Flying Rivers & Mega-Droughts

When it comes to areas of the world being racked by drought, one of the few that has had at least as hard a time as California is central and southern Brazil. Whereas the US's biggest state has gotten a handful of solid drenchings in the past three years, this particular portion of South America has seen almost no rain at all. The most populous city in the Americas, Sao Paolo, is marked by endless, chaotic sprawl that has grown, unchecked, for decades. The main reservoir that supplies the 19 million people who live there has recently gone as low as five percent of capacity.

One of the main factors that has caused the California drought is climate change. The warming of the atmosphere has increased the size and persistence of the high-pressure ridge that historically prevents rain from reaching California's Mediterranean climes for much of the year.

What about in Brazil? Researchers there have pinpointed the absence of “flying rivers” — vapor clouds from the Amazon rainforest that normally bring rain to the center and south of Brazil — as a main reason for the recent lack of precipitation. These massive volumes of vapor rise from the forest, travel west, and then, blocked by the Andes Mountains, turn south. The Amazon is akin to a gigantic hydrological pump that brings the humidity of the Atlantic Ocean into the continent.

The world's greatest forest, however, has been logged and burned to such an extent that the “flying rivers” failed to form this past year, as satellite images from the Center for Weather Forecasts and Climate Research of Brazil’s National Space Research Institute (INPE) demonstrated. Antonio Nobre, a researcher in the Brazilian government's space institute, Earth System Science Center, published an authoritative study on the topic. In his study, he has noted that the Amazon has lost 763,000 square kilometers — an area the size of two Germanys — in the past 20 years.

No rainforest, no rain.

Here, there may be a parallel between Brazil and California that goes beyond the fact that each has received only a fraction of their normal rainfall in recent years. The Pacific Northwest is home to part of the largest continuous temperate rainforest in the world: the conifer-dominated “Pacific temperate rainforest” (so named by the World Wildlife Fund), which runs from Prince William Sound in Alaska through the British Columbia Coast to Northern California.

California's so-called “coast redwood zone” is at the southern end of these forests, which run along the western side of the Pacific Coast Ranges. They are characterized by high rainfall and moderate temperatures. And they contain the largest sheer mass of living and decaying material of any ecosystem on the planet. Has the enormous depletion of this region's forests been a cause of the growing intensity and frequency of California's multi-year droughts? Not necessarily the cause, but one among varied underlying sources?

Scientists don't have a clear answer. No published research links forest depletion in the Pacific Northwest to Western U.S. drought. It's as obvious as the fact that the sun comes up every morning, though, that waterways depend on healthy forests in the long-run, as a 2012 study in the Mattole River watershed forests of Mendocino and Humboldt counties demonstrates.

As part of the study, called “Summer Water Use by Mixed-Age and Young Forest Stands, Mattole River, Northern California,” researchers affiliated with Humboldt State University inserted probes into various Douglas-firs to measure the amount of water they use. While mid-and-large sized trees use much more water than young trees as individuals, the amount the forest as a whole uses declines steeply as the forest ages. The young trees die out as the canopy closes, the trees compete for available light, and the suppressed trees die out. A study in western Oregon, which these researchers cited, determined that young mature Douglas-fir stands (40 years) had 3.27 times higher water use than 450-year-old Douglas fir stands.

“An implication of this finding is that clearcut harvesting of existing stands would not be beneficial for water yield in the basin beyond the initial regeneration period,” the authors note. “It would result in a new crop of dense small trees, and delay the stem exclusion stage that much longer. Selective harvest of small and mid-size trees might be expected to increase water yields without producing a thicket of young trees if remnant trees were able to quickly grow into the light gaps.”

So, even taking climate change and so-called “flying rivers” out of the equation, one of the best ways of preventing drought is to nurture and restore Douglas-fir and other forestlands.

In 2010, I investigated the devastation that vineyard development in the upper Mark West Creek watershed of Sonoma County had wrought on that particular waterway. Since the late-1990s, several hundred acres of ridgeline vineyards have supplanted oak woodlands and other forests, causing this vital tributary of the Russian River to run dry for the first time in recorded history. Local residents were up in arms because the infamous investment banking firm Goldman Sachs' director of merchant banking, whose name is Henry Cornell, had purchased a big chunk of Upper Mark West land and clear-cut it to install a vineyard, causing a 10,000 cubic yard landslide to wash into the creek. So far, project opponents have prevented a winery from being constructed on the property.

The antithesis of Cornell's vineyard is Ranchero Mark West: a 122-acre redwood forest with accompanying 10-acre commercial Christmas tree farm located at 7125 St. Helena Dr. When Jim Doerksen purchased the property in 1967, it was badly damaged by more than a century of logging, ranching, and wine-grape production. Only about 30 acres were forested. Doerksen meticulously removed all of the standing vines, as well as the shrubs and other fruit trees, and replaced them with redwood trees.

Today, the average growth of a tree in the Doerksen forest is greater than an inch in diameter a year — a vivid reminder of the fact that California's largest redwood trees, prior to the 1860s, were located in the Russian River Valley. Visitors from the American Forestry Foundation say that the Doerksens are growing more timber per acre than anyone they know.

Redwood trees' roots are extremely efficient at enhancing groundwater retention in local ecosystems. The trees also capture fog that drifts in from the ocean, causing it to drip out onto the ground, where much of it enters streams and creeks. Ranchero Mark West includes 4,000 feet of creek frontage.

In the 1980s, the California Department of Fish & Game conducted a long-term study of Mark West Creek fishery habitat and concluded that the stretch running through the Doerksens' ranch was perhaps the most ideal spawning area for Coho salmon in all of Sonoma County. When I poked around in the upper Mark West in the late summer of 2011, Doerksen's property was the only stretch of the upper Mark West where I witnessed water flowing. Though redwood forests historically spanned the areas surrounding Mark West's waterways, healthy forests are now almost entirely absent in other areas of the watershed.

These other areas were completely dry.