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    • Read the Amazon article that is attached, it is on recent fires and its relation to deforestation in this week’s session and discuss the role of Government environmental policies in avoiding such large scale forest fires.

ENVIRONMENTAL POLICY from the proportions and the known half- life of the uranium, he and his colleagues could calculate an age. They ended up with a date of 2.229 billion years old, plus or minus 5 million years. Amazon fires clearly linked to deforestation, scientists say That puts the impact at a turbulent time in Earth s history. Life had existed for more than 1 billion years, but photosynthetic life Brazilian government deflects blame for rise in fire activity cyanobacteria living in shallow waters-was a recent evolutionary invention, one that triggered a sharp rise in atmospheric oxy- gen about 2.4 billion years ago. Previously, high levels of methane in the atmosphere had generated a greenhouse effect that warmed the planet. But many scientists think the methane was destroyed by chemi- cal reactions with Earth s first ozone, pro- duced when ultraviolet light from the sun struck the oxygen molecules. They suspect loss of methane sent Earth crashing into a set of severe and long-lived ice ages, even at low latitudes. Three or maybe four of these icy episodes took place between 2.45 billion and 2.22 billion years ago, which means Australia might have been covered in ice at the time of the Yarrabubba impact. Scientists have assumed that volcanic eruptions ended the ice ages, by belching carbon dioxide and warming the planet. But Erickson and his colleagues speculate that Yarrabubba could have helped. They modeled the effect of a 7-kilometer-wide as- teroid striking an ice sheet between 2 and 5 kilometers thick. They found the impact could have spread dust thousands of kilo- meters, darkening ice and enhancing its ability to absorb heat. It also would have sent half a trillion tons of steam into the stratosphere orders of magnitude more water vapor than in today s stratosphere- where it would have trapped heat. By Herton Escobar B razil s government claims its policies aren t responsible for the fires that are ravaging the Amazon rainforest and triggered worldwide indignation last week. President Jair Bolsonaro suggested nongovernmental orga- nizations were setting the forest ablaze to discredit his government; his minister of the environment, Ricardo Salles, tweeted that dry weather, wind, and heat were to blame. Scientists dismiss those claims. There is no doubt that this rise in fire activity is as- sociated with a sharp rise in deforestation, says Paulo Artaxo, an atmospheric physicist at the University of So Paulo in So Paulo. Thousands of fires occur in the Amazon annually, but the numbers have risen since Bolsonaro became president on 1 January and began to encourage development. In satellite images, Brazil s National Institute for Space Research (INPE) counted more than 41,000 fire spots between 1 January and 24 August, compared with 22,000 in the same period last year. The Global Fire Emissions Database, a collaboration be- tween NASA s Goddard Space Flight Center in Greenbelt, Maryland and two universi- ties, sees a similar trend. The numbers are the highest since 2010, when the Amazon Deforestation can, at least partly. To clear land for farming, settlers fell trees, remove valuable timber, and then set fire to the re- mainder. Recent INPE data showed defores- tation to be on the rise, although Bolsonaro called the numbers a lie and had INPE Director Ricardo Galvo fired (Science, 2 August, p. 419). The 10 municipalities with the highest rate of fire activity are also the ones where the forest disappeared most rapidly this year, according to the Amazon Environmental Research Institute in Belm, Brazil. And many of the recently detected spots are active for more than a day, burn- ing with intense heat and producing tall, thick, smoke pillars-all indicators that trees are on fire, not overgrown pastures, crop residues, or roadside vegetation. Bolsonaro has so far rejected interna- tional pressure to protect the rainforest. He hurled insults at Norway and Germany after they suspended contributions to the Amazon Fund, which supports conserva- tion and sustainable development, and re- fused $20 million offered by the G-7 nations to help fight the fires. But facing mount- ing criticism at home, Bolsonaro ordered the military to help combat the fires and made a 5-minute TV address to profess his deep love and respect for the Amazon and promise that his administration would act Downloaded from http://science.sciencemag.org/ on February 13 PHOTO VICTOR MORIYAMA/GREENPEACE and 2.22 billion years ago, which means Australia might have been covered in ice at the time of the Yarrabubba impact. Scientists have assumed that volcanic eruptions ended the ice ages, by belching carbon dioxide and warming the planet. But Erickson and his colleagues speculate that Yarrabubba could have helped. They modeled the effect of a 7-kilometer-wide as- teroid striking an ice sheet between 2 and 5 kilometers thick. They found the impact could have spread dust thousands of kilo- meters, darkening ice and enhancing its ability to absorb heat. It also would have sent half a trillion tons of steam into the stratosphere orders of magnitude more water vapor than in today s stratosphere- where it would have trapped heat. Andrey Bekker, a geologist at UC Riverside, doubts that the water vapor would have per- sisted for the centuries needed to thaw Earth. I m not convinced that by itself it could do this job, he says. Christian Koeberl, an im- pact expert and the director general of the Natural History Museum in Vienna, shares those doubts, but says paleoclimate research- ers need to model the effects explicitly. If the Yarrabubba impact did thaw the planet, allowing life to reclaim icy conti- nents and oceans, it wouldn t be the first example of life benefiting from a cosmic blow, Koeberl says. Although the public tends to associate impacts with extinctions, he notes that impacts 4 billion years ago could have jump-started life. Asteroids de- livered phosphorus, a key nutrient, and the impacts also created the protected, energy- rich hydrothermal systems where some biologists believe life began. Impacts can be bringers of life, impacts can be destroy- ers of life, he says. no doubt that this rise in fire activity is as- sociated with a sharp rise in deforestation, says Paulo Artaxo, an atmospheric physicist at the University of So Paulo in So Paulo. Thousands of fires occur in the Amazon annually, but the numbers have risen since Bolsonaro became president on 1 January and began to encourage development. In satellite images, Brazil s National Institute for Space Research (INPE) counted more than 41,000 fire spots between 1 January and 24 August, compared with 22,000 in the same period last year. The Global Fire Emissions Database, a collaboration be- tween NASA s Goddard Space Flight Center in Greenbelt, Maryland and two universi- ties, sees a similar trend. The numbers are the highest since 2010, when the Amazon. experienced a severe drought triggered by El Nio and a warming of the North Atlan- tic Ocean. This time, climatic anomalies can t explain the uptick, scientists say. spots are active for more than a day, burn- ing with intense heat and producing tall, thick, smoke pillars-all indicators that trees are on fire, not overgrown pastures, crop residues, or roadside vegetation. Bolsonaro has so far rejected interna- tional pressure to protect the rainforest. He hurled insults at Norway and Germany after they suspended contributions to the Amazon Fund, which supports conserva- tion and sustainable development, and re- fused $20 million offered by the G-7 nations to help fight the fires. But facing mount- ing criticism at home, Bolsonaro ordered the military to help combat the fires and made a 5-minute TV address to profess his deep love and respect for the Amazon and promise that his administration would act strongly against the blazes. Herton Escobar is a science journalist in So Paulo, Brazil. A forest fire in Altamira, in Brazil s Par state. President Jair Bolsonaro has rejected help from G-7 members. ed from http://science.sciencemag.org/ on February 13, 2020