WEEKLY
WALKER
By Tom Davids
A Close Encounter with the
Salt Marsh
The Don Edwards San Francisco Bay National Wildlife Refuge, Fremont
"Birth, growth, death, and decay. . .it's all here in this short walk around the tidelands trail." From the Activities newsletter, November 1997
Directions: East on the Dumbarton Bridge, past the toll station (free this
direction), exit at Thornton Avenue. South on Thornton Avenue for 0.8 miles to
the refuge entrance on the right. Turn into the refuge, and follow Marshlands
Road to the stop sign. Turn left into the parking lot.
Grade: Level.
Distance: 1.3 miles for Tidelands Trail, five miles for Newark Slough Trail.
Time: hours.
Special Conditions: Dogs on leash allowed on the Tidelands Trail, but not on the Newark Slough
Trail. Restroom and water available at the trail head. The trails will be muddy
after heavy rain, but they drain quickly. The park closes at sunset, and the
rangers close the gate on time, so don't be late. Administration by the
National Fish and Wildlife Service. For information call 510-792-0222.
There's something inviting about the mud flats and salt marshes of San Francisco Bay. It could be the 250 or so species of birds that use these waters. Or maybe it's the endangered species--the California clapper rail and the salt marsh harvest mouse that depend on the salt marshes for their survival. It could be the thought that a double handful of bay mud may contain ten thousand tiny living creatures. Then there is the refreshing salt-water breeze that typically greets you from the north and west and the beautiful sunsets over the water.
But to many, the marshes and mud flats are a vast wasteland that smells bad and are plagued with clouds of insects. If you're of this mind, I encourage you to spend some time on these trails to understand the real purpose and true value of this "wasteland."
For starters, consider that sunlight and fertile soil brought into the bay by streams and rivers combine with nutrients and oxygen brought in by the tides to produce a luxurious growth of marsh plants. Outgoing tides carry food and nutrients from these marshes to the deep-water bay and into the ocean. Along the way, the lower part of the food chain--clams, worms, and young fish--get their share of food. These, in turn, are eaten by seals, birds, and other large fish and animals, which in turn are lunch for others and eventually for us. So we begin to understand that the marsh "wasteland" has a deeper purpose in which we all share.
The San Francisco Bay National Wildlife Refuge was formed in 1972 with the setting aside of 23,000 acres. It circles the South Bay extending from Redwood Shores to Coyote Hills in Fremont. About two-thirds of the refuge contains reclaimed or working salt ponds, 2,500 acres of fresh water wetlands along riparian corridors, 182 acres of natural tidal salt marsh, and almost 400 acres of mud flats and open water. (For additional information, pick up a copy of "San Francisco Bay Shoreline Guide" produced by the California State Coastal Conservancy, which is available at the Nature Center Bookstore.) The name Don Edwards was added to the title a few years ago to honor the south Bay congressmen who tirelessly campaigned to make this refuge a reality.
There are two hiking trails from the Visitors Center parking area. The first is the short and easy 1.3-mile Tidelands Trail, and the second is the longer 5-mile Newark Slough Trail. For both trails, start at the signed trailhead leading down from the asphalt service road below the Nature Center. (The Tidelands Trail has other starting points leading from the Visitors Center, and all take the same loop.) Soon you will pass by an area with several picnic tables and then on a massive wood bridge over the Newark Slough. Ahead are several old fishing cabins now used for instructional purposes such as school field trips. After crossing the Newark Slough, the trail splits right or left. To the right is the Newark Slough Trail. The short Tidelands Trail goes left past a hunters' cabin and exhibits related to the history of waterfowl hunting in the South Bay. We hiked along this portion of the Tidelands Trail studying each exhibit in our quest for a better understanding of the slough and surrounding marshland. The exhibit topics include hunting; pickleweed and dodder; animal species going (California least tern, clapper rail, brown pelican), and long gone (tule elk and grizzly bear); and how salt water gets converted to table salt. After one-half mile you can turn left and continue on the Tidelands Trail or go straight on the Newark Slough Trail. If you elect the Newark Slough Trail, plan about two hours and be sure you have enough time to get back to your car by sunset. (We pushed the limit and came close to receiving a citation and spending the night in the parking lot behind a closed gate.) The Newark Slough Trail follows the waterway to near its point of beginning at Thornton Avenue, then continues south on the salt levee to a point near the large, partially buried Hetch-Hetchy water pipes that carry water from Yosemite to the Crystal Springs Reservoir System on the Peninsula. The trail parallels the water pipes for about 1.5 miles, then turns north and follows the Newark Slough back to the trailhead.
While you encircle the salt pond, note that there are many such ponds in this refuge--some "operating: and others with levees breached to provide a resting and feeding place for many species of water birds. The process of producing salt from bay water is an interesting interaction between sun and wind. The typical yield is one ton of salt for every 10,000 gallons of captured bay water. During the five-year curing process, the water moves from pond to pond through 10 stages of evaporation. As the solution ripens, it changes color due to algae growth until the concentrated brine turns to "pickle." Salt has been harvested in the bay since the 1850s. The major producer is now Cargill Salt Company (formerly Leslie Salt) with 32,000 acres of salt ponds.
There are many other levee hikes in the South Bay area, and we find them especially inviting during the winter months. Watch future "Weekly Walker" columns for information on the Alviso Slough Trail, the Ravenswood Trail, and the Palo Alto Baylands Nature Preserve.