48 



or that the same forest ecosystem will emerge. That may be more related to the con- 

 ditions under which the trees died, and the environmental conditions for a decade 

 or two following, than it is to the "site" involved. This is consistent with the "chaos 

 theory, which holds that many events and trends in nature are shaped by the 

 events and trends that happen to be occurring around them at critical times. Tree 

 seedlings trying to grow during a long drought will probably fail; the fact that they 

 happened to sprout during a (fry period instead of a wet period is a random event, 

 but a critical one that may determme the forest's fate for centuries. 



When.anewforeat is becoming e8tablished,^.8mall_change8 in environmental con- 

 ditions tend to be magnified. It's like starting across the ocean on a slightly wrong 

 bearing; by the time you reach the other shore, you'll be a long ways fi-om your in- 

 tended destination. Likewise, a new forest that starts up with a different nutrient 

 cycle or micro-climate regime may be vastly different than the forest that preceded 

 it. 



A new forest that suffers repeated re-bvuns during the seedling establishment 

 years, or that hosts an unusually high population of grazing animals, may turn into 

 grassland or a brush field, and trees may not return for decades, or centuries. If 

 the soil conditions and climate change enough, that ecosystem shift could go so far 

 as desertification and be, so far as we know, permanent. Some of today's deserts 

 were once thriving forests, but they won't be again without major climate change 

 or human intervention. , . , 



Most of the species that live within an ecosystem live out of sight, and many of 

 the critical processes that drive the system are also invisible. Our observations and, 

 for the most part, our scientific inquiry, have focused on the parts and processes 

 we can see. So we know a lot about trees and how they grow, about large wildlife, 

 and about how watersheds react. We don't know nearly as much about the little 

 brushy species, or soil organisms, or liow carbon arid nutrients cycle through the 

 species and the system. But some of those "minor" species, and the processes in 

 which they play a vitel role, may be a critical key in keeping the whole system 

 healthy. 



GLOBAL CHANGE 



The industrial age has resulted in a rapid and continuing buildup of atmospheric 

 gases such as carbon dioxide, methane, and chlorofluorocarbons. Those gases work 

 m the atmosphere to trap heat in a somewhat similar manner to the glass on a 

 greenhouse, thus the concern over "greenhouse gases" and the "greenhouse effect. 

 Industrial processes also emit oxides of nitrogen and sulfur into the atmosphere that 

 have changed atmospheric chemistry and altered the nutrient input into natural 

 and managed ecosystems. Some of these compounds may also have a climate impact; 

 probably a net cooUng Uiat may have helped offset the effect of rising greenhouse 



gas levels. , , , • • jix- i. 



Science has a hard time with these issues, because what s happenmg is difterent 

 than anything that happened in the past, and it is happening on a global scale, so 

 there's no way to carve off a little piece, move it into the laboratory, and test it for 

 certainty. We can't replicate events to prove cause and effect, so the debate reste 

 on theories and models which, while absorbing the world's most sophisticated com- 

 puters, are still, in the words of their operators, "very crude approximations of 

 what really goes on in the world. 



In spite of all that uncertainty, the likelihood of significant climate change is too 

 high to ignore, primarily because the potential effects on human societies could be 

 so enormously disruptive. When the stakes are high enough, even a small prob- 

 ability of occurance is enough to send us scrambUng tor our insurance company. 



"Global warming," as it is often discussed, is not the most serious threat. An aver- 

 age rise of 1-3° Cby 2050, which most scientists feel is Ukelv, would mask signifi- 

 cant regional changes, most of which cannot be predicted with current models. And 

 it will proceed, if those predictions are correct, at a speed with which natural proc- 

 esses may not be able to cope. 



Regional effects that reduce precipitetion and increase summer temperatures will 

 be the most important to agricultural and forest production. Those are felt to be 

 most Ukely in mid-continentel regions at mid- to upper latitudes, such as the United 

 Stetes, Canada, and Russia. Some changes, such as a warming expressed primarily 

 as an increase in winter minimum temperatures, might be of little impact. 



Natural forests may have a hard time adjusting to the rate of climate change, 

 which many feel will be 3 to 10 times faster than the fastest recorded species migra- 

 tion rates. Another aspect of changing and unstable climate conditions will almost 

 certeinly be an increased occurance of mtoor hurricanes and wind storms, which can 

 increase the area of forest destroyed each year by natural events. 



