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A Comparison of Yeast Cultures and Human Globalized Society from an Ecological Perspective

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Edited by Neal Grout, Thursday, 18 Mar 2010, 18:36

A Comparison of Yeast Cultures and Human Globalized Society from an Ecological Perspective

 

“Are Humans Smarter than Yeast?” Bob Shaw

 

Introduction

On an individual basis your average man can out smart, and out run, a typical yeast cell. But what about on a communal level? What are the similarities and differences between our modern human society and yeast colonies in regards to environment, growth and sustainability?

Ecological Definitions

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From an ecological perspective a species is considered to be in overshoot of its environment when the population exceeds the carrying capacity of said environment. Carrying capacity is the maximum number of individuals of a given species that an environment can support. To exceed the carrying capacity a surplus energy resource is needed to do so. A drawdown of the surplus resource then takes place while the population of organisms grows.  At the same time degradation of environment occurs as waste products build up. The resource is, at an exponential rate, eventually used up by the growing numbers of the organism and the environment is degraded from the effects of pollution. The species, no longer able to support its numbers because there is insufficient energy or because the environmental degradation can no longer support them, experiences a crash in numbers. The die off takes the population down lower than the original starting number of organisms because the environment has been degraded and the carrying capacity therefore reduced. (The Language of Ecology)

Mead

Mead was a tradition drink made in many parts of the world especially where a Northerly climate did not allow good grape production. Although not often made commercially due to ingredient costs, mead making is still popular for small time enthusiasts (myself included) because of its ease of production and usually gives a good quality end result.

The main ingredients to make mead are honey, water and yeast. At a basic level the fermentation process begins by creating the must. This is the water/honey solution, the energy source needed, that the yeast will ferment in, the ration being 4 or 5 to 1 respectively. The must is stored in a sanitized container called a carboy. It is essential the carboy is clean so the yeast can ferment without having to compete with other micro organisms. The must is almost always acidified because a slightly acidic environment is conductive for yeast growth but not so for other micro organisms such as bacteria. It’s important that the must is oxygenated in the beginning of fermentation because the yeast will for the first few days grow aerobically before later convert to anaerobic production.

The yeast is pitched into the carboy and begins to multiply. Its population grows exponentially, doubling in size every 90 minutes (Pines, 2001), making a drawdown on the sugars in the honey to feed and reproduce whilst at the same time producing the waste products, Carbon Dioxide and Alcohol.  C02 is released from the carboy through an airlock system. This is necessary as any build up of gas within the carboy can cause it to eventually explode especially when fermentation is vigorous. The alcohol level builds over time within the carboy. This is the byproduct looked for to produce an alcoholic beverage but it is at the same time detrimental to the yeast producing it. The yeast degrade their own environment with the pollution they themselves make.

 

 

A Tale of Two Yeast Colonies

Depending on whether a sweet or dry mead is wanted, two different species of yeast are used. For  sweet mead, Saccharomyces cerevisiae and for dry Saccharomyces bayanus respectively.

S. cerevisiae; Leaves 2-3% residual sugar in most meads. Rich, fruity profile complements fruit mead fermentation.


Flocculation: Medium
Temperature Range: 65-75°F, 18-24°C
Alcohol Tolerance: 11% ABV

S. bayanus; Low foaming with little or no sulfur production.


Flocculation: Low-medium
Temperature Range: 55-75°F, 13-24°C
Alcohol Tolerance: 18% ABV

We can see above that S. cerevisiae does not have the same level of alcohol tolerance as S. bayanus. Unable to tolerate the alcohol it has produced S. cerevisiae experiences a die-off because of it’s over polluted environment. This leaves residual sugars in the final product, therefore creating a sweet mead.

On the other hand S. bayanus can tolerate the increasing alcohol levels but is then able to make a complete drawdown on the sugars in the must and therefore also experiences a die-off. With no residual sweetness, dry flavored mead is created. (Wyeast Laboratories, Inc)

We can see above then that there are two distinct possibilities for a yeast population die off, degradation of environment and resource depletion, each equally as devastating to the yeast population as the other.

 

Our Global Society in Comparison

Human population has been growing exponentially, doubling approximately every 40 years, and currently stands at 6.793 billion people. The growth rate of 1.19% increases the world population by 77 million per year. (International Database Information Gateway, 2009)

What evidence do we have to show that humanity is in overshoot of its environment, the Earth?

