Growing Degree Days

Most gardeners are familiar with the idea of hardiness zones — the USDA hardiness zone map, for example, breaks down regions of the U.S. by their expected minimum winter temperature. The idea is that, for example, in Zone 10a (which I’m in), which is listed as 30-35F minimum temperature, the expected low each winter will not be below 30F. Most plants sold are described in terms of their hardiness zone — a plant that is listed as say USDA hardiness Zone 8b should survive in Zones 8b and above. Zone 10a is almost the warmest you can get in the continental U.S. — there are only parts of Southern California and Southern Florida that are in higher zones. And so you would think by virtue of being in 10a that where I live it’d be possible to grow just about anything.

But common sense says that something is missing in this analysis, as does the fact that there are plenty of plants and trees that survive but don’t thrive here. The climate here is the usual Pacific marine climate that predominates along the California coast — a fair amount of fog and wind, moderate rainfall and essentially no frost in winter, and not a lot of warmth. Even in the peak month of summer — which is September here, delayed by the ocean’s thermal inertia — the average high temperatures barely make it into the low 70s F. By the hardiness zone concept, one might expect it to be a great place to grow things, but it’s only okay. I’ve often wondered what concept might explain why gardens in hotter, more inland areas nearby tend to flourish while those here struggle.

I think the concept I’ve been looking for is Growing Degree Days (GDD), which provides the key missing information. GDD is a strange concept, with a stranger unit of measurement. Instead of measuring temperature, or time, it’s in units of temperature multiplied by time. GDD is often based on 50F or 10C, as follows: take the average temperature of the day, A, by averaging the day’s high and low, and subtract from it the baseline B (usually 50F or 10C): X = A – B. X is the number of degree-days you accumulate for that day. Do the same for each day in the year (or growing season, for annuals) and sum it up (ignoring days that have negative values), and you get a measure of how much growing heat was accumulated by plants. 50F is used as a standard baseline, under the assumption that 50F is the minimum temperature for many plants to grow. Below that temperature they are effectively dormant.

You can easily find your local GDD information using this Growing Degree Days calculator. I put in local info and it was a revelation — it explained to me why tomatoes, peppers, squash, and many other annuals struggle to mature here before autumn weather kicks in — they just don’t get the accumulated warm growing time they need. And I saw that nearby inland locations have a 50% higher GDD50 than along the coast.

For fruits that need more heat to mature and sweeten — say Oranges or Pomegranates — you can select 60F or even 70F as a baseline. There again, I found that we just don’t have the heat along the coast here to grow sweet Oranges — something many gardeners in this area could attest to. Not all fruit trees require high GDD to produce mature, good tasting fruit. And indeed some fruits actually need lower values to produce well — some grapes for instance don’t like too much heat while other cultivars require it. Avocados, as it happens, don’t seem to need much heat to produce good fruit, but they can’t stand too much cold in the winter. Some fruits — like bananas — seem to need a combination of heat and no frost, and so they’re among the hardest to grow outside of the tropics.

So this post isn’t to say that the hardiness zone concept isn’t useful — GDD doesn’t tell you what will survive the winter. But both concepts are needed to determine a) what will survive the winter (hardiness) and b) what will grow well (GDD).

Growing Avocados

There isn’t much widespread knowledge about growing Avocado trees, especially outside of the few regions they’re grown commercially. I’ve been pretty singularly focused on growing Avocados in the last few years, but in sub-optimal climates, and wanted to share some of the hard-to-find information I’ve come across. (Disclaimer: I don’t claim any special knowledge beyond a serious interest in the subject and I don’t want to duplicate much of what’s already written in the Avocado wikipedia entry among other sources.)

There are a number of reasons I think Avocados are worth growing: they’re one of the few sources of plant-based fats (and non-starch calories), they have a broad spectrum of nutrients, they can be harvested over a long period and don’t drop off the tree that easily, they’re relatively pest free, and, of course, they’re delicious. Also, a new and somewhat sad reason has come up: Citrus greening disease, which is wiping out Citrus trees worldwide. Avocados can grow well in most places that Citrus grow today; Citrus that succumb to greening could be replaced by Avocados.

So suppose you want to want to grow Avocados. Well first let’s examine the optimal climate, and then see how far we might be able to stretch it. Some of the best climates for growing Avocados in the United States have December average daily low temperatures in the mid-high 40s F (8 C) and average daily high temperatures in the mid 60s F (18 C), and August average daily highs in the high 70s F (25 C). (Since they get little rainfall in Southern California, Avocado orchards are of course irrigated at great expense.)

My interest has been growing Avocados outside of that optimal climate. So there are a few things to know. First, the three types have different properties both in fruit and in growing conditions. Second, it’s possible to give them what they need outside of their optimal climates.

