From a few thousand feet up, there is something mesmerizing, sensual even, about the ribbons of lush green foliage encasing the creeks that drain the summer’s dry and golden hills. From the sky, they look like ribbons of fur highlighting soft and rumpled folds of skin on the back of some mammoth creature. What a relief it must be for a neotropical migrant, say a rare western yellow-billed cuckoo exhausted by its flight from South America, to spot that ribbon of green and fly down into its hospitable cover.
This fecund terrain, known as riparian habitat, is one of the richest and most diverse habitat types in California. It provides a moist, nourishing, and relatively cool summer sanctuary for many of the East Bay’s plants and animals. Creeks and the riparian habitat that lines them also act as circulatory and nervous systems connecting distant portions of the landscape into a living whole and facilitating the transport of nutrients, seeds, water, and animals throughout the watershed.
There are 44 East Bay watersheds that feed into the Bay, but the majority of the sizable creeks that drain them have been buried or channelized for all or most of their courses and, of course, no creek means no riparian habitat. Some creeks, however, still emerge in places, gracing lucky neighborhoods with occasional bursts of life.
A rare few East Bay creeks remain aboveground for most of their journeys from headwaters to the Bay. Even fewer have a substantial amount of intact riparian habitat left that links their heads to their souls.
From this last and rarest group, I have chosen two of my favorites to look at more closely: Alameda Creek, representing the southern portion of the East Bay, drains the region’s largest watershed, an area encompassing nearly 700 square miles that includes densely populated Fremont, Livermore, Pleasanton, and San Ramon. It also courses through some of the Bay Area’s wildest and most spectacular habitats.
Wildcat Creek, at the opposite end of the Bay, runs north from the Berkeley hills to its mouth in Richmond. Wildcat drains a much smaller watershed and is only 13 miles long. Yet much of its riparian corridor is intact and there are several stunning access points and hikes along its course. Wildcat is also a creek holding its own, even on the mend, both in its park-protected upper stretches and mouth and in its urban reaches, which have been, over the decades, the focus of remarkable community-based restoration efforts. Those efforts were recognized in December 2003 by a Governor’s Environmental and Economic Leadership Award, and the project, which pulls together federal and state agencies, the East Bay Regional Park District (EBRPD), and local citizens groups, has become a model for creek restoration around the country.
Alameda Creek’s headwaters are on Mount Hamilton in the western Diablo Range east of San Jose. It runs through Ohlone and Sunol Regional Wildernesses, where it supports an array of oak, bay, willow, and sycamore woodland along its banks. Fed by the persistent water supply, these trees hug the creek, often reaching across and closing the canopy above it. Blocked from the sun, the water stays cool and hospitable to native freshwater fishes: California roach, hitch, Sacramento blackfish, hardhead, Sacramento pikeminnow, Sacramento sucker, prickly sculpin, rainbow trout, and tule perch. All of these fish eat the insects and other invertebrates that live on or in the creek and are in turn fed by one another and by leaf litter falling from creek-side trees and shrubs.
We megafauna lovers too often consider insects little more than food for more muscular vertebrates. For example, it is hard for me to view Alameda Creek’s abundant caddisflies and mayflies as much more than dietary staples for fish, bats, and birds. But there are some charismatic mega-insects here that demand respect, says Katie Colbert, a naturalist at Sunol Regional Wilderness. Big old dragonflies and damselflies love the water, of course, but so do hellgrammites, the giant, succulent larvae of dobsonflies, whose powerful pincers can draw human blood. They spend a few years in their larval stage hiding and hunting under rocks in fast-moving parts of the stream. Once adult dobsonflies, they stop eating and start reproducing. Their eggs, deposited on creekside plants, look remarkably like guano, presumably a camouflaging technique.
Another Alameda Creek insect is the toe-biter, a one-and-a-half-inch-long giant water bug that will inflict a painful stab with its powerful needlelike mouth if disturbed by a naked foot. They are not at all intimidated by vertebrates, and eat tadpoles, small salamanders, fish, and snails as well as insects.
The many small birds that live off insects exploit the dense streamside vegetation, so bird life is especially rife here. Downy woodpeckers nest in tree holes along Alameda Creek, as do wood ducks. California and spotted towhees, marsh wrens, and red-winged blackbirds all require dense vegetation and make their nests in the thickest regions of brush. Several migrating warblers, including the yellow warbler and Townsend’s warbler, rely on Alameda Creek and other East Bay riparian habitat.
Riparian habitats are as endangered as they are biodiverse. With the massive 19th- and 20th-century alteration and channelization of creeks and rivers for power, agriculture, and drainage, only about 5 percent of the state’s riparian forests remain intact. This has spelled endangerment for the once abundant western yellow-billed cuckoo, a robin-sized migrant that spends its winters in the lowlands of South America. Sometimes seen along the upper reaches of Alameda Creek in the spring, says EBRPD Stewardship Manager Joe DiDonato, these extremely rare birds eat both insects and an occasional tree frog. Males make a cooing call to beckon potential mates, and a short but impressive “kowlp!” that warns avian intruders to stay out of a couple’s territory . . . and signals lucky birders to grab their binoculars.
When the creek’s flow slows and ceases in summer, deer and other mammals come to the standing pools in their search for forage and water. Mountain lions, in turn, are drawn by the deer, their favorite prey. It is not uncommon to find the remains of a kill near pools in the riparian zone during the dry months, says wildlife biologist and artist Hans Peeters, who has long studied and painted mammals and birds along Alameda Creek.
Mountain lions also use riparian corridors, and even drainage channels, to pass through urban parts of Alameda and Contra Costa Counties, says Steve Bobzien, EBRPD wildlife biologist. This may play a key role in preserving the genetic variability of otherwise isolated populations. Alameda Creek, for instance, allows mountain lion populations on the east side of the deadly 680 highway corridor to connect with those on the west, preventing the kind of genetic bottleneck that can spell curtains for an already marginalized species.
While Alameda Creek’s upper riparian corridor is mostly populated with bays, oaks, sycamores, and willows, once below Sunol Valley into Niles Canyon, mature sycamores dominate for a while. It is a beautiful sight, this sycamore grove. And it is an important reach, says Jeff Miller, director of Alameda Creek Alliance, because the balled root structures of these trees create streamside pools, which sometimes, in the dry season, provide the only surface water available to amphibians, insects, or fish.
Several raptors, drawn by the abundant prey, conduct business here. Cooper’s hawks and sharp-shinned hawks are both accipiters, woodland raptors well adapted for the quick, agile flight necessary to hunt small, avian prey among the trees. Cooper’s hawks prefer to nest right in riparian habitat, says Peeters, while their cousins, the sharp-shins, rarely nest here but frequently come to hunt the abundant prey birds. While riparian habitat may be quite lush, just beyond it arid summer grassland can open up again. American kestrels, small raptors that prefer to hunt in the open, often take over the abandoned nests of yellow-billed magpies in riparian trees. Kestrels, as well as screech and pygmy owls, will occupy the holes in sycamore trees left by nesting northern flickers. Red-shouldered hawks also prefer to nest in the riparian zone, feeding on the rodents, snakes, and amphibians concentrated here.
California red-legged frogs still persist in the habitat lining Alameda Creek and its tributaries. Once abundant enough to be a regular on the menu of San Francisco restaurants, these frogs (Mark Twain’s famous jumping frogs of Calaveras County) are now on the list of federally threatened species. They need the riparian corridor for its persistent moisture, abundant insects, and shade. Bobzien says they mate and lay their eggs in deep, protected parts of the creek. But the young also disperse up and down the creek, possibly fleeing their own parents, who will eat them if they get a chance.
Rarer still, and smaller in stature, is the foothill yellow-legged frog, a prey species of the larger red-leggeds. Alameda Creek is a “hot spot” for these amphibians, which live only in creeks in the Bay Area, though they range more widely in other parts of the state, says Bobzien. Their presence in Alameda Creek is a hopeful sign because foothill yellow-legged frogs need a creek to be in “pretty pristine shape” for them to flourish, he says. One gathering place for foothill yellow-leggeds is also a favorite of human creek-seekers: Little Yosemite just outside Sunol Regional Wilderness. This deep and beautiful gorge is just about a two-mile walk along Alameda Creek from the visitor center, but it is a world apart. It was carved from the sandstone deposits that still hold fossils from the time when this area was a seabed. Today, though, the gorge is littered with the huge greenstone, metachert, and schist boulders that give it the scaled-down sublimity for which the gorge was named. In the high-water season, the creek roars through Little Yosemite in a way that dissuades the red-leggeds from laying eggs or hatching tadpoles here, leaving the field open for yellow-leggeds to flourish.
A living creek is a moving one, says Christopher Richard, an aquatic biologist at the Oakland Museum who has been documenting and studying East Bay creeks for more than two decades. Before they were hemmed in by development, our creeks and their riparian habitat regularly shifted their paths. In the alluvial flatlands, Alameda Creek would wag back and forth from season to season. Old riparian habitat was periodically left behind, and new corridors established. The ecological significance of this was great. Alder leaves, for example, are the best available food source for aquatic insects. And alders sprout best on freshly scoured gravel bars formed by meandering creeks. “No meandering, no new alders, no great food source for insects, no great food source for fish,” says Richard. “It’s a system, not a static object. The whole watershed structure ends up in trouble if you forget that.”
