ANNUAL BUTTERFLY COUNT SHOWS DRAMATIC DECLINE IN PACIFIC GROVE'S MONARCH GROVE SANCTUARY
By Kera Abraham November 30, 2009
An annual count of monarch butterflies shows dramatically low turnout at Pacific Grove's Monarch Grove Sanctuary this year, confirming the suspicions of monarch enthusiasts who blame heavy tree pruning done by the city in late September.
According to El Dorado-based entomologist Paul Cherubini, this year's monarch population estimates, as compared to Thanksgiving 2008, are:
Up 34 percent in Santa Cruz's Lighthouse Field State Park;
Down 38 percent at Moran Lake, Capitola;
Down 34 percent at a private property near Big Sur:
Down 96 percent at P.G.'s Monarch Grove Sanctuary.
Cherubini blames the disproportionate decline in the P.G. sanctuary on the trimming. He predicts that the butterflies will abandon the sanctuary between mid-December and mid-January, and may not
return to it as a regular overwintering spot.
"The city itself inadvertently ruined its own butterfly habitat via the tree pruning," Cherubini writes by email. "The city could have used tree rope or wire cables to secure the dangerous branches instead of cutting them."
City Public Works Director Celia Perez Martinez has said that the low butterfly turnout this year could be due to any number of factors besides the trimming. She is awaiting a more comprehensive
assessment by Cal Poly professor Francis Villablanca.
The relative absence of butterflies in P.G. comes in the context of what appears to be a long-term decline in the western monarch population, which may be caused by a variety of factors, including
summer droughts, invasive parasites, habitat degradation and the disappearance of the Central Valley's native milkweed, the only plant on which monarchs will lay their eggs.