How the Earth Operates Supply Chains for Life
The “supply chain crisis” in the news underscores the need for complex systems to have access to the parts they need in time. Breakdowns in the supply chain for one system can cause ripple effects with other systems.
During World War II, the science of Operations Research, a branch of engineering dealing with time and space efficiency, was founded to optimize interconnected systems. With new diagrams like Pert charts, efficiency experts identified nodes where supply breakdowns could slow or halt production of complex systems like aircraft or ships. Some nodes can be worked on in parallel; others cannot. For instance, if parts for a subsystem are plentiful at the Norfolk shipyard but specific widgets must be shipped from Peoria on unreliable transports, laborers could find themselves being paid for idle time waiting for the parts to arrive. Tracing a project’s critical path through these nodes allows managers to estimate the time required to complete a project, and then look for ways to eliminate showstoppers or inefficiencies. Advances in Operations Research led to innovations like buffering and Just-in-time delivery. As with engineering, so with life. For one example, I’ve reported on how toxic heme molecules, essential for many life processes, are synthesized, stored, and buffered for just-in-time delivery without endangering the cell. See here as well for three other examples.
Elemental Abundance vs. Availability
The most abundant elements in our bodies (carbon, hydrogen, oxygen, and nitrogen, comprising 96 percent) are available plentifully in the crust and atmosphere. Proximity, though, does not equate to availability. As we saw here and here, nitrogen is a tough nut to crack despite being the most abundant gas in the atmosphere, and oxygen is highly toxic to cells unless handled carefully. Similarly, carbon and hydrogen come in many molecular forms that are not directly useful to cells. The supply chain problem, therefore, depends not only on proximity but on packaging. Essential ingredients are not helpful if locked in a metal box without a key. The Earth is blessed with a crust and an atmosphere that provide essential elements for life. But it’s no help having the elements in the Earth’s crust if they can’t get where the organisms need them. One of the most fascinating aspects of Michael Denton’s Privileged Species series of books, especially The Miracle of Man (2022), concerns the synergy between geology and biology that satisfies life’s supply chain requirements. Let’s look at some new discoveries about getting chemical elements where they are needed, on time.
The Geological Supply Chain
Denton spoke of the combined benefits of glaciers and the unique properties of water for grinding down rocks to expose minerals. The process works like sandpaper, he says (The Miracle of Man, pp. 37-38), creating “rock flour” that brings elements to soils and clays usable by plants.
From Penn today, we learn that “Biogeochemist Jon Hawkings of the School of Arts & Sciences and his lab study glaciers to understand the cycling of elements through Earth’s waters, soils, and air in its coldest regions, with implications for climate change, ecosystem health, and more.” Collecting freezing water in Greenland without contamination is not glamorous work, Hawkings says, but is leading his colleagues at the University of Pennsylvania to appreciate the rivers of ice as habitats for algae and bacteria. In addition to harboring life, glaciers also move, albeit fairly slowly, says Hawkings. They are sometimes referred to as “ice rivers.” As they flow, the ice can act like sandpaper, grinding up the bedrock upon which they sit. “Anything that’s in that bedrock can become mobilized and, if it’s reactive, will dissolve into water,” he says.
The team’s work on “elemental mobilization and global systems” has only been possible in the past decade, Hawkings says.
The geological supply chain also includes volcanoes, which enrich soils with nutrients. One “striking” non-biological supplier is lightning, which can break N2’s triple bonds and create nitrates usable by organisms. Many planetary scientists, furthermore, believe that other essential elements, like zinc (Imperial College London), and perhaps Earth’s ocean water, were delivered air mail: via meteorites and comets. Micrometeoroids deliver a steady rain of Elements that include biological essentials like manganese, iron, magnesium, calcium, phosphorus, and even chromium. Some of these are also supplied by volcanoes. Chromium (Cr, atomic number 24) is another essential trace Element not just for shiny bicycle handlebars and stainless steel kitchenware but also for insulin utilization. Though it is toxic in excess, our metabolism depends on it. We usually get sufficient chromium in a variety of foods. A paper by Bertinotto and Griffin in PLOS one reported that “A low chromium diet increases body fat, energy intake and circulating triglycerides and insulin in male and female rats fed a moderately high-fat, high-sucrose diet from peripuberty to young adult age.” Without the volcanic and meteoritic supply chains, there might not be sufficient chromium on the surface. That could be true of other trace elements needed by organisms, including rare earth Elements.
The Biological Supply Chain
As stated above, lightning can make atmospheric nitrogen available, but most biologically available nitrogen is “fixed” by microbes containing the nitrogenase enzyme. These biological marvels are located in root nodules of legumes and other plants that have symbiotic relationships with the microbes. It’s more irreducibly complex than a mousetrap, but if you could build a mimic of nitrogenase the world would beat a path to your door.
Another interesting case of microbial delivery concerns cobalt. Many do not think of this shiny metal in their diet, but Co (element 27) is incorporated in the active site of Vitamin b12, essential for the synthesis of nucleic acids and for cellular metabolism. The vitamin is also involved in the synthesis of fatty acids for the myelin sheath that supercharges neurons. Watanabe and Bito (2017) describe how we obtain vitamin B12 with its cobalt ion in the center: Vitamin B12 is synthesized only by certain bacteria and archaeon, but not by plants. The synthesized vitamin B12 is transferred and accumulates in animal tissues, which can occur in certain plant and mushroom species through microbial interaction. In particular, the meat and milk of herbivorous ruminant animals (e.g. cattle and sheep) are good sources of vitamin B12 for humans. Ruminants acquire vitamin B12, which is considered an essential nutrient, through a symbiotic relationship with the bacteria present in their stomachs. In aquatic environments, most phytoplankton acquire vitamin B12 through a symbiotic relationship with bacteria, and they become food for larval fish and bivalves. Edible plants and mushrooms rarely contain a considerable amount of vitamin B12, mainly due to concomitant bacteria in soil and/or their aerial surfaces. Thus, humans acquire vitamin B12 formed by microbial interaction via mainly ruminants and fish (or shellfish) as food sources.
From volcano to ore to microbe to cow to lunchtime hamburger, this unexpected metal makes its appearance through both geological and biological supply chains. (The role of the ruminant forestomach I discussed here. You can listen to the episode on ID the Future.)
Limiting Factor?
Of the essential elements for life, phosphorus (P, atomic number 15) may be a limiting factor. See “The Problem of Phosphorous” and “Is There Enough Phosphorus for Us?” Those articles gave circumstantial evidence that P availability has been adequate through the history of life on Earth, and noted that microbes and plants are good recyclers of phosphorus, able to implement pre-programmed remediation measures under P starvation.
Phosphorus shortages have become a global concern (Auburn University). Nature Communications is worried that soil warming may decrease phosphorus availability. There may be better supply chain strategies at work in the biosphere than we realize. The Chinese Academy of Sciences reported via Phys.org that phosphorus availability is enhanced in some cases by — of all things — termites. Termites are social insects of the infraorder Isoptera and are widely distributed across tropical and subtropical ecosystems. These insects are the most important soil bioturbators and have been called “soil engineers.”Phosphorus concentrations are usually low in highly weathered tropical acid soils, but termite nests form bioaggregates that serve as carriers for P protection and stabilization.
As this is a new finding, it is reasonable to expect other biological processes will be found working to maintain just-in-time delivery of phosphorus in other ecosystems.
A Hidden Hand
One hopes these glimpses into Earth’s “operations research” solutions help give us confidence that life will continue to thrive as it has since the beginning. And maybe the success of the biosphere will point to a hidden hand of engineering that knew all about critical paths and just-in-time delivery.
