SignificanceGrowing food in cities for human consumption could be one means of increasing global food supply in the face of rising population growth and global food security concerns. While previous studies have shown that urban agricultural systems are productive, few studies provide yield figures that incorporate data on the inputs used to achieve the outputs. Across 13 urban community gardens, we show that yields were nearly twice the yield of typical Australian commercial vegetable farms. However, economic and emergy (embodied energy) analyses indicated they were relatively inefficient in their use of material and labor resources. Balancing the sustainability of urban food production with the cost of inputs is important to determine the trade-offs required to achieve high yields.

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BACKGROUND: Agricultural insecticides are believed to play a role in global pollinator decline. In mass-flowering orchard crops, recommendations to reduce exposure of pollinators to insecticides include spraying at periods when bees aren't foraging, such as dusk and dawn and outside of crop flowering times. However, the presence of flowering weeds within orchards mean pollinators may still be found foraging throughout the growing season, increasing the likelihood that exposure will still occur. We hypothesized that removing these weeds within orchard groundcover may reduce pollinator foraging post-bloom and thus reduce exposure of this group to pesticides. We tested this hypothesis by using herbicide to remove flowering broadleaf weeds in the sod middles ('groundcover') between rows of a nectarine orchard in New Jersey, USA, and assessing the effect on pollinator visitation via three different methods.RESULTS: Significantly lower abundance, richness, diversity, and evenness of pollinators were found in plots where herbicide treatment had removed the majority of flowering weeds, compared to untreated plots. This was the case for bees, and for pollinators overall, and was reflected in both visual observations and active sampling through sweep netting. Passive sampling with blue vane traps failed to detect a difference between treatments.CONCLUSION: Groundcover management in orchards is often employed as part of integrated pest management programs to remove alternative host plants of insect pests. The findings of this study show that it is also effective in reducing post-bloom pollinator foraging in orchards, thus potentially preventing exposure of these beneficial organisms to harmful insecticides.

Understanding cues for diapause termination in insects can be valuable in predicting phenological events in their lifecycles. Once identified, such cues can be utilized as a biofix, the point at which the majority of individuals within a population begin to accumulate degree days. We investigated the impact of photoperiod on completion of reproductive diapause in the invasive eastern North American population of the brown marmorated stink bug, Halyomorpha halys (Stål) (Hemiptera: Pentatomidae), by exposing diapausing females to varying light regimes in otherwise identical environments. The critical photoperiod estimated to initiate reproductive development in at least 50% of the potential reproductive population was 13.0–13.5 h, with increasing photoperiods coinciding with increased probability of females reproducing, earlier time to first oviposition, and higher rates of fecundity. These data on the species’ response to photoperiod are in agreement with previous modeling that predicted the twin constraints of photoperiod and temperature on H. halys reproduction prevents populations that undergo diapause from producing more than two generations annually anywhere within the continental U.S. However, the facultative nature of diapause in H. halys leaves open the possibility that sub-populations may not enter diapause in some conditions, potentially allowing for additional annual generations.

Urban agriculture has increased in many cities and has the potential to provide an array of benefits including increased local food production, nutrient recycling, urban green space, and biodiversity. While certain environmental benefits of urban agriculture are evident, it is not clear what the optimal extent of urban agriculture would be in designing a sustainable city. Closing the loop by recycling waste products into new resources is fundamental to sustainability, but the extent to which this should occur at local, regional, or global scales is an open question. We analyze how potential benefits and costs associated with urban agriculture scale with the extent of implementation, and compare potential tradeoffs in different metrics of sustainability. We assess how the appropriate metrics to optimize in a given city are context-dependent. For example, maximizing production in a small land footprint could be important in densely developed urban environments, whereas filling vacant land with food-producing gardens may be a more appropriate goal in certain post-industrial cities. We assess the potential role that urban agriculture plays in making urban food systems more resilient to climate change and other disruptions. Finally, we consider a case study comparing the resources required and pollution generated to produce the lettuce supply of on U.S. metropolitan area through outdoor urban agriculture and indoor urban agriculture, compared to conventional production and cross-continental transportation. This analysis illustrates the importance of considering multiple metrics in assessing sustainability of urban agriculture.