Category Archives: Long Form

The Great Transition: A Foundational Concept for an Emerging Global Culture

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David P. Turner / October 11, 2020

Given the gathering storm of global environmental change, our world is in dire need of new ways of thinking.  Culture is, in part, the set of beliefs, customs, and knowledge shared by a society; and cultural evolution happens when new ideas or concepts are generated by individuals and spread by way of social learning.  If a concept is successfully replicated in the minds of most of the people in a society, it could be said to become part of the culture of that society.  Here, I examine the concept of the “Great Transition”, an idea that may help a nascent global society grapple with planetary scale environmental change issues.

The “Great Transition” is a theme employed by authors from a variety of disciplines to characterize how humanity must change in the coming decades. 

We can begin with Kenneth Boulding (1910-1993).  He was an academic economist who published The Great Transition in 1964.  Boulding was an expansive thinker and an early advocate of the spaceship Earth metaphor.  Because he was publishing in the middle of the Cold War era, he was concerned about human self-destructive tendencies associated with both the global geopolitical situation and the global environment. 

Boulding’s Great Transition called for a gradual augmentation or replacement of “folk knowledge” with scientific knowledge.  Both are honed by cultural evolution, i.e. specific beliefs are generated, spread, and retained as part of the cultural heritage within specific social groups.  Faith in folk beliefs is based on tradition rather than on an understanding of underlying mechanisms.  Folk knowledge sometimes serves mainly to foster group identity (e.g. creation myths that build a shared sense of destiny) but other folk beliefs may have practical significance (e.g. knowledge of medicinal plants). 

Various alternative ways of knowing (epistemologies) operate quite differently from folk knowledge.  In the scientific epistemology, a consensus model of how the world is structured, and how it functions, is built up over time by way of hypothesis formation and testing.  One great virtue of the scientific epistemology is that the consensus model of reality can change based on new observations, ideas, and experiments.  Specifically, regarding global environmental change, the scientific community has discovered anthropogenically-driven trends in the global environment and has suggested that they pose a threat to human civilization.  As is evident in today’s political battles over climate change, scientific discoveries and science-based mitigation strategies are not always consistent with folk knowledge.

Boulding advocated a more consistent reflexivity in human thinking, i.e. a questioning attitude and an openness to changing beliefs.  This thinking strategy was something he wanted all humans to share, even though they might be supporting different ideologies. 

Another economist (Mauro Bonaiuti) also wrote a book entitled The Great Transition.  For Bonaiuti, a global economic crisis is imminent driven by 1) limits on natural resources such as fossil fuels, and 2) an overshoot in societal complexity. 

Bonaiuti focused on a trend in growth of Gross Domestic Product (GDP) for developed countries in recent decades.  He found a long-term decline in GDP growth (% per year) across a wide range of developed countries.  The driving mechanism was Diminishing Marginal Returns (DMR) on investments associated with reaching the biophysical limits of natural resources (e.g. land available for agricultural expansion). He feared this economic trend portended eventual collapse of capitalism and the ascendancy of autocratic regimes.

Bonaiuti’s Great Transition away from that trajectory was characterized by degrowth − reduction in the importance of market exchange, reduced production and consumption, and transitioning towards forms of property and company ownership that feature local communities, small shareholders, and public institutions.     

As an Earth system scientist, I agree with Bonaiuti about the human enterprise on Earth hitting the biophysical limits of the Earth system.  Regarding complexity though, I am more sanguine.  A transition to global sustainability is likely to require more complexity, especially in the form of a more elaborate set of global governance institutions. The energy costs could be paid by an expanded renewable energy infrastructure (hopefully without the expansion hitting its DMR).

Physicist Paul Raskin developed another version of the “Great Transition”, this one aimed more directly at addressing the problems of biophysical limits.  The Tellus Institute, with which he is affiliated, produced a broad program of policy prescriptions designed to foster societal change towards sustainability.  One of their prescriptions is a renewable energy revolution (which, not surprisingly is also the subject of a recent book by Lester Brown called The Great Transition).  The Tellus Institute published Journey to Earthland in 2016, with Earthland here referring to an emerging “country” that includes all nations on Earth (hence a planetary civilization). 

