segunda-feira, 4 de maio de 2015
Global decline of large herbivores may lead to an 'empty landscape'
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This is a mountain zebra, Equus zebra. Credit: Halska Hrabar The decline of the world's large herbivores, especially in Africa and parts of Asia, is raising the specter of an "empty landscape" in some of the most diverse ecosystems on the planet, according to a newly published study. Many populations of animals such as rhinoceroses, zebras, camels, elephants and tapirs are diminishing or threatened with extinction in grasslands, savannahs, deserts and forests, scientists say. An international team of wildlife ecologists led by William Ripple, Oregon State University distinguished professor in the College of Forestry, conducted a comprehensive analysis of data on the world's largest herbivores (more than 100 kilograms, or 220 pounds, on average), including endangerment status, key threats and ecological consequences of population decline. They published their observations in Science Advances, the open-access online journal of Science magazine. The authors focused on 74 large herbivore species -- animals that subsist on vegetation -- and concluded that "without radical intervention, large herbivores (and many smaller ones) will continue to disappear from numerous regions with enormous ecological, social, and economic costs." Ripple initiated the study after conducting a global analysis of large-carnivore decline, which goes hand-in-hand, he said, with the loss of their herbivore prey. "I expected that habitat change would be the main factor causing the endangerment of large herbivores," Ripple said. "But surprisingly, the results show that the two main factors in herbivore declines are hunting by humans and habitat change. They are twin threats." The scientists refer to an analysis of the decline of animals in tropical forests published in the journal BioScience in 1992. The author, Kent H. Redford, then a post-doctoral researcher at the University of Florida, first used the term "empty forest." While soaring trees and other vegetation may exist, he wrote, the loss of forest fauna posed a long-term threat to those ecosystems. Ripple and his colleagues went a step further. "Our analysis shows that it goes well beyond forest landscapes," he said, "to savannahs and grasslands and deserts. So we coin a new term, the empty landscape." As a group, terrestrial herbivores encompass about 4,000 known species and live in many types of ecosystems on every continent except Antarctica. The highest numbers of threatened large herbivores live in developing countries, especially Southeast Asia, India and Africa, the scientists report. Only one endangered large herbivore lives in Europe (the European bison), and none are in North America, which, the authors add, has "already lost most of its large mammals" through prehistoric hunting and habitat changes. The authors note that 25 of the largest wild herbivores now occupy an average of only 19 percent of their historical ranges. Competition from livestock production, which has tripled globally since 1980, has reduced herbivore access to land, forage and water and raised disease transmission risks, they add. Meanwhile, herbivore hunting occurs for two major purposes, the authors note: meat consumption and the global trade in animal parts. An estimated 1 billion humans subsist on wild meat, they write. "The market for medicinal uses can be very strong for some body parts, such as rhino horn," said Ripple. "Horn sells for more by weight than gold, diamonds or cocaine." Africa's western black rhinoceros was declared extinct in 2011. Co-author Taal Levi, an assistant professor in Oregon State's Department of Fisheries and Wildlife, said the causes of the decline of some large herbivores "are difficult to remedy in a world with increasing human populations and consumption." "But it's inconceivable that we allow demand for horns and tusks to drive the extirpation of large herbivores from otherwise suitable habitat," Levi said. "We need to intensify the reduction of demand for such items." The loss of large herbivores suggests that other parts of wild ecosystems will diminish, the authors write. The likely consequences include: reduction in food for large carnivores such as lions and tigers; diminished seed dispersal for plants; more frequent and intense wildfires; slower cycling of nutrients from vegetation to the soil; changes in habitat for smaller animals including fish, birds and amphibians. "We hope this report increases appreciation for the importance of large herbivores in these ecosystems," said Ripple. "And we hope that policymakers take action to conserve these species." To understand the consequences of large herbivore decline, the authors call for a coordinated research effort focusing on threatened species in developing countries. In addition, solutions to the decline of large herbivores need to involve local people. "It is essential that local people be involved in and benefit from the management of protected areas," they write. "Local community participation in the management of protected areas is highly correlated with protected area policy compliance."