There are broadly speaking three types of Avocado: Mexican, Guatemalan, and West Indian (there are of course numerous crosses between them). Avocado trees, like many other fruit trees, don’t grow true to type if grown from a seed — start an Avocado from seed and you never know what you’ll get (and it’s generally thought to be unlikely you’ll get a tree that produces tasty fruit or any fruit at all, though you will most certainly get a beautiful tree). If you have land to spare and live in a marginal climate, I would recommend starting many Avocado trees from seed to find what survives in your region, but this approach can take many years of patience. So most Avocados come from grafted trees of a specific cultivar. Hass, the most common cultivar grown today, was discovered in Southern California in the early 1900s, and is thought to be mostly Guatemalan with a bit of Mexican genetics. But there are many, many more cultivars, some of which I’ll talk about below.

West Indian Avocados grow well in the Caribbean, Florida, and similar areas that have hot, humid, and wet climates. However the large light green-skinned fruit they produce aren’t generally as flavorful as the Guatemalan / Mexican varieties I’ve come to love — West Indian Avocados are low in oil content and more watery. I have to admit that I don’t have much to say in their favor, and will focus on the other two types.

Guatemalan Avocados are most similar to the rich, nutty, creamy varieties available at the store — Hass and its relatives. Guatemalan cultivars are the most sensitive to frost, and when young can barely handle any time below freezing without protection, but as mature trees can handle a few degrees below freezing before succumbing. They do best in regions with a smaller temperature range, such as along the coast. Other Guatemalan or mostly-Guatemalan cultivars include Reed, Gwen, Queen, Kona Sharwil, and Pinkerton.

Mexican Avocados are also quite tasty though not quite as rich in flavor as Guatemalan varieties — Mexicola Grande is one of the better known cultivars — and are able to thrive in locations with more winter frost and more summer heat. They have been known to survive temperatures of 20 F (-7 C) (some claim even lower). Their fruit is generally smaller than the other two types, and has very thin skin (that is often deep purple-black). Other Mexican cultivars include Mexicola (non-Grande), Bacon, and Zutano.

Mexican-Guatemalan hybrids thrive in in-between climates — regions with some coastal influence but more heat in the summer and cold in the winter. Fuerte is one among many such half and half cultivars, and Ettinger is another such hybrid.

In their optimal climates, Avocados are split into type A and type B, which indicate their flowering pattern. It’s thought that you’ll need a type A and a type B for cross-pollination to get fruit. However outside of regions that are as warm and temperate as Southern California, the trees get confused about their flowering schedule and having the two types is less important. In general, though, Avocado trees produce better when they have cross-pollinators.

The trees don’t appear to be too picky about soil, but they don’t like waterlogged soil (which can cause root rot) and have shallow feeder roots so do best with a thick layer of coarse, weed-free mulch underneath (e.g. leaves, tree trimmings, wood chips, etc.). Planting them a little above natural grade can help avoid waterlogging and keep them slightly warmer. A deep watering once per week when there isn’t rain seems to be sufficient, though there are plenty of mature Avocado trees I’ve seen that are growing and fruiting in Northern California without any care at all, surviving year-round just on the rain they get during rainy winters. While they will grow in containers, it’s unlikely they will fruit. Generally they need full or near-full sun to do well, though cloudiness doesn’t seem be an issue as they grow in plenty of cloudy / foggy coastal locations in California.

Most Avocados are grown in tropical, subtropical, and Mediterranean climates, but I suspect that it’s possible to grow Avocados much further North than they are currently grown. And beyond that, as climate zones slowly shift pole-ward, places that an Avocado might just barely survive now might be able to get fruit in a few decades.

As it stands, I know that it’s possible to grow Avocados in most parts California, much further North than most people are aware — virtually to the Oregon border. Within the U.S. I’d bet that Mexican cultivars (or hybrids that are mostly Mexican and part Guatemalan) could grow in a number of spots along the Oregon and Washington coast (and/or on hillsides of near-coastal sheltered valleys — assuming the hillsides get less frost than the valley floor, which is usually the case). Outside of the U.S. it might be possible to grow them in regions like Southern England, along the West Coast of France, and maybe even protected coastal areas of Belgium and the Netherlands; also much of coastal Japan could likely grow Avocados. Elsewhere they can be grown in large greenhouses, but you’d need to ensure a moderate temperature range and that (for Mexican and Guatemalan varieties) the humidity doesn’t get too high. When living outside of the right climate it can be hard to get grafted trees of specific cultivars; however I’ve found that local fruit tree nurseries will often do a special order if you ask.

When grown outside of their optimal climate, Avocado trees will sometimes lose their leaves when young or when stressed by cold or over-watering. Sometimes the leaves will just turn brown and hang on the tree for months through the winter, only to drop in the spring when new leaves come in. So don’t assume the tree is dead just because it’s lost its leaves in the winter.

