UC Santa Cruz

This dissertation examines the local and landscape drivers of biodiversity, ecosystem service provisioning and human well-being in urban agricultural systems (agroecosystems). I explore three major themes: 1) urban biodiversity and ecosystem services; 2) climate change, water management and sustainability; and 3) urban gardens as socioecological systems. In an interdisciplinary approach, I use quantitative and qualitative methods in natural and social systems.

In the first section, I examine the local and landscape scale drivers of biodiversity and pest control within urban gardens. I focus on the abundance and species richness of ladybird beetles – an important and mobile natural enemy of garden pests. I measure ladybeetle diversity within gardens, and experimentally test factors predicted to influence ladybeetle fidelity to gardens. I find that ladybeetle dispersal is higher from gardens in more impervious landscapes, albeit overall high taxonomic richness supported by these habitats. In comparison to other contexts, these results may be unique to California due to water availability maintained through garden irrigation.

In the second section, I investigate how gardens become irrigated oases in an otherwise drought landscape. I use citizen science to collect water use data and ask how environmental concern and water governance are affecting water use behavior by gardeners. I also investigate how climate variability and increasing extremes influence water management and plant species cultivated in gardens. I find that gardeners lack an understanding of water use, are responding to weather patterns by changing watering behavior, and that garden rules can limit water use. Moreover, research participation can improve gardeners’ water conservation literacy. This work informs our understanding of how climate change may impact urban agriculture sustainability and alludes to the socioecological complexity of gardens.

In the third section, I focus on the social aspects of urban gardens and their management. I show that gardens provide many well-being benefits to gardeners, and are used more by people in urban areas. Yet I explain that there are crucial issues that undermine social and ecological sustainability in these gardens: the resources that create a habitat for biodiversity dually create social-political rifts within gardener communities. Gardens, and their biophysical and social elements, are relatively novel in the scope of contemporary land use transformations.

In summary, I show that urban gardens are sites of biodiversity, climate challenges, and social-ecological complexity that add to urban novelty. Using our understanding of complexity can inform management to improve urban and agricultural sustainability.