 We were camped at 10,430 feet above sea level, just east of the Sierra
crest, looking at small glaciers clinging to the north slopes of Mt. Conness
and North Peak. Wispy clouds turned pink and there was the beginning of
alpenglow overhead. It was our first evening on a 17-day trek across
California in September 2008, closely following the 38th parallel from our
home near Mono Lake to the Point Reyes lighthouse, exploring some of the
mountains-to-the-sea watershed that sends water to San Francisco Bay and,
finally, out to the Pacific Ocean.
At the slow pace dictated by travel on foot, bicycle, and boat, we explored
the 38ºN latitude “water line,” where battles have been fought over dams,
aqueducts, and wetlands, and where critical water issues still are being
played out. The list includes Mono Lake, the snowpack at the Sierra Nevada
crest, Hetch Hetchy, New Melones Reservoir, the Sacramento-San Joaquin
Delta, San Francisco Bay, and Point Reyes. At each site we met with experts
involved with resource protection and restoration.
Our starting point at Mono Lake, east of the mountain range, might seem
hydrologically separate from the San Francisco Bay watershed, were it not
for relationships that Los Angeles and metropolitan southern California have
with this entire “water line.” Stresses on the water supply system in one
place are today felt throughout the state.
At a sendoff party at Mono Lake we spoke with Geoff McQuilken, director of
the Mono Lake Committee, about such connections. Reducing diversions from
Mono Basin streams required Los Angeles to conserve water, which, Geoff
noted, “affects how much is drawn out of the Bay-Delta for southern
California and in turn affects users right there along your route. It’s all
linked together.” Of course, all water bodies are part of the planetary
water cycle, sharing vapor with the atmosphere until rain and snow return it
to the Sierra Nevada range.
We live just a mile north of Mono Lake. The next morning we walked out the
door of our house and headed west up Lundy Canyon, where Mill Creek gathers
snowmelt from the surrounding peaks before flowing below our house into the
lake. The canyon steadily angled southwest and, at the top, we stood exactly
on the 38º line.
The Sierra Crest
Connie Millar met us as the afternoon sun dropped toward the crest. She is a
U.S. Forest Service paleoecologist who explores connections between mountain
vegetation and changing climate patterns. She told us that photographs taken
80 years ago documented how the nearby glaciers had shrunk by at least 80
percent during the last century. In the last 30 years, shrinkage has
accelerated. “North Glacier may be gone in a decade,” Connie told us, “and
all of the glaciers in the central Sierra in our lifetimes.”
Some of the clearest signs of climate warming are visible at high
elevations. Scientists have been trying to understand what global changes
mean for local areas, because the effects vary. “In much of the eastern
U.S., temperatures are actually cooling,” Connie told us, “while the West is
warming much faster than the global average.”
A rising temperature trend has been recorded in California through the last
120 years, but the slope of that curve has steepened over the last 30 years,
and “in the last ten years everything has shot up,” said Connie. Forecasts
give two-to-one odds that much of California will be drier by the end of the
century--a 20 percent decline in precipitation--with more water falling as
rain, less as snow. A trend of earlier snowmelt runoff, shorter spring
seasons, and longer summers is already apparent in the Sierra Nevada.
We were sitting near the tree line. Scattered clumps of trees across the
basin were primarily whitebark pine and some limber pine. Connie explained
how “drier” added to “warmer” has been killing limber pines. That year she
was also seeing whitebark pines starting to die, with “whole hillsides going
in a flash of mortality.”
“It sounds like worse news than I think it is,” she added. “Even where there
is a lot of mortality, it’s not total.” Slower-growing trees were being
taken out, producing very strong selection for trees that do better under
the altered climate.
“Are trees going to move upslope, chasing suitable conditions?” we asked.
“We don’t see whitebark pine moving up; if it were, there should be baby
pines right here.”
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