Beyond the Last Ice Age - Global Good Times for our Species
Temperatures on planet Earth have been relatively stable for the last 10,000 years or so. During this time human civilization has flourished. For ninety percent of our species time on this planet, we have lived nomadic lives, small groups moving to find food and water. Sedentary farming, the formation of permanent communities were only possible once climatic conditions permitted regular rainfall, and appropriate growing conditions for food crops and the raising of livestock. It may be difficult to grasp this point, especially when a hurricane (Irene) is threatening to sweep up the eastern seaboard of the United States and parts of East Africa are experiencing the worst period of drought for the last twenty years or so, but when we view climate trends using the geological time scale it can be concluded that we are living in the most benign and settled global climate that the Earth has experienced for the last 250,000 years. Ten thousand years ago, a cold glacial period (our planets most recent Ice Age) came to an end, between then and now our species H. sapiens has prospered almost unlike any other type of mega fauna in the long history of terrestrial life. From just a few million ten thousand years ago our population has increased over the last hundred years at an astonishing rate. By 1970, the United Nations estimated that there were as many as four billion people living on planet Earth, this year (2011) statistics that provide an estimation of human population put the figure close to seven billion. Some scientists have postulated that by 2030 the human population could reach nine billion. Perhaps Thomas Malthus had a point.
Earth's Amazing Biodiversity
A team of international scientists have been trying to calculate just how rich and diverse life on planet Earth really is. Calculating the total number of species alive today is important; without this knowledge scientists would be unable to accurately measure the decline in biodiversity as a result of climate change and other factors. Research has shown that humans as a species are having a considerable global impact. The greenhouse effect has been well documented, our influence on climate has grown dramatically ever since the Industrial Revolution and our burning of fossil fuels such as coal, oil and natural gas does not seem likely to diminish given the expected rate of human population growth. The destruction of habitat, the amount of waste we produce, the conversion of wild areas over to farming - all are having an impact on other organisms that share our world. Unfortunately, our true impact is difficult to measure unless scientists can calculate with a degree of accuracy how many species share the world with us at the moment.
The research team, included scientists from Dalhousie University (Nova Scotia), Microsoft Research, the Department of Geography at the University of Hawaii and the United Nations Environment Programme World Conservation Monitoring Centre based in eastern England. They have published a report on their research estimating that at present there are approximately 8.7 million species on planet Earth, plus or minus 1.3 million, a margin of error for their extremely complicated calculations. The margin of error may seem quite large, however, this has to be expected as when viewed in context we simply have not studied in detail a great many of the species on our planet, or indeed explored much of the habitats where organisms live. For example, we know more about our moon than we do about the abyssal plain that covers a significant proportion of the bottom of the world's oceans.
Putting 8.7 million species (+/- 1.3 million) into Perspective
Previous estimates regarding Earth's biodiversity have varied widely. In the mid 1970s it was estimated that there were around one million species of insects on planet Earth, we know now that this seriously underestimates insect biodiversity. Other estimates for the total number of species have put the figure at around 100 million, when considered alongside this new research these figures look like a little excessive. The truth is no one is really sure, there is a background extinction rate and new species are evolving all the time. However, this new research, utilising an analysis of known aspects of Linnaean hierarchy, at least provides a starting point for our assessment on the impact of our species on the rest of life on Earth.
A point worth making is that the international team did not set out to assess all life on our planet. Their analysis only covers what is termed those organisms that fit into the domain known as Eukarya. Eukarya are organisms that have a membrane bound cell nucleus. In effect, the scientists have assessed the total number of plants, animals and fungi on our planet. The calculations do not include those organisms that first evolved, hundreds of millions of years before the first Eukaryotes - bacteria and those organisms that are classified in the domain known as the Archaea.
The Sixth Mass Extinction Event - It is All Around Us
One of the intriguing aspects of this new research, is that it used the hierarchical classification of organisms first proposed by the 18th Century Swedish physician Carolus Linnaeus to calculate the total number of species. In simple terms, the international team of scientists looked at the known members of the Linnaean Hierarchy from the Eukarya Domain right down to species level and used statistical analysis to fill in the gaps to produce their final figures. Their study reveals that some 86% of all terrestrial species and approximately 91% of all marine species await formal scientific description.
Being unsure as to how many species we share planet Earth with has a number of consequences. One of these consequences is that if we don't know what we are starting with it is very difficult to calculate current extinction rates. One of the authors of this new study, published in an online scientific journal commented that the recently updated Red List issued by the International Union for the Conservation of Nature assessed 59,508 species, of which 19,625 are classified as threatened. This means the Red List, the most sophisticated continuous analysis of extinction rates, monitors less than 1% of world species.
Palaeontologists studying the fossil record are aware that the history of life on our planet has experienced a number of "booms" and "busts", mass extinction events alongside a background level of extinctions and a gradual level of new species origination. During the entire Phanerozoic Eon, the period of visible life that extends from approximately 545 million years ago to the present there have been five major mass extinction events. The most famous of these is the Cretaceous mass extinction that occurred around sixty-five million years ago and resulted in the demise of the dinosaurs. With this new assessment of the biodiversity of Earth scientists can use this information as the basis upon which to establish current extinction events. Here is the bad news, many biologists now believe that at this time we are living through a sixth mass extinction event, with as many as three species an hour going extinct. That is 26,280 species dying out every year. What is worse the rate of species destruction seems to be increasing, certainly over the last forty years or so.
The causes for this extinction, whether human influenced or not, are not going to matter in the long-term. Those organisms at the top of the food chain, apex predators such as ourselves for example tend to be the most vulnerable. We primates had better enjoy ourselves whilst we can as we may not be around much longer.
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