National Geographic : 1990 Aug
NATIONAL GEOGRAPHI MAGAZINE AT LMNC"AUUT19 Greening of an Argentine City, a Century Old The millions of trees planted a few months ago as part of Earth Day activities will not seriously affect Global pollution for years. It's worth the wait, say citizens of Men doza, Argentina. Each year a mature tree can con sume as much as 50 pounds of carbon dioxide, one of the major contributors to the greenhouse effect. A city of 660,000 on a formerly tree less plain at the foot of the Andes, Mendoza began a tree-planting pro gram after an earthquake leveled the town more than a century ago. Today the "City of Trees" counts as many trees as inhabitants, a ratio matched by few metropolises in the U. S. Planted for shade in a time of car riages and pedestrian traffic, the large sycamores and white mulberries are believed to reduce air pollution by nearly one-third. Mendoza's natural air conditioning also provides relief from the dust and direct sun of the nearby desert. Buried "Marshmallows" Save Irrigation Water Electronic snoops are growing in popularity among farmers con cerned about overwatering their Crops. Buried near plant roots, marshmallow-size gypsum blocks con taining electrodes soak up moisture at about the same rate as the surrounding soil. A wet block conducts more elec tricity than a dry one. When a charge is sent from a portable metering device through the sensors, farmers can deter mine when the roots need water. Excessive irrigation depletes the groundwater supply, increases runoff of farm fertilizers and pesticides, and SERGIOPENCHANSKY promotes salinization of the soil. When introduced in the 1940s, the gypsum block found little market, be cause water was cheap and plentiful. Today it isn't; farmers in 17 western states, who use about 85 percent of their area's annual water supply, can't afford to waste the precious resource. "To make sure their crops don't dry out, farmers have tended to over water," says Gail Richardson of IN FORM, an environmental research group. "These sensors have cut down water use by 20 to 40 percent a field." With startup costs under $500 and per-acre costs averaging a dollar in ensuing years, one California farmer saved $18,000 in expenses. Another increased his alfalfa yield by $124 an acre, because he did not damage the plants by overwatering. Getting to the Root of the Firewood Problem oots of common gourds could serve as cooking fuel in under developed countries, reducing Street and shrub loss caused by gathering firewood. Some 60 percent of women in the Third World spend one day a week scavenging scarce fuel, adding to deforestation, say Eugene B. Shultz, Jr., and Wayne G. Bragg of Washing ton University in St. Louis, Missouri. Their laboratory tests have shown that the taproots of gourds and squashes of the Cucurbitaceae family, after being dried in the sun, burn more efficiently than wood. Women in Mexico, Sene gal, and Niger tried the fuel and de clared it highly satisfactory. The plants, found in North and Cen tral America, Africa, and India, grow in nutrient-poor soils. Most are inedi ble. Noel Vietmeyer, research scientist for the National Academy of Sciences, has called the concept "innovative and farsighted." Prairie Winds Blowing Help to the Sioux he persistent wind that sweeps across the South Dakota plains could change the financial climate Sof the Oglala Sioux, who want to sell wind-generated electricity to power companies. An agreement signed with Wintec, Ltd., of North Palm Springs, Califor nia, calls for construction of 400 wind powered generators on the Pine Ridge Reservation, one of the poorest re gions in the United States, where annu al incomes average $2,800. Electric bills often consume more than half of a family budget because of high rates and drafty housing. Each 80-foot-high windmill could power 33 homes on the reservation, but the electricity will go instead to area utility companies. They must, under federal law, buy power produced by independents at competitive prices. Royalties from the sale of electricity plus rent paid by investors for the ground where the windmills stand are expected to bring hundreds of thou sands of dollars annually to the 18,000 member tribe. To help the Oglala reduce their per sonal electric bills, Wintec has offered to install small windmills at individual homes, with payment coming out of the family's monthly savings in electric ity costs. "If the windmills reduce a monthly billby $300, the customer pays us $150 toward the cost of the machine [about $4,000] until it is paid for," says MARY L. KLINGER Jim Dowty, a Wintec engineer and an Oglala Sioux himself. Tribal members find no conflict with Sioux tradition in harnessing Tatiya the wind-to produce income, says Dowty. "Indians believe anything put on the earth is a gift. You shouldn't destroy it, but you should use it."