Water, Water Everywhere

Thank you for Peter Rogers's timely article on the increasing threat to freshwater resources, “Facing the Freshwater Crisis.” I was, however, disappointed in the headline “Running Out of Water” and accompanying graphic on the cover. I speak frequently to the public about water and attempt to explain the hydrologic cycle. There are several bits of information that people have consistently told me were new to them, including that the cycle works on a global scale, that so little of the planet's water is readily available for human use and that the total amount of water has been relatively stable for eons. Unfortunately, because many people do not well understand the global, cyclical nature of our water system, they believe that water is literally disappearing. We need to consistently emphasize that water availability is decreasing not because the amount of water has changed but because we are placing greater demands on the resource.

Kristan Cockerill
Appalachian State University

Starvation Solutions?

In addressing responses to hunger in “developing nations,” particularly in Africa, in “We Can Do More” [Perspectives], the editors advocate more effective aid programs (with policies to better ensure that aid reaches the poor, results in improved roads and farmer education, and affords better seeds, soil conditioning, irrigation, and so on), along with the eventual introduction of genetically modified organisms (GMOs). But these steps taken alone will only exacerbate the long-term conditions of poverty, deprivation and ecological catastrophe. The editors leave out an essential part of improving human welfare in a sustainable manner: control of population growth. To create effective long-term assistance for the poor worldwide, you must first target aid to support government policies that promote family planning and responsible procreation.

Ed Middleswart
Pensacola, Fla.

GMOs are not the solution to Africa's hunger. The editors' support of their use is based on the faulty premise that there is not enough food to feed the world and if only we could increase crop yields, people would not starve. Hunger is primarily a political and economic problem. The original green revolution was an overall failure for the poor throughout the world, and I have little hope for a new GMO-based green revolution. Patented seeds and the chemical pesticides and fertilizers they require benefit the large agribusinesses and not the hungry of developing countries.

Catherine Clarkin
Long Beach, Calif.

Aura of Mystery

“Why Migraines Strike,” by David W. Dodick and J. Jay Gargus, claims that 30 percent of migraine sufferers experience an aura (illusions of sparks and lights, often followed by blind or dark spots in the same configuration), whereas 100 percent experience headache. For the past 30 years I have experienced the aura once or twice a year. But I never get a headache.

David E. Ross
Oak Park, Calif.

THE AUTHORS REPLY: As many readers have suggested, aura symptoms may occur without headache. With increasing age, it is not uncommon to retain the aura but lose the headache or to develop aura symptoms without a prior history of headache. This phenomenon has been referred to as “late-life migraine accompaniments” or “migraine equivalents.” The International Headache Society recognizes it as “typical aura without headache” and notes that some individuals, primarily men, only ever experience the aura.

Although the reasons for the dissociation of aura and headache are unclear, several facts are worth noting: First, aura may occur with primary headache disorders besides migraine, and an aura can occur in patients with structural brain lesions. Second, the tendency to experience aura may be inherited as a trait that is distinct from the inherited tendency to experience recurrent attacks of migraine headache and its other associated symptoms.

The reason aura is more common in migraine sufferers (30 percent) than in the general population (1 to 2 percent) may be that the physiological consequences of one trigger the symptoms of the other when the two traits coexist. For example, cortical spreading depression (CSD) can activate trigeminal pain fibers and may trigger a migraine headache in migraine sufferers. In those not predisposed to migraine, CSD may lead to a mild nonmigraine headache or to no headache. Conversely, the putative brain stem generator for migraine may generate changes in metabolic activity of cortical neurons and glia, altering cerebral blood flow, which may trigger aura symptoms in an individual predisposed to CSD. The reason for aura symptoms' connection with age is unknown. Future research will, we hope, unravel this mystery.

▪ Benefits to Burning?

“The Puzzling Inferno,” by Keren Blankfeld Schultz [News Scan], discusses the finding that suppressing forest fires reduces carbon sequestering because frequent fires favor the growth of more mature trees, which store carbon more effectively. The story refers to prescribed fires as a solution, but other news media have reported the severe health effects of smoke from this year's wildfires. Frequent harvesting of immature trees and dead debris would also promote growth of mature trees. A good, technical assessment on the costs and benefits of forest burnings is sorely needed.

Dick Windgassen
Venice, Fla.

ERRATUM “The Puzzling Inferno,” by Keren Blankfeld Schultz [News Scan], incorrectly describes the physical characteristics of trees. The measurements of 90 centimeters and between 10 and 30 centimeters refer to the diameters of the stems, not the heights. The article also states that larger trees are often the victims of drought partly because they require more oxygen. There is currently no evidence linking oxygen requirements to drought susceptibility.

CLARIFICATION “A Glimpse of the Past” [Updates] reports that FUNAI, Brazil's National Foundation for Indigenous Peoples, had used a low-flying airplane to photograph an indigenous tribe in Amazonia that had never been contacted by the modern world. Although the tribe is not known to have been contacted, Jos Carlos Meirelles of FUNAI has admitted that its existence was already known and that he sought to photograph the group to create publicity about the existence of such tribes in the area and to thereby protect their habitat from the threat of logging.