 

Environmental Degradation

Global Warming: Humanity adds carbon dioxide to the atmosphere through the use of fossil fuels such as petroleum, natural gas and coal, which increases in concentration over time as is evident from the Keeling curve. Carbon dioxide is by far the largest greenhouse gas emitted by human activity (along with methane and nitrous oxide) and is the prime agent affecting global warming and climate change. (Weart, 2007)

Climate Change: The latest core sample evidence suggests climate change can happen drastically when tipping points occur, altering weather patterns and atmospheric temperature within months. (Leake, 2009)

Water pollution:  Excess fertilizer run off from modern intensive agriculture in the form of excess nitrogen fertilizer creates dead zones in coastal regions. Fresh Water Rivers become polluted due to industrial processes making the water unfit for human consumption and killing native wildlife. (Dead Zone (Ecology))

Soil Erosion: Intensive modern agriculture strips the soil of its nutrients which then have to be replenished artificially using nitrogen made from natural gas and mined potash and potassium. Soil also suffers from erosion especially when tilled and during deforestation. Urbanization reduces land available for agriculture. (Draggan, Soil Erosion, 2008)

Desertification:  Spreading desert reduces the available land usable for agriculture and reduces biodiversity. This then leads to human populations migrating (Draggan, Desertification, 2008)

Sea Ice loss:  An indirect consequence of climate change. The melting of Arctic sea ice reduces the albedo effect and increases global warming creating a feedback loop. Current models predict Summer Arctic sea ice will completely disappear within the next decade. (NSIDC)

Glacial Melt:   Millions of people, especially in Asia and South America, rely on glacial melt water for drinking and irrigation of crops. (Glacier retreat and disappearance)

Chemical Toxicity:  Poisoning (McGinley, 2009)and feminization (Lean, 2008)can affect people and wildlife on many levels from dumped industrial waste materials to unsafe consumer goods. Bioaccumulation means species higher in the food chain (humans) suffer most from persistent organic  pollutants.

Biodiversity Loss: loss of wildlife is currently 50 to 500 times above background rate according to IUCN figures (International Union for the Conservation of Nature). In an effort to increase crop yields many species previously used in agricultural production have become extinct.

 

 

Resource Depletion

Deforestation: Wood is used as a fuel and building material. Forests are cleared for agricultural production. When large areas of forest are cleared this can also alter the local climate by increasing temperature and reducing rainfall.  Deforestation has been implicated in the fall of previous civilizations including the Maya (Fall of the Maya), Nazca (Coghlan, 2009)and Easter Islanders (Diamond, 1995).

Fossil Fuel Use: Industrialization has only been possible since the introduction of high energy sources such as fossil fuels. Of the three, crude oil, natural gas and coal, crude oil production is due to peak within the next decade. Petroleum fuels 95% of world transport infrastructure (Anderson, 2009).

Metal and Mineral Depletion: many of these are now at the point where extraction takes place from deep mines and/or from poor quality ores which require large amounts of energy. (Cohen, 2007)

Aquifer Depletion: Aquifers worldwide are being depleted much faster than they naturally replenish making it ever more difficult to irrigate crops. China, India, and the United States along with a number of other countries where water tables are falling, are home to more than half the world’s population. There are two types of aquifers: replenishable and nonreplenishable (fossil) aquifers. Most of the aquifers in India and the shallow aquifer under the North China Plain are replenishable. When these are depleted, the maximum rate of pumping is automatically reduced to the rate of recharge. (Brown, 2007)

Fisheries Collapse:  fisheries world wide are collapsing from intensive overfishing. Although overfishing has been going on since industrialization began (whale and Oyster populations collapsed over 100 years ago) it has only been since the 1950s when industrial scale fishing started that the most serious problems have be seen. The depletion of top predator species such as tuna, swordfish, marlin, cod, halibut, skate, and flounder can cause a shift in entire ocean ecosystems (Greenpeace International).

 

 

The Missing Link

Is it possible to correlate the actions of two very different life forms under such conditions even if they do share a large amount of the same genes? Can we find an example of a another life form, more closely related to Homo sapiens , a mammal, that displays the same characteristic boom and bust life cycle of the yeast in a carboy?

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In 1944 a herd of 29 reindeer were introduced to St Mathews Island which is located in the Bering Sea Wildlife Refuge. With no predators to keep the population under control and an ample supply of vegetation (lichen, willow, and sedges) as a food energy source, the herd increased from 29 animals to 6000 in the summer of 1963 and underwent a crash die-off the following winter to less than 50 animals in 1957. (Klein)

Other organisms including bacteria, and higher life forms such as mice and rats, all go through a boom and bust cycle of population as long as there is an ample energy source to make a drawdown on.

