Posts Tagged ‘photosynthesis’

What living things on Earth have been in existence the longest? I don’t mean which individual animal or plant has lived the longest, such as species of coral or sponge that are known to have been living upwards of 2,000 years, or terrestrial animals such as tortoise that have lived for over 150 years. Nor plants such as the bristlecone pine from North America, one of which is 5,062 years old (measured by ring count), nor the Llangernyw Yew in the churchyard of the village of Llangernyw in North Wales, one of the oldest individuals tree in the world, and believed to be aged between 4,000 years and 5,000 years old. I mean what life forms have been in existence the longest and are still living today?

stromatolites, shark bay, western australia

Stromatolites in Shark Bay, Western Australia

The answer is Stromatolites (or stromatoliths). These are rare rock-like structures found in just a few hypersaline lakes and marine environments around the world, and which, from the fossil record, are known to have been in existence for some 3.5 billion years. They existed in abundance after the earth had been formed when there were no animals or plants.  Because they were prodigious photosynthesizers, their waste product, oxygen, entered the atmosphere in great quantities, making the earth suitable for other forms of life. Over time, organisms developed that grazed on stromatolites, and by the end of the Pre-Cambrian Period (about 570 million years ago), they numbered only 20% of their peak.

Stromatolites are created by the accumulation of photosynthesizing cyanobacteria (often incorrectly called blue-green algae). These bacteria are prokaryotic bacteria, and are neither algae nor plant. When they colonize to form a stromatolite, they number some 3 billion organisms per square metre. The bacteria secrets a mucus coating that traps sediment, and calcium carbonate precipitates from the water providing a hard, cement-like material to fuse the sediment together. New cyanobacteria grow over the sediment and over time a rock-like structure is formed.

fossil stromatolites, cross section, 1.8 billion year old, great slave lake, canada

Cross section of 1.8 billion year old fossil stromatolites from rock formations at Great Slave Lake, Canada

Scientists had long known about stromatolites from the fossil record, but were surprised to find them still in existence, when they were discovered in 1956 at Shark Bay, Western Australia (now the Hamelin Pool Marine Nature Reserve). Other places where stromatolites are found are Lagoa  Salgada, Rio Grande do Norte in Brazil and two inland sites in Mexico at Cuatro Cienegas and Lake Alchichica. Unexpectedly, there is one marine site that is not hypersaline, Exuma Cays in the Bahamas.

And according to the BBC, a very young colony of stromatolites, just a single layer thick, was found at the Giant’s Causeway in Northern Ireland in 2011.

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Financial markets are gambling trillions of dollars on a bet that governments will never seriously curb carbon emissions say Mike Berners-Lee and Duncan Clark in The Burning Question: We can’t burn half the world’s oil, coal, and gas, so how do we quit? published by Profile. Why do they claim this? Because to address climate change would mean leaving most of the remaining fossil fuels in the ground. But that would mean the future value of the fossil-fuel energy companies falling to a fraction of their current market valuation. In any event, sudden action forced on governments by a period of catastrophic climate change and food shortages would cause the collapse of the energy industry, far greater than the banking crash of 2008. Something will have to give.

The authors explain the maths very well. CO2 in the atmosphere has now reached 400 parts per million from 280 ppm in pre-industrial times. The switch to renewable energy has so far had no impact upon global carbon emissions (since this book’s publication, figures released for carbon emissions show that in the UK, emissions went up by 3% in 2012, the highest in Europe). What is the amount of fossil fuels we can safely burn to stay within the agreed 2 degree C rise in average surface temperatures above which the lives of millions of people are a risk. The answer is 565 gigatonnes of CO2 by 2050. But established reserves of fossil fuel are 2,795 gigatonnes, and the 565 gigatonne emission limit will be hit by 2030.

Areas of the UK with potential shale gas

Areas of the UK with potential shale gas

And this does not allow for the dramatic increase in potential shale gas fields world-wide. In the UK, estimates of reserves of shale gas are continually being revised upwards, with claims that just the fields in the north of Englad could meet UK energy needs for five years. In the USA, the extraction of shale gas is welcomed, it is cheaper and it is the solution to their dependency on imported oil from dictatorial regimes. So it’s carry on as normal. (more…)

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