Download The Effect of Living Beings on Climate

81
M E G H A N A D WA R A K A :
The Effect of Living Beings on Climate
I
t is a well-known fact that climate has a direct impact on life. For example, rising
global temperatures are causing the Edith’s checkerspot butterflies to move northward, in search of cooler climates. (Than) Corals are becoming more heat tolerant
and many are now able to survive in hot water pools. (Marris) We see instances of living organisms adapting to climate change on a daily basis. But does climate also adapt
to inhabitation? If so, is it possible that living organisms themselves created conditions
that make our planet habitable?
In 1953, two landless laborers, Thimmakka and Chikkanna, planted hundreds of
banyan trees alongside the highway connecting Kudur and Hulikal in Karnataka, India. In that year, the annual temperature range of this region was approximately 20˚C
to 44˚C and the total annual rainfall recorded was 792.2 mm. At present, the trees have
grown to their full size. Now the recorded temperature of this region ranges from 15˚C
to 35˚C (Yr.no) and the annual precipitation has risen to 877.24 mm. (Ravindranath)
This fall in temperature and rise in precipitation is opposite to the climate change
trends demonstrated by all other regions of Karnataka where temperatures are rising
and precipitation is falling.
In the above example, the lower temperatures and higher precipitation near Kudur
can both be attributed to the banyan trees. Trees have a low albedo—the measure of
“how well the earth’s surface reflects solar energy” (NSIDC) that enables them to
absorb sunlight and therefore cool their surroundings. Moreover, in order to carry out
photosynthesis, they absorb carbon dioxide (a greenhouse gas) from the atmosphere,
which helps reduce the temperature further. Transpiration (the loss of water vapor
through leaves) by trees boosts the formation of more clouds, which results in higher
rainfall. It is therefore evident that the vegetation of a region plays a significant role in
regulating its climate.
Interestingly, it has been observed that when a region’s original vegetation is supplanted by a different plant type, the climate of the region changes in response. In the
1990s, the cotton fields in most of Georgia were being destroyed by boll weevils and
were eventually replaced by pine tree forests. The change in vegetation attributed to
the subsequent cooling of the region, according to many climatologists. (NCSCO)
This idea of biological organisms altering climate has been demonstrated in a more
scientific manner through a computer simulation called Daisyworld.
82
When this simulated world is populated by white daisies, the temperature of the
planet lowers because white daisies reflect light. Contrarily, when it is populated by
black daisies, the temperature increases because black daisies absorb all of the light.
However, when the temperature of this planet gets too high or too low, the daisies are
unable to survive and die. This means that plants can only control climate within the
constraints of the environmental conditions required for their survival.
The examples of Karnataka and Georgia are not proper scientific evidence because
it is based more on observation than experimental results. Therefore, variable factors
have not been controlled. For instance, the lower temperature in Georgia may also have
been due to the cool winds blowing through that region in that year. It must also be
recognized that there have been studies that have shown that, as the quantity of carbon
dioxide in the air increases, the carbon dioxide uptake of plants does not necessarily
rise. Therefore, plants may not be efficient regulators of climate by themselves.
Animals also have a substantial impact on climate due to their biological processes
and physical activities. The Daisyworld experiment was extended to include animals
such as foxes, rabbits and other species. Temperature regulation significantly improved
when a larger number of species interacted with each other: “the system was robust and
stable even when perturbed.” (Lovelock 215)
Earth’s climate is not only influenced by the bigger forms of life, but also by microscopic organisms. A study conducted by marine biologists of University of California,
San Diego demonstrates that “ocean microbes can influence cloud brightness, which
in turn helps determine if solar energy is absorbed on Earth’s surface or reflected away
from it, and thus influences temperature.” (Iacurci)
Furthermore, recent evidence shows that the Southern Ocean, the cloudiest region on Earth, owes its clouds to microscopic plants called phytoplankton, which live
in the ocean: “A new study has measured how particles and gases emitted by these
creatures enter the atmosphere,” (Gramling) and “act as nuclei around which clouds
form.” (ibid.) An international research team found three-billion-year-old microfossils of phytoplankton, (Messer) which suggests that these organisms were living in
the oceans three billion years ago. This implies that cycles of cloud formation and
precipitation came into existence at the same time oxidative photosynthesis came into
existence. Hence, the link between biological activity and climate might have actually
originated when very basic forms of life emerged.
