PREFACE
I love a sunburnt country,
A land of sweeping plains,
Of rugged mountain ranges,
Of droughts and flooding rains.
DOROTHEA MACKELLAR, “My Country”
A noise woke me in the middle of the night. I sat bolt upright in bed, my heart pounding, but heard only the sound of rain pelting the roof. Peering out my bedroom window, I saw a flashlight bobbing in the blackness of the backyard. My father, wearing a yellow raincoat, was pointing the flashlight toward the edge of our yard. The rain had been heavy on and off for weeks, soaking the ground, causing erosion, and undercutting our yard and those of our neighbors. Where once we had an ample yard, now only about fifteen feet of grass separated our house from the precipitous edge of the canyon. My father was discovering that one of our trees had vanished with the latest chunk of our property to disappear down the slope.
We lived on a steep mountain ridge in Santa Barbara, a small, beautiful city in Southern California nestled between the Santa Ynez Mountains and the Pacific Ocean, about sixty miles west of Los Angeles. By the end of that wet winter of 1969, several homes on our street had been largely destroyed. The house to our right balanced precariously on the edge of a newly formed cliff face, the former backyard entirely gone. Those neighbors, in an effort to save their home, shored up the eroding property by piling truckloads of large gray boulders onto the slope below. But nature finally won out, and they were forced to leave. The neighbors on the other side also lost most of their backyard; only their concrete swimming pool remained, fully intact, surreally suspended over the canyon.
Although our home was spared that year, the torrential rains saturated hillsides and triggered massive landslides and mudflows all across Southern California. Roads were transformed into rivers and flat lowlands into muddy lakes. The river flows in Santa Barbara doubled their normal levels. More than 100 people were killed, and hundreds of homes were destroyed. Southern California was declared a federal disaster area, and the National Guard was brought in to help with cleanup and restoration. As an eight-year-old, I had no way of understanding these events.
Pouring rain is a common occurrence during Southern California winters, but so are sunshine and heat. This hot-weather climate extreme is of greater long-term concern, because it is the cause of perennial scarcity of freshwater in California and the Southwest. Many of my childhood summers were spent in central Arizona on my grandparent’s ranch in the Sonoran Desert south of Phoenix, with more climate lessons. Central Arizona and Southern California are similar in climate—different ends of the same desert. The surreal temperature contrast between the cool of the air-conditioned houses and cars and the oven-like heat outdoors is still a vivid memory. Summer temperatures in the central Arizona desert are routinely among the hottest in the nation, commonly reaching 115–20°F, and, though I noticed the cotton and alfalfa fields, I never questioned how these crops could grow in a desert. Nor did I wonder how water could flow freely from faucets in the Arizona desert, just as it did in arid Southern California.
Occasionally, the limitations of living in a desert become more evident. I clearly remember the drought of 1976–77, which was the year that California—and much of the western United States—had virtually no rain. As a teenager, I was struck by the realization that water is a finite resource, one that can actually run out. My friends, my family, and I had always used water liberally with little thought about supply. But in 1977, suddenly every drop counted. We were prohibited from washing cars, watering lawns, and taking baths or long showers. Of course these “sacrifices” paled in comparison to the far harsher impacts we heard about on the news: farmers with less water, ski areas with no snow, and forests drying and burning.
A decade later, drought returned to California, this time one of the longest on record, lasting from 1987 to 1992. I was then a graduate student at Stanford University, ready to begin researching California’s climatic past. As an adult, I wanted to understand the forces that led to the 1969 rainstorms and the 1977 “year with no rain.” I had been fortunate to grow up during two decades when California experienced a dependable abundance of precipitation. In my third decade, however, we were seeing only half the normal amount of rain and snow each year. Which was the “real” California climate, I wondered. Was there such a thing as a “normal” climate for California and the West?
The goal of my graduate research was to look at how California’s climate, especially its rainfall, had varied over the hundreds and thousands of years before records were kept. I focused on the past 11,000 years, the Holocene period, which extends from the end of the last ice age—when the enormous North American glaciers melted—to the present. I focused my research on the San Francisco Bay, an estuary in the heart of one of the largest population centers of the West Coast. The bay is an excellent place to search for clues about California’s past climates, because at its bottom are layers of sediment containing subtle chemical signals that reflect the strengthening and weakening of the flow of California’s two major rivers, the Sacramento and the San Joaquin.
San Francisco Bay and its inland delta receive river water that begins as rain and snow in locations that span almost half the state. During years with high rainfall, the rivers bring abundant water to the bay, causing the salt content of the water to decrease. During the dry years, the rivers bring less freshwater to the estuary, and the bay becomes saltier—more like the Pacific Ocean waters that meet those of the bay at the Golden Gate.
In my research, I came to focus on the chemistry of fossil shells from sediment cores taken from beneath San Francisco Bay. The chemical signals embedded in those cores allowed me to estimate how the amount of river water entering the bay had changed over many centuries. I found that the river flow fed by rainfall in California has undergone major swings over the past 5,000 years. The alternating wet and dry periods lasted decades or even centuries—much longer than the six-year drought of 1987–92. To check these findings, I worked with my colleagues Roger Byrne, Frances Malamud-Roam, and Scott Starratt on studies of marshlands surrounding San Francisco Bay to examine how these long climate swings affected the marsh ecosystems. Our studies showed that marsh vegetation comprised more species adapted to saltier water during the dry periods and more species adapted to fresher water during wet periods. And, like the sediment fossil records, these swings in the marsh ecosystems lasted decades or longer.
My family had spent a year in southeast Australia, where I later returned for two sabbaticals. The landscapes and the climate there in many ways mirror those in the western United States, with water just as sporadic and extreme. Yet only when I was well into my research career did I realize that these places I loved—California, the American Southwest, and Australia—were vulnerable and growing more so every decade. Long periods of drought punctuated by catastrophic floods over the past millennia are a part of the climate history of Australia, just like that of the American West. These regions are also likely to share a similar future, according to climate models. As the global climate warms, the American West and Australia will become drier, with longer and deeper droughts interspersed with catastrophic floods.
As so eloquently expressed by Australian poet Dorothea Mackellar in “My Country,” written in 1911 at the end of a long Australian drought, we too love our “sunburnt” land here in the western United States, despite its extreme and variable climate. Knowing more about how climate has changed in the American West, we can now anticipate what may be in store for the region, and we can begin preparing for that future today.