Bay Terraces/Lower Santa Clara Valley

Laurel Creek is listed as impaired under the Clean Water Act and has a TMDL in place. The stream is among 12 assessed water bodies in the area, with its impairment status confirmed in the 2026 assessment cycle. A TMDL identifies the maximum pollution load a water body can receive while still meeting water quality standards.

Bay checkerspot butterfly has designated critical habitat overlapping the Bay Terraces/Lower Santa Clara Valley area. The species is federally threatened and the critical habitat designation provides legal protection under the Endangered Species Act for habitat features necessary for its recovery.

A California ground squirrel was observed at Don Edwards San Francisco Bay National Wildlife Refuge on 2026-10-03. The species remains active through October while foraging on seeds before entering dormancy, with individuals using burrows as safe havens in the refuge's grassland habitat.

Coast redwood, the world's tallest tree species, was observed on 2026-10-04 in South San Francisco and has been documented 17 times across the region in the past 30 days. This threatened native species inhabits the wet redwood forest habitat spanning from Purisima Creek Redwoods Preserve south through La Honda to Fremont.

Pappose tarplant, a threatened native wildflower, was observed on 2026-10-05 at Highway 1 and Rockaway Beach Avenue in Pacifica. This species is uncommon in the coastal scrub and dune habitat where it was recorded.

Alkali Heath was observed on 2026-10-06 at Ravenswood Open Space Preserve in Menlo Park. This threatened native perennial has been documented 33 times in the region over the past 30 days, primarily in salt marsh habitat around San Francisco Bay. Recent observations across multiple Bay Area locations confirm the species is active.

River otters are being seen along the East Bay shoreline again this month, at the Albany waterfront on August 27 and off Emeryville five days earlier. Both spots are old fill and riprap pushed out into the bay, which sounds like poor otter ground until you look at what the animal actually needs. A river otter (*Lontra canadensis*) is a long, low member of the weasel family, ten to thirty pounds, with a thick tapering tail that makes up about a third of its length. On this shoreline the animal it gets confused with is the sea otter, and the differences are easy once you know them. A river otter swims belly down, head and back breaking the surface; a sea otter floats on its back. A sea otter is several times heavier, with a short stubby tail, and almost never leaves the water. Any otter hauled out on the rocks at the Bulb or trotting along the Emeryville breakwater is a river otter. They cross land readily and will travel considerable distances overland between one body of water and the next. They eat whatever is easiest to catch: fish first, then crabs and other crustaceans, and on occasion frogs, ducks and eggs. On brackish shorelines studied elsewhere, finfish and crustaceans make up most of the diet, and the animals take readily to man-made structure, using riprap and pilings as latrines. Those latrines, piles of scat full of fish scales and crab shell on a prominent rock, are often the first sign of otters on a stretch of shore, well before anyone sees the animal. The catch with living in salt water is the fur. An otter has no blubber; it stays warm because a dense underfur traps air, and that only works if the coat is kept clean. Otters groom after every meal, and in salt water they need fresh water to rinse with, which is why their haul-outs and dens cluster around creek mouths, seeps and freshwater ponds rather than open rocky shore. Codornices Creek, the one creek in this stretch that runs year round from the Berkeley Hills to the bay, reaches the water at the Albany-Berkeley line just south of the Bulb. Most of its neighbors, Cerrito and Temescal among them, are culverted for much of their length and deliver what little September flow they carry through storm-drain outfalls. A shoreline with a living creek mouth is better otter ground than one without. For most of the twentieth century there were no otters to see here. Fur trapping and the condition of the bay's water are the usual explanation for their absence, and it was after trapping was ended in California and water quality rules took hold that they began turning up around the estuary again, by the 2010s in places where they had been gone for generations. Cesar Chavez Park, stewarded by the Chavez Park Conservancy, sits on the Berkeley waterfront between the two places otters were seen last month, and the rocks along that shore are where to look for tracks and scat.

