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n November 2008, millions of avid fans were tuning in to watch their favourite celebrities battle it out on Strictly Come Dancing. Meanwhile, the Earthwatch Institute was holding its own Strictly Come Species event, “Irreplaceable — The World’s Most Invaluable Species.” Irreplaceable is a complex concept in terms of terrestrial organisms. It is both subjective and timesensitive; ask a Tyrannosaurus rex about irreplaceable species and it would tell you the world could not do without its favourite snack, an herbivorous hadrosaurid. We must also appreciate that the judgement is from our very human perspective — not from that of a cow, an oak tree or a mamavirus, to which very different organisms would be essential. Just like Strictly Come Dancing, the ‘Irreplaceable’ debate is part-popularity contest, but with an added measure of scientific argument. There are between 90 and 225kg of microbes per acre of good agricultural soil and, according to estimates, the total mass of microbial life on Earth is so large it is almost incalculable. In fact, microbes account for an estimated 5-25 times the total mass of all animal life and almost the mass of plant life (animals account for a measly one thousandth of the Earth’s biomass). It comes as little surprise, then, that two of the five contenders were microbes — fungi and plankton. The creatures themselves were unable to self-represent due to insurmountable communication difficulties (the waggle-dance is an excellent way for honeybees to exchange messages, but most humans would find it difficult to understand. Chemical signals are perfect for plankton but don’t project so well in a room at the Royal Geographical Society). So scientists were asked to debate on behalf of their preferred species using a language that we can all understand.
The debate Dr Kate Jones of the Zoological Society of London thinks one of the reasons bats should be protected is their diet — some bats consume tonnes of insect pests, quashing the need for pesticides. Dr Jones was keen to draw attention to the “extraordinary uniqueness” and variety exhibited by bats, which range from the size of a bumblebee to a flying fox. They are the only mammals capable of powered flight and account for one in five mammalian species. Bats communicate via a sonar system using the loudest (ultrasonic) noises in nature. They are also used as headline indicator species; ecologists monitor them closely as they give an early warning if other species are in danger.
How irreplaceable are microbes?
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Some 20,000 species of bee have evolved extremely close symbiosis with 250,000 species of flowering plants, started Dr. George McGavin of Oxford University Museum of Natural History. Three quarters of our agricultural crops are also pollinated by bees. In 2005 the total economic value of bee pollination was estimated to be £130 billion, representing 10% of the world’s food value. Despite their economic and ecological value, “Bee populations all around the world are in freefall… this trend is expected to continue.” March 2009
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