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Drought and Beetle Impacts to Native Trees in the Santa Monica Mountains

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Rosi Dagit

Published May 2019 in International Oaks No. 30: 169–176


Since 2014, hundreds of native trees (alders, oaks, sycamores, willows) in the Santa Monica Mountains have died, mostly due to the drought, but many are also victims of the Euwallacea sp. (invasive shot-hole borer)/Fusarium complex (ISHB) and a pathogen newly carried by Pseudopityophthorus pubinpennis (western oak bark beetle; WOBB). Concerned about the ecological implications of massive native-tree loss, the Resource Conservation District of the Santa Monica Mountains (RCDSMM) initiated a citizen-science-based study of drought impacts in 2015 using 41 randomly selected plots measuring 625 m2, tagging over 350 trees in critical park areas. The trees are located near the urban/wildland interface throughout the western Santa Monica Mountains National Recreation Area. This effort was augmented in 2017 by the deployment of 46 homemade beetle traps in sensitive riparian areas to monitor direction and rates of spread of invasive beetles, and to document tree responses. Concurrently, this data provided on-the-ground information used in a NASA DEVELOP Project using remote-sensing tools and satellite data to help understand the landscape-level impacts over time. Results show that extensive drought impacts occurred in 2015, followed by increased loss associated with invasive pathogens in 2016-2017. To date, infected tree removal is the only recommended way to reduce impacts from reproductive host trees. The RCDSMM is working with regional and local parkland managers and other concerned stakeholders to develop a more appropriate and realistic management strategy for urban/wildland interface trees to meet the forecasted challenges of a changing climate.


Quercus agrifolia, coast live oak, drought, invasive shot-hole borer, western oak bark beetle


Anderegg, W.R.L., J.M. Kane, and L.D.L. Anderegg. 2012. Consequences of widespread tree mortality triggered by drought and temperature stress. Nature Climate Change. Review article published online: September 9, 2012. doi: 10.1038/NCLIMATE1635.

Carnicer, J., M. Coll, M. Ninyerola, X. Pons, G. Sanchez, and J. Penuelas. 2011. Widespread crown condition decline, food web disruption, and amplified tree mortality with increased climate change-type drought. PNAS 108(4): 1474-1478.

Dagit, R., S. Contreras, R. Dauksis, A. Spryka, N. Queally, K. Foster, A. Nickmeyer, N. Rousseau, and E. Chang. 2017. How can we save our native trees? Drought and Invasive Beetle Impacts on Wildland Trees and Shrublands in the Santa Monica Mountains. Topanga and Pasadena, CA: RCD of the Santa Monica Mountains and NASA JPL.

Eskalen, A., R. Stouthamer, S.C. Lynch, P.F. Rugman-Jones, M. Twizeyimana, and T. Thibault. 2013. Host Range of Fusarium Dieback and its Ambrosia Beetle (Coleopter: Scolytinae) Vector in Southern California. Plant Disease 97(7): 938-651.

Federico, F., S. Ostermann-Kelm, C. Brigham, and P. Bunje. 2012. A Collaborative Science Agenda on climate Change for Southern California Coastal National Parks. Natural Resource Report NPS/MEDN/NRR-2012/583. Fort Collins, Colorado: U.S. Department of the Interior, National Park Service.

Hüve, K., I. Bichele, B. Rasulov, and Ü. Niinements. 2011. When is it too hot for photosynthesis: heat-induced instability of photosynthesis in relation to respiratory burst, cell permeability changes and H2O2 formation. Plant, Cell and Environment 34(1): 113-126. doi:10.1111/j.1365-3040.2010.02229.x

i-Tree. 2017. www.itreetools.org. Accessed November 2017. 

Ma, S., J.L. Osuna, J. Verfalliee, and D.D. Baldocchi. 2019. Photosynthetic responses to temperature across leaf-canopy-ecosystem scales: a 15-year study in a Californian oak-grass savanna. Photosynthesis Research 132(3): 277-91. doi: 10.1007/s11120-017-0388-5. Epub April 19, 2017.

Monahan, W.B., and N.A. Fisichelli. 2014. Climate Exposure of US National Parks in a New Era of Change. PLOS ONE 9(7): e101302. doi.org/10.1371/journal.pone.0101302. 

Swain, S., A. Eskalen, S. Lynch and S. Lathan. 2017. Scolytid beetles and associated fungal symbionts threaten California hardwoods. Western Arborist Spring 2017: 54-60.

U.S. Drought Monitor. 2018. National Drought Mitigation Center (NDMC), the U.S. Department of Agriculture (USDA), and the National Oceanic and Atmospheric Administration (NOAA). 

Tietje, W.D., W. Weitkamp, W.A. Jensen, and S. Garcia. 1993. Drought takes toll on Central Coast’s native oaks. California Agriculture 47(6): 4-6.