That concept was forgotten when the Army Corps of Engineers girdled the final 12 miles of Alameda Creek’s extent in a concrete flood control channel kept clear of vegetation. This stretch now serves as a “great smorgasbord for birds,” says Miller. Snowy egrets, herons, seagulls, terns, and cormorants stand watch over the shallow-water gauntlet and can easily pluck out any fish but the mud-loving bottom feeders. These birds are beautiful to watch, but they already have an abundance of good habitat in the South Bay. For the fish, this stretch of creek is a death trap.
Wildcat Creek drains a much smaller watershed than Alameda Creek does, but nearly half of it is both easily accessible and protected in Tilden and Wildcat Canyon Regional Parks. Margaret Kelley, Tilden Park’s Supervising Naturalist, has studied and taught at Wildcat Creek for nearly two decades and she knows it intimately. In early October she took me to the headwaters: a somewhat disappointing drain grate in the parking lot of the steam trains in the Berkeley hills. Actually, the high point in the watershed is the nearby and more noble Vollmer Peak, but the first evidence of collecting water is found in this little culverted drain, so it is from here that Kelley and I start to follow the creek’s descent.
We stop near the golf course on South Park Drive. Each year in October or November, thousands of California newts emerge from their dry-season burrows near here, where they’ve been sheltering from summer heat and building their reserves for their winter mating regimen. Shortly after the season’s first big rain, they launch a massive migration to Wildcat Creek, forcing road closures in Tilden Park. After mating, the newts remain in the creek-side leaf litter bulking up on insects for the hike back up through the grasslands to their dry oversummering estivation sites.
You can never step in the same creek twice, said Heraclitus (or even once, Lao-tzu might have answered), and despite their parkland status, the upper reaches of Wildcat have changed a lot over the decades. There was once even a 90-foot waterfall along the creek in Tilden Park. It was filled and submerged in 1938 with the creation of Lake Anza. You would never know to look at it now, but Anza covers a deep and dramatic valley. “Berkeley’s own Glen Canyon,” says Kelley.
Kelley is a creek person, and I can tell that she wishes the Lake Anza waterfall were still a part of her landscape, but she appreciates lakes, too, and easily fits them into her creek-centric perspective. “They’re just places where the creek widens,” she says. “The creek is not just the water in the bottom of the creek bed; it’s the entire watershed.” From that perspective, trying to distinguish the creek from its riparian corridor would be senseless. Neither one can be coherently defined, let alone managed, independently of the other.
In the early 1980s, when the Army Corps of Engineers, in the name of flood control, proposed doing the same thing to the lower stretches of Wildcat Creek that it had done to Alameda, the predominantly working class and African American neighbors of the creek organized against the plan, forming the Wildcat San Pablo Creeks Watershed Council. Instead of accepting concrete trapezoids, the council worked to restore the natural flood-controlling vegetation and meanders in the creek, which slow floodwaters and absorb their impact. Today the creek, which has a restored marsh at its mouth, is a source of pride, and a rare and nourishing contact point with the natural world for the flatland residents of Richmond. The council hopes one day to have a riparian trail connecting the urban stretches of Wildcat to the park-protected uplands.
There is already much spectacular and accessible terrain along Wildcat Creek. The Wildcat Creek Gorge Trail, for example, follows the riparian corridor as it curves sharply around the edge of a lava flow. On the south side of the bay-and-oak-wooded trail jut tall cliffs pocked with large riparian caves formed ten million years ago by bursting lava bubbles. It looks like the remotest of Ishi country. I have not always been able to resist my temptation to scale that cliff and explore those caves. It feels so isolated here; the first time I climbed I was flabbergasted to find the Tilden Park merry-go-round spinning just beyond the top of the cliff.
A couple of miles downstream, after Wildcat Creek has passed out of Tilden and into neighboring Wildcat Canyon Regional Park, Kelley takes me to what is obviously one of her own favorite local creek-side hangouts. At a horse-watering tank, a hidden deer trail forks off the main one and into the brush and down to the streamside.
The vegetation is diverse and dense, downed and living trees crisscross the creek, and the bed is cobbled and varied. Broad, meandering curves make good habitat as they slow the flow of water, the rate of erosion, and my blood pressure. “This reach of the creek is doing just what it is supposed to do,” says Kelley. “When a creek is healthy, the entire watershed and all its creatures benefit, even us.”
Most recent in Habitats: Freshwater, Bay, Marine
The harmful algae bloom that sickened marine mammals and caused the closure of California's crab fishery this winter is slowly dissipating, while researchers are still trying to understand what caused it to happen.
Habitats: Freshwater, Bay, Marine
Marine ecologists have long been alarmed at the potentially dangerous summertime growth of the single-celled algae Pseudo-nitzschia -- but there are still significant blind spots in our knowledge and research funding has been scarce.
El Nino | Habitats: Freshwater, Bay, Marine