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Energy, Diminishing Returns and the Future of Food

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It was another warm summer morning as I set off on a lightly used trail, venturing east through the forest and then through a wetland left dry by sparse rain over the previous few weeks. After passing through a bottomland forest I find, off to the trail’s right, the elm I’d met the previous year. The tree’s seen better days. While a few of its branches were dead the previous year, as I looked up only a few branches had green leaves, while most were bare. An American elm with a diameter of perhaps six inches at breast height, the tree was showing signs of Dutch elm’s disease and given its downward spiral I doubted it would make it through this next winter.

American elmRather than watch the once beautiful elm rot over the coming years, I cut it down to put it to a higher purpose, at least from my perspective. After spending a few minutes felling the dying tree, I split its six-inch trunk in half using an assortment of steel wedges, a small sledgehammer and a hatchet. The halves will eventually become wooden hunting bows after they dry for a year or two, and the bows, whether used by me or someone else, will hopefully fill a few deer tags, or at least nab some squirrels or rabbits.

As I sweated against the elm’s tough, interlocking grain, I reflected on how much effort I was expending, and how much energy I would invest in the bows the log would eventually yield. Owing to my attention to detail and stubborn refusal to use power tools, I commonly invest 40 hours of labor into each wooden hunting bow I make by the time they’re ready to shoot. When I carry a finished bow from this particular elm back into the forest a couple years from now it will carry a substantial energy debt associated with it, a debt measured as the food calories I burned while crafting it. To be a worthwhile investment, the bow needs to pay that energy debt back by making meat.

This game of investing energy towards the procurement of food is one that Homo sapiens – and all living organisms – have played for millennia. From our days as hunter-gatherers to today’s dependence on a global, industrialized food system, we’ve always invested energy in the process of food production. The goal of this essay is to explore the energetics of food systems in greater detail, but perhaps more importantly to point out that, due to the emergence of diminishing returns, the future of food production might not follow the same process of intensification and industrialization that we’ve grown accustomed to. These diminishing returns will define our experience throughout the 21st century, and hopefully this essay will bring them to light in a way that prompts broader discussion.

* * *

Figure 1Energy is the capacity to do work. Energy mediates all physical transformations, including those involved in the production and processing of food. All organisms sustain themselves by capturing metabolically valuable energy flows from their surroundings, and because organisms must expend energy to capture energy it’s possible to gauge the efficacy of an organism’s food procurement efforts by calculating its energy return [1]. Energy return is calculated as the food energy consumed by an organism divided by the metabolic energy expended to acquire that food. If this ratio is less than one – the denominator is larger than the numerator – it means the organism invests more energy finding food than it gets back as food energy, yielding a negative return on investment that, over the longer term, means starvation. If, on the other hand, the organism acquires more food energy than it invests, its food procurement strategy yields a return greater than one – a positive energy return – and creates the energy surplus needed for growth and reproduction.

Positive returns are good. Negative returns, not so much. A species’ ability to generate a positive energy return with its food procurement strategies influences its ability to persist in a landscape and defines its geographic range. While individuals might be found occasionally over a larger region, they can only live, grow and successfully reproduce over a smaller area where their foraging behavior consistently yields at least a modest energy surplus.

Homo sapiens, as a species, is subject to these same constraints. Anthropologists have for decades acknowledged this, with many studying isolated groups with the goal of furthering our understanding of how people’s pursuit of food energy influences their relationships with their surroundings [2]. While controversial – if for no other reason than because it acknowledges we’re subject to the same constraints that act on other animals, and other living organisms more generally – this line of research has helped shape a view of our species that accentuates the important role of energy capture in human biological, social and cultural development.

Several million years ago our distant ancestors were bipedal apes. They used nothing but their two hands and the sweat of their brow to procure food, and no more than the fur on their back and their metabolism to maintain their body temperature within a tolerable range [3]. Their geographic range, like that of other species, was limited to areas where their food acquisition strategies yielded a positive energy return, which for these bipedal apes meant wandering through the forests and savannahs of Africa foraging for fruit, edible vegetation, insects and perhaps the occasional scavenged animal carcass [4].