Lower and South San Francisco Bay, the receiving waters for everything that drains off Bay Terraces and the lower Santa Clara Valley, are now officially listed as impaired under the Clean Water Act. Each bay segment carries a total maximum daily load determination from the latest assessment cycle, the regulatory tool used when a waterbody can no longer absorb the pollutant load reaching it without exceeding water quality standards. Laurel Creek, in San Mateo County, carries the same designation. The verdict isn't uniform across the watershed. San Francisquito Creek and Marina Lagoon are currently meeting their designated uses, and Matadero Creek simply lacks enough monitoring data to say either way. The impairment finding is specific to these bay segments and to Laurel Creek, not a blanket statement about every waterway feeding this stretch of coast. What stands out is less the impairment itself than what sits upstream of it. Within the immediate area, 35 facilities hold active Clean Water Act discharge permits. Seven are currently in violation, eight more had violations within the past year, and yet only four of the 35 have ever been inspected. No penalties have been assessed on any of them locally. Widen the lens to the broader watershed and the picture inverts: nine facilities there carry a documented history of significant violations, with more than $7 million in penalties assessed over time, though none of them are currently in serious non-compliance. Taken together, this reads less like an active spill and more like a long-standing gap between the paperwork of permitting and the follow-through of actually checking it. No single facility here has been tied to a specific pollutant load reaching the bay, and none of this pins the impairment on any one source. But a bay already on the impaired list, with a total maximum daily load in place and little assimilative capacity left, has correspondingly little room to absorb inattention upstream. The gap between permits issued and permits inspected is exactly the kind of quiet condition that tends to go unnoticed until a wet winter or a failing outfall turns it into something more visible.

Yellow Star-Thistle (Centaurea solstitialis) has turned up in 52 observations over the past two months, with records stretching from the bay-edge trails at Byxbee Park and the San Francisco Bay Trail through Palo Alto, Redwood City, Los Altos Hills, and into the La Honda foothills. Late July is the critical moment in its lifecycle: the spiny flower heads are ripening and locking in next year's infestation before the first rains arrive. This Mediterranean annual is one of California's most aggressive rangeland invaders, capable of forming near-monocultures on dry slopes that once supported diverse native forbs and grasses. The thistle's persistence reflects several advantages. It is highly toxic to horses and largely avoided by cattle and other grazers, giving it a competitive edge once established. It exploits the same dry summer conditions that stress native plants — a wet spring followed by sharp summer drought tends to favor it — and its deep taproot draws water from soil depths that shallow-rooted native annuals cannot reach.

The San Francisco Bay Ridgway's Rail (Rallus obsoletus obsoletus) is calling from the pickleweed marshes along the bay edge this week, a sound that carries far across the Palo Alto Baylands during the height of breeding season. Of all the tight-range subspecies clinging to existence on this coast, this one is perhaps the most acutely place-bound: it lives nowhere else on Earth, entirely dependent on the tidal marshes of a single estuary. That context makes every observed nest, every territorial call, ecologically charged in a way that few other bird encounters can match. Nests are constructed as floating platforms woven from cordgrass and pickleweed, anchored just above the waterline — a strategy that works well under stable tidal regimes but becomes precarious the moment water runs high. Bay levels this week have been measurably above predicted tides, driven by summer wind setup pushing water against the South Bay's shallow margins and compounded by the slow, relentless background signal of sea-level rise. For a ground-nesting bird whose clutch can be swamped by a few centimeters of unexpected inundation, a week of elevated water is not an abstraction — it is a direct threat to this year's cohort of chicks. Rails do re-nest after flooding events, but each failed attempt compresses the breeding window and draws down adult condition heading into fall. The bay these birds wade through carries a chemical burden inherited from more than a century of industrial and agricultural use. The South Bay is formally listed as an impaired water body under the Clean Water Act, with legacy loads of mercury, PCBs, and selenium still cycling through the food web. Rails are sit-and-wait predators of invertebrates in the marsh mud — precisely the organisms that bioaccumulate these contaminants most efficiently. Long-term monitoring has documented elevated mercury in rail eggs and tissues across the estuary, a physiological drag on reproduction that operates invisibly beneath the surface of what looks, at a distance, like a thriving marsh. The fact that the rail is nesting here at all is a hard-won outcome. The subspecies dropped to fewer than 500 individuals by the early 2000s, the low point of a collapse driven by the wholesale conversion and diking of tidal marsh that began in the nineteenth century and continued well into the twentieth — the South Bay lost roughly 80 percent of its historic tidal marsh extent. Baylands restoration work, including the managed breaching of agricultural levees and active revegetation of pickleweed and cordgrass communities, began clawing back usable habitat in the years that followed. What is nesting along this bay edge today is a direct ecological consequence of that effort: recovered marsh structure producing recovered bird presence. The coming weeks will be critical to watch. Chick survival in rails is strongly tied to tidal stability during the first fortnight after hatch, when young are flightless and have limited ability to retreat upslope if water rises. If wind-driven water setup persists through late June, nest success rates across the Baylands could be significantly reduced even in the absence of any new stressor. The longer question — how tidal marsh restoration keeps pace with projected sea-level rise across this century — will determine whether the ground these birds are nesting on today remains viable habitat at all. For now, the calls carry. That itself is something.