Risk Assessment: Tools, Techniques, and Their Applications

4.1 Introduction

Widespread ecological disasters are nothing new on Earth. The Earth has experienced countless such natural disasters over its history. One of the first such disasters that could most likely be the first step in progress toward current life forms on Earth is the advent of oxygen. Oxygen-producing organisms began spewing free oxygen into the atmosphere around 2.45 billion years ago, plus or minus a couple years (1). This free oxygen tended to oxidize iron and the resulting iron oxide precipitated out on the floors of the oceans. It thus removed the dissolved iron from the oceans. These iron deposits are mined even today (2, 3). Maybe if those inconsiderate cyanobacteria or blue-green algae had not released free oxygen into the atmosphere, there would be some other forms of life on the Earth.

The Earth has also had ice ages that have covered the entire globe or a major portion of the northern or southern hemisphere with ice. Thus, reducing the space that organisms could live to either in the depths of oceans or on land closer to the equator. The Earth has experienced hot, moist periods of time that allowed for the explosion of new plant and animal species that drastically changed the environment. In fact, what is amazing is that the Earth remained habitable for some forms of life for hundreds of millions of years.

Plants and animals, in general, have the tendency to destroy their living environment as they consume the resources they need to live. The production of ...