A few million years ago our ancestors began using tools [5]. The earliest tools were likely unmodified sticks and stones, but these were eventually supplemented by shaped stone tools with cutting edges used to assist in processing foods, even splitting animal bones and skulls to afford access to their rich marrow and brains. These tools allowed early humans access to calorie dense foods that greatly increased the returns generated by their food procurement strategies, both at the individual and population level. Use of stone tools multiplied the value of human labor, compensating for our lack of sharp claws and teeth and bone-crushingly strong jaws and allowing our geographic range to expand beyond earlier boundaries because our tool-enhanced life ways generated a positive energy return over a broader area. Stone would eventually give way to metal, affording tools not only greater durability but also greater design flexibility [6].

Not long after we learned to use stone tools we also began using fire, sometimes for warmth but also as an aid in food processing [7]. Use of fire opened still more food procurement opportunities, not only because it allowed us to detoxify and disinfect foods that might not be safe to eat in their raw forms but also by protecting our ancestors and their food from predators and scavengers. Fire afforded early humans the ability to subsidize their muscle power with energy stored in surrounding combustible biomass, wood, grass and perhaps dried animal dung, energy that originated from the sun. As our mastery of combustion expanded we turned from biomass fuels to those derived from ancient sunlight such as coal, oil and natural gas, and eventually to the energy stored in the nucleus of the atom [8].

* * *

Food systems of our ancient past were quite simple, and consisted of people migrating over the landscape in small to modest groups hunting for wild game and gathering various plant foods. These subsistence strategies delivered a modestly positive energy return with respect to human labor. Anthropologists studying African bushmen estimated they acquired 5-10 calories of food energy for every calorie of metabolic energy expended, a stunningly high return given the harsh desert environment in which they lived [9]. Among hunter-gatherer societies this appears to be the norm rather than the exception, with most groups that persisted to the present day showing similar energy returns [10]. These groups owe their success partly to the use of tools and fire, but also to their intimate knowledge of their natural landscape.

Modern industrial food systems deliver far higher energy returns than those of hunter-gatherers when calculated based solely on human labor. Based on data from the US Bureau of Economic Analysis and US Department of Agriculture, the US food system delivers roughly 90 calories of food energy for each metabolic calorie of invested labor. These extraordinary energy returns derive from the fact so few people have to work in the food sector anymore; machinery does work that humans had done in decades past, and non-motorized tools magnify the value of the comparatively little human labor that remains.

Figure 2Obviously, there’s more energy being invested in food production in the United States than what’s invested as human labor. In the same way that our ancient ancestors began subsidizing their food procurement strategies with the chemical energy stored in biomass, we do so today by using the chemical energy stored in fossil fuels, uranium and, to a lesser degree, other energy sources. Data from the US Department of Agriculture suggests that the US food system required at least 14 calories of energy to deliver a single calorie of food in 2007 once losses due to waste and spoilage were accounted for [11]. Whereas the US food system delivers a mighty surplus when only labor energy is counted, it operates at an energy loss when all energy is counted, illustrating the difference made by counting the industrial energy inputs we use to subsidize our labor. Prior to 1900 the US food system likely delivered more food calories than it required as labor and non-labor energy inputs, but this changed as the US industrialized and as its systems for producing, processing and distributing food were mechanized [12]. While the US food system’s energy intensity may represent a global extreme, other countries’ food systems are also quite energy intensive.

Figure 3

Up through 1980 in the United States, analysts’ estimates showed a consistent upward trend, with Poincelot’s figure pushing 20 calories of input energy for each calorie of consumed food. Canning et al’s lower estimates beginning in 1997 are at least partly due to more conservative boundaries around what the researchers counted against the US food system; they left out a range of food system energy inputs including those associated with water provision, waste disposal and food system governance, among others. If Canning et al’s analysis had been more inclusive, it’s possible data from their report would have estimated food energy inputs in excess of 20 calories for each calorie of food produced. Energy efficiency practices adopted within food systems as a result of the Oil Shocks of the 1970s may have reduced the energy intensity of food production too though.

