ECOSCIENCE AFTER NUCLEAR WAR

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Paul Ehrlich (Bing Professor of Population Studies and Professor of Biological Sciences, Stanford University) and Anne Ehrlich (Senior Research Associate, Department of Biological Sciences, Stanford) are familiar names to ecologists and environmentalists everywhere. But while most folks are aware of the Ehrlichs' popular writing in the areas of ecology and overpopulation (most of us for instance - have read Paul's book The Population Bomb), few people have any idea of how deeply the Ehrlichs are involved in ecological research (the type that tends to be published only in technical journals and college texts). That's why we're pleased to present this regular semi technical column by these well-known authors/ ecologists/educators.

by Anne and Paul Ehrlich

Recent studies indicate that our previous evaluation of the ecological impact of nuclear war (in MOTHER NO. 71) was probably much too optimistic! Put simply, the potential effects of the production of huge amounts of smoke and dust (resulting from a nuclear attack), upon which we speculated in our earlier column, have now been subjected to the scrutiny of atmospheric scientists. And the results of that research are frightening.

The most thorough of these studies owes its inspiration, in part, to a catastrophe that occurred long before Homo sapiens arrived on the scene. About 65 million years ago, at the transition between the Cretaceous and Tertiary geological periods (it's called the KT boundary), a number of groups of unspectacular microscopic marine creatures went extinct quite suddenly. Furthermore, the last of the dinosaurs accompanied them into oblivion.

The cause of the K-T extinctions-as well as the actual speed with which they took place remains rather controversial. One recent hypothesis suggests that they were the consequence of a thick cloud of dust that was thrown into the atmosphere by the impact of a gigantic meteor. A good bit of interesting geological evidence supports this theory, too, and it-in turn-has stimulated scientific consideration of the potential climatic (and other) effects of suddenly introducing massive amounts of particulate matter into the atmosphere.

A COMPLICATED SYSTEM

Of course, evaluating the effects of such a hypothetical event is far from simple, partly because the workings of the atmosphere are not yet completely understood. In particular, predicting the results of relatively minor atmospheric changes is often impossible. However, the effects of major changes can sometimes be more readily calculated (for example, the primary differences between winter and summer are easily forecast).

Today, projections produced by computers are made with models that are very simplified, compared with actual weather systems, and carry uncertainties about the effects of even large-scale disturbances. Nonetheless, such projections can provide valuable insights into the climatic results of atmospheric changes.

Once the investigation of massive particulate injections into the atmosphere was stimulated by interest in the K-T extinctions, it was a logical step to apply computer analysis to the meteorological consequences of an atomic war. This is precisely what a small group of physical scientists did. A draft paper based on their work was subjected to the scrutiny of a conference of leaders in that field this past April, and the results were then immediately presented to a group of distinguished biologists. Both meetings were closed to the public in order to prevent the premature release of tentative conclusions.

The authors of the paper on atmospheric effects-R.P. Turco, O.B. Toon, T. Ackerman, J.B. Pollack, and the well-known astronomer Carl Sagan-gave the document the lugubrious (and, unfortunately, appropriate) acronym TTAPS. The TTAPS conclusions can be summarized briefly: If a nuclear exchange exploded as little as 100 megatons (about 1% of the combined megatonnage contained in U.S. and Soviet strategic arsenals), it could produce sufficient dust and smoke to prevent 99% or more of the sunlight from reaching the Earth's surface for weeks!

We do want to emphasize the word "could", because of the many variables involved. While as little as 100 megatons -if distributed over cities in a manner that would maximize soot producing fires might produce such a catastrophe, a larger war that expended 5,000 to 10,000 megatons would be far more likely to bring about a worldwide "blackout". Yet even in a larger war, the size and altitude of the explosions could produce a variety of effects. High-yield ground bursts-used to dig out the enemy's missile silos-would inject vast amounts of dust into the upper atmosphere (the stratosphere), and smaller air bursts used against cities and troops-would ignite huge, widespread fires, injecting soot into the lower layer of air (the troposphere).