For Raskin, the key factor that could unify humanity is the systemic environmental crises that are rapidly engulfing the world (e.g. climate change).  People will be forced to work together to address these crises.  He sees the needed change as a bottom-up driven process, i.e. a “global citizens movement” with strong participation of civil society.

Considering this convergence by earlier authors on the theme of transition, I adopted the “Great Transition” label for a phase in what I call A Positive Narrative for the Anthropocene.  From an Earth system science perspective on the Earth’s history, I developed this six-phase story of humanity’s relationship to the rest of the Earth system.  The Anthropocene Epoch alludes to the recognition by geoscientists, social scientists, and humanities scholars that humanity (by way of the technosphere) has become the equivalent of a geologic force.  My Great Transition phase comes between a Great Acceleration phase (1945 – 2020) and an idealized future of global sustainability.

An essential aspect of my Great Transition usage is that a new social entity is born – a collective humanity working together to manage (or at least avoid wrecking) the Earth system as we know it.  The coalescence of the United Nations − and its successes such as the Montreal Protocol −  hints at the possibilities. 

The great inequality in wealth at all scales, the differential responsibility for causing the current global environmental problems, and the differences among people regarding their vulnerability to anthropogenic environmental change, makes it fair enough to question whether there even can be a global “we”.  However, a majority of humans (5.2 billion out of 7.7 billion) now have a cell phone.  Almost all contemporary humans aspire to use energy and natural resources to achieve and maintain a reasonably high standard of living.  That striving is, of course, causing global environmental change.  So, indeed, there is a global “we”.  And a transition to global sustainability is impossible unless most people on the planet acknowledge membership in that “we”.

The Great Transition must be a global scale phenomenon.  However, the actual changes required will be made across a range of scales from individuals (decisions as consumers and voters), to nation-states (e.g. subsidies for renewable energy), to global (e.g. resolutions of the United Nations).  Let’s consider several of the important dimensions of the Great Transition.

The Biophysical Dimension

Earth system scientists have identified a set of nine planetary boundaries (e.g. the atmospheric CO2 concentration), and the Great Transition will mean regulating human impacts on the environment enough to stay within those boundaries.  At present, the quantitative estimates for those boundaries have significant uncertainties and a robust commitment to continued research is needed.  The research will include continued improvement in our capability to monitor and model the Earth system.  Model simulations are needed to evaluate the consequences of overshooting the planetary boundaries, as well as possible mitigation strategies (e.g. a carbon tax) that could prevent the overshoot.

The Technological Dimension

The technological dimension of the Great Transition is concerned with discovering and implementing the changes to the technosphere that are needed to achieve global sustainability.  As noted, a key requirement will be a new renewable energy infrastructure.  Pervasive advances are also needed in transportation technology, life cycle analysis, and in closed loop manufacturing.  Technological fixes must be carefully scaled up since unintended impacts may emerge in the process.  The field of Science and Technology Studies is beginning to systematically address the relevant issues.  I have previously characterized the product of integrating the technosphere and biosphere as the sustainable technobiosphere (Figure 1).

Figure 1. A stylized rendering of the integration of biosphere and technosphere. Image credit: Original Graphic.

The Psychological Dimension

We all have a personal identity.  It begins with the self-awareness that we grow into during childhood; and it evolves over the course of our life.  We typically identify ourselves as members of various groups and there is often a psychological tension within a human being between independence and group membership. 

These groups may include family, ethic group, professional group, and religious affiliation, as well as citizenship in a city, a state, and a nation.  Membership in a group is recognized as conveying rights and responsibilities. 

As noted, an essential feature of the Great Transition will be that individuals augment their multiple existing group memberships with membership in new groups focused on addressing human-induced environmental change. 

The Education Dimension

One of humanity’s most important evolved traits is the capacity to transfer knowledge by way of social learning.  Language is a tool for efficient communication of information horizontally (within a generation) and vertically (across generations).  The Great Transition will require a global society with citizens who understand enough Earth system science to appreciate the need for humanity to manage its impact on the biosphere and the rest of the Earth system.  They must generally be literate, so as to assimilate basic information about what is going on in the world, and to some degree be scientifically literate so they can understand the underlying mechanisms that explain what is going on.   

The Geopolitical Dimension

Since the Treaty of Westphalia in 1648, what happens within national borders is in principle largely left to the inhabitants of the nation.  Nations have subsequently become protective of their national sovereignty.

