Thoughts on Sustainability

By Bradley Jarvis

Around Thanksgiving of 2004 I read a book about the future of the Earth called The Life and Death of Planet Earth. This book, written by an astrobiologist and a paleontologist, described how life on Earth will likely come to an end, largely as the result of the Sun’s growing warmer as it ages. According to the authors, the Earth is already past its prime and on its way toward old age. Having evolved for some four billion years, life has probably a half-billion years to go, supporting progressively simpler life until even microbes can’t survive. Within only 100 million years, we are likely to experience a severe and long ice age, the Earth’s last, which will all but wipe out civilization – if something else doesn’t get us, such as an asteroid or comet, a nearby supernova, or a gamma-ray burst. As for escape, they advocated the creation of intelligent self-replicating machines that would spread throughout the Galaxy.

My pattern-seeking brain couldn’t help but link all these themes together. The United States was past its prime, becoming more primitive in its values and its social behavior. World civilization was being forced to conserve rather than grow at youthful rates. The Earth’s natural systems were currently experiencing a major illness, us, and even if they survived, would continue the slide into old age, having reached middle age some 300 million years before we even came on the scene. And I was personally passing middle age: soon I would be 45 years old, with likely much fewer years ahead of me.

Over the course of the next several months, I thought a lot about the long-term future of life on Earth, and how it relates to decisions made on a day-to-day basis in what I had already realized was one of the most critical times in our planet’s history. Following, in chronological order, are some of those thoughts.

Holistic View

The pursuit of sustainability and the near-worship of natural systems that I saw among environmentalists were, on the surface, antithetical to the seeming exploitation of Nature espoused by the space activists. It was tempting to treat each group as a constituency that needed to be courted independently, but this would ignore the potential impact of a fundamental insight from the space sciences: that human influence on the health of Earth’s systems is not the greatest threat to them over the long term. “Sustainability” as defined by most environmentalists is limited by physics to an extremely limited future, bounded in the best case by the next ice age, and in the worst case by the next major asteroid or comet collision. The space community was facilitating the understanding of Earth and its future while working on the development of technologies that might ultimately keep us from dying off for good; and the environmental community was struggling to stop and possibly reverse the current mass extinction event, which was rivaling, if not surpassing the one that killed off the dinosaurs. Put in the larger context of life’s history on Earth, humans were both a major threat and provided a major opportunity. Like a woman in childbirth, Earth life was suffering from pouring its resources into the child and the birth process, risking death to have a better chance at genetic immortality by spreading life to the stars. From this perspective, the interests of the space community were in protecting the child and the interests of the environmental community were in protecting the mother, with neither fully recognizing the need to protect both the mother and child.

The people in the space community, who I knew well, were sold on the ability of technology to solve every problem, including the health of the Earth. If we needed more resources, we could just import them from an asteroid or another planet. If we needed more energy, we could harness fusion here on Earth or trap more of the Sun’s output. If we needed more water, we could desalinate the oceans. To them, these were not insurmountable problems. The space community was full of perpetual optimists.

From what I could tell of the environmental community, changing human behavior was the tool of choice. If we could get people to stop wasting so much energy and material resources, to keep from polluting, to stop being so greedy, and to accept a more “natural” lifestyle, then we could ensure that many future generations of humans and other species would be able to live and live well (at least according to a new and better definition of wellness). To Americans trained in the “get all you can get” philosophy, this message was one of going backward rather than forward.

What was missing was a holistic view, which began with one question: What is life? This would lead to the following questions:

How much life is there?
What is the overall quality of life?

The following questions would then need to be answered:

What does life need to exist?
What does life need to thrive?

The answers to each question of need would take the form of lists. For each item in each list, the following questions had to be answered:

Where is it located?
How can life acquire it?
How will acquiring it and using it affect the ability to acquire and use the other things life needs?

All of these questions would need to be evaluated over time as both life and non-life would be changing.

To most people, filling out this holistic view might be seen as a meaningless academic exercise unless it could be brought into the realm of everyday experience. It would also have to demonstrate verifiable personal and societal gain. Religions had successfully bridged the gap between long term gain and personal welfare by creating what I thought of as “virtual wealth”: the promise of a pleasurable afterlife or oneness with the Universe. Unless someone created another belief system based upon unverifiable personal outcomes, we would need to accept the idea that we were all part of a larger whole, connected throughout both time and space, and that increasing the extent of that whole in the future enhanced all the parts. Further, it was going to have to be provable.

For the first time in history, the tools and information were available to assess the impact of actions on the future of life. But to be useful, the assessment had to be reduced to a relatively small number of key indicators that everyone could understand and whose values they could identify as the result of their actions; and these indicators would have to be closely related to the amount and quality of life.

