Have you ever wondered how our ocean’s salinity always remains constant? Or how our earth’s temperature remains relatively constant as well? Even our atmospheric concentration, remains stable! Lynn Margulis, together with James Lovelock, wondered this too and set out to find the answer.

 

Imagine if you will, all living things on earth, that is the biosphere, functioning as one SUPER organism that changes its environment to create conditions that best meet its needs, with the ability to self-regulate critical systems needed to sustain life. A system that we are all apart of, that self-regulates, finding its own balance; homeostasis at its finest! That is the Gaia Hypothesis. The Gaia Hypothesis was founded by both Lynn Margulis and chemist, James Lovelock. It proposes that living organisms interact with their inorganic surroundings on Earth to form a synergistic and self-regulating, complex system that helps to maintain and perpetuate the conditions for life on the planet. 

 

The Gaia hypothesis was initially criticized for being teleological and against the principles of natural selection, but later refinements aligned the Gaia hypothesis with ideas from fields such as Earth system science, biogeochemistry and systems ecology. Even so, the Gaia hypothesis continues to attract criticism, and today many scientists consider it to be only weakly supported by, or at odds with, the available evidence. 

 

 

Daisyworld:

 

The best way to understand this theory is through Daisyworld, a computer simulation. Imagine a hypothetical, cloudless world orbiting a star whose radiant energy is slowly increasing or decreasing. Daisyworld has a negligible concentration of greenhouse gases in its atmosphere. Its ground is grey and it is inhabited by two species of daisies with different colors, black and white. Black daisies absorb light and warm the planet, while white daisies reflect light and cool the planet. The black and white daisies are distinct species and there is therefore no possibility of mixed replication of the types.

 

As the luminosity of the sun’s rays increases, the black daisies germinate. Because black daisies absorb more of the sun’s radiant energy, they are able to increase their individual temperatures to healthy levels on the still cool surface of Daisyworld. As a result, they thrive and the population soon grows large enough to increase the average surface temperature of Daisyworld. As the surface heats up, it becomes more habitable for white daisies, whose competing population grows to rival the black daisy population. As the two populations reach equilibrium, so too does the surface temperature of Daisyworld, which settles on a value most comfortable for both populations.

 

 

Illustration of the Daisyworld simulation

 

This illustrates how the biosphere works to regulate the climate, making it habitable over a range of solar luminosity and can be compared to our earth’s biosphere and the regulatory system associated with microorganisms.