Issues of global environmental change now disrupt and challenge that principle.  National emissions of greenhouse gases sum up to a major global scale impact on the environment.  National sovereignty is thus not sacrosanct; nations must cooperate, or they will all suffer.  The current global wave of nationalism, especially the push back against commitments to international negotiations and agreements, is inhibiting movement towards a Great Transition.  A significant step forward would be formation of a new global environmental governance institution, such as the proposed World Environment Organization.

The Great Transition concept has thus far spread rather thinly across humanity.  But as a global society forms in response to global environmental change, it should become foundational.

Peak Human Population and the Global Environment

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David P. Turner / September 11, 2020

Introduction

A key pursuit in the field of Earth System Science is measuring and monitoring global scale structures and processes.  These measurements have led to the concept of the “Great Acceleration”, a name given to the period since around 1950 during which many global scale attributes related to the human enterprise (the technosphere) began rising in an exponential fashion.  The increase in global population is the iconic example.

Intuitively, it seems unlikely that this level of population increase and associated resource consumption could continue indefinitely on a finite planet.  Practically speaking, problems have begun to arise both with resource shortages and environmental degradation from excess waste production (e.g. global warming and ocean acidification from massive fossil fuel combustion).

Humanity clearly must transition to a more sustainable relationship with the rest of the Earth system.  The way forward lies in bending those exponentially rising Great Acceleration curves for population and resources use, hitting the peaks, and engineering declines.

As noted by ecologists long ago, total resource use (Impact) is a function of the number of people (Population), their per capita use (Affluence), and the efficiency with which raw resources are converted to useful products (Technology).

Resource use per person obviously varies tremendously, hinting at the special responsibility of the more developed countries to limit population growth (the net effect of births minus deaths and immigration minus emigration).  But all humans consume natural resources.  Thus, the high projected population growth rates in less developed countries must also be brought down.  The sooner global population peaks, the less natural capital (e.g. biodiversity) will be degraded, the less likely that competition for resources will lead to human conflict, and the less likely that climate change will trigger tipping points in the Earth system that precipitate extreme impacts on humans.

Past, Present, and Future Global Population

The global population size doubled between 1927 and 1974 and has nearly doubled again since 1979.  It is now 7.8 billion.

However, the rate of annual global population growth has fallen in recent decades (from > 2% per year to 1.05% per year), mostly associated with a decreasing trend in fertility (children born per woman during her reproductive lifetime).

Family planning programs by governmental and nongovernment organizations have significantly impacted the trend towards lower fertility rates.

Projections by demographers of peak global population range widely.  The median estimate from the United Nations Population Division is for a population of 10.9 billion in 2100.  Most of the increase from the present is in Africa.

However, recent research points toward lower values, possibly a peak of 9.7 billion around 2064 and a decline to 8.8 billion by 2100. 

Factors Influencing Demographic Projections

Projections of peak global population have significant policy implications.  Relatively low estimates may have the effect that national commitments to stabilize population are downgraded and that overhyped media accounts of depopulation sap political will to continue family planning programs.  Relatively high estimates for peak global population foster the impression that humanity it doomed to an overcrowded and overheated planet, hence favoring lifeboat ethics.

Despite the critical implications of their results, the models used to predict peak population are very sensitive to the assumptions made about trends in fertility. 

The recent lower estimates for peak global population rely on continued or increasing reductions in fertility in the high fertility countries.  But demographers in the past have sometimes overestimated declines in fertility, and may be doing so now as well.  Historic trends of declining fertility have stalled in some high fertility countries, possibly related to falling support for family planning.  The Catholic Church still formally prohibits artificial birth control. 

Nevertheless, several emerging trends may support lower projected peaks in global population. 

One is that efforts to shift cultural norms favoring large family size increasingly include family planning messaging in popular media (e.g. serial dramas), which are having significant success with both genders. 

Another is that the incidence of unplanned pregnancy is declining globally (1990-2014), probably as a function of improving access to family planning resources.

The Covid-19 pandemic could push birth rates down (at least in the more developed countries) because financial insecurity will dispose women in developed and developing countries to postpone or forgo having children.  