Beyond selecting the right cultivars, it’s also fairly easy to create a microclimate that is a few degrees warmer than the surroundings by adding more temperature buffers (e.g. rocks, water features, concrete, etc.), cold air drainage (e.g. downslopes from the Avocado so cold air can flow away on cold nights), and placement so that the tree gets sun as early as possible on winter mornings. Growing against a South-facing wall (in the Northern Hemisphere) can help. With these steps, plus protection while the tree is young, and I think Avocados could be grown far and wide.

Rube Goldberg Nature

The more I learn about it, the more Nature looks like a Rube Goldberg machine: energy and materials flow through convoluted paths to accomplish something seemingly simple. Take the process by which a leaf decomposes. The sheer number of biogeochemical processes involved in the use of that leaf during decomposition is amazing: consumption by fungi and bacteria, use as shelter / habitat by soil nematodes and other microscopic organisms, consumption at a macro scale by larger soil organisms like earthworms, beetles, and crustaceans, use by natural geochemical processes in soil formation or water storage, and far more that I don’t know about (and that I’m sure even researchers in the field are still discovering).

A wild ecosystem involves countless intricate relationships, some essential to the functioning of the broader ecosystem (e.g. those between keystone species and others). Many of the relationships in such ecosystems produce yields of energy (and thus life) for creatures that have no immediate use to humans, and may even be pests on some level.

In many of our human systems, however, in the name of efficiency we engineer out the middle steps. Obvious examples of this abound in the industrial food system. An industrial CAFO is a bastion of efficiency, of a narrow sort. Food arrives (from the outside, typically) in a highly energy-dense and processed form, ready for conversion by the machine-animals from carbohydrates into meat and other products. Any waste products that can be used by humans are siphoned off during this process for sale; any that can’t be used are sent to waste lagoons and the like. The process is linear and of low complexity — food comes in one end, meat and waste on the other.

Consider how it’s often found that eating a fruit delivers vitamins more efficiently than taking a multivitamin. What in the mimicry of the natural vitamins is the multivitamin tablet missing? Instead of opting for the complexity of the fruit, we get orange tablets that can be churned out much faster and cheaper than growing oranges.

The problems inherent in such a way of thinking about and working with Nature is well known. What’s a better way of approaching it? It’s often been argued that the solution is to mimic nature. (This is indeed the approach taken by several agroecology systems, like permaculture.)

But there’s something missing here — and maybe the problem is inherent to some (but hopefully not all) attempts at biomimicry. Suppose I were to build a computer system that tries to learn from Nature. We spend some time analyzing how the natural system works, but to simplify matters we use the usual techniques of scientific reductionism and make the natural system much simpler than usual. Then we take a subset of the natural system and simulate or mimic it. Have we captured the right parts?

More than just capturing the relationships between the parts correctly, such a reductionist approach is at risk of opting for efficiency over resilience or even sacrificing both efficiency and resilience. That is, such an approach could confuse a Rube Goldberg machine that mimics Nature for the real thing. One of the hallmarks of a Rube Goldberg machine is not only its complexity but also its fragility — its lack of resilience. If even one step along the way fails, the whole system fails to achieve its objective, and is not self-repairing.

Thus there might be an important distinction between inherent complexity and apparent complexity. That is, if biomimicry is an important approach to solving problems to meet human needs in a more sane way, we need to be able to differentiate between the Rube Goldberg machine and a bona fide web of life. While Nature might look like a Rube Goldberg machine, it has inherent complexity.

I think this distinction between inherent and apparent complexity arises is many contexts. Consider the subfield of mathematical topology known as knot theory, which is about the study of, well, knots. A circular piece of string might be of low apparent and inherent complexity — the “unknot”, which is just an open loop. Take that string, jumble it in your pocket, and take it out and lay it flat on a piece of paper. You can write labels for crossings that you see using dowker codes, and may arrive at the conclusion that the knot is complex — that it has many crossings (that, presumably, could be hard to untangle). However if you haven’t actually changed the loop of string in any way, and if you were to hold it in just the right position, it’d be clear that all you have is the unknot — that the inherent complexity is low despite high apparent complexity. In this context inherent complexity is captured in the concept of crossing numbers.

When we build a complex system using biomimicry — say the construction of a watercourse, selection of plants in a fruit-tree guild, design of a composting system intended to prevent phosphate loss, or any number of others — is the inherent complexity high or just the apparent complexity? How can we tell? Perhaps one easy way to tell is to break the system. If I identify, say, 10 places I could break the system, and break it in those spots, what happens? Does the system route around the failure, or does it fail catastrophically due to my actions? If a leaf is decomposing and there are no appropriate fungi present, bacteria will get the job done, and vice versa; if neither are present, something else will take over. Only in degraded ecosystems — ones that have low inherent complexity — will decomposition not take place at all.

Perhaps then we should evaluate our systems not only by whether they mimic Nature well in the ways that they function but also how well they mimic Nature in the ways that they don’t.

Tree Debt Revisited

Another perhaps more straightforward way to look at tree debt is to consider the following: what population of trees do I need to personally plant and sustain to equal my carbon emissions? Thinking of it this way tries to equalize two rates: the rate of emissions on one hand and the rate of absorption by trees on the other. So tree debt could be thought of as an obligation to personally plant and maintain a grove of trees (not necessarily all in one location) of a certain size.

