By GENEVIEVE BOOKWALTER
Yosemite National Park ecologists have three years to turn an old parking lot back into a fen.
So, armed with a topographical map from 1919, Park Service Ecologist Marie Denn directed teams of dumptruck, excavator and Bobcat drivers last summer to clear 1,200 cubic yards of fill-dirt that have covered one-quarter of the Happy Isles Fen since 1928.
A fen is a wetland fed mainly by underground springs, instead of raindrops or the ocean's high tide. Fens are common in the Midwest, central Canada and Northern Europe. But hot, dry Sierra Nevada summers usually prevent their fruition here.
Despite their Heartland existence, "Most Americans don't know what a fen is," Denn said.
The Happy Isles Fen, so named because it sits across the path from Merced River's Happy Isles in Yosemite Valley, has two arms that stretch across 2 acres. The arms run parallel to a path that used to be a road for visitors to drive to the parking lot and then walk to Happy Isles.
Now guests can walk or take a shuttle bus from Yosemite Village to the Isles and fen.
Before pouring asphalt over the east arm of the fen, the Park Service dredged sand from the Merced River bottom and filled in the wetland, Denn said.
They laid culverts to divert water from the fen to the river, then paved the top.
Asphalt was removed and the parking lot closed in the 1970s, Denn said. But because the culverts and sand remained until last summer, few plants grew without water and fertile wetland soil.
"As the culverts were removed, we started liberating all this water," Denn said.
"You could tell that it was disturbed because you didn't have anything growing here."
The west arm stood untouched, and is now a popular spot for visitors to sit on rocks, listen to warblers and take in the dogwood trees, horsetail ferns and white-stemmed raspberry plants, Denn said.