To me, the modern world is largely a product of the Enlightenment – the European intellectual movement that emerged in the late 17th and 18th centuries and that emphasizes reason, progress and individualism rather than tradition. During this period humanity made great strides in defining the scientific method and technological progress, ethical behaviors and democratic social structures. We see the ongoing fruits of these ideas all around us today in the huge improvements in the quality of life that ever more people have enjoyed in the last few centuries.
These dramatic improvements in human living conditions have not come without significant costs, and rising atmospheric CO2 levels is one existential concern. The resulting global warming is here for all to see, and in my view only the most ignorant Luddites imaginable can deny it – people with no understanding of the ideas of the enlightenment. It is simply a scientific fact that atmospheric CO2 levels have risen by 44% since the early 1800s and the only plausible explanation is that this change results from human actions; the burning of fossil fuels and so on.
I recently learned that this atmospheric change is actually doing more than raising global temperatures and thus affecting the ice caps, sea levels and weather patterns. Plants use photosynthesis, whereby water drawn up through their root systems combines with CO2 drawn in from the atmosphere, to create the carbohydrates needed to increase their body mass, with oxygen given off as a waste product. Plant stomata (pores) open to facilitate this reaction – the open pores draw up water from the roots where it transpires to the atmosphere. The open pores also let in CO2 for photosynthesis to occur.
It has been scientifically proven that higher concentrations of CO2 in the air allow photosynthesis to progress faster so that plants grow faster and transpire less water. This can increase plant growth by 20%-60%. Unfortunately, the resulting plants are poor in nutrients (Iron, Phosphorus, other minerals and, especially, Nitrogen) because these are drawn from the soil and into plant tissues by the transpiring water and in the presence of excess CO2 plants transpire about 20% less water.
From our perspective, the biggest problem is Nitrogen deficiencies in plants. All herbivorous and omnivorous animals (including people) need to eat plants containing Nitrogen to be able to convert the carbohydrates they are made up of into amino acids, which are the major constituent of animal body tissues. To counter the reduced water transpiration by plants in CO2 rich environments you need to raise soil Nitrogen levels, which can be done by adding fertilizers or by planting (and eating) more legumes. Legumes, which are particular kinds of plants, exist symbiotically with bacteria called Rhizobia in their root systems which have the ability to absorb atmospheric Nitrogen and allow it to be easily taken up by the plant during transpiration. Therefore, legumes are especially rich in Nitrogen even at low water transpiration rates and so are exceptionally good animal feedstock.
So, rising atmospheric CO2 levels creates many more problems than just warming the atmosphere. The natural world has had billions of years to develop incredibly complex and interdependent systems (unless you are a creationist who believes the world was created 4,000 odd years ago by some super-being without leaving any supporting scientific evidence). These systems are often finely balanced and small changes can lead to dramatic shifts in equilibrium. Our world will continue to exist until the Sun eventually explodes or shrivels up from a lack of Hydrogen, but if we mess too much with the current equilibrium state, it will dramatically shift to another equilibrium state that does not support Homo Sapiens – this has happened many times in the past, just think asteroids and dinosaurs.