The importance of GDP to economic growth is exceeded by the importance of CNP in nature
It all started with the discovery by American oceanographer Alfred C. Redfield (1890-1963) that the ratio of Carbon (C) to Nitrogen (N) to Phosphorus (P) (C:N:P) of free-floating marine phytoplankton (seston) throughout the world was quite static and reflected the differences of dissolved nutrients in associated waters. The Redfield Ratio as it is known today is 106:16:1 for C:N:P, which means that for every unit of phosphorus there are 16 units of P and 106 units of C. The importance of this discovery for biologists was equated to Avogadro’s number or the speed of light in a vacuum by some scientists according to Sterner & Elser’s book “Ecological Stoichiometry”. Redfield’s Ratio has since been proven an overly generalized depiction of aquatic C:N:P, with an average of 354.4:20.1:1 across all manner of aquatic phytoplankton (See Chart 1).
Out of this discovery grew a very specialized but extremely important discipline called Ecological Stoichiometry, which is essentially a bunch of balanced equations describing how C, N, and P are transferred and transformed in ecosystems. It is quite a revolutionary and at the same time elementary concept, with detractors noting that Ecological Stoichiometry is either too complicated to be understood or too simple to be true. Another way to look at it is that Ecological Stoichiometry gives scientists the opportunity to quantitatively attach elemental importance to the balance of energy and materials. The name stoichiometry comes from the Greek root stoicheion for element and metron meaning measure. Broadly speaking the field focuses on C, N, P, to some extent sulfur (S), and rarely hydrogen (H) and oxygen (O) or as scientists like to call them “The Big Six” for their ubiquity and import in all organic and some inorganic processes. Every constituent of this planet, whether living or dead, flora or fauna, above or belowground, land or sea has a unique stoichiometric ratio of these elements. Organisms must vigilantly maintain these ratios in order to survive, which is also the case for humans (homeostasis). In their book “The Natural Selection of the Chemical Elements: The Environment and Life’s Chemistry” Williams & Fraústo da Silva hypothesized that evolution from early to late prokaryotes, to unicellular eukaryotes, and eventually to complex multicellular eukaryotes was coupled with an increased affinity for homeostasis.
Homeostatic stoichiometry is the struggle to maintain a consistent internal chemistry, while an organism’s environment particularly the elemental makeup of its food fluctuates quite drastically. Some organisms – usually of the sedentary variety – display a flexible Ecological Stoichiometry. Their lack of mobility means they must capitalize on the resources available at any given point in time. Truly homeostatic creatures, whether they be ants (C:N:P = 4.8:12.0:1), snakes (C:N:P = 4.4:3.7:1), or the Dalai Lama (C:N:P = 13.3:6.3:1) are not, in the strict sense, what they eat, rather they maintain their C:N:P by a variety of unsavory and malodorous activities we won’t expand on here for fear of offending the faint of heart. Needless to say organisms that must maintain a narrow C:N:P will go to great lengths in pursuit of that goal even if it means no one to sit next to in the lunchroom. You know that stuff you accidently stepped in while walking down the sidewalk or in your local park? That present Fido left for you has a C:N:P of 9.7:0.9:1.
The question is why should we care about these ratios? Well for the answer let’s look to the most famous examples of balanced chemical reactions, photosynthesis [Eq. 1] and decomposition [Eq. 2]. After all when you peel away the layers of scientific mumbo-jumbo this is what Ecological Stoichiometry is all about. If you are starting to have horrible images of your Intro Organic Chemistry class now would be a good time to stop reading. Are you still here? Good. These two reactions drive plant growth [Eq. 1] and decay of everything from tree leaves (C:N:P = 18.6:8.2:1) to septic waste (C:N:P = 12.0:2.7:1). These reactions and those that produced the Redfield Ratio rely on what is called the Law of Definite Proportions.
The importance of the “Big Six” in nature is not hard to find. One need not look further than Adenosine Tri (ATP) and Diphosphate (ADP) the primary energy transfer molecules in cells for the importance of phosphorus, while sulfur is crucial to amino acids (i.e. cysteine) the primary precursors of proteins. Researchers have shown that the Stoichiometric formula for humans in number of atoms is:
Thus, we humans have a “Big Six” H:O:C:N:P:S Stoichiometry of 2.8:1.5:13.3:6.3:5.0:1. This may seem confusing but understanding how these elements flow into and around the human body or for that matter ecosystems tells us a great deal about the so-called “velocity of elements”. Many reading this have heard about the “velocity of money” in recent years and the importance of keeping the flow of money brisk and consistent. Well the same is true of elements and Ecological Stoichiometry is an important tool in determining where elements are backed-up or where they are moving too fast to be utilized. Two interconnected examples of the human condition’s influence on Ecological Stoichiometry are the Haber-Bosch process that fixes nitrogen gas to produce ammonia for N, P, and Potassium (K)-rich fertilizers and the Gulf Coast algal blooms in the US that have created consistent and ever expanding deadzones in the waters off the United State’s Gulf Coast. The latter is a direct function of excessive fertilizer application and manure production in the Mississippi River watershed, with manures having C:N:P of 20.3:7.0:1 and most fertilizers either having equal parts N:P:K (10:10:10) or an excess of P (10:20:10). Thus, Gulf Coast’s aquatic ecosystems are experiencing an increase in the velocity of Ecological Stoichiometry – specifically P – via the Mississippi river, which is leading to increases in algal production and decay all of which deplete the waters of oxygen.
Plants and animals adhere to relatively strict C:N:P (:S), because in theory they are trying to fulfill their maximum growth potential, even though such conditions in actuality might be completely illusory. Living beings want to find that stoichiometric “Sweet Spot”. Ecological Stoichiometry explains why we crave certain foods and can’t stand the sight of others. Ecological Stoichiometry, and specifically the C:N:P:S ratio, is a field of study and a natural process that will receive increasing attention in the coming years given the fact that humans are rapidly depleting the world’s supply of P, with 62 Gigatons remaining according to the USGS’ most recent estimates.
In addition, this ratio and its variability is responsible for phenomena such as acid rain in the northeastern US and Europe, and groundwater contamination in and around areas of heavy agriculture. Scientists have known since Redfield and earlier the importance of understanding the interconnectedness of the “Big Six” and more specifically C, N, P, and S. In 2000 Falkowski and colleagues compared natural and human-induced changes in the stoichiometry of earth and found that the change due to anthropogenic causes was 13%, 108%, 400%, and 113% for C, N, P, and S, respectively. Thus, our fascination with Carbon Capture and Storage (CCS) may be at best myopic and at worst dangerous. Forget the GDP what is your country or state’s CNP?
Complete Chart 1 From Above: