10 million trees dead in the Sierra… and counting


An aerial detection survey conducted this past summer in many of California’s forests has revealed that more than 10 million trees are dead or dying in the central and southern Sierra Nevada Range. The findings of the study conducted by a team of Forest Service researchers were released December 7 in the “Forest Health Protection Aerial Detection Survey.”  

What is surprising to some observers is that tree mortality continues to increase and dramatically in some areas even though these locales have received significant rainfall in the past 90 days. The recent rainfall has had little or no effect in undoing the impact of four consecutive years of drought.

The study area for the central and southern 2015 survey was conducted primarily in Sequoia, Kings Canyon, and Yosemite national parks  and Inyo, Sierra,  Stanislaus, and Humboldt-Toiyabe national forests, as well as portions of Sequoia  and Eldorado national forests along with some state and private lands along the western foothills. 

Aerial surveys of the project area were begun in July 2015 but had to be delayed because of smoke and safety concerns created by this summer’s Rough Fire. The survey crew mapped recently dead or currently stressed trees using a digital aerial sketch-mapping system while flying in a light, fixed-wing aircraft approximately 1,000 feet above ground level.

Data recorded included the species affected and estimated number of recently killed trees and noted any other defoliation or die-back. More than 8.5 million acres were surveyed; significant mortality was found to be present on 613,000 acres.

Pine mortality in particular was severe and became more widespread as the survey proceeded south. Ponderosa pine is the most common component of the lower mixed conifer type and was also the most impacted species. Sugar pine and other conifers also showed significant damage.

In the higher elevations, red fir, Jeffrey, sugar, and lodgepole pine exhibited heightened rates of mortality. Scattered live oak and gray pine mortality was also pronounced in the low-elevation foothills.

Drought-induced discoloration and defoliation of blue oak and other oak species was noted as “severe” on private lands in the lower-elevation foothills. On the east side of the Sierra, Marssonia leaf blight was common on quaking aspen and willow in many locales.

Requests for more information and questions about the findings of the survey may be directed to Jeffrey Moore via email at jwmoore02@fs.fed.us or by calling (530) 759-1753. 

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