain interception results in less water reaching the ground. However, fog interception can increase the overall water storage capacity of the vegetation and once the storage is exceeded, fog drip is a common hydrological input. Fog interception is disregarded in water budgets of semiarid regions, but for some plant communities, it could be a mechanism offsetting evaporation losses. <i>Tillandsia recurvata</i> is a cosmopolitan epiphyte adapted to arid habitats where fog may be an important water source. Therefore, the interception storage capacity by <i>T. recurvata</i> was measured in controlled conditions and applying simulated rain or fog. Juvenile, vegetative specimens were used to determine the potential upperbound storage capacities. The storage capacity was proportional to dry weight mass. Interception storage capacity (<i>C</i>_min) was 0.19 and 0.56 mm for rainfall and fog respectively. The coefficients obtained in the laboratory were used together with biomass measurements for <i>T. recurvata</i> in a xeric scrub to calculate the depth of water intercepted by rain. <i>T. recurvata</i> contributed 20 % to the rain interception capacity of their shrub hosts: <i>Acacia farnesiana</i> and <i>Prosopis laevigata</i> and; also potentially intercepted 4.8 % of the annual rainfall. Nocturnal stomatic opening in <i>T. recurvata</i> is not only relevant for CO₂ but for water vapor, as suggested by the higher weight change of specimens wetted with fog for 1 h at dark in comparison to those wetted during daylight (543 ± 77 vs. 325 ± 56 mg, <i>p</i> = 0.048). The storage capacity of <i>T. recurvata</i> leaf surfaces could increase the amount of water available for evaporation, but as this species colonise montane forests, the effect could be negative on water recharge, because potential storage capacity is very high, in the laboratory experiments it took up to 12 h at a rate of 0.26 l h⁻¹ to reach saturation conditions when fog was applied