To determine my own grove size, I used a reputable carbon calculator to determine our household emissions. The result was 20.5 metric tonnes of CO2 per year. Then I divided that in half for my share, and then again by 3.67 to convert into C from CO2. That’s 2792 kg of C per year. Using the value of 10 kg C / year / tree, this results in a grove size of 280 trees. If I plan to build up this grove over 10 years, this means I should be planting 28 trees a year. I’ll also need to ensure that all the trees I plant stay alive and healthy and plant additional trees if some don’t.

Of course this isn’t to say that I can’t or shouldn’t decrease emissions — and indeed I should. But I’ll take 28 trees per year as my personal target going forward.

Trees, 2013

About a year ago I wrote about Tree Debt, the idea that we might measure our carbon emissions in terms of the number of trees that we’d need to plant to consume an equivalent amount of carbon from the atmosphere. After a few calculations, I arrived at a rough rule of thumb that those who are responsible for an average American’s amount of carbon emissions should plant one tree per week and those that are closer to the worldwide average should plant one tree per month. I don’t know where exactly I fall, but I’m somewhere in between.

In any case, here’s my scorecard for this year. Here’s a list, in roughly the order that I planted them:

  1. Kona Sharwil Avocado
  2. Nectarine
  3. Wonderful Pomegranate
  4. Moro Blood Orange
  5. Gala Apple
  6. Meyer Lemon
  7. Reed Avocado
  8. Pinkerton Avocado
  9. Meyer Lemon
  10. Valencia Orange
  11. Fuji Apple
  12. Queen Avocado
  13. Coast Redwood
  14. Eureka Lemon
  15. Lamb Hass Avocado
  16. Grapefruit
  17. Strawberry Guava

I clearly fell short of one tree per week. (There were also several Figs and Lemons in containers, but those won’t be able to grow to full size so I’m not including them.) The main challenge I ran into was finding places with good enough soil. To deal with this, I started a few soil remediation projects — two sheet mulches (using tree trimmings from local tree companies) in two different formerly-grass covered yards, and a stretch of sidewalk-strip soil restoration using Daikon Radishes, Fava Beans, Comfrey, and coffee grounds from a local coffee shop to break up rock-hard clay soil. In the spring, the plan is to plant several more trees in these spots.

Changing Terminology

This is a short post, but it’s one I’ve been thinking about for a while.

Lately I’ve succumbed to the trend of labeling certain gardening and landscape-design practices as being permaculture or permaculture-like, and I realized that a) the term isn’t particularly descriptive and b) there is a certain quality to the permaculture community that has confused me that I’d like to describe a bit further.

As for issue a): the term permaculture is now used to mean everything and nothing, including ordinary organic gardening, earthworks, perennial agriculture, local currency systems, and much, much more. It’s starting to be hard for me to keep track. Part of this stems from the generality (and vagueness) of the core permaculture principles, and part of it is a bandwagon effect, in which people are using the term because it’s gaining widespread popularity, thereby making it more popular. A key aspect of what is often called permaculture is really agroecology. While agroecology may not be a better-defined term, it as least has a more limited scope.

Issue b) is a sensitive topic, but it’s my sense that there’s a certain closedness to permaculture — there are remarkably few books that really get into the details on permaculture, especially given its popularity. Hemenway’s Gaia’s Garden is still the only explicitly-categorized permaculture book that I find myself referencing regularly and recommending to others. Most of the original Mollison and Holmgren writing is too disorganized and sometimes even a bit questionable, and few other leaders in the field provide sufficient actionable detail about their methods (consider, for example, the books by Holzer, Bane, and others). While I understand, in general, the value of taking a permaculture design course, not everyone can afford (in the sense of money or time) to take one, nor should the knowledge be closed off to those who don’t, as some people don’t learn well in such environments anyway. Beyond the courses, there are now permaculture conferences that are extraordinarily expensive. Personally, I’ve found that I get a lot more out of digging into lots of books, talking to other gardeners who are doing something I’d like to try, and then just trying out new techniques. Some of these experiments fail, but it’s that trial and error that I find valuable. I often find myself wondering why more isn’t known about what works and what doesn’t, or more likely why such knowledge isn’t shared.

I do believe that new terms can have meaning when an effort is made to define them clearly but also when they aren’t held tightly, as in my discussion of terraforming. So going forward I won’t explicitly avoid the term permaculture (or terms like it) but I will prefer agroecology and similar terminology where possible.

the planet you can save, maybe

Recently Barath wrote to me:

Peter Singer’s ‘The Life You Can Save’ argument came to mind listening to last weeks’ C-Realm episode.  This was the question of whether we each have an obligation to do as much as we can to save the lives of others and if so (a) why limit it to just human life (given Singer’s anti-speciesist thinking) and (b) is Singer’s narrow formulation right?  Specifically, Singer argues that we should contribute to feed the hungry, etc. but I wonder if ecological restoration projects that have very long but big payoffs are actually better, but harder to quantify.  That is, how does one reason about such ethical questions once they depend upon unknowable or hard to quantify evolving scientific understanding?

