Like a Tree. Jean Shinoda BolenЧитать онлайн книгу.
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.
Easter Island
In Collapse: How Societies Choose to Fail or Succeed, Jared Diamond's description of what happened to Easter Island could be a scenario for planet Earth if we continue to cut down or lose the trees and the population increases. (Diamond, a professor of geography at UCLA, was awarded the Pulitzer prize for Guns, Germs, and Steel: The Fate of Human Societies.) Easter Island is an all-by-itself island in the Pacific Ocean. Chile is 2,500 miles (4,020 kilometers) to the east; the Pitcairn Islands are 1,300 miles (2,090 kilometers) to the west. It is small, only 66 square miles (226 square kilometers), a mere dot in the vast ocean. It is now a barren place, famous for numerous mysterious and massive strange stone statues. These are look-alike huge heads with long ears and prominent noses and chins on legless male torsos carved from volcanic rock.
When Polynesian settlers arrived around 900 CE, Easter Island was covered with dense forests. There were twentytwo different kinds of trees, including the largest palm tree ever to exist in the world. We know about the species of trees from palynology, the study of pollen. Samples are obtained by boring out a column of sediment, the age of each layer is dated by radiocarbon methods, and then through tedious microscopic work, pollen is examined, counted, identified, and compared with pollen of known species. We know about the palm tree from fossil nuts that turned out to be very similar, but larger than those of the world's largest existing palm tree, the Chilean wine palm, which grows up to sixtyfive feet (about twenty meters) tall and three feet (.9 m) in diameter. Fossilized casts of the Easter Island palm trunks and root bundles found buried in the lava flow from a few hundred thousand years ago proved that the Easter Island palm, with a trunk that was twice the girth of the Chilean palm, would have dwarfed it. While it existed, the biggest, most magnificent palm tree in the world could be found on Easter Island. Reading this brings to mind the threat to the old growth redwood trees in California, which are the tallest and largest trees in existence now.
The Polynesians who settled on Easter Island found trees that provided lumber to build houses, thatch for roofs, and strong rope. There were big trees whose trunks could be made into seagoing canoes, hardwood trees from which harpoons were made, trees that provided wild fruit and nuts, and the wine palm whose sap could be fermented. The islanders had all they needed to live well. They prospered, and as they grew in numbers, they used more wood and cut down their forests to clear land to grow crops as well.
Like Shel Silverstein's Giving Tree, the trees of Easter Island kept giving and giving until there was no more that could be taken. Once trees go, further loss follows. Through the hydrologic cycle, trees transpire water into the atmosphere and attract rain. Trees provide a habitat for birds, animals, insects, fungi, and microscopic life. Trees protect soil from erosion by wind and rain, and make more soil as their roots break rock into gravel and their leaves compost into organic matter.
The growth of the economy and the population growth based on what trees provided on Easter Island could not be sustained. Diamond describes how deforestation and wind led to a disastrous erosion of the topsoil. Six hundred years after the first settlers arrived, the population of Easter Island had grown to between six thousand and thirty thousand and there were more mouths to feed than food. Widespread starvation led to a descent into cannibalism and the population died off.
When the Dutch explorer Jacob Roggeveen came upon the almost deserted and barren island on Easter Sunday, April 5, 1722, the few human survivors and the mute, mysterious, and monumental stone heads (the moai) were all that remained. The trees had all been cut down. Since Roggeveen first sighted Easter Island, there has been fascination, speculation, and fairly extensive study about the moai. There had apparently been competition between priests or chiefs to outdo each other in erecting larger and larger stone heads, as the size of the moai increased over time. There were hundreds in various stages of completion in the volcanic quarries, some were found as if abandoned near the roads, and every single one of those that had been erected had been toppled, many deliberately felled so that they would break at the neck. The moai were erected on elaborate, large platforms built of stone (ahu) and always faced inland. It's a surprise to learn that the heads that we see in photographs of Easter Island were re-erected much later, and never faced the sea as they do in the pictures.
Deforestation of Earth
Once upon a time, like Easter Island, most of Earth was covered with forests. Almost half of the United States, threequarters of Canada, almost all of Europe, and much of the rest of the world were forested. Most of the deforestation occurred in Europe, North Africa, and the Middle East prior to this century. The United States was logged extensively. Most old growth forests, particularly in the East, were clearcut by 1920. Now old growth trees and forests are being cut at an accelerated rate in the tropical rain forests and boreal rain forests. Deforestation is a major contributor to global warming. Al Gore, in his 2009 book, Our Choice: A Plan to Solve the Climate Crisis, wrote that 20 percent of carbon emission is due to deforestation—more than the amount produced by all of the world's cars and trucks combined.
Easter Island is an extreme example of deforestation. People object to the idea that the islanders created their own downfall. Surely, they wouldn't be so foolish as to cut down all their trees, when the consequences would have been so obvious to them? Jared Diamond comments that this question nags everyone who has wondered how it happened, including himself. He writes: “I have often asked myself, ‘What did the Easter Islander who cut down the last palm tree say while he was doing it?’ Like modern loggers, did he shout ‘Jobs, not trees!’? Or: ‘Technology will solve our problems, never fear, we'll find a substitute for wood’? Or: ‘We don't have proof that there aren't palms somewhere else on Easter, we