I looked into the issue of mass extinction (Google: “species extinction”) and found a wealth of information and discussion. Among the most interesting pieces of information was the species-area relationship, which I had run across elsewhere. Based on this rough assessment of how many species could be supported in a given area, it looked like we would need 100 Earths to just double the number of species. If we settled an Earth-like planet around every star in the Galaxy, there would only be about 45 times the number of species on Earth. There were currently between one and 10 million species here.

One of the many books I was reading was called Affluenza: the All-Consuming Epidemic. The book was based on a PBS feature and presented the case that much of the world was afflicted by something strongly resembling a disease. This pseudo-disease (which the authors called “Affluenza”) was cultural in nature and was leading to the exhaustion of natural resources as well as the exhaustion of people who were driven to always consume more. Many of the arguments for sustainable living could be found in this book, along with some practical suggestions for dealing with the affliction.

I was planning my family’s financial future, and wanted to create a lifestyle compatible with our needs and our values. I had already decided on my New Year’s resolution for 2005: not to buy anything new for the whole year. This meant only replacing things I already had, and, where possible, buying used things rather than newly produced things. I learned from Affluenza that there was a name for this, voluntary simplicity, and that it was actually a movement that included some five percent of the U.S. population. Voluntary simplicity was one way I could help the world along with me and my family to get off the path of pain and disaster.

Edward Wilson’s The Future of Life was next on my reading list. Like The Life and Death of Planet Earth, it was a downer. In the book, Wilson, a prominent naturalist, detailed the loss of biodiversity since the rise of humans and made the case for sustainability from the perspective of valuing the natural world. Wilson also described the “natural capital” perspective, evaluating the ecosystem’s value in strictly economic terms (almost double the world GNP), and asserted that it would be impractical in the extreme to attempt to provide nature’s services with artificial services (his earlier book Consilience detailed the reasons; I would add it to my reading list).

I learned that the causes of extinction were summarized by the acronym HIPPO:

H – Habitat loss
I – Invasion (by alien species)
P – Pollution
P – Population (of humans, exacerbating the effects of the others)
O – Over-harvesting (excessive hunting)

These causes tended to interact in most situations, with varying degrees of influence.

Interestingly, the longer humans were in contact with a species, the more likely it would survive. Species with relatively recent exposure to humans, such as those in Hawaii, tended to be more at risk. The reasons had to do with evolution. Species that had coevolved with humans had made adaptations that favored survival. Those that had not coevolved with us didn’t have a chance to adapt before being overcome by us.

We were also a force for reverse evolution, simplifying the natural environment and thereby reducing the complexity of life. As we took over land and converted it for our own uses, there were many fewer niches for other species to occupy. We were also doing the same with members of our own species, as powerful cultures and their attendant organizations (typically businesses and governments) overcame smaller, more unique organizations, and forced conformity to a smaller number of characteristics and behaviors.

Limits

I moved on to Limits of Growth: The 30-Year Update by Donellla Meadows, Dennis Meadows, and Jorgen Randers, coincidentally finishing the book on the day that George Bush gave his 2005 State of the Union address. The authors made a strong technical argument for sustainability, projecting a major population collapse in as soon as 20 years if action wasn’t taken immediately. Limits of Growth counseled reducing the human “ecological footprint” by substituting growth in quality for growth in quantity and spreading wealth more evenly among people so that population pressure could be reduced. Bush, on the other hand, was aggressively promoting totally opposite ends with policies that claimed to favor economic growth, and that increased population pressure by discouraging family planning and increasing disparities in wealth. Pollution mitigation was also important, and on this score Bush was also on the wrong side of the issue. His “Clear Skies” initiative and energy policy relied on industry to make changes they were not likely to make until it was too late. Scientists had just released a study that forecast even greater temperature increases due to global warming, and warned that unless major corrective action was taken within 20 years, the warming would be self-sustaining. Bush and his people continued to oppose action on the issue, apparently still in denial that it was a real problem.

The companion CD to Limits to Growth gave details for each of the ten scenarios described in the book. I had broken my New Year’s resolution, buying the CD so I could get a better feel for the assumptions and behavior of the authors’ “World3” computer model. I also used it for a purpose the authors would have cringed at: estimating the impact of the scenarios on prices to integrate into my long term financial planning.

Each scenario represented a different set of assumptions about efforts to deal with the overshoot of sustainable limits. The first scenario represented a likely future based on present trends. Each successive scenario employed new technology to deal with a major problem along with those that had been dealt with in previous scenarios. The final scenario employed more technology for most of the problems. Significantly, all new technologies would be created in 2002 and take 20 years to have an effect.

