Читать книгу Like a Tree - Jean Shinoda Bolen - Страница 24

When I traveled to the Feathered Pipe Ranch outside of Helena, Montana, I could see from the air the indirect damage to trees brought about by climate change. There were large swaths of reddish brown running through hills that used to be covered by green trees. Montana is called “Big Sky Country” for the visual impact of vast blue skies over mountainous horizons. Only now, it was more like flying into Los Angeles on a smog-alert day. Fires set off by lightning had hit parts of the forests that were now tinderboxes.

Once on the ground and driving up through Colorado Gulch to the ranch, I could see individual rust-colored dead lodge pole pines everywhere. The cause: the pine beetle that is threatening pine forests from New Mexico to British Columbia. It is the largest known insect infestation in the history of North America. Drought and global warming together have made trees vulnerable. The black hard-shelled beetle, the size of a fingertip, drills through pine bark and digs a gallery in the wood where it lays its eggs. When the larvae hatch under the bark, they eat the sweet, rich cambrium layer and inject a fungus to stop the tree from moving sap, which could drown the larvae. The tree's vascular system (the phloem and xylem channels) is blocked, cutting off nutrients and fluids. The Latin name for the pine beetle is Dendroctunus ponderosae, which means “pine tree killer.”

To fend off an infestation, pine trees emit white resin, which looks like candle wax, into the beetle's drill hole. Sometimes the tree wins and entombs the beetle. Often, though, the attacker puts out a pheromone-based call for reinforcements and more of the beetles swarm the tree. In a drought, the tree has trouble producing enough resin, and is overwhelmed. As with infectious diseases in humans, whether a body is overwhelmed and succumbs depends on the strength of the body's immune system compared to the strength of “the bug,” the virus, bacteria, or parasite.

Drought-weakened trees lose resistance and can't fight off an infestation as well as a healthy tree, and when winters are not cold enough to freeze the eggs, they will develop into the larvae that will kill the tree in the spring. The pine forests are dying as a result, and when they die, the fire hazard increases. Summer thunderstorms bring both welcome rain to green trees and lightning that can set off raging forest fires as dead pine trees are highly flammable. Flying home from Montana, just after the autumn equinox, I hoped for a cold winter, for snow and ice that would kill the beetle eggs that were probably already in the living pines I could see out the small window in the plane.

While my thoughts were on the green trees, I was seeing them through the air pollution. As trees burn, they send smoke and particles into the air, using up oxygen and releasing carbon dioxide, one of the major greenhouse gases, which traps heat in the atmosphere and contributes to global warming. The thinning and the depletion of the ozone layer caused by pollution from man-made chemicals (chlorofluorocarbons or CFCs) reduces the ability of the atmosphere to protect living things from harmful ultraviolet radiation, which causes skin cancer and cataracts in humans. Part of Patagonia at the tip of South America lies directly under the hole in the ozone layer, where hunters report blind rabbits, and fishermen catch blind salmon. Less widely known is that ultraviolet radiation affects the ability of trees to photosynthesize, diminishing the production of oxygen.