Fuels derived from biomass and particularly fossil energy resources drove the industrial revolution, and transformed how Homo sapiens produced our food. Rather than using human and later animal labor as the primary source of power for food production, people developed machines as lower cost substitutes. Machines generate far more power – energy per unit time – than human or animal labor ever could, paving the way for an unprecedented increase in the scale of food production, processing, storage and distribution enterprises. These not only reduced the cost of food in monetary terms, but also allowed for the geographic expansion of food systems over regional, national and eventually global scales.

The global food system that exists today is the end result of a long line of innovations in how humans use energy to acquire their food. Prior to the use of tools our ancient ancestors were constrained to a very narrow geographic range due to their limited capacity to generate a positive energy return from their food procurement efforts. Through the development of tools, the taming of fire, and eventually the mechanization of food production and the subsidization of human labor power with that derived from industrial fuels, we’ve learned to generate the enormous metabolic energy surpluses needed to expand not only our range but also our population [13]. As I write this there are over 7 billion people on earth living on every large continent for at least part of the year, and our total weight exceeds that of any other species except that of our favorite domestic animal, the humble cow.

* * *

All organisms are consistently faced with a need to acquire enough food, to gain access to enough metabolically accessible calories to allow them to live, grow and reproduce. Acquiring adequate food is one of the preeminent problems faced by all living organisms, including Homo sapiens. Those of us living in developed nations have chosen to solve the problem of food procurement by tossing huge amounts of non-metabolic energy at it, mostly from fossil fuels like crude oil, natural gas and coal. By heavily subsidizing food systems with industrial fuels, we’ve reduced the amount of labor needed to produce, process and distribute food while increasing food production overall.

This strategy has two dark sides associated with it. The first is path dependence. Path dependence refers to three emergent properties of a particular problem solving strategy: increasing returns, self-reinforcement, and lock-in [14]. Increasing returns refers to an instance when problem solvers invest in a novel strategy and find that it yields returns on investment that increase faster than increases in the rate of investment. Seeing this, the problem solvers make the perfectly rational decision to reduce investments in other strategies and increasingly put their investments in this novel approach to maximize returns. This can lead to self-reinforcement, a situation where one problem solving strategy attracts an overwhelming share of available resources, effectively starving alternatives of the investments they need to remain viable competitors in the marketplace of ideas. Once a particular strategy becomes adequately self-reinforced, society is locked-in to that strategy because others, due to lack of investment, seem antiquated by comparison.

Figure 4Increasing returns never continue indefinitely. Eventually a threshold is reached where increasing returns give way to diminishing returns, an inflection point beyond which the return on a given investment increases at a diminishing rate and eventually turns negative [15]. If diminishing returns emerge once a particular problem solving strategy has become locked-in, the society that made the initial investments will face the terrifying proposition of either continuing on their failing problem solving path while hoping for a miracle, or writing off their substantial investments in the failing strategy and turning to alternatives that, due to a history of neglect, are poorly developed and inspire little confidence.

Path dependence and diminishing returns have been studied throughout economic and social systems, but within food systems the best-researched example is the use of chemical pesticides [16]. Here it must first be recognized that to grow crops at a commercial scale without the use of chemical pesticides requires maintaining a substantial knowledge base on companion planting, crop rotation and other non-chemical pest control strategies. This knowledge based costly to maintain, and when chemical pest control methods first emerged on the market they were a relatively easy sell; little was understood about their long-term implications, they made growing unblemished food easier and farmers who adopted them could replace the constant necessity of innovation with simple application instructions supplied by the chemical manufacturers.

Due to the substantial savings of time and effort afforded farmers by chemical pesticides, they initially yielded increasing returns to their use. Over time pests developed resistance to chemical pesticides however, instigating an agricultural arms race characteristic of the transition from increasing to diminishing returns. In the 1960s Rachel Carson’s book Silent Spring ushered in a new era where scientists, activists and policy makers increasingly realized that chemical pesticides weren’t as harmless as previously thought, often exhibiting broad-spectrum toxicity that led to a range of short- and long-term consequences. Even today it seems we’re still trying to grasp the true implications of decades of synthetic pesticide use [17].

