Going: One planet
The Earth Summit on the environment opens today in Rio de Janeiro. But looking at all the damage that man has done, the delegates have their work cut for them.
MAN has always exploited nature in the belief that the all-encompassing biosphere, the seamless, wondrously resilient fabric of life, land, water and air, was so vast and enduring, people could never do it basic harm.
Events of the last decade shattered that comforting perception.
The moment of awakening may have come in the mid'80s when governments finally accepted and acted on the evidence that waste industrial chemicals were weakening the stratospheric ozone shield that protects living things from the Sun’s harmful ultraviolet rays.
But that is almost the least of it. Scientists say that human beings have now transformed the biosphere on so many fronts that Man rivals grand forces like the movement of continents, volcanic eruptions, asteroid impacts and ice ages as an agent of global change.
The transformation has sharply escalated in both scale and pace since World War II. And it is raising serious questions not only about the ability of nature to sustain the global economy, but also about the future of the biosphere itself. That is why delegates from around the world are preparing to gather at an Earth Summit today in Rio de Janeiro, Brazil.
Delegates at Rio hope to sign legally binding treaties to cope with the threats of climate change and species extinction. They also hope to adopt a statement of principles and an agenda for action to prevent broad damage to the biosphere while accommodating the economic needs of the surging population.
The question of limits to economic and population growth has come to the fore once again. But this time, it has been joined by the newer and more pressing question of the degree to which the biosphere is in jeopardy.
Scientists are still struggling towards an answer in each case. Until now, humans have always been able to push back the physical limits imposed on their expansion by the rest of the biosphere.
When limited food supplies have threatened to check the proliferation of people, for instance, people have employed technology and social organization to grow crops and then clear forests, plough grasslands and, finally, harness science to agriculture.
Humanity has not repealed the laws of ecology, but it has bent them; it continually expands to fill its ecological niche, then stretches the niche — at some cost to other elements of the biosphere.
No, argue Donella Meadows, Dennis Meadows and Jorgen Randers, three authors of the "limits to growth" thesis propounded 20 years ago under the sponsorship of the Club of Rome, an informal group of academics, civil servants and business leaders.
The thesis, based on cornputerised simulations of the workings of the global ecosystem, held that limits to growth on the planet would be breached within a century and that a sudden and uncontrollable decline of population and industrial capacity would ensue. Damage to the biosphere’s natural resources were one element in the predicted collapse.
In a new book called Beyond The Limits, the three authors argue that if human activity continues as at present, it will "overshoot" the carrying capacity of the biosphere and cause a collapse within the next few decades.
The new analysis puts more emphasis on deterioration of the biosphere, and Dennis Meadows said that it convinced., him that less time is available to halt the expected collapse than had earlier been thought.
He said that 20 years ago, "it seemed to us there was a period up to 2030 or 2040 in which to fashion a sustainable society. Now, it looks as if unless a new set of attitudes and policies are In place in the next 20 years, it will be too late to avoid an eventual collapse". — NYT
Reasons for concern
• People have transformed or manipulated ecosystems constituting about half the planet’s ice-free land surface and have made a significant impact on most of the rest.
• They have used about 40 per cent of the photosynthetic energy produced by plants.
• They have steadily reduced the number of other species in the world through pollution, hunting and destruction of natural habitat. Now, as the inroads become deeper and more widespread, many biologists fear that human activity could bring about a mass extinction of epic scale, wiping out 25 per cent of the world’s remaining species in the next 50 years.
• By burning coal, oil, natural gas and trees they cut down, Man has altered the global flow of energy within the biosphere. Atmospheric concentrations of heat-trapping carbon dioxide have increased by 25 per cent since pre-industrial times — well above levels recorded at any other time in the last 160,000 years — and catastrophic warming of the Earth could take place.
• Global population, which was 2.5 billion 40 years ago, is expected to reach six billion by the year 2000 and swell to perhaps 10 billion 60 years from now. - NYT
Ozone hole did not form in the Arctic
DESPITE earlier fears, an ozone hole did not form over the Arctic last year. But, said scientists, the threat would reappear each year because of man-made pollutants in the upper atmosphere.
The record levels of chlorine and other ozone-depleting chemicals found over parts of Europe, Russia, Canada and the United States apparently were prevented from doing their worst by unusually warm winter air.
Using measurements taken by space satellites and aircraft, scientists with a US National Aeronautics and Space Administration (Nasa) atmospheric study programme said levels of protective ozone in the northern latitudes dipped about 20 per cent below normal this winter.
Said Dr James Anderson of Harvard University, the study’s chief scientist, at a briefing: "It is not an ozone hole." But he added: "Is it a significant loss of ozone? Yes it is."
Dr Joe Waters of Nasa’s Jet Propulsion Laboratory, said a rise in stratospheric temperatures in January apparently eliminated polar stratospheric clouds filled with tiny ice crystals. These crystals promote high levels of the most potent ozone-destroying chemical, chlorine monoxide.
Conditions in the upper atmosphere are in a very delicate balance, Dr Waters said. "With so much chlorine in the stratosphere, a slight temperature difference can make an enormous difference in the potential for ozone depletion."
Ozone is a form of oxygen that protects the Earth from harmful ultraviolet radiation from the Sun. Some scientists and environmentalists fear that depletion of atmospheric ozone as a result of human pollution will result in an increase in skin cancer, cataracts and impaired immune systems, as well as disruption of plant growth.
The layer of ozone between the altitudes of 14km and 50km is believed to be under attack by natural and man-made chemicals that drift up into the stratosphere. Destructive chlorine from chlorofluorocarbons, chemicals used in refrigerants, and the bromine compounds created by the use of halons in fire suppressants, are believed to be the chief culprits.
In February, researchers in Nasa’s Airborne Arctic Stratospheric Expedition said their satellite and aircraft readings showed alarmingly high levels of chlorine monoxide and bromine monoxide, the most potent ozone destroyers, over Europe, Asia and North America north of 50 degrees latitude.
The ideal conditions for ozone depletion are high concentrations of chlorine and similar chemicals, extreme cold, sunlight and time for chemical reactions to take place.
Dr Anderson said that although unusual warmth interfered with the process, it is increasingly likely that Arctic ozone levels will decline substantially during cold, protracted winters. — NYT
Source : The Straits Times, June 3, 1992
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