When I looked at life expectancy, I became downright despondent. By 2060, if the projections could be believed (and the authors cautioned against taking literally this part of their curves), we would be back where we were in 1935, at 40 percent of the current value, but with one critical difference. Many natural systems would be extremely stressed, reducing the chances of recovery in any reasonable time span.

It was clear that the best answer was to reduce consumption, and quickly. According to the World3 data, the last year that the world was consuming resources at a sustainable level was 1970 (and perhaps as late as 1985). To reach that level again, the average person in the U.S. would need to consume (and spend) 20 percent of the 2005 amount. I found this number in most places I looked in the sustainability literature, matching with estimates of the American ecological footprint. Getting anyone to cut back 80 percent would be extremely difficult, especially in a culture that encouraged increasing consumption. But one way or the other, it was going to happen; and the turnaround was likely going to be forced on us in the next ten years.

Perceptions

In February, I attended two events which crystallized much of my thinking on these issues. The first was a public lecture about sustainability at the University of Colorado. The second was a rally for local Democrats.

Al Bartlett, a professor emeritus in the CU physics department, had for years been promoting public understanding of the exponential function and its impact on the world. During the morning lecture I attended, Bartlett started with an overview of the mathematics, and then discussed some important applications, focusing on the use of resources by an exponentially growing population. Bartlett’s main point was simple: the biggest problem with people is their lack of understanding of the basic “arithmetic” of growth.

He started with a simple calculation, relating the doubling time of a quantity to its growth rate in percent:

Doubling time = 70 / percent growth

Then he showed how our perception of growth tends to be linear, equating the fraction of total resources used (such as area) to the fraction of total time used. In other words, if we’ve only used a given fraction of a resource, we will believe that we have used that same fraction of the total time to consume that resource. Unfortunately, our perception would only be valid if we were using the resource at a fixed rate (units of resource per unit of time), not if we were using it at a rate that itself was some fraction of what we had.

I did some calculating of my own when I got home and came up with an approximation for the time it would take to reach a given multiple of a starting amount:

t = n + 232( n / p )

Here, t is the time, n is the logarithm (base 10) of the ratio of the maximum amount to the starting amount, and p is the percent growth.

When I looked up the annual growth rate of the ecological footprint in the World Wildlife Fund’s Living Planet Report, it was averaging between 1.1% (between 1985 and 2001) and 2.3% (between 1961 and 2001), with a current value of over 1.2 planets. The more limited estimates in the World3 model indicated that the rate was increasing, with a 20 year average rate of 2.5% in 2000.

We were now living off of non-renewable resources. If the amount of these resources was twice the amount of renewable resources, at a two percent growth rate we would exhaust them in 2020 (35 years after the 1.0 footprint was reached in 1985). A one percent growth rate would push the date out to 2055, which curiously corresponded closely to when Bartlett forecast that all the oil would be gone. And of course, none of this considered the costs of retrieving and processing those resources, both in effort and in health (due to pollution). World3, which did consider these factors, showed peak footprints also occurring around 2020 and 2050, with maximum values of up to four planets.

Many prominent state politicians were in attendance at the local Democratic Party rally I attended. Like a lot of Democrats, the people there were still reeling over the loss the national election and they were regrouping to decide how to expand on their gains at the state and local levels. The only mention of the environment during the speeches was a reference to the desire for “clean air and clean water” which I had heard before in public discussions. The future of entitlement programs was heavy on people’s minds, especially Medicare and Social Security, which the Bush Administration had taken special aim at. I got the distinct impression that the amount of wealth wasn’t perceived as a problem, only its fair distribution.

I struggled with the problem of broaching the subject of resource depletion with these people, who I had so recently identified as sharing most of my values. I hypothesized that the perception of remaining time was most likely the culprit behind their lack of concern. Their attitudes made sense if there were no limits; and that we could continue increasing consumption into the far future, subject only to the will of the people and the imagination and diligence of scientists and engineers. There were, however, some people who were sensing limits on the horizon, and might have been seeing those limits as being far enough off to adapt. They, too, could be tragically wrong.

To test my hypothesis, I attempted to graph perceptions based on how near-term changes in the ecological footprint would vary over time based on the first World3 scenario. I assumed that the moderately enlightened person (or business) would extrapolate the most recent five years of change and would have an “accurate” view of the limit’s value. If this scenario was correct, then the peak would occur in 2020. In 2005, projections would anticipate the peak in 2069, which would leave enough time to comfortably lay the groundwork for a sustainable economy. Around 2010 there would be grounds for believing that a considerable amount of progress was being made, as the perceived amount of time left began increasing instead of decreasing. Unfortunately, however, this would be the equivalent of a light bulb brightening just before it died. That date was only five years away.

