At Cosumnes, Sweet explains, biologists essentially created new oak woodland from former farmland. They pulled out levees and roads and planted thousands of new oak trees. They allowed the Cosumnes, the last unregulated river to flow freely from the Sierra Nevada to the Central Valley, to meander in its historic path across the land, its floodwaters depositing silt to build the deep rich soil that encourages extra-large oaks.
As we stroll near the Cosumnes River, Sweet says we’ve entered valley oak riparian habitat, once widespread through California, now reduced to scattered patches. Biologists consider this habitat California’s most diverse in terms of the animal life it supports. Wrentits dart from tree to tree so quickly they’re almost invisible—only their trilling gives them away. Newly emerged tiger swallowtail butterflies flutter at eye level. Sweet notices an oak titmouse with, she says, “an adorable feather crest on top of its head.” A beaver in a slough noses out of the water, trailing a gentle wake.
It’s an amazing sight, but not the most amazing of all. That comes near the end of the trail’s loop, where we emerge into open space, 70 acres of green grassland, a savanna of widely spaced, mature trees, many reaching 60 feet tall, gnarled and weathered, separated as if each had staked out its own territory: an arboreal Gothic cathedral indeed.
There’s no oak national park, but we have this. Sweet spots two white-tailed kites perching on a branch, then hovering as they hunt for rodents below. The birds were once nearly extinct in California, but here they seem perfectly at home, reunited with their ancient oak companions. Looking at the scene, I decide that being an acorn is no bad fate after all.