Mortality rates may also be higher than expected.  Life expectancy has generally increased in recent decades throughout the world.  Much of that increase is associated with reduced child mortality but increasing longevity is also a factor.  However, life expectancy in the U.S. went down from 2014 to 2017 because of increasing fatal drug overdoses and suicides.  Climate change is expected to bring an increase in extreme weather events causing mortality directly (as in flooding), and indirectly by way of impacts on agriculture and possibly the incidence of war.

Implications Beyond Absolute Population Size

A leading concern about a rapid peak and then decline in national populations is the associated increase in the ratio of older retired people to younger working people.  As the population ages, the number of active workers available to support each elderly person tends to decline.  Hence, taxes may have to be increased to provide income and health care to the elderly.  Various mitigating factors include the improving health of elderly people, significant intergenerational transfers of wealth, increases in labor force participation by the elderly, and volunteer efforts by the elderly.

Also, a larger proportion of elderly people generally means decreased per capita demand for resources and a more peaceful society.

A decline in the number of children per family can have many beneficial side effects including: 1) more resources (parental attention and ability to finance education) per child, 2) improved quality of life for parents (less stress and more free time), and 3) rising per capita income.

Conclusion

The sooner global population peaks and begins to decline, the greater the possibilities for achieving global sustainability.  Since about 40% of pregnancies globally are still unplanned, a primary tool for insuring children are born into a welcoming and opportunity-rich environment is continued and improved provision of family planning support in both the developing and developed world.  More political will and contributions to NGOs are needed.  At this point in human history, the local and global challenges (environmental, economic, and social) that arise from a stable or declining population are likely more manageable than those arising from high rates of population growth.

A Positive Narrative for the Anthropocene

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David P. Turner / July 16, 2020

Humans are story-telling animals.  Our brains are wired to assimilate information in terms of temporal sequences of significant events.  We are likewise cultural animals.  Within a society, we share images, words, rituals, and stories.  Indigenous societies often have myths about their origin and history.  Religious mythologies remain prevalent in contemporary societies.

The discipline of Earth System Science has revealed the necessity for a global society that can address emerging planetary scale environmental change issues – notably climate change.  A shared narrative about the relationship of humanity to the biosphere, and more broadly to the Earth system, is highly desirable in that context. 

The most prevalent narrative about humanity’s relationship to the Earth system emphasizes the growing magnitude of our deleterious impacts on the global environment (think ozone hole, climate change, biodiversity loss).  The future of humanity is then portrayed as more of the same, unless radical changes are made in fossil fuel emissions and natural resource management.

In the process of writing a book for use in Global Environmental Change courses, I developed an elaborated narrative for humanity − still based on an Earth system science perspective but somewhat more upbeat.  I used the designation Anthropocene Narrative to describe it because Earth system scientists have begun to broadly adopt the term Anthropocene to evoke humanity’s collective impact on the environment. 

There are of course many possible narratives evoked by the Anthropocene concept (e.g. the historical role of capitalism in degrading the environment), all worthy of study.  But for the purposes of integrating the wide range of material covered in global environmental change classes, I identified a six stage sequence in the relationship of humanity to the rest of the Earth system that serves to link geologic history with human history, and with a speculative vision of humanity’s future (Figure 1).  The stages are essentially chapters in the story of humanity’s origin, current challenges, and future.  The tone is more hopeful than dystopian because our emerging global society needs a positive model of the future.  

Figure 1.  An Earth system science inspired Anthropocene narrative with six stages.  Image credits below.

The chapters in this Anthropocene narrative are as follows.

Chapter 1.  The Pre-human Biosphere

The biosphere (i.e. the sum of all living organisms) self-organized relatively quickly after the coalescence of Earth as a planet.  It is fueled mostly by solar energy.  The biosphere drives the global biogeochemical cycles of carbon, nitrogen, and other elements essential to life, and plays a significant role in regulating Earth’s climate, as well as the chemistry of the atmosphere and oceans. The biosphere augments a key geochemical feedback in the Earth system (the rock weathering thermostat) that has helped keep the planet’s climate in the habitable range for 4 billion years.  By way of collisions with comets or asteroids, or because of its own internal dynamics, the Earth system occasionally reverts to conditions that are harsh for many life forms (i.e. mass extinction events).  Nevertheless, the biosphere has always recovered − by way of biological evolution − and a mammalian primate species recently evolved that is qualitatively different from any previous species. 