These are really good questions.  To begin to answer them, here’s Singer’s argument from The Life You Can Save website:

If we could easily save the life of a child, we would. For example, if we saw a child in danger of drowning in a shallow pond, and all we had to do to save the child was wade into the pond, and pull him out, we would do so. The fact that we would get wet, or ruin a good suit, doesn’t really count when it comes to saving a child’s life.

UNICEF estimates that about 19,000 children die every day from preventable, poverty-related causes. Yet, at the same time almost a billion people live very comfortable lives, with money to spare for many things that are not at all necessary. (When did you last spend money on something to drink, when drinkable water was available for nothing?)

This is a slightly less formal version of an argument he made in the 1970s in his (in)famous “Famine, Affluence, and Morality”, and which was also formulated (independently, I believe) by Louis C.K.  The upshot is that affluent people ought to devote more—a lot more—of their resources and effort to helping those in direst poverty.

It makes sense to ask, when presented with this argument, whether it can be generalized beyond specifically human harms and benefits.  What about harms and benefits to the greater environment?  In fact, this kind of generalization is what I took Kris de Decker to have done  when I tried to reconstruct his argument for bottled water consumption.  But as Barath points out, Singer holds  anti-speciesist commitments which appear to broaden the scope of the conclusion.  The principle at work in Singer’s original argument, for example, is:

If it is in our power to prevent something bad from happening, without thereby sacrificing anything of comparable moral importance, we ought, morally, to do it.

What kind of things count as the “something bad” we should be worried about preventing?  Human suffering, certainly.  But anti-speciesism tells us that we can’t simply neglect the moral significance of nonhumans.  Are we thereby also obligated to prevent environmental harms?

The answer to this is pretty long, actually.  First, it’s true that Singer’s against speciesism, but speciesism is just the idea that species membership alone justifies differential treatment.  So it’s consistent to be against speciesism but still hold that some species are more important than others, morally speaking, if the reason isn’t simply species membership.  And in fact this is what Singer holds.  Singer’s variety of utilitarianism is based on interest- or preference-satisfaction.

Detour into moral theory

Technically, Singer’s famous argument is not utilitarian, and its soundness doesn’t depend on accepting utilitarianism.  But it’s close to utilitarianism in a crucial respect, and I’m going to ignore the differences in what follows.  (Pedants and/or ethicists be damned.)

So.  Utilitarianism can be thought of as a conjunction of two ideas.  First, that rightness consists in maximizing the good.  Second, that the good is happiness.  (There are many, many variations on these ideas but the family of utilitarian theories generally adheres to them.)  But now we need to know what happiness is.  The classical utilitarians—James Mill, Jeremy Bentham, and (arguably) John Stuart Mill—held that happiness is pleasure.  Hence they’re known as hedonistic utilitarians. For hedonistic utilitarianism, all pain and pleasure count alike, no matter what kind of being you are.  Hence Bentham’s famous plea on behalf of nonhuman animals: “the question is not, Can they reason? nor, Can they talk? but, Can they suffer?”

But there are widely acknowledged difficulties with the idea that happiness is pleasure, and later utilitarian writers substituted different conceptions of happiness.  Singer opts for happiness as interest- or preference-satisfaction: roughly, getting what you like, or what’s good for you given the kind of being you are.

Because there is a spectrum of animal complexity, different species will have different interests.  Some animals merely have interests in staying alive and avoiding pain.  Human beings have many interests on top of that, and those interests are influenced by our individual makeups, our cultural setting, our level of education, our past struggles, and so on.  Thus a human who is badly off (say, living a life of grinding poverty) is, according to Singer, much worse off than a nonhuman animal (even an intelligent one like a pig) in analogously impoverished circumstances, because the human has many more interests, and most of those interests are more serious than the pig’s.  And death for a human is worse than death for other animals, since human beings have interests in their life plans, in their family’s well-being, etc.

So although Singer takes all interests equally, some interests are more serious than others, and some beings will have a greater number of interests frustrated by adverse conditions.  It turns out, then, that humans are—in a sense—more important than other species, although not every human interest trumps other animals’ interests.  Singer thinks e.g. vegetarianism is obligatory because no human interest in pleasure can outweigh an animal’s interest in staying alive.  But IIRC he is ok with some restricted kinds of medical testing on nonhuman animals, due to the importance of medical science.

The planet you can save?