This analysis clearly showed that a market-driven response to what I began thinking of as “the global resource crisis” was almost sure to fail. There just wasn’t enough time.

My best friend had an optimistic view which naturally followed from his fundamentalist belief in the power of free markets and unfettered technological innovation. Basically, he believed, when things get bad enough, people will pay whatever it took to have the technologies to fix it. If projections of the future were pessimistic, it was because they weren’t considering the impact of new technologies. Meadows, et al had considered the impacts of such new technologies, with each taking 20 years to be universally applied, but in all cases current consumption growth rates could not be maintained, because industrial capacity would be strained just dealing with the problems of increased pollution and reduced resources. And we needed the “new technologies” to have already been developed by now.

As Bartlett pointed out, even a passing familiarity with exponential growth should have tipped off more people that we couldn’t continue much longer, even if they couldn’t concede the closeness of the limits. With the world population growing at over one percent per year and production of such things as minerals and metals growing at around two percent per year, the mathematically inclined among us should have been more worried. With species extinctions and climate change getting more and more news time, we should have been more concerned. The environment wasn’t just a place that furnished products and food through human labor, it was our home, and we were tearing it apart at an accelerated rate.

As I studied the graph of perceived time until resource use peaked, I was struck by several interesting coincidences. During the 1960s and 1970s, where the graph showed a steep decline in the perceived remaining time, there was a marked increase in interest in the environment and in reduced lifestyles. In the late 1980s the interest seemed to drop off, and in the early 1990s it resurged, corresponding to an increase followed by a decrease in the perceived remaining time. While the effects of pollution and localized energy sources were definitely in the public consciousness during the flat period that began in the late 1990s, there was virtually no talk in public forums about limiting consumption.

I personally became more conscious of the impact of consumption because during the 1990s I reinvented myself following my father’s death, focusing on big-picture issues to shape my values and my definition of acceptable behavior. Growing quantity and quality of life having become the basis of my new value system, I gravitated toward the sustainability movement while even more strongly embracing space exploration, which had been an interest for many years.

If smart people like my friend and the more educated among the members of the space community weren’t taking the global resource crisis seriously, then the odds of having the critical technologies in time were much lower than I hoped. They were, of course, a self-selected sample, focused on creating a galactic civilization rather than improving the planetary one. To them, there is no lack of natural resources, but rather lack of will to get them from space. Until we can get them, well, some brave new technology (my friend’s bets were on nanotechnology) will help bridge the gap.

Maximum Growth

I decided to revisit the ultimate future imagined by space enthusiasts, and try to quantify what the maximum possible growth rate of the human species might be.

The simplest model of human expansion into space is probably an expanding sphere, centered on the Sun’s position in the Galaxy.

The Galaxy, also known as the Milky Way, has three main components: a disk, a central bulge, and a halo. The disk is about 30,000 parsecs in diameter (one parsec is about 3.26 light years), and is composed of a thick disk and a thin disk. The Sun is imbedded in the thin disk, about 8,500 parsecs from the center. Most stars considered likely to have habitable planets may be found in the thin disk, which is about 600 parsecs thick. The density of stars in the neighborhood of the Sun is about one star per cubic parsec; density increases the closer you get to the center of the Galaxy, to about 100 stars per cubic parsec at a distance of 100 parsecs, to from 1,000 to 50,000 stars per cubic parsec inside the central bulge. The halo, surrounding the rest of the Galaxy, is very sparsely populated, and composed of mostly older stars. Recent studies of star systems where planets have been detected indicate that there may be as many as 150 billion Earth-like planets in the Galaxy; if they are in the thin disk, then the density of habitable planets is around 0.4 per cubic parsec.

To simplify the model, I assumed an even distribution of stars throughout the disk. As the radius of human expansion increased, the inhabited region could be roughly modeled as the intersection of a sphere and a cylinder. In reality, there would be a “smearing” effect due to the relative motions of the stars, since the expansion would most likely consist of “jumps” from settled worlds.

The first things I noticed were the time scales involved. At the maximum speed currently achievable, it would take several billion years (about the age of our Sun) to colonize the Galaxy. If we could achieve the maximum speed allowable by natural laws, the speed of light, this time would decrease to a few million years, roughly the age of our species.

I built some limits on population per world into the model, expecting that each population would saturate after natural resources had been depleted. Based on our one known data point, saturation would occur when a little more than the Earth's current population was reached. This assumption limited the Galaxy's population to about 10²¹ people.

