Climate Change? Blame the Fungi!

-- How the fungi (with help from their friends, the trees) created coal and caused climate change...

With thanks to Susan Goldhor of Wonalancet Outdoor Club for this article and associated illustrations.

It seems that some folks have troubleunderstanding climate change.  Here’s asimple explanation.

Once upon a time, about 360 millionyears ago, the plant kingdom started producing trees.  Up until then, plants were limited to softer,shorter products, like moss.   The breakthroughthat made trees possible was the invention of lignin; a tough, plastic-likematerial that contributed structural strength to the cellulose that was allplants had had to work with up until then. The invention of lignin gave rise to wood and especially to bark, andonce wood and bark had been developed, plants could stand upright and treescould evolve.

When the plant kingdom inventedlignin, it behaved like a kid who discovers candy; it went overboard.  The first trees had bark that was up to 80times thicker than modern bark, and about half of that was lignin.  The problem arose when those trees reachedthe end of their lives; fungi are the major rotters of wood but at that time,no organism on earth had the ability to break down lignin, and especially notlignin in such quantities.  So, as moreand more trees died, they simply lay where they fell and turned to peat.  This long period — lasting for about 90million years — was the Carboniferous era. When the sea rose to cover the swamps, marine sediments covered the peatand, eventually, heat and pressure transformed these organic remains intocoal. 

During those 90 million years, plantssucked up enormous amounts of CO2, which was not released since they couldn’trot.  CO2 levels in the atmosphere felland O2 levels rose to a point that generated spontaneous fires.*  All that CO2 was sequestered in the deadtrees, which then became coal.  A lot ofcoal; there are carboniferous beds just below ground level that are almostforty feet deep.

Why so much?  Well, carboniferous forests were especiallyvast because sea level was lower then leaving large tracts of lowland swampavailable for plant growth.  And, sincemuch of our nation and Europe were then hanging around the equator, courtesy ofcontinental drift, we’re the ones who ended up with a lot of buried coal.

Why did the Carboniferous eraend?  Well, there were two reasons.  First, the trees calmed down in theirproduction of lignin.  They began toresemble modern trees, with thinner bark, more cellulose and less lignin.  Second, fungi figured out how to break downlignin.   Lignin is so tough (think ofbakelite, that black plastic in your grandparents’ telephones) that it can’treally be digested.  No one has developeda lignase enzyme.  What the fungi did wasto develop enzymes that generate hydrogen peroxide — a really powerfuloxidizing agent — and the peroxide literally explodes the lignin apart.  (How fungi are able to do this withoutblowing themselves apart is one of their many secrets.)  This is still the only way we know of forlignin to rot.

360 million years passed (give or takea bit).  Continents drifted.  Species arose and went extinct either singlyby natural selection or massively through great disasters.  Homo sapiens** evolved and, afterabout 150,000 years, came up with the industrial revolution.  It’s no surprise that it started first inEngland and then here, just where the two nations had been joined together onthe equator so many millions of years ago. Mills were built; engines invented; ores smelted; all powered bycoal.  More and more coal was dug up andburned; more and more was needed. Fortunes were made by those lucky enough to own land underlain bycoal.  And, as the coal burned, all theCO2 that had been sequestered in it was released.  We reversed 90 million years of theCarboniferous in less than two centuries. CO2 formed an increasing blanket over the earth, preventing heat fromdissipating and changing patterns of air flow and precipitation.  CO2 warmed the ocean, changing currents andexpanding water volume, which was already expanded by the ice that the blanketof CO2 had melted and continues to melt. (How much ice?  Well, in the lastdecade Antarctica has been losing about 250 billion tons of ice per year.  That’s one and a half trillion tons ofice added to the ocean’s water in the last ten years.  Just from Antarctica.)

And that, my friends, is how the fungicaused climate change.  It’s good to havea culprit.

Footnotes:

*These high O2 levels are the reasonwhy insects became so large.  (Dragonflies with wingspans of a yard or so seem to be the poster children for thisphenomenon.)  Insects don’t have lungs;they take in oxygen through minute holes called spiracles in theircuticles.  The entry of O2 is passive,driven by the partial pressure of O2 in the atmosphere.  The higher levels of O2 in the Carboniferousera meant that it could penetrate further and allow larger bodies.

**Why are we the only species named “sapiens”meaning intelligent?  Because we’re theonly species that got to name ourselves.