Singer himself probably would not extend the argument from “the life you can save” to include the environment, broadly construed.  That’s because that argument depends on comparing outcomes as to their relative goodness/badness, and the way Singer assesses goodness/badness is in terms of interest-satisfaction.  Only a few animals (the sentient ones) have morally relevant interests in his sense, plants have none, rocks have none, ecosystems (indeed anything above the level of an individual organism) have none.  To the extent that ecological properties figure into his argument, they will figure indirectly as things conducive to good human lives.

That said, we could ask a couple of questions.  First, what kind of position would we get if we took Singer’s argument seriously, but jettisoned his conception of the good?  E.g. we could take up a conception of the good which is not only non-anthropcentric but fully ecocentric.  (The resulting position would probably be something like what I think of as Derrick Jensen’s: radical action to destroy civilization.)  Second, what happens if we stay with Singer’s view but amend it to take into account future people?

This is getting toward question (b), about whether even the narrow formulation of the argument is correct, given future human interests.  Tim Mulgan (Ethics for a Broken World) is someone who takes utilitarianism seriously, but who thinks that most ethicists haven’t yet learned to take future people into account.  When you do, he thinks, you realize that future persons stand to us in (almost) exactly the same way that today’s global poor do.  One group is distant in time, the other is distant is space, but exactly the same principles of justice apply.  So, Mulgan would say, Singer’s insights haven’t been pressed far enough, and once we see they apply to future people we find that we are behaving grossly immorally.  We ought to stop taking resources which future people need, we ought to take radical action to stop our destruction of future people’s climate, and we ought to live much, much more modestly, devoting our nonessential time and effort to making things right by the future.

But this conclusion is arrived at by entirely anthropocentric means—the only things considered morally significant  are people, and all other goods are instrumental to the welfare of people.  So we can make a case for taking the environment seriously, indeed for radical preservation of ecological systems, purely on anthropocentric utilitarian grounds, just by treating future people as equally important.  And if we, like Singer, extend moral consideration to some nonhuman animals, then the case for ecological preservation becomes even stronger.

(Interestingly enough, these ideas have played out between two utilitarians I know (call them ‘P’ and ‘T’).  After taking a flight to a conference in Europe, P mentioned to T that he’d bought carbon offsets.  T responded, “Why would you ever buy carbon offsets when you could donate that money to poverty relief?”)

Action and uncertainty

But now there is the question of how to evaluate actual proposed courses of action when the outcomes are uncertain.  The standard utilitarian answer is to do an expected utility calculation: multiply the value of an outcome by its probability of occurring, and, for evaluating actions, sum the expected utility of each action’s possible outcomes.  Then go with the action that comes out on top.  Of course, this is going to be difficult even for  short-timeframe decisions, and there’s idealization involved in assigning numerical values to outcomes, but your meat-and-potatoes utilitarian will say that that’s the ideal to aim for.

This answer becomes much less helpful when the far future is concerned, since it’s so hard to predict, and it becomes deeply complicated when there is uncertainty not only about future outcomes, but about which model for estimating future outcomes we should use in the first place. (Or do we combine models, and if so, how should we do that? etc.)  I certainly don’t have an answer to that, but because I’m not a utilitarian, I don’t really feel the need to have one.  I would guess that some philosophers who work on climate change have made proposals, but I’m not actually very familiar with that literature.  And there might be something helpful in the literature on evidence-based policy, though I’m not sure.

A shorter answer to all this might be that, no matter what ethical theory you’re working with, ethical reasoning always happens by conjoining normative premises about what one ought to do with descriptive premises about empirical fact.  When those descriptive premises become highly uncertain, then one’s reasoning about what to do is concomitantly uncertain.  But how much of a problem that is depends on your ethical theory to begin with.  Utilitarians will insist there is always a right thing to do; virtue ethicists (for example) not so much.  But I think this whole discussion is illustrative of a real problem for utilitarianism, given uncertainty about the future: all of an action’s consequences for happiness matter.  Thus utilitarianism might tell us to help the global poor (as Singer thinks), but it might also tell us to let them eat cake.  Everything depends on the empirical facts about which policy will yield the most happiness over time, but in many cases we just don’t have access to those facts.

For my part, I think that very broad principles for decision-making under uncertainty, such as the precautionary principle, go a long way, and needn’t rely on utilitarian justification.  But that’s another conversation, and anyhow I have never really achieved equilibrium in my own ethical convictions.

We Can Feed the World / No We Can’t / No We Won’t

There are, and have been for a few decades now, competing narratives about food, hunger, and population. And supporting these narratives are a large number of divergent arguments from people with an even larger array of ideological perspectives. I’ve been puzzled for some time that these narratives not only have co-existed for as long as they have, but that it’s still unclear which is true, and more than that, which of the supporting arguments make sense and which don’t isn’t clear.

Below I’d like to attempt to break these narratives into three (oversimplified) categories and highlight a few recent and not-so-recent arguments supporting them.

