The concept of the Gaia hypothesis originates from the 1960s when British scientist and independent researcher James Lovelock began his work with NASA on developing methods to detect life on Mars. Along with NASA colleague Dian Hitchcock, Lovelock found that the current state of Mars’ atmosphere was in what appeared to be a state of equilibrium. Specifically, Mars’ gaseous atmosphere showed to be in a consistent chemical balance made up of a stagnant composition of mainly carbon dioxide, some nitrogen, and trace amounts of methane, hydrogen, and oxygen (Ward, 2009). These findings contrasted Earth’s atmospheric conditions, which have fluctuated in oxygen and carbon dioxide in its 4.6 billion years of existence. Lovelock associated this history disequilibrium with life on Earth, namely the photosynthetic and aerobic processes. He also stated that without life on Earth, our atmosphere would be completely different from its current life-sustaining compositions, including an abundance of oxygen, and would be more similar to Mars’ pool of stagnant carbon dioxide (Schneider, 1990). Aside from atmospheric conditions, Lovelock concluded other abiotic factors on Earth have remained stable over the past billion years too, including surface temperatures and ocean chemistry, salinity, and acidity. Eventually Locklock’s initial theory began to evolve and develop into the concept that the planet itself was almost a kind of superorganism or a cellular being (Ward, 2009).
Lovelock’s Gaia hypothesis was the first of its kind at the time and with such a broad and unique concept, it was met with numerous interpretations from fellow scientists and researches in a vast array of both scientific and non-scientific fields. For example, some scientists used the theory as a basis for researching more into the cycles that occur on the planet and conducting experiments on how life can continuously sustain itself. Some non-scientists thought of it as a way to encourage smart sustainability of the Earth for the sake of the future of humankind (Miller et al., 2005).
Discussion: Critical Evaluations of the Gaia Hypothesis
However, new discoveries have made convincing arguments against Lovelock’s Gaia hypothesis. Specifically models showing extrapolation of the future and the study of ancient rocks have threatened the concreteness of the Gaia hypothesis. Both of these discoveries suggest that life on Earth hasn’t been constant since it was created 4.6 billion years ago and that Earth has gone through a series of events where there were extreme drops in the number of species and the abundance of remaining species.
Important supporting evidence for the Gaia hypothesis is the concept of chemical weathering processes. Volcanic activity puts a large amount of carbon dioxide in the atmosphere and without a way to cycle the carbon dioxide, it would increase in abundance constantly and the temperature would continue to increase until life could no longer exist due to the extreme conditions. Chemical weathering helps keep carbon dioxide constant by locking it into limestone deposits and the shells of aquatic creatures (Schneider, 1990). Plants also aid in removing carbon dioxide from the atmosphere through the process of photosynthesis (Ward, 2009).
One of the main and extremely valid arguments against the Gaia hypothesis is that Earth’s temperatures have not remained constant over its history as shown through the concept of “Snowball Earth.” In this widely accepted theory, the Earth was part of a huge glaciation around 2.3 billion years ago. It’s theorized that this 100 million year glaciation was due to microbes that used up mass amounts of carbon dioxide with little or no processes putting carbon dioxide back into the atmosphere (Turney, 2005). This reduced the greenhouse effect so much that oceans froze and the Earth plunged into a massive glaciation. “Snowball Earth” is one of the events that are part of Peter Ward’s Medea hypothesis or anti-Gaian hypothesis. Ward claims that several past mass extinctions contradict the validity of Lovelock’s Gaia hypothesis. He cites two Snowball Earth events, as well as the oxygen catastrophe as other occurrences that have caused the Earth to break the Gaia hypothesis cycle (Ward, 2009).
Besides Ward’s anti-Gaian hypothesis, there has been criticism against Lovelock’s Gaia hypothesis because it doesn’t factor in outside influences on the self-sustaining cycle. An example of this is meteor impacts, which have the capability of causing mass extinctions as well and are caused by an outside factor as opposed to Ward’s examples of where life itself caused conditions too extreme for its survival (Turney, 2005).
While there are numerous valid points that are derived from the Gaia hypothesis, there are still very logical criticisms of it. Many of the feedback systems of Lovelock’s theory are shown through scientific findings. However, it’s vital to recognize the critical standpoints on the Gaia hypothesis. The Gaia hypothesis does not take important past events into account, including two Snowball Earth events, or mass extinctions caused by outside factors, specifically meteor impacts on the Earth. Regardless, there is the opportunity to apply the Gaia hypothesis to the current climate change issues, specifically that humans may be causing a severe imbalance in the sustainability of the Earth.
Miller, E. C., & Crist, P. J. (2005, September). Gaia out of equilibrium? BioScience. 55(9). 799-801.
Schneider, S. H. (1990, May 1). Debating Gaia. Environment. 32(4). 9-31.
Turney, J. (2005). Gaia: nice is not enough. Interdisciplinary Science Reviews. 30(1). 5-10.
Ward, P. (2009, June 20). Gaia’s evil twin. New Scientist. 202(2713). 28-31.