Today it’s increasingly acknowledged that the negative impacts associated with chemical pesticide use outweigh the overall benefits [18]. Yet so little investment has been made to maintain the knowledge base needed to grow crops on a commercial scale without chemicals that adopting less impactful pest control strategies isn’t perceived as a viable option. To abandon our use of chemical pesticides will require a pervasive re-education and re-skilling campaign for farmers, gardeners and horticulturalists, one that might be worthwhile over the long-term but seems an insurmountable challenge over the short run. In effect, the use of chemical pesticides has followed a path dependent trajectory, offering first increasing returns that resulted in self-reinforcement and lock-in, but now yielding diminishing or perhaps even negative returns and a growing sense of regret.

Figure 5While chemical pesticides represent one particularly well-studied case of path dependence within food systems, it is by no means the only one. The transition from increasing returns to diminishing returns has shown up in several aspects of food production, among them the use of synthetic fertilizer, tillage practices, and the nutrient content of commercial crops [19]. The yield of corn and wheat have progressed from the stage of increasing returns on investments in fertilizer and pesticide application prior to the 1970s into the stage of diminishing returns after about 1980. Yields of these two commodity crops are still increasing of course, just at a diminishing rate. At some point in the future, regardless of how much fertilizer, pesticides and genetic modifications we might throw at them, yields will reach the natural upper limit for these species and level off. Maintaining yields on this plateau in the face of continued pest adaptation, new pest emergence and declining soil quality may well require still more investments, forcing yields into the stage of negative returns.

While none of the above examples might seem to explicitly relate to energy, in fact they all do. All inputs into food systems, be they chemical pesticides, synthetic fertilizers, machinery used for tillage and even the research infrastructure used to study and implement genetic modification, all require energy in their manufacture, use, or both. Glyphosate, the active ingredient in Roundup®, is estimated to require 49,000 kilocalories of energy per pound of active ingredient during its manufacture, while diammonium phosphate fertilizer requires 1,200 kilocalories of energy per pound [20]. If we use the embodied energy in automobiles as a proxy for that in farm machinery, tractors and other farm implements require over 10,000 kilocalories of energy in their manufacture per pound of total weight [21]. All food system resource inputs require energy in their manufacture and distribution, from the fertilizers and compost applied to farm fields to food packaging and finally to the garbage trucks that pick up our food waste once it’s been discarded. All processes within food systems that currently or might soon exhibit diminishing or negative returns on investment require energy as a key input, which means that to continue producing the types and quantities of foods we’re accustomed to will demand, over time, larger investments of energy per unit of food produced unless we make radical changes in our food system. This is precisely the trend illustrated the previous figure plotting the energy intensity of the US food system over time, one of increasing energy investment per calorie of consumed food.

Figure 6If path dependence and diminishing returns represent the first dark side of our current food production path, the second is the obvious reality that those who depend on energy subsidies to fuel their food systems must find ways to continue accessing those energy resources at a reasonable cost. Emerging constraints in crude oil, natural gas, coal and even uranium markets suggest these energy sources may not grow to meet continued increases in demand, at least not at the low prices common to much of the previous century.

High-grade energy resource deposits are becoming scarce, and access to them increasingly limited by a range of environmental, technical, economic and political constraints. Despite the emergence of hydraulic fracturing as a novel oil production technology, it appears global oil supply is nearing a point where producers are struggling to increase supplies in response to rising prices [22]. This reality is made plainly evident by price and supply data. When producers are readily able to respond to price increases with increases in supply, plots of price versus quantity form a nearly linear curve. When constraints prevent producers from responding to rising prices by increasing supply, the curve slopes upwards as producers approach their upper supply limits. The supply curve for global oil production illustrates a constrained pattern, sloping sharply upwards after 2005 despite high oil prices. Hydraulic fracturing is seen by some as the new frontier in oil and gas development, but analysts are already questioning the longevity of the supply boom this technology promised in North America due to overstated reserves, rising costs of production and rapid field depletion rates [23]. Rising prices in coal and uranium markets suggest that these resources may not serve as the foundation of cheap industrial energy either [24].

