The Earth is no stranger to calamity:- tsunamis and earthquakes are relatively small occurrences when compared to some of the upheavals experienced by the planet – magnetic reversals, change of rotation axis, impacts by meteors, ice ages, changes in sea level of 100’s of feet, submersions of continents, uplifting of sea-beds, temporary global cooling caused by volcanic effluent – 1815, the “Year without a Summer”, after Tambora erupted – the Earth has seen it all in the 4.5 billion years of its existence.
Humans and other creatures, however, living in much shorter timescales, may never experience any of these phenomena, and consequently regard a period of temporary stability as normal and permanent. This is most often the cause of their undoing, for when disaster strikes, they are totally unprepared.
Note that although a species itself may not be directly threatened, if the food supply is disrupted, it will die of starvation anyway.
Scientists define five global mass extinctions in the past 500 million years. Three of these are thought to have been caused by meteor impacts. (M)
|Period||Million yrs ago||Percentage of species lost|
Without Man’s intervention, the Earth would normally be getting cooler at this time, as the next glaciation (subdivision of an Ice-Age) is expected to start. In fact, however, the opposite is occurring – Earth is getting warmer, and the available evidence clearly shows that it is Man’s activity that has caused the reversal.
Furthermore, it is also clear that Man’s influence was taking effect before the Industrial Revolution, but since that time the influence has become even more pronounced, and is gathering pace.