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CITRIS Research Exchange – Laurel Larsen on Climate Change

A CITRIS Research Exchange Seminar with speaker Laurel Larsen 

TALK TITLE: “The drought cascade: Linking changes in climate extremes to changes in watershed function”

SPEAKER: Laurel Larsen, Associate Professor and Delta Lead Scientist, UC Berkeley and Delta Stewardship Council

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Bio: I grew up in Florida, where I spent my childhood playing outdoors, mostly around water, reading, and solving puzzles. I never grew out of those things, and now they constitute a major part of my job. The puzzles that motivate me are: What makes landscapes evolve distinct patterns? How can we restore or manage landscapes to optimize particular functions? How do physical-biological interactions control large-scale geomorphology and biogeochemical processing? Water flows as a theme through this research as one of the components of the environment most critical to life and, indeed, perhaps the single most dominant factor sculpting the geography of Earth’s natural and human landscapes. Water is also one of the features of the physical environment most sensitive to global climate change and human management. In my research, I try to tease apart the direct and indirect ways in which hydrologic changes impact ecosystems, and, conversely, how those ecological changes impact hydrology. It is only through a firm understanding of these dynamic interactions that we can predict future change in the hydrological and ecological components of landscapes.

One of the things I love about this area of research is that it requires a variety of tools and creativity in the design of new experiments and methods. A common approach is to study small-scale processes in the field and laboratory and then extrapolate that information to larger spatial scales and longer timescales using numerical simulations. I’ve used that approach in the Everglades to study the formation and degradation of a strikingly patterned landscape that is of prime interest in restoration activities. There, I needed to perform experiments in the field and laboratory flumes to understand how organic sediment moved through canopies of marsh vegetation, monitor surface water, and groundwater biogeochemistry to understand how evapotranspiration affected nutrient availability, and plant growth and develop new optical techniques for fingerprinting organic particles. The findings of this field and laboratory research led to the development of a simulation model that I used to test different hypotheses of landscape evolution. Now I am using similar techniques to evaluate whether radical new practices for restoring streams are sustainable (field site in Lancaster, PA), understand how hydrologic connectivity affects water quality and vegetation community patterning in the Brazilian Pantanal, and examine interactions between vegetation, biofilms, and land building processes in coastal marshes and river deltas.
Although fieldwork and laboratory work are fun and create great stories (some of which I put into my children’s book about the Everglades!), they are also very expensive, time-consuming, and difficult. One thing I would like to accomplish in my career is to find new ways to generalize across geographically and physically diverse landscapes. Is there a finite set of processes—albeit in different combinations—controlling these diverse environments, and if so, how do we detect what those processes are with a minimum set of data and then use our knowledge of them to predict the future? This ability would be particularly useful for solving water resource problems in ungauged basins in the developing world. To that end, I have an ongoing fascination with emerging quantitative analysis tools, particularly in information theory and medicine.

ABSTRACT: Climate models project that changes in patterns of temperature and precipitation delivery will be ubiquitous, but how those changes cascade through watersheds is less certain. Indeed, the widespread disconnect between changes in extreme precipitation and extreme streamflow contrasts with model projections and underlies what has been referred to as a “grand challenge” of hydrology. Using CHOSEN (Comprehensive Hydrologic Observatory Sensor Network), we conducted a data-driven analysis of multidimensional hydrologic and climatic extremes. We found that drought and warming likely explain many of the observed changes in streamflow extreme but that wetter extremes arise from more complex phenomena. The talk concludes with a summary of some of the remaining “grand challenges” for understanding drought’s cascading effects on California’s ecosystems.

ABOUT THE SERIES: CITRIS Research Exchange delivers fresh perspectives on information technology and society from distinguished academic, industry, and civic leaders. Free and open to the public, this series highlights leading voices on societal-scale research issues. Each seminar takes place on Wednesdays from 12:00 pm to 1:00 pm PT. Have a suggestion for a great speaker? Please use this form to suggest potential speakers for our series.

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