Figure 7Our use of industrial energy resources seems to be following its own path dependent trajectory, and the emergence of diminishing returns in this arena will have far reaching consequences. Since energy is such an important input in industrial food systems, it should come as no surprise that changes in energy prices matter when it comes time for food producers to figure their costs of production and determine their selling price. Commodity price data from the International Monetary Fund shows the strong correlation between fuel and food price indices, and as long as food production remains so energy intensive rising and more volatile energy prices will likely translate into rising and more volatile food prices. Given the tendency of food price volatility to contribute to food insecurity and political unrest, this does not bode well [25].

* * *

Archeologists and anthropologists recognize how important it is for a society to maintain adequate food production. Historical analyses have demonstrated that the inability to maintain adequate energy throughputs contributed to the demise of many past societies, among them the Roman, Egyptian and Mayan Empires [26]. Part of this energy throughput, indeed the most biologically relevant segment of it, comes as food. Societies that fail to maintain adequate food supplies will suffer from famine and starvation, and if political institutions cannot overcome these challenges through effective problem solving those political institutions will lose their legitimacy in the eyes of the citizens they govern and either be dismantled or abandoned.

Looking far back through human history, the development of stone tools and the harnessing of fire were problem solving strategies that either enhanced the value of human labor or expanded the range of foods available for consumption, or both. They were strategies developed, at least in part, to solve problems of food supply. More recently, the mechanization of food production also attempted to solve problems related to food supply, as did the development of chemical pesticides, fertilizers, plant breeding, and more recently genetically modification. None of these technological developments are inherently bad or good, but like all problem solving strategies their initial phased of increasing returns didn’t, or won’t, last indefinitely.

Figure 8While each of these strategies solved certain problems, at least temporarily, they created others that themselves demand solutions. Pesticide use created a toxic landscape that we must now clean up, or adapt to. Mechanization created a need for ubiquitous, inexpensive fuel, which we must now search out even as easily accessible energy resources dwindle. Soil tillage causes soil erosion, which we must somehow counteract even as we’ve come to depend on crop varieties that lack the vigor to grow without the practice. The issue of diminishing returns to fertilizer application is particularly vexing; cereal yields per unit of fertilizer input are declining globally, and rock phosphorus, a key ingredient in many fertilizer mixes, is a non-renewable resource that may face shortfalls in the coming decades [27]. And, of course, all food system problems will demand solutions with the risks and uncertainties of climate change as a backdrop.

We persist in our reliance on a food system that requires substantial energy subsidies from non-renewable energy resources because we can. At present, fuels derived from crude oil, natural gas, coal and uranium are relatively abundant, and inexpensive. The same is true with mineral inputs needed for food production, among them bioavailable nitrogen and phosphorus. Many historical societies passed through comparable periods of abundance, but those periods were temporary and those societies now remembered only through their written records or artifacts [28].

Modern food systems suffer from path dependence. Institutions throughout food systems have invested overwhelmingly in input-intensive technologies and practices, leaving those that are less input-intensive to flounder in the dustbins of history. These decisions seemed reasonable when they were made, as problem solvers gravitated towards strategies that yielded increasing returns and the possibility that diminishing returns were inevitable was far from their minds. Today the realities of diminishing returns are staring us squarely in the face. While it’s impossible to discern when diminishing returns will lead our food system into a crisis state, this will occur and unless we radically reduce the inputs – particularly energy – required to produce, process and distribute food our global society may find itself struggling desperately against social and political upheaval. The challenge of the 21st century will be to acknowledge the consequences of diminishing returns, and of path dependence more generally, and find constructive ways to adapt to them.

* * *

What, then, is the future of food? When the time comes, will we write off past investments in failed food procurement strategies and invest in alternative practices that are less resource intensive? Or will such a ghastly idea end up relegated to isolated locales while most people are drawn deeper into the fight against diminishing returns by government and business enterprises too invested in the mistakes of the past to let them go? If localized, adaptive responses are the best we can muster, what happens to those who live outside of these proverbial lifeboats when food crises hit? Do they riot in the streets, destroy the infrastructure that supports them, and starve? Do they descend on the lifeboats, their sole focus leveled at short-term survival? Pundits heap praise on our modern global food system for delivering food from the four corners of the Earth to anyone with the ability to pay, but what happens when the day arrives that the only commodity this global system can deliver is scarcity?