We Can Feed the World, part 1.
This argument comes in a number of forms. The first, most obvious, and most prominent one is that of the agribusiness world, which says and has said for decades that new chemistry and new genetic engineering can and will continue increasing yield. The claim they often make is stronger than this, saying that only such agribusiness science and engineering can increase yields and feed the world, and that without them people will starve. (Scientific American had a recent issue dedicated to this, and it was, frankly, a bit embarrassing to see such a magazine be so narrow in what science they considered in making their judgments.)

However, often ignored in this perspective is the fact that a billion people around the world are going hungry already, and many more are food insecure. Many farmers who have switched to using these agribusiness methods have found themselves struggling to pay for them. They have also found that the techniques, when they work at all, have little staying power: artificial fertilizers only provide a boost for so long before already-depleted soil is stripped of structure, other nutrients, and soil life and can no longer produce high yields; GMO, pesticide, and herbicide manufacturers struggle to keep pace with natural adaptations against their methods. So while it’s true these systems are feeding the world, it’s not clear they can continue to.

We Can Feed the World, part 2.
A less common but still prominent argument made by Lappe and others in books such as Diet for a Small Planet and Hope’s Edge, is that scarcity of food is a matter of proper distribution of food and/or income, and a matter of not wasting food via the present-day industrial food system. That is, there is enough food being grown to feed the world, but that instead of going to feed the world, this plant-based food is either used as animal feed for heavy meat eaters in wealthy nations, is used in the production of highly-processed industrial food, or is simply wasted.

This argument is based upon a slightly shaky premise. Even if the world were short, say, enough food for 1 billion people, and there were no waste in the current food system, there are probably enough other sources of calories that could be turned to that are outside of the human economy — that is, plants and animals that are currently not viewed as food but could be. That’s not to say that it’s preferable to increase the human footprint on the planet, but rather that the argument is premised on the footprint we have today and that footprint isn’t fixed.

Turning this reasoning on its head, we find that the argument that we can feed the planet using the food that’s grown today, with today’s footprint, doesn’t squarely face the fact that humanity has already far overshot carrying capacity and has appropriated far too many ecosystems for its use. That is, for this argument to hold — making the big assumption that the economic systems that make today’s food system exist were to be radically altered — we’d need to be able to replace all of the food growing going on across the globe in a way that puts it on a sustainable footing. Maybe this is possible, and Lappe and others give plenty of examples of how it can be done better on a small scale, but as I’ll discuss later, a large question is whether we will, not whether we can.

No We Can’t, part 1.
There are some in the mainstream of this discussion who are nevertheless pessimistic about food availability. In this camp I’ve seen arguments for decreasing the birth rate in poor nations (primarily) as they view the problem as a matter of population, and that energy/resource footprints aren’t an issue in the discussion. I’ve never found mainstream “no we can’t” arguments to be particularly well thought out, as they’re often used as a bludgeon to make a political point (e.g. “people in country X are hungry not because globalization destroyed their local economic and agricultural systems but because they have too many people, and we can’t fix that”).

No We Can’t, part 2.
Many eminent, less-mainstream thinkers fall into a second category of “no we can’t feed the world” thinking, including Meadows, Catton, Diamond, and others who take a large-scale, long-term ecological view of the predicament humanity is in today. They argue that all societies and all systems that overshoot their ecological basis a) are eventually forced to return to within that basis, b) often degrade the basis itself by being in overshoot, and that c) this process happens so slowly (over many human generations) that it’s easy for these societies to believe that they have agency, d) no past societies have been able to avoid this consequence and there is little reason to believe that now is different, and e) no one subsystem (e.g. food, manufacturing, etc.) is independent and thus all subsystems rise and fall together.

Surprisingly even mainstream commentators like Thomas Friedman have gotten in on this kind of argument, though of course after making the argument that we’re in overshoot, he manages to ignore its fundamental conclusion and instead argues that we’ll find a way out.

No We Won’t, part 1.
Last year Adam wrote a nice analysis of a Toby Hemenway article on the resilience of the food system. He made the case that while Hemenway’s arguments on how the industrial food system might continue to function and feed humanity (even while fossil fuels become more expensive and scarce) make sense in the way Lappe’s arguments make sense, there’s reason to be concerned that market conditions and public policy will make entrenched actors in the food system slow to adapt to changing conditions. Thus it’s likely that people will continue to fall off the back of the truck as things decline. Beyond simply the monetary incentive to continue growing crops for non-food uses, there is also significant inertia and sunk costs in the system that are likely to make change difficult. I find myself in agreement with this part of the argument: “I’m optimistic about the proliferation of kitchen gardens in urban and suburban spaces, but transforming land currently zoned for industrial monoculture is a much more daunting task.” I’d like to consider where this leaves us next.