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Surprisingly Simple Longevity Tests
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How can your longevity be measured?. BSIP/UIG/Getty Images Updated May 01, 2015. No one can predict exactly how long you'll live, but researchers have devised some surprisingly simple tests that are strongly correlated with a risk of early death - or a longer life - in the years to come. Here's a look at some basic ways scientists are attempting to assess your physical capability and the associated chances of living longer. 1. Sitting Rising Test: Developed in the late 1990s by Brazilian scientist Claudio Gil Soares de Araujo at Gama Filho University in Rio de Janeiro, this test simply involves going from a standing position in a small (2 meters by 2 meters) area, to a sitting position on the floor, and then rising again. Subjects are scored according to how many supports they require to perform the cycle: a point lost for using a hand, forearm, or knee, for example, to either sit or stand. Another half-point is deducted for generally unstable execution. A total of 10 points can be achieved for each full cycle. In a 2014 paper published in the European Journal of Preventive Cardiology, Araujo and others discovered that older adults had a 5-6 times greater risk of mortality during the 6.3-year followup period, if they scored only 0-3 points on the test, relative to the top-performers scoring between 8-10 points. A total of 2002 adults between the ages of 51 and 80 years participated in the study. Araujo's team writes that the Sitting Rising Test (SRT) is a simple gauge of musculoskeletal fitness, with the capacity to predict mortality among community-dwelling adults in this age range. Another version is the Chair Rise Speed Test, which calculates how many times you can rise from a chair and sit back down again, within a minute. A 2014 paper published in the British Medical Journal compared the fastest sitters with the slowest among 2766 53-year old adults. At baseline, women performed anywhere from 21 stands/minute on the low end, to almost 37 stands/minute. The range among men was just under 22 stands/minute for the low performers, to 39 stands/minute at the high end. After 13 years, those of either gender who performed poorest at the outset had more than twice the risk of death from any cause when compared with those with a higher chair rise speed at the start of the study. 2. Grip Strength: The strength of your hand grip is typically measured using an electronic dynamometer. In numerous studies a stronger grip has been linked with lower all-cause mortality, especially among older adults. In the 2014 UK study of adults aged 53, women's grip strength ranged from 21kg (46lb) to almost 34kg (75lb), while the men squeezed from 36kg (79lb) to 54.5kg (120lb). Averaged across both sexes, and taking other risk factors like body mass index, smoking status and physical activity levels into account, the 53-year olds with the poorest grip strength had anywhere from a 29% to 98% greater risk of death from any cause during the 13 years of followup. 3. Standing Balance Time: The same 2014 BMJ paper examined how long its subjects could stand on one foot with their eyes closed. The resulting times were short, with a maximum average of just 19 seconds for men, and 10 seconds for women. The good news: achieving simply those brief standing balance times was linked with lower mortality. Poor performers of the standing balance test - clocking in at just 3 seconds for both women and men - had a 2.5 greater chance of dying from any cause, during the 13-year study. 4. Sitting Height: If you think your overall height is the only tallness measure researchers are interested in, you're wrong. Sitting height, an anthropometric measurement which compares the relative proportions of the torso and legs, has been linked in Western populations to the incidence of heart disease. Greater leg length (and less relative sitting height) has been viewed as an indicator of better childhood health, which may protect against age-related illnesses like heart disease and diabetes in adulthood. Data on other ethnic populations are less clear, however; a 2007 Chinese study found that greater sitting height was linked with more diabetes and abnormal lipid levels (dyslipidemia), whereas a 2011 paper published in the International Journal of Epidemiology found no relationship between height (including sitting height) with mortality among 136,202 adults in the Shanghai Women's and Men's Health Studies. 5. Gait Speed: Can how fast you naturally walk say anything about your longevity? Yes - according to epidemiologists from the University of Pittsburgh and elsewhere, in their 2011 paper published in JAMA. The researchers examined 9 separate studies involving a total of 34,485 participants, and found that among both sexes, gait speed was linked with survival at all ages. A natural gait speed of 0.8 metres/second (about 1.8 miles/hour) corresponded with average life expectancy for each age; walking faster than that as a natural pace was linked with better than average longevity. Since walking requires energy, balance, and engages multiple organ systems to work together, the researchers suggest slower speed may indicate hidden illness or poor overall conditioning. 6. Waist to Height Ratio: Some researchers believe that waist to height ratio - calculated by dividing the waist circumference in centimetres by a person's height (also measured in centimetres) is a better predictor of disease than weight, or body mass index. The advice is simple: keep your abdominal fat down, and make sure your waist measurement is not greater than half your height. Bottom line: These tests are simple tools to measure the statistical probability of an early death, as indictors of overall health and conditioning. You can improve your own odds of living a long, healthy life by staying physically active, eating an anti-aging diet, staying active within your social circle, keeping stress at bay, not smoking, and drinking only in moderation. Build Healthy Habits for Better Longevity: Sources: C. Mary Schooling, Chaoqiang Jiang, Tai Hing Lam, G. Neil Thomas, Michelle Heys, Xiangqian Lao,Weisen Zhang, Peymane Adab, Kar Keung Cheng, and Gabriel M. Leung. "Height, Its Components, and Cardiovascular Risk Among Older Chinese: A Cross-Sectional Analysis of the Guangzhou Biobank Cohort Study." Am J Public Health. 2007 October; 97(10): 1834–1841. Cooper R, Kuh D, Hardy R; Mortality Review Group. Objectively measured physical capability levels and mortality: systematic review and meta-analysis. BMJ 2010;341:c4467. Cooper Rachel, Strand Bjørn Heine, Hardy Rebecca, Patel Kushang V, Kuh Diana. "Physical Capability in Mid-life and Survival over 13 years of Follow-up: British Birth Cohort Study." BMJ 2014; 348 :g2219 Leonardo Barbosa Barreto de Brito1, Djalma Rabelo Ricardo, Denise Sardinha Mendes Soares de Araujo, Plınio Santos Ramos, Jonathan Myers and Claudio Gil Soares de Araujo. "Ability to sit and rise from the floor as a predictor of all-cause mortality." Eur J Prev Cardiol. 2014 Jul;21(7):892-8. doi: 10.1177/2047487312471759 Stephanie Studenski, Subashan Perera, Kushang Patel et al. "Gait Speed and Survival in Older Adults." JAMA 2011;305(1):50-58. Wang N1, Zhang X, Xiang YB, Yang G, Li HL, Gao J, Cai H, Gao YT, Zheng W, Shu XO. "Associations of adult height and its components with mortality: a report from cohort studies of 135,000 Chinese women and men." Int J Epidemiol. 2011 Dec;40(6):1715-26.
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