The characteristics of these two layers are very different. The troposphere is relatively well mixed vertically, and particles in it usually settle out rather rapidly. The stratosphere, in contrast, is quite stable, and particles tend to remain in it for a long time. But the presence of huge quantities of dust and soot could change those characteristics, possibly even destroying the division between troposphere and stratosphere!

The degree to which atmospheric effects would spread from the Northern to the Southern Hemisphere would be determined by the geographic placement of the nuclear bursts and by what happened to the structure of the atmosphere. A final uncertainty is that the simple TTAPS model doesn't include the effects of atmospheric motions. Nevertheless, despite its built-in uncertainties, the study's basic findings have recently been supported by a more complex, dynamic model run by Dr. Stephen H. Schneider's group at the National Center for Atmospheric Research.

A GAME WITH NO WINNERS

Basically, then, TTAPS and related studies can't tell us precisely what will happen in an atomic war . . . but they can tell us what consequences can't be ruled out. Such "worst case scenarios" are vitally important to decision makers (and to the rest of us!) . . . and the TTAPS description of the possible effects of a war fought largely in the Northern Hemisphere is enough to make any sane strategist forget all about "winning" a nuclear battle.

The blocking of incoming solar radiation would produce severe climatic disturbances, the most important of which would be a pronounced surface cooling of the globe . . . especially in the continental regions of the Northern Hemisphere. In a matter of weeks, the average temperature could drop to far below freezing and remain very low for months. (The Schneider group's model also shows that in three weeks much of this land area would be plunged into below-freezing weather ... even in the month of July!) And the TTAPS study predicts that, for as long as a year after the war, temperatures might remain subnormal. At worst, the planet's entire surface would be dusky or dark at noon . . . and most land areas would be in the grip of temperatures well below the freezing point.

The biologists who were consulted were unanimous in their opinion that any war that caused widespread cooling and darkness would have no less than a catastrophic impact on natural and agricultural ecosystems. (Again, however, the precise nature of the consequences would depend on such unknowns as the season in which the war broke out and the degree to which atmospheric changes spread southward.) The combination of freezing cold with light levels too low to permit photosynthesis would destroy most of Earth's growing vegetation . . . upon which all animals, including people, are completely dependent. Much of the flora, especially in temperate zones, would eventually regenerate from seeds and roots, but by then most of the animals would be beyond saving. Standing crops in the Northern Hemisphere that survived fires would be destroyed by the freezing temperatures and lack of sunlight.

As all the streams, rivers, and lakes froze, water would become scarce. Low light levels would reduce the productivity of the ocean, too. And all of these disasters would occur in combination with the presence of toxic smog over the entire Northern Hemisphere . . . higher levels of radiation than previously forecast . .. and a variety of other assaults on both people and ecosystems (many of which we discussed in our earlier column).

DOWN THE PATHOF THE DINOSAURS

If you put all this information together, just what have you got? Well, you have a rather clear idea that-after a nuclear warcivilization would have almost no chance of surviving in the Northern Hemisphere. The vast majority of its inhabitants would be dead . . . and those not killed outright by blast, fire, and lethal radiation would quickly succumb to exposure, thirst, starvation, disease, or radiation sickness in the freezing, smoggy darkness.

You can also see the likelihood of an epidemic of sudden extinctions of nonhuman organisms even more dramatic than the one that occurred at the K-T boundary. Finally, you may now have the chilling suspicion that humankind itself might be pushed rapidly down the path to oblivion once trod by the dinosaurs.

The basic results of the TTAPS study and the conclusions of the biologists are summarized in two manuscripts recently submitted to Science magazine. A more detailed discussion of post-war ecological effects can be found in Paul's chapter in The Counterfeit Ark: Crisis Relocation for Nuclear War edited by Jennifer Leaning and Langley Keyes. The book is available in paperback for $11.95 postpaid and in hardcover for $28.00 postpaid from Ballinger Publishing Company (Dept. TMEN, P.O. Box 281, Harvard Square, Cambridge, Massachusetts 02138).

The Ehrlich's work is supported in part by a grant from the Koret Foundation of San Francisco.

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