Sierra sights: Bevy of butterflies adds to the allure of Donner Pass
June 22, 2015
TRUCKEE, Calif. — As a vital gateway for America's 19th century westward expansion to the Pacific Ocean, Donner Pass, just west of Truckee, is arguably one of the most storied locations in America.
One of the lowest passes in the Sierra Nevada, at about 7,000 feet, the gap in the granite has always been a highway of sorts.
For thousands of years before California-bound pioneers with farm wagons first breached the Sierra there in 1844, Great Basin natives used the trail over the mountains to trade with tribes from the Sacramento Valley and near the Pacific Coast, and vice versa.
At its location on the Sierra Crest, Donner Pass represents the Pacific Divide, where its western watershed begins above the broad, tilted flank of the Sierra range.
“There’s a tremendous diversity in the butterfly species that live at Donner Pass, more than virtually anywhere else in North America.”
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The North Fork of the American River gets its start near here, as does the South Fork of the Yuba River, long before their final destinations in the Pacific Ocean.
The steep and rugged eastern watershed of Donner Pass, however, drains quickly to Donner Lake, which in turn feeds into the main stem of the Truckee River.
These waters flow into the Great Basin, where they feed Pyramid Lake, the terminus of the Truckee. This system of rivers created a viable trail across the mountains for early pioneer settlers, while providing nourishing water for fatigued people and livestock.
Beyond the myriad hikes, rock climbs, bike rides and historical exploration opportunities that abound there, Donner Pass also offers something more subtle that most people won't notice. There's a tremendous diversity in the butterfly species that live at Donner Pass, more than virtually anywhere else in North America.
Truckee has a long history associated with butterflies because town patriarch Charles F. McGlashan — an author, attorney, teacher and noted entomologist — was well known for his own extensive collection and expert field knowledge of the fascinating insects.
McGlashan was in the right spot. With well over 100 distinct species, the Donner Summit area boasts such diversity that the site ranks as one of the richest butterfly faunas documented in North America north of Mexico.
Professor Art Shapiro, a renowned world-class entomologist and ecologist with the University of California, Davis, has been monitoring butterflies in the area for more than 35 years.
Shapiro's butterfly research has uncovered the negative impacts urban development and climate change are having on butterfly diversity at his 11 study sites.
Species diversity at all his sites — including near sea level, the Central Valley and Sierra foothills — is declining rapidly.
In the mountains, the loss is slower. At the highest-elevation monitoring sites near tree line, butterfly diversity is actually increasing as lower-elevation species escape the warming climate by moving up to cooler regions.
When you explore the Donner Pass area this summer, don't forget to keep an eye out for the butterflies.
Lake Tahoe historian Mark McLaughlin is a nationally published author and professional speaker. His award-winning books are available at local stores or at http://www.thestormking.com. He can be reached at firstname.lastname@example.org. Check out his blog at http://www.tahoenuggets.com.