Restoring a safe haven for endangered species
In a vast and flat oak savannah outside Central Point lies a panoramic vista with Table Rock in the background. No house, road or power line is visible. Here is perhaps the only location in Jackson County where the valley floor appears as it did to the first European settlers in 1850 — a gently undulating landscape carpeted with calf-high wild grasses and dotted with white oaks and vernal pools.
Thanks to ongoing ecological restoration by the Oregon Department of Transportation and The Nature Conservancy, this 80-acre, ODOT-owned lot provides, for the first time since the 1920s, habitat for three vernal pool-dependent threatened and endangered species.
Vernal pools — ranging in size from two square meters to a fifth of an acre — once covered the landscape of much of White City and Central Point. A concrete-like hardpan soil layer just a few feet below the surface slows the infiltration of rain water enough to maintain these small pools well into spring.
A former owner leveled this land with bulldozers in the 1920s to create a pear orchard. The current restoration was aimed at re-contouring the land to its original format without breaking through the hardpan, an action that would possibly drain this delicate wetland.
"They (ODOT) were out here with heavy equipment and using soil pits, soil profiles to get a clear indication of where the hardpan was, to guide us to where those (natural) depressions were," says Darren Borgias. "(They took) the dirt that had been leveled out and removed it from those depressions and put it on the surrounding mounds."
Borgias is an ecologist and the Southwest Oregon program manager for the Nature Conservancy. He has served as a restoration advisor to ODOT and is monitoring the results.
A formidable challenge to restoring these vernal pools has been a 1,600-foot section of irrigation ditch that cuts through the property. Not only did water still need to be delivered to the irrigators, the ditch cut through the hardpan soil layer.
"We piped it below the hardpan" says Paul Benton, ODOT wetland specialist. "Then we sealed it with a slurry mix of concrete and bentonite to mimic the hardpan."
Even though the vernal pool restoration was completed only last November, the results for the threatened fairy shrimp that live there already are evident.
"Forty-four pools were restored," says Benton. "Four of them had shrimp before we did the restoration, and this year when we did the monitoring, about 26 of the pools had fairy shrimp."
To help spread the shrimp to the newly restored pools, specimens were taken from the few remaining naturally intact pools and placed into the restored ones.
Though the fairy shrimp is making a comeback here, the fate of two endangered plant species is not as certain. Vernal pools in the Rogue Valley are the habitat not only of fairy shrimp but also of Cook's lomatium and large-flowered woolly meadowfoam.
"Cook's lomatium was extirpated from the ODOT tract," says TNC's Darren Borgias. "So it was reintroduced here from seeds from the TNC's Agate Desert."
The Nature Conservancy owns two preserves with functioning vernal-pool habitat: the Agate Desert in Eagle Point and Whetstone Savannah in Central Point. The Whetstone property abuts the ODOT land, making the combined 224 acres the largest intact oak savannah ecosystem in the Rogue Valley.
The goal for each of the two plant species is a minimum of 2,000 individuals, with success counted only when a plant flowers. Two thousand is considered the threshold for a self-sustaining population.
"Now in year two of seed collection, we count only one for the lomatium," says Benton with a sigh. "Only 1,999 to go."
The woolly meadowfoam is faring better, but has its own challenges.
"We have 296, but the numbers are dropping," Benton says. "It's because of the late season rain events this year and last year, and because of last year's dry fall. They get drowned in the late spring and dry out in the fall."
ODOT's restoration functions as a conservation bank, the first in Oregon. The banking metaphor works like this. In exchange for restoring vernal-pool habitat, ODOT receives a deposit from the federal government. This deposit is in the form of credits, each of which may be spent to pay for impacts created by ODOT road projects. This payment is the latest form of wetland mitigation, expanded now to mitigate for impacts to species listed under the federal Endangered Species Act.
Credits become available as restoration milestones are met. Vegetation management is tied to one of these milestones and is a critical piece of the restoration.
"Our main reason for thinning the oaks is that the evapotranspiration pulls water out of the ground," Benton explains. "We're improving the hydrology so the pools won't dry out as fast."
Younger oaks, as well as those near the pools, are the targets for thinning. The common Oregon fairy shrimp thrives around oaks and competes with the threatened vernal-pool fairy shrimp. Thinning oaks near vernal pools gives the threatened shrimp a fighting chance.
The larger wood that's thinned has been donated to the nonprofit ACCESS for firewood. The smaller wood is collected in piles and burned.
"We're sterilizing the soil with the burns, where we will plant native species," Benton says. "There are several invasive species here, and this gives us an opportunity to restore the balance."
Daniel Newberry is a freelance writer living in the Applegate Valley. You can reach him at email@example.com