When I shared my conclusions with my friend, he refused to accept that there was a limit to population size. In his view, we should be able to get all the resources we need from the asteroids and comets in each star system, even if they are not present on the colonized planets. He was more concerned about what he called "pressure" which I interpreted as the equivalent of population density, and how it was influenced by the speed of expansion.

I thought about my friend's point of view and it dawned on me that the answer to my dilemma might be found at the small scale. His argument depended on people being able to develop new technologies that could more efficiently and effectively exploit resources; when one approach stopped working, another would be ready to take its place, effectively making the resources inexhaustible. If, however, a new approach could not be developed before the existing approach reached its limit, then disaster would surely strike. Sustainability was a long-term way to make do, to keep a population's draw on naturally replenished resources from exceeding the replenishment rate. In a quest to continue growth, it functioned more as a way to buy time until a new approach could be developed.

For a more optimistic view on population growth, I turned to John S. Lewis’s Mining the Sky: Untold Riches from the Asteroids, Comets, and Planets, which I had read years ago. Lewis had argued forcefully that there was no lack of resources, a point the space community repeated whenever sustainability was mentioned. He estimated that up to 10¹⁶ people could ultimately be supported in the Solar System, mostly by using asteroid and comet material to create space habitats and using the Sun as the main energy source.

What Lewis apparently failed to take into account was the impact of population growth. At a one percent growth rate, this maximum population size would be reached in about 2,130 years. After that, it would take only 70 years fill up an entire star system. The time available to seek out each new star system would decrease exponentially, so that within 2,600 years from the start, the time to find each new star system would be a year or less.

The most absurdly optimistic scenario I could imagine was literally packing space with humans, so that each person only had their personal space. Forgetting that space must be shared with, among other things, stars, the resources we need to survive, and a huge black hole at the center of the Galaxy, this amounts to a maximum population of about 5 × 10⁵⁹. At a one percent growth rate, it would take less than 11,600 years to reach this population size. In one of the odd coincidences of Nature, it would take almost exactly twice that long, at the speed of light, for the sphere of human presence to encompass the disk of the Galaxy. I didn't need an elaborate model to estimate the maximum growth rate for a population constrained by human-packing, the speed of light, and the amount of space in the Galaxy's disk; that value was half of one percent.

When I used my galaxy colonization model to evaluate more realistic scenarios, the maximum growth rate was closer to half of one percent of one percent. The driving variables were speed and density, which combined to affect the number of habitable star systems available per unit of time. To my surprise, the geometry of the Galaxy turned out to have a minimal role, influencing the details of the acceleration of growth more than its long term outcome. In the most likely example I could think of, the Galaxy would have a population growth rate of about 0.003 percent for a maximum population of 10⁴⁸ people, reached when the entire Galaxy was colonized (about three million years from the time it started), with a density of 0.4 habitable system per cubic parsec, and a peak speed of one-third the speed of light (I used an average speed of half the peak in all my "realistic" cases). The last time the world had this kind of growth rate was about a thousand years ago.

Lessons

I kept coming back to the core of my new philosophy: that all that is good comes from the optimization of both the quantity and the quality of life. These last several months of research and reflection had offered some clues about how this should be approached.

First and foremost, population growth needs to be reduced as much as possible. This will have the immediate benefit of extending our collective lifetime on Earth as much as possible. In addition, we will need to reduce per capita resource consumption to a level that is sustainable for the most number of people with as high a quality of life as possible. This will be a dynamic process, in the near-term, and especially in the long term, as the climate changes dramatically in response to both our impacts and the astrophysics of our planet and an aging Sun.

Second, we need to increase the human presence in space. This has both near-term and a long-term benefits. In the near-term, we can develop more options for resource acquisition and waste disposal, and prevent asteroids and comets from hitting the Earth. In the long term, if we don’t move into space, all life on Earth will surely melt into oblivion when the Sun gets hot enough. We have the chance to increase our population by factors too large to imagine. Indeed, the settled region of space could ultimately grow much larger than our Galaxy: faster spacecraft can be sent to other galaxies (in another weird coincidence, light-speed spacecraft, launched first, could reach the nearest galaxy, Andromeda, about the time we finished colonizing ours). On the worlds that we either settle or build, people will have to adopt the same strategy for long-term survival that those on Earth will soon be forced to, for many of the same reasons and one more: interstellar communication and transport would take years, effectively isolating them from other worlds on the scale of a human lifetime (at least until space really fills up).

Whatever we choose to do, natural constraints will limit how fast our population can grow, both now and into the farthest future we can imagine. While technology may increase both accessibility and uses for resources, improving quality of life, the number of people using those resources will need to grow at a pace that does not exceed their long-term availability.