Energetic limits of land productivity.
To understand what sorts of physical limits might exist on food production, I did a quick calculation. While I’m sure there are many better estimates out there, this should give us a rough idea of whether it’s even reasonable to imagine that 7 billion or more humans can be fed sustainably. Let’s start with an estimate of 200 W/m^2 of sunlight, globally averaged over night and day, arriving at the Earth’s surface. Average photosynthetic efficiency is about 1-2% for normal plants (only some algae and a few rare plants like sugarcane get higher efficiency). So that’s 2-4 W/m^2 of plant energy assuming the ground is entirely covered. Then let’s allow 50% for the plant to perform its own metabolic functions, so that’s 1-2 W/m^2 of harvestable energy (edited to add: on average — if we factor in growing degree days, we might say roughly 1-2 W/m^2 is for mid-latitude/subtropical regions, with 2-4 W/m^2 in the tropics and 0.5-1 W/m^2 in high-latitude temperate regions). Given that a person requires 100 W (about 2000 kcal / day), that results in 50-100 m^2 of land requirement per person, which is about 500-1000 sq ft, which happens to be about what David Duhon and John Jeavons found is the minimum land area on which one can feed oneself growing and eating mostly potatoes in a perfectly-managed, intensively-cultivated smallholding.

So no new technology is needed, nor is new technology possible, to improve the efficiency with which we can produce food. That is, the arguments made by those in the first camp — those who argue we must increase yields through new techniques in industrial agriculture — are bunk, as techniques have already been developed to deliver the maximal yield possible given the sunshine falling on the Earth. Literally the only way out of this (energetically), I think, is to build nuclear fusion plants and then use the energy from that to produce food somehow — that’s the only possible renewable non-solar source of energy — but this remains firmly in the realm of science fiction.

However, when we look at the amount of farmland under cultivation today, we see that it’s far more than is required to feed all of humanity ten times over if such intensive cultivation were used — perhaps 500 billion people (as my friend John pointed out). The catch, I think, is twofold.

The first catch is that we must consider total human energy consumption rather than simply what humans require to stay alive. In the absence of fossil fuels, this energy will come in large part from plant sources. To begin with, intensive cultivation requires cycling back all nutrients perfectly to keep it within 100 m^2. Otherwise it requires about 3x the land area, with the remainder used for compost crops and letting the land rest (with 3x being a rule of thumb I’ve seen in a number of sustainable agricultural methods). This ignores the water cycle and other limits for simplicity. Average energy consumption globally today is 2kW / person (16 TW / 7 billion = 2285 W). So that means we need to roughly scale down the arable land by a factor of 20 (to get the portion used for just food), and that’s with perfect nutrient cycling. Take a factor of 3 on that for compost crops, and we’re at 8 billion people living at 2kW. If we had no other impact on the planet and could do perfect sustainable organic agriculture with most people living in lower-latitude temperate and tropical regions we could sustain 8 billion people on the planet.

A couple big flaws in this estimate is that a large fraction of arable land is used to feed animals for meat, and that the 2kW used per person often involves taking the products of nature and processing them, thereby consuming an outsized portion of nature relative to that energy budget (e.g. it takes much less energy to cut down a tree than it took the tree to grow). The first could be fixed by saying that we could sustain 8 billion people on a perfectly managed vegan organic diet, and with meat, somewhere between 2-4 billion. Even this ignores the possibility of getting some of the 2kW / person from photovoltaics and wind turbines. Nevertheless, the crux of this calculation is that sustainable techniques exist to produce roughly as much food as the industrial food system produces today, but also roughly as much as is possible given energetic limits.

The second catch is the one Adam identified — converting backyard gardens is one thing, but turning the farmed-out land of the American Midwest into Jeavons-style smallholdings is another thing altogether.

Premises and Conclusions.
It’s a bit odd to end on both premises and conclusions, but there are a couple of premises that are unstated in this discussion that span the categories. Specifically, this discussion is premised on the notions that feeding the people of the world is a) good and b) hard to do either now or in the future. I think both of these are true, but I’ve seen arguments that b) isn’t fundamentally true. Neoprimitivists tend to make this argument, among others: that the world is naturally abundant and that as long as societies remain uncivilized (i.e. not living in cities with high resource consumption) then the Earth will provide with little effort. Whether this was true in the distant past, it’s certainly not applicable now and won’t be for many centuries.

Pulling these strands of thought together it seems to me that there’s good evidence all these perspectives are right, but on different timescales. We have a core industrial food system that can and will feed most of (but, crucially, not all of) the world in roughly the ways it is today, with feedback loops that will keep it stable. These feedbacks include the entrenched food distribution system, political lobbying of industrial farmers and agribusiness that want to keep subsidies flowing to keep their business models viable as long as possible, and the eating habits of the world. However since this system is not on a solid foundation, it will slowly (and, perhaps in short bursts, quickly) leak people and land into the two other categories — “no we can’t” and “no we won’t” — in which people go hungry due to lack of food or because the system is imbalanced and prioritizes other things over feeding people. I do think that, like Adam wrote, that kitchen gardens are likely to pick up some of the slack and my calculations indicate that quite a lot of food can be grown that way. However, in the long run, we’re unlikely to escape the ecological fate of so many past societies; our task is make the ride down as smooth as possible.