In addition, research indicates that “microbes have been absorbing and releasing
greenhouse gases ever since they first evolved in the ocean more than 3.5 billion years
83
ago.” (Zimmer) Microbes, especially the ones involved in carbon and nitrogen cycles,
decompose organic matter which releases carbon dioxide as a result. This has interesting implications on the impact of microscopic organisms on climate. Since the luminosity of the sun during the time of its formation 4.567 billion years ago was only
70% of its current luminosity, the earth should have initially been frozen solid. (CC 111
lecture notes) However, there is strong evidence that the Earth was warm enough to
have liquid water 3.6 billion years ago. Scientists believe that this warm temperature of
the earth was due to the presence of greenhouse gases, which may have been released
by primitive microbes as described above.
Furthermore, it has been observed that these primitive microbes are highly adaptable and can survive even in the most extreme temperatures. Therefore, it may be fair
to hypothesize that microscopic organisms emerged when the Earth initially had an
extreme climate; these organisms then created greenhouse gases that warmed the
planet and created an atmosphere favorable to the evolution of life. Although there
is uncertainty as to how the first living organisms actually came into existence, it is
strongly supported they played a role in creating the conditions for evolution and the
perpetuation of life.
This hypothesis is in accordance with the Gaia hypothesis, which suggests that
“the organic and inorganic components of Earth have evolved together as a single
living, self-regulating system,” and that the Earth’s “living system has automatically
controlled global temperature, atmospheric content, ocean salinity, and other factors,
that maintains its own habitability.” (GaiaTheory.org) The examples outlined in this
paper demonstrate this relationship perfectly—the microscopic organisms are linked
to greenhouse gases just as plants are linked to the regulation of carbon dioxide.
The hypothesis that living organisms have helped shaped the climatic conditions
necessary for survival, however, has many limitations and uncertainties. Firstly, this
hypothesis still does not explain how the very first living systems originated. It is commonly believed that the very first organisms “alive” were very tiny, basic systems that
later evolved into larger and more complex forms. But a titanic number of such tiny
beings would have to be present to raise the temperature of the entire planet to levels
necessary for liquid water to exist.
It is, in fact, easier to believe and prove that life originated due to pre-existing
favorable conditions. Moreover, there is also a lot of uncertainty regarding the processes that these primitive organisms may have used to produce greenhouse gases that
warmed the earth and made it habitable. Thus, the view that living organisms them-
84
selves created habitable conditions on earth might be too optimistic. However, it is safe
to say that climate and life are inter-dependent, and have helped shape each other over
millennia, to produce the conditions of the world in which we live today. „
Work Referenced
CC 111. Lecture notes on the development of the Earth’s climate, Fall 2015.
GaiaTheory.org. “Overview.” 04 December 2015. <http://www.gaiatheory.org>
Gramling, Carolyn. “Tiny Sea Creatures Are Making Clouds over the Southern
Ocean.” Science Magazine. 17 July 2015.
Iacurci, Jenna. “Ocean Microbes: How They May Directly Impact Climate
Change.” Nature World News. 19 May 2015. <http://www.natureworldnews.com/
articles/14761>
Lovelock, James. The Ages of Gaia. Oxford: Oxford UP, 1995.
Marris, Emma. “How a Few Species Are Hacking Climate Change.” National
Geographic. 28 November 2015.
Messer, A’ndrea Elyse. “3-billion-year-old microfossils include plankton.” Penn State
News. 06 June 2013. <http://news.psu.edu/story/278723/2013/06/06/research/3billion-year-old-microfossils-include-plankton>
NCSCO. “Vegetation: Its Role in Weather and Climate.” State Climate Office of
North Carolina. Accessed 30 Nov. 2015. <http://climate.ncsu.edu/edu/k12/.
vegetation
NSIDC. “Thermodynamics: Introduction.” National Snow and Ice Data Center.
Accessed 28 November 2015. <https://nsidc.org>
Ravindranath, Nandeesha. “Analysis of Rainfall Intensity of Kunigal Taluk, Tumkur
District, Karnataka Using GIS Techniques.” International Journal of Research in
Engineering and Technology. (2014): 125-35.
Than, Ker. “Animals and Plants Adapting to Climate Change.” LiveScience. 20 June
2005. <http://www.livescience.com/3863-animals-plants-adapting-climatechange.html>
Yr.no. “Weather Statistics for Kadur.” Yr (“Drizzle”), a joint service of the Norwegian
Meteorological Institute and the Norwegian Broadcasting Corporation.
Accessed 28 November 2015. <https://www.yr.no>
Zimmer, Carl. “The Microbe Factor and Its Role in Our Climate Future.” Yale
Environment 360. 01 June 2010. <http://e360.yale.edu/features/the_microbe_
factor_and_its_role_in_our_climate_future>