 

Conclusion

Humanity is showing clear signs of population overshoot. In the same way yeast degrades its environment (the carboy) with carbon dioxide and alcohol, we also degrade ours (the Earth) also with carbon dioxide and toxins hazardous to life. In the same way yeast makes a drawdown in the sugars contained within the must, humanity makes a drawdown on a variety of resources to support its ever growing population and consumption.

Either environmental degradation or resource depletion can on their own cause a crash in population and many, if not all, life forms are susceptible to these problems under the correct conditions. Although there is a clear understanding that climate change (environmental degradation) is a possible serious problem, peak oil (resource depletion) is being mostly ignored by our society.

 

References

 

(n.d.). Retrieved November 12th, 2009, from Greenpeace International: http://www.greenpeace.org/international/campaigns/oceans/overfishing

Anderson, B. (2009, June 16th). Peak Oil Primer. Retrieved November 8th, 2009, from Energy Bulletin: http://www.energybulletin.net/primer.php

Brown, L. (2007, Febuary 12th). Aquifer depletion. Retrieved November 15th, 2009, from Encyclopedia of Earth: http://www.eoearth.org/article/Aquifer_depletion

Coghlan, A. (2009, November ). Clearing Oasis Trees Felled Ancient Peru Civilization. Retrieved November 20th, 2009, from New Scientist: http://www.newscientist.com/article/dn18091-clearing-oasis-trees-felled-ancient-peru-civilisation.html

Cohen, D. (2007, May). Earths Natural Wealth. Retrieved November 11th, 2009, from New Scientist: http://www.newscientist.com/article/mg19426051.200-earths-natural-wealth-an-audit.html

Dead Zone (Ecology). (n.d.). Retrieved November 21st, 2009, from Wikipedia: http://en.wikipedia.org/wiki/Dead_zone_(ecology)

Diamond, J. (1995, August). Easter Islands End. Retrieved November 19th , 2009, from http://www.hartford-hwp.com/archives/24/042.html

Draggan, S. (2008, September). Desertification. Retrieved November 20th, 2009, from Encyclopedia of earth: http://www.eoearth.org/article/Desertification

Draggan, S. (2008, March). Soil Erosion. Retrieved November 22nd, 2009, from Encyclopedia of Earth: http://www.eoearth.org/article/Soil_erosion_and_deposition

Fall of the Maya. (n.d.). Retrieved November 20th, 2009, from pyysorg.org: http://www.physorg.com/news174152911.html

Glacier retreat and disappearance. (n.d.). Retrieved November 22nd, 2009, from Wikipedia: http://en.wikipedia.org/wiki/Effects_of_global_warming#Glacier_retreat_and_disappearance

International Database Information Gateway. (2009, September 10th). Retrieved November 20th, 2009, from US Census Bureau: http://www.census.gov/ipc/www/idb/worldpopinfo.php

International Union for the Conservation of Nature. (n.d.). Retrieved November 21st, 2009, from http://www.iucn.org/

Klein, D. R. (n.d.). The Introduction, Increase, and Crash of Reindeer on St. Matthew Island. Retrieved November 9th, 2009, from http://www.greatchange.org/footnotes-overshoot-st_matthew_island.html

Leake, J. (2009, November). Climate change catastrophe took just months. Retrieved November 20th, 2009, from Times Online: http://www.timesonline.co.uk/tol/news/science/earth-environment/article6917215.ece

Lean, G. (2008, December). Men really are the Weaker Sex. Retrieved November 10th , 2009, from The Independent: http://www.independent.co.uk/news/science/its-official-men-really-are-the-weaker-sex-1055688.html

McGinley, M. (2009, October). Retrieved November 20th, 2009, from Encyclopedia of Earth: http://www.eoearth.org/article/Human_impacts_on_the_biodiversity_of_the_Arctic

NSIDC. (n.d.). Retrieved November 22nd, 2009, from NSIDC: http://nsidc.org/arcticseaicenews/faq.html

Pines, M. (2001). The Genes We Share. Retrieved November 14th, 2009, from Howard Hughes Medical Institute: http://www.hhmi.org/genesweshare/

The Language of Ecology. (n.d.). Retrieved November 22nd, 2009, from Dieoff.org: http://dieoff.org/page14.htm

Weart, S. (2007, June). The Discovery of Global Warming. Retrieved November 20th, 2009, from http://www.aip.org/history/climate/summary.htm

Wyeast Laboratories, Inc. (n.d.). Retrieved November 20th, 2009, from http://www.wyeastlab.com/

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