The magnitude, patterns, and processes of ecosystem services in the urban environment are poorly understood, however, and their management may create disservices that cause other environmental problems or unanticipated socioeconomic impacts. While urban forests and ecosystems mitigate stormwater flows, remove pollutants, and cool the urban environment, they also have associated costs, including extensive water requirements. Urban forests are complex to create, maintain, and protect, and the distribution of vegetation and associated benefits are often unevenly distributed. As water resources become scarcer, this distribution of urban ecosystems will involve even more complex trade-offs. Los Angeles is located in a semi-arid region, and widespread development has created an artificial urban ecosystem through extensive use of irrigation. In the face of current water shortages, decision-makers have responded by raising water rates and restricting residential landscape watering. Projected population and urban growth as well as future climate change (higher temperatures and lower precipitation) are creating unparalleled challenges for resource managers. Better tools are needed that allow urban managers to balance the trade-offs between ecosystem services and disservices associated with water and vegetation. This collaborative research project will focus on water management and water consumption associated with the urban forest and outdoor landscaping in the city of Los Angeles, California. The investigators will focus on the following questions: (1) What is the institutional framework for water management in the city of Los Angeles? (2) What is the magnitude and variability of landscape water use in the city? (3) What is the spatial distribution of urban vegetation, and how does it relate to landscape water use and to socio-demographic differences? (4) What ecosystem services are supported by landscape water use and what are some of the potential costs of such services? The investigators' goal is to integrate ecohydrology into a comprehensive understanding of ecosystem services and disservices, and their interactions with the human dimension of institutional management and organizational structure in the broader Los Angeles region. They will use a range of research methods combining a diverse set of data, models, and experimental and theoretical approaches to develop a first-order model of the ecohydrology of the city of Los Angeles. They will attempt to proximate indoor and outdoor water use within defined regions of this highly complex urban environment, and they will develop schemes for better understanding the effects of institutional water management and water use, including differential impacts across the city.
This project will address critical uncertainties in the understanding of the costs and benefits of ecosystem services, examining both the biophysical and human institutional dimensions and the interactions between ecosystem services, ecohydrology (coupled interactions of ecosystems and hydrological processes), and institutions. Project findings will be conveyed to numerous non-profit agencies in the region devoted to a range of ecosystem activities, including restoring local river watersheds and improving indoor and outdoor water use. Project scientists will collaborate in annual public seminars with non-profits and other groups that are addressing watershed health and runoff (intimately related to urban landscaping and water consumption). The project also will support the interdisciplinary education of undergraduate and graduate students and will provide comprehensive mentoring for a postdoctoral scholar in the various disciplines associated with the proposed project. This award was funded as an Urban Long-Term Research Area Exploratory (ULTRA-Ex) award as the result of a special competition jointly supported by the National Science Foundation and the U.S. Department of Agriculture Forest Service. Funds for this specific award were provided by the U.S. Department of Agriculture Forest Service.
This award allowed us to estimate indoor and outdoor water use in the city of Los Angeles. We obtained address level billing data from the Los Angeles Department of Water and Power (LADWP) for 10 years, including drought years during which LADWP instituted 2 different types of drought restrictions -- voluntary and mandatory. Mandatory restrictions also include hikes in water rates. We compared water use in representative neighborhoods: different climate zones and different sociodemographic characteristics. Using NDVI satellite imagery, we also examined whether vegetation greenness was impacted by the restrictions. Our results are the following: under mandatory restrictions, water use overall was reduced by 23% in the residential sector, under voluntary restrictions far less. Higher income neighborhoods used 3X the amount of water lower income neighborhoods did even during mandatory restricitons. Thus lower income neighborhoods reduced their water use more than the higher income neighborhoods, displaying more sensititivity to price. The NDVI results showed no impact on vegetation greenness even with 23% water savings. We conclude by finding that even when water use is restricted, the non-climate appropriate landscaping of most residents of Los Angeles, remains green. This implies that landsacpes are generally overwatered under non-drought conditions and that if the city developed programs to assist residents to change landscaping to more climate appropriate plantings, outdoor water use could be considerably reduced. Over the long term, implementation of indoor and outdoor water meters would provide an opportunity to adjust water prices to ensure people could afford indoor water use for human needs, while pricing scarce water appropriately for outdoor use.