Believe it or not, I’m not into doom and gloom. I do enjoy a healthy dose of realism though, and my motivation for writing this essay stems from the realization that the next century of food production and consumption, both in the United States as well as around the globe, will necessarily be very different than that of the previous century. I expect changes in both what we eat and how we produce it, as well as shifts in the numbers of people directly involved in the act of food production. Perhaps more people will become farmers or farm laborers, or perhaps that food production strategy, known for degrading and eroding soil while producing progressively less nutrient dense foods, will fall out of favor [29].

I don’t pretend to know when elements within our food system will reach their respective breaking points. These systems are complex enough that the only thing we can be sure of is that the future holds plenty of surprises, and given the emergence of diminishing returns in many areas of food production, processing and distribution some of those surprises will likely show up sooner rather than later. While no one can wave a magic wand and change food systems today, we all have the power to change our positioning within them. We can choose to depend entirely on the global model with all of its emerging challenges, or we can invest our time and effort building a more community centered one where we live. We can hold desperately onto the individualistic models of food engagement that have ruled the development of food systems for hundreds of years, or we can experiment with more community minded alternatives that involve sharing the work of food production and, of course, consumption. We each have the power to shape our local food system by abandoning old problem solving strategies in favor of new ones.

My hope is that, over the coming years, we’ll use our influence more mindfully than we have in the past. Diminishing returns has driven many past societies to extinction. It’s a phenomenon that, even today, most researchers, professionals and laborers within food systems don’t have a word for. Without a label it goes unnoticed, remains invisible. As this changes – and hopefully this essay contributes to just such a shift – I expect people to wake up to the tensions emerging in today’s food production strategies, and find creative ways to relieve them. The future of food will be what we make it.

4 Comments on "Energy, Diminishing Returns and the Future of Food"

  1. Makati1 on Tue, 14th Oct 2014 9:42 am 

    We are going to become extinct. If there are any humans left in 2100, they will be hunter-gatherers in some far north or far south area. That is IF the hundreds of nuclear fuel and weapons dumps don’t get then first.

  2. paulo1 on Tue, 14th Oct 2014 4:31 pm 

    I’ll take a chainsaw over my hand tools, anyday. I must confess I have too much to do than dick around making a bow by hand. This winter I am making outside furniture for 4 families from salvaged red and yellow cedar, bucked up with stihl, hauled to a local mill on a trailer, and hauled home again. I will be pleased to use my table saw, jointer, planer and assortment of clamps, as well as deck screws hidden with plugs.

    I taught carpentry and joinery for years and all I will say is that these power tools exist for a reason. Having said that I have met painters who try and make their own paints and potters who dig clay out of the clay banks.

    Despite recent rises in food costs, industrial agriculture produces a pretty consistent product for an affordable price…..provided there are standards and oversight. Mind you, we live on our own garden, our own fish, and elk.


  3. Makati1 on Tue, 14th Oct 2014 9:34 pm 

    paulo1, bows may become necessities in the near future. Chairs, not so much. Better to have experience making necessities than future junk. If you taught carpentry, I guess you are skilled at using hand tools. I worked under a master cabinet maker for several years and learned a lot about wood and joinery. Built two homes for myself myself and some furniture.

    As for your machine shop. I would love to have one like that, but I do have a great collection of quality hand tools that could be usable for several lifetimes. My grandfather( WWI and Depression era) taught me how to use hand tools and how to keep them sharp and useable for a lifetime.

    I do not loan them out, but will help someone with a project needing them. I have some lower quality tools that I do lend but only if I know they will be returned. Would you lend your neighbor your last knife if it was irreplaceable?

    Sounds like you have a great location and set-up. I wish you all the luck in the future. Climate change might even warm up your winters.

  4. JuanP on Wed, 15th Oct 2014 9:41 am 

    Other than the “novel” oil fracking error and rising oil prices mentioned(which probably means this was written before the most recent price declines), I found this article to be an excellent overview of the relationship between food and energy.

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