Question

1.) This forests in California provides 60% of the state's drinking
water and is an important carbon sink for the entire planet.
Unfortunately, it is threatened by pest, fire, urbanisation and
mining interests. Hummingbirds are one of the remarkable
features of this forest.​

Answer 1

Answer:

Forest pests and diseases are a natural part of a forest ecosystem. While most native pests or pathogens occur at low population or infection levels, there are times when they can become epidemic. Of particular concern is watching out for introduced pests and pathogens that can cause substantial problems. Forest management can influence habitat and survival of pests and pathogens.

Forest pests and disease affect forest fuels and wildfire, by killing trees and other vegetation and making them more susceptible to ignition and severe Wildfire. Bark beetles related tree mortality has followed California's multi-year drought that began in 2010 and has been especially pronounced in the Southern Sierra Nevada where most of the affected forests are federally owned and managed. However there are many cabins on USFS leases as well as private parcels where dead trees now present public safety hazards. UC's publication on bark beetles, Bark Beetles (Seybold, Paine, and Dreistadt 2008), provides excellent information on beetle identification and control. They point out that "except for general cultural practices that improve tree vigor, little can be done to control most bark beetles once trees have been attacked." Techniques to improve tree vigor such as thinning to bring tree water use in line with available water supply and thereby reduce drought stress at the individual tree level, providing irrigation water to high value trees, involving specialists to apply behavioral chemicals in traps or repellents, and other chemical controls are described in the UCANR IPM publication.

North American Boreal Forests