Editorial Could wildlife survive a nuclear winter? More than 100 scientists attending the Con- 10,000-megaton war. In this case, immediately ference on the World after Nuclear War were after the explosion an estimated 30 per cent of the unanimous in concluding that a large-scale northern hemisphere mid-latitude areas would nuclear war would gravely and permanently receive a dose of radiation comparable to or more damage the ecosystems of the world. The find- than the acute mean lethal dose for healthy adult ings presented at the conference, which took humans. In the weeks after, fallout would carry place between 31 October and 1 November radiation to 50 per cent of the northern mid- 1983 in Washington DC, detailed effects far latitudes and months of darkness and sub-freez- worse than any which have been predicted ing temperatures would follow. Photosynthesis previously. would cease, cutting off the food base of eco- systems. Animals would die from starvation or Two of the conference's key papers have since from exposure. Thick ice would cover bodies of been published in Science*. One, entitled freshwater. In the tropics temperatures and light Nuclear Winter: Global Consequences of levels would also fall, sufficiently to decimate Multiple Nuclear Explosions, describes the many tropical species. The year that follows could potential global atmospheric and climatic con- witness the extinction of many tropical species, sequences of nuclear wars of magnitudes ranging the collapse of marine ecosystems that depend on from 100 to 10,000 megatons. All the nuclear phytoplankton, the loss of a huge number of exchanges within this range would, the authors freshwater species and terrestrial vertebrates. predict, create a pall of smoke and dust that After the dust and smoke settle, survivors would would quickly encircle the earth. After a 10,000- suffer damaging doses of ultraviolet radiation megaton exchange they calculate that light would from the sun through destruction of the ozone be reduced to approximately one per cent of layer. normal and that land surface temperatures in continental interiors could fall to -40°C. It would Although this picture results from considering the take at least one year for light and temperature effects of a large-scale nuclear exchange, it is by values to recover to normal. But even a 'small- no means the worst that could be imagined given scale' attack, using bombs totalling 100 megatons the present world nuclear arsenal. And a war of a (and equal to only 0.8 per cent of the combined more limited extent would have qualitatively strategic arsenals of the world) could, if the bombs similar effects. The possibility exists that darkened were dropped on major urban centres, where the skies and low temperatures could envelop the resulting fires would be enormous, create suf- entire planet and the majority of the world's ficient smoke to obscure the sun for weeks and to species could become extinct. In that event, the depress surface temperatures to well below freez- authors conclude, 'the possibility of the extinction ing (from -15 to -25°C) for many months. of Homo sapiens cannot be excluded'. The effects would not be confined to the northern With such findings before us and with such terrify- hemisphere—where it is assumed that a war is ing prospects ahead, it seems no longer possible most likely to take place. The large differences in that biologists or conservationists anywhere in the temperature gradients, caused by the absorption world can avoid becoming involved in the nuclear of sunlight by dust and smoke clouds, could dis- debate. turb global circulation patterns and result in the transport of nucler debris to the southern hemi- *The two papers referred to here are : Turco, R.P., Toon, sphere. O.B., Ackerman, T., Pollack, T.B. and Sagan, C. 1983. Science, 222, 1283, and Ehrlich, Paul R, Harte, John, In the paper, Long-Term Biological Con- Harwell, Mark A., Raven, Peter H., Sagan, Carl, Woodwell, sequences of Nuclear War*, the 20 authors trans- George M., Berry, Joseph, Ayensu, EdwardS., Ehrlich, Anne H., Eisner, Thomas, Gould, Stephen J., Grover, Herbert D., late these climatic changes into their significance Herrera, Rafael, May, Robert M., Mayr, Ernst, Mckay, for the living organisms of the earth. They take the Christopher P., Mooney, Harold A., Myers, Norman, worst of the range of scenarios studied, the Pimentel, David and Teal, John M. 1983. Science, 222,1293. Editorial 65

Downloaded from https://www.cambridge.org/core. IP address: 170.106.33.19, on 03 Oct 2021 at 17:48:30, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1017/S0030605300018718