Fitting on the Earth: Challenges of Carbon and Nitrogen Cycle to Preserve the Habitability of the Planet

Our small planet is now vulnerable to the cumulative effects of our normal activities. There are two specific grand challenges associated with sustainability that are worth our attention—the global carbon cycle and the global nitrogen cycle. Human beings are disrupting the carbon cycle by releasing carbon, dug out of coalmines and oil fields, into the atmosphere. Mainly due to human beings’ activities, the concentration of carbon dioxide in the atmosphere has increased by more than 30% over the last 250 years, with an annual increase of about 0.5%. Two-thirds of the rise has occurred during the past 50 years. Fossil fuel accounts for 85% of the world’s energy system, and has been the principle agent of interference with the natural cycle for carbon. Such a disrupted carbon cycle, with a high carbon dioxide concentration, is posing tremendous challenges, including wide-spread global warming, rising sea level, significant threats to human health, more frequent extreme weather, and harmful disrupted ecological systems, and so on. Unless there is a change, the world will see much higher concentration of carbon dioxide, and it is thus a must for the world to redesign its energy system to become much less dependent on fossil fuels and less harmful to the carbon cycle. Besides the carbon cycle, the nitrogen cycle is another fundamental feature of life on the planet. The nitrogen cycle is also being disrupted by human beings. Organisms on this planet require nitrogen to survive, but the nitrogen in the atmosphere must be modified to...