Australia: The Land Where Time Began

A biography of the Australian continent 


Aerobacter spp.

Aerobacter bacteria are released into the atmosphere from the leaves of trees during transpiration. It has been found that these bacteria are responsible for the rain formed by the air rising from rainforests, the bacterial cells forming the nuclei around which raindrops form. It has been known for many years that forests, in particular rainforests, alter the climate downwind from them, now Dr Mary White said the sustainable science team, based in Canberra, found that the bacteria are very important in the process of rain formation. The bacteria are released by all broad-leafed plants, but rainforests are much more efficient emitters than other vegetation types. The clouds formed by the condensation around the bacterial particles don't just increase the amount of rain, but contribute greatly to the albedo of the planet, the amount of sunlight, and hence heat, that is reflected back into space, and keeping the temperatures of the earth comfortable.

Global Warming

It has been known for some time that it is necessary to reduce the amount of carbon dioxide, methane and nitrous oxides in the atmosphere to try to halt continuing global warming. It is also known that the reduction of greenhouse gases alone is not sufficient to keep the temperatures down, a number of other factors influence the climate - cloud cover, by reflecting solar radiation (heat) back into space, the albedo of land and water surfaces. Again, the reflectance of radiation, the transfer of heat to the upper atmosphere from the surface of the Earth, via evaporation and/or transpiration of water from foliage, in that it governs the amount of heat, that is not trapped by greenhouse gases, that is re-radiated to space. And finally the levels of greenhouse gases in the atmosphere. These gases include water vapour, that accounts for 60 %, carbon dioxide 20 %, methane and nitrous oxide combined account for 20 %.

At least 2 scientific expeditions to the Arctic Ocean have recently reported large areas of the ocean where methane is bubbling to the surface from the methane ice that is currently trapped in the permafrost, beneath the sea as well as on the land. The scientists were studying the expected increased concentrations of methane in sea water, but were shocked to see that it is being released so rapidly that large patches can been seen in the sea, as well as in lakes, where it is bubbling to the surface and dispersing into the atmosphere. As methane is 20 times more potent than carbon dioxide as a greenhouse gas, and considering the vast quantities of methane present in the permafrost, it has the potential to contribute a much larger fraction to the warming than it presently does. This is another good reason for the addition to the atmosphere of greenhouse gases to be reduced. Whether caused by fossil fuel burning or not, the increasing temperatures of the oceans are leading to the release of  increasing amounts of methane from the permafrost. This is an observable fact, no longer a theory or a prediction.

In past episodes of global warming, when it could only have been the result of natural processes, there were vast areas of forest and expanses of ocean containing algae that could eventually help bring the temperatures back to the sort of levels preferred by humans. This is no longer the case. Most of the rainforest of the Earth, and probably even more of the non-rainforest broad-leafed vegetation, has been removed for various reasons. This has now been shown to have potentially a much greater effect than previously believed, before the role of bacteria released from foliage in cloud formation was known.

It has previously been found that rainfall over areas of rainforest was higher than over other areas, and it was not always the result of high ground (orographic effect). In Western Australia it can been seen that natural woodland areas tend to have more rain than areas cleared for agriculture. These drier agricultural areas are often closer to the coast were the air tends to be more humid than further inland, so would previously have received more rainfall.

Sources & Further reading

  • Mary E. White, The Greening of Gondwana, the 400 Million Year story of Australian Plants, Reed, 1994


Biological Options for Mitigating Global Warming: A Sustainability Science Discussion Paper


Author: M. H. Monroe
Last updated 04/01/2015
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