Figure 2.  The pre-human biosphere was a precondition for the biological evolution of humans.  Image Credit: NASA image by Robert Simmon and Reto Stöckli.

Chapter 2.  The Primal Separation

Nervous systems in animals have obvious adaptive significance in term of sensing the environment and coordinating behavior.  The brain of a human being appears to be a rather hypertrophied organ of the nervous system that has evolved in support of a capacity for language and self-awareness.  These capabilities are quite distinctive among animal species, and they set the stage for human conquest of the planet.  The most recent ice age receded about 12,000 year ago and a favorable Holocene climate supported the discovery and expansion of agriculture.  With agriculture, and gradual elaboration of toolmaking, humanity ceased waiting for Nature to provide it sustenance.  Rather, Nature became an object to be managed.  This change is captured in the Christian myth of Adam and Eve’s expulsion from the Garden of Eden (Figure 3).  They lived like all other animals in the biosphere until they became self-aware and began to consciously organize their environment.

Figure 3.  The story of Adam and Eve symbolizes the separation of early humans from the background natural world.  Image Credit: Adam and Eve expelled from Eden by an angel with a flaming sword. Line engraving by R. Sadeler after M. de Vos, 1583. Wellcome Trust.

Chapter 3.  The Build-out of the Technosphere

The next phase in this narrative is characterized by the gradual evolution and spread of technology.  An important driving force was likely cultural group selection, especially with respect to weapons technology and hierarchical social structure.  The ascent of the scientific worldview and the global establishment of the market system were key features.  Human population rose to the range of billions, and the technosphere began to cloak Earth (Figure 4).  The Industrial Revolution vastly increased the rate of energy flow and materials cycling by the human enterprise.  Telecommunications and transportation infrastructures expanded, and humanity began to get a sense of itself as a global entity.  Evidence that humans could locally overexploit natural resources (e.g. the runs of anadromous salmon in the Pacific Northwest U.S.) began to accumulate.

Figure 4.  The Earth at night based on satellite imagery displays the global distribution of technology dependent humans.  Image Credit: NASA/GSFC/Visualization Analysis Laboratory.

Chapter 4.  The Great Acceleration

Between World War II and the present, the global population grew from 2.5 billion to 7.8 billion people.  Scientific advances in the medical field reduced human mortality rates and technical advances in agriculture, forestry, and fish harvesting largely kept pace with the growing need for food and fiber.  The extent and density of the technosphere increased rapidly.  At the same time, we began to see evidence of technosphere impacts on the environment at the global scale – notably changes in atmospheric chemistry (Figure 5) and losses in global biodiversity.

Figure 5.  The impacts of the global human enterprise on various indicators of Earth system function take on an exponential trajectory after World War II.  Image Credit: Adapted from Steffen et al. 2015.

Chapter 5.  The Great Transition

This phase is just beginning.  Its dominant signal will be the bending of the exponentially rising curves for the Earth system and socio-economic indicators that define the Great Acceleration (Figure 5 above).  Global population will peak and decline, along with the atmospheric CO2 concentration.  Surviving the aftermath of the Great Acceleration with be challenging, but the Great Transition is envisioned to occur within the framework of a high technology infrastructure (Figure 6) and a healthy global economy.  To successfully accomplish this multigenerational task, humanity must begin to function as a global scale collective, capable of self-regulating.  Neither hyper-individualism nor populist tribal truth will get us there.  It will take psychologically mature global citizens, visionary political leaders, and new institutions for global governance.

Figure 6.  A critical feature of the Great Transition will be a renewable energy revolution.  Image Credit: Grunden Wind Farm

Chapter 6.  Equilibration

Human-induced global environmental change will continue for the foreseeable future.  The assumption for an Equilibration phase is that humanity will gain sufficient understanding of the Earth system – including the climate subsystem and the global biogeochemical cycles – and develop sufficiently advanced technology to begin using the technosphere and managing the biosphere to purposefully shape the biophysical environment from the scale of ecosystems and landscapes (Figure 7) to the scale of the entire planet.  Humanity is a part of the Earth system, meaning it must gain sufficient understanding of the social sciences to produce successive generations of global citizens who value environmental quality and will cooperate to manage and maintain it.  The challenges to education will be profound.

Figure 7.  An idealized landscape in which the biosphere and technosphere are sustainably integrated.  Image Credit: Paul Cézanne, Mont Sainte-Victoire, 1882–1885, Metropolitan Museum of Art.

As noted, this Anthropocene Narrative is largely from the perspective of Earth system science.  In the interests of coherence, humanity is viewed in aggregate form.  Humanities scholars reasonably argue that in the interests of understanding climate justice, “humanity” must be disaggregated (e.g. by geographic region or socioeconomic class).  This perspective helps highlight the disproportionate responsibility of the developed world for driving up concentrations of the greenhouse gases.  The aggregated and disaggregated perspectives on humanity are complementary; both are needed to understand and address global environmental change issues.

The Anthropocene Narrative developed here is broadly consistent with scientific observations and theories, which gives it a chance for wide acceptance.  The forward-looking part is admittedly aspirational; other more dire pathways are possible if not probable.  However, this narrative provides a solid rationale for building a global community of all human beings.  We are all faced with the challenge of living together on a crowded and rapidly changing planet.  The unambiguous arrival of global pandemics and climate change serve as compelling reminders of that fact.  A narrative of hope helps frame the process of waking up to the perils and possibilities of our times.

Recommended Video:  Welcome to the Anthropocene (~ 3 minutes)

This blog post was featured as a guest blog at the web site for The Millennium Alliance for Humanity and the Biosphere (MAHB).

https://mahb.stanford.edu/blog/a-positive-narrative-for-the-anthropocene/

The Biodiversity Bottleneck

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lead image
Figure 1. The biodiversity bottleneck displays the ongoing reduction in biodiversity caused by human actions. The fate of biodiversity after the bottleneck is uncertain, but some degree of recovery is possible if humanity self-regulates. Image Credit: Monica G. Whipple and David P. Turner

David P. Turner / May 29, 2020

Earth’s biodiversity is under siege by the global human enterprise (the technosphere).  Most species will survive into the distant future, possibly a future in which the human population has shrunk, and the value of biodiversity is more widely appreciated.  But many species will go extinct along the way. 

Biologist E.O. Wilson and others have evoked the image of a bottleneck in this context (Figure 1).  A bottleneck implies a tightening of constraints on flow.  In the case of the biodiversity bottleneck, flow refers to the survival of species through time.

As the future unfolds and the technosphere continues to grow, the possibilities for species to pass through the biodiversity bottleneck diminish.  But there is a lot of room for maneuver here.  A worthy project for humanity – especially over the next few decades − is to keep that bottleneck as wide as possible.  After passing through it, global biodiversity may recover to some degree as the technosphere begins to weigh less heavily on the biosphere.  It all depends on us.

Background

Evidence of human impacts on biodiversity surrounds us.  Comparisons of current rates of extinction and those in the fossil record indicate that vertebrate species are now going extinct at a rate 100 or more times faster than is observed in most previous geologic periods.  The human-driven Sixth Extinction began perhaps 50,000 years ago when primitive humans arrived on Australia and wiped out many prey species that were unfamiliar with the new bipedal super predator.  Anthropologists refer to the “Pleistocene Overkill” to describe the wave of mammal extinctions that occurred when humans first crossed from Asia to North America about 15,000 years ago.

Modern humans continue to exterminate species directly by overhunting for food (e.g. the passenger pigeon) but also by widespread trafficking in wildlife and animal parts for food, as well as for medicinal and prestige purposes.  Various plant species are also endangered, notably several tropical hardwoods known as rosewood.  Sustained pressure on wildlife habitat from land use change and disruptions in geographic ranges caused by climate change adds further stress on top of overexploitation.  Genetic variation within many species is shrinking as their populations and geographic ranges contract, hence reducing their capacity to survive environmental change (formally termed a population bottleneck).

In essence, the expansion of technosphere capital (the mass of human made objects) is consuming biosphere capital (the biodiversity and biomass of the biosphere).  This loss of biodiversity − usually defined in terms of diversity of species and ecosystems − will likely continue over the coming decades.  As noted, though, the magnitude of the loss will depend heavily on human decisions. 

There are pragmatic, aesthetic, and ethical rationales for conserving Earth’s biodiversity.  Conservationists argue that retaining biodiversity maintains the functional integrity of ecosystems, and hence the full array of their ecosystem services.  Each species has a unique niche and contributes to ecosystem processes like nutrient cycling and recovery from disturbances.  With respect to aesthetics, the earlier mentioned Professor Wilson has suggested that humans have genetically determined biophilia − we get spontaneous pleasure from interacting with diverse forms of life.  The ethical argument is made strongly by the Deep Ecology movement.  For supporters, there is no human exceptionalism – all species have an equal right to survive and prosper on this planet.

Given the multiple rationales for wishing to widen the biodiversity bottleneck, what collective actions (besides the overriding one of limiting climate change) can help?  Scientists and policy experts have identified biodiversity-friendly practices such as reducing pesticide use, buying certified products, reducing invasive species, and reducing water pollution.  But here are four others that have high relevance.

1.  Stop Trafficking in Wildlife and Wild Animal Parts

The global trade in wild animals and wild animal parts puts tremendous downward pressure on the populations of many species.  Wild animals are commonly sold in Southeast Asian food markets despite laws against it.  Tigers, rhinos, and pangolins continue to be poached for dubious medicinal purposes.  Wild caught animals are sold as “bush meat” in parts of Africa and South America.  

A global trade in live animals intended as pets also flourishes.  Millions of  songbirds are collected every year in the primary forests of Indonesia and sold as pets or trained as contestants in bird song competitions.  Tropical fish are collected in the wild for marketing to aquarium owners.  

Multiple international agreements aim to stem wild animal trafficking, especially the Convention on International Trade in Endangered Species of Wild Fauna and Flora.  Under its auspices, national law enforcement agencies regularly confiscate illegal shipments of wild animals, animal parts, and wood from endangered tree species.  However, these efforts face deep resistance for cultural and economic reasons. 

A new brake on wild animal trafficking is fear of zoonotic pathogens.  The SARS-CoV-2 virus that is causing the Covid-19 global pandemic likely jumped from a wild animal host to a human in a market where wild animals are sold illegally.  New legislation passed in China limits sales of wild animal meat.  Unfortunately, enforcement is spotty, and the new law still allows sales of wild animal parts for medicinal purposes.  Sustained international pressure on wildlife traffickers is needed.

The Covid-19 pandemic is apparently impacting wildlife protection in other ways.  Conservationists fear that the loss of the tourist ‘halo’ or proximity effect, because of Covid-19 shutdowns, will increase the incidence of poaching in nature reserves.  Resumption of tourism would help in that regard.

2.  Expand the Size and Number of Protected Areas

A key driver of declining biodiversity is habitat loss.  To bring as many species as possible through the biodiversity bottleneck will require protection of representative areas for all unique types of ecosystems.

The Rewilding Movement has argued for creating protected areas that are large enough to support the whole complement of native species characteristic of each ecosystem type, along with the entire range of abiotic processes such as floods and fires that help maintain it.

Presently, about 15% of global land plus inland waters is protected to some degree.  For the oceans within national jurisdictions, the figure is about 13%.  Not all ecosystem types are represented.  For many types of ecosystems, the current protected area is quite small relative to its original geographic distribution (e.g. the Atlantic rain forest in Brazil).

Aspirations for expanding the protected areas of land and ocean range from 17% of land to half of Earth as a whole (the latter courtesy of the illustrious Professor Wilson).

Protected area plans can be developed over large domains, e.g. the entire United States.  These plans rely on integration of different managed lands such as wilderness areas, national parks, national forests, urban areas, and private reserves.

An international scientific advisory body (IPBES, Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services) is dedicated to biodiversity assessment and conservation.  Like the Intergovernmental panel on Climate Change, IPBES produces periodic assessments and examinations of policy options.  IPBES is supported by member countries, including the U.S., and sustained national contributions are warranted.

In the private sector, land trust organizations such as The Nature Conservancy have as their key strategy the purchase of lands for conservation purposes; contributions are encouraged.  Public/private conservation partnerships are proliferating; participants are welcomed.

3.  Design Sustainable Cities

The proportion of the global population that lives in an urban setting recently passed the 50% mark and is expected to keep climbing in the coming decades.  A potential benefit to biodiversity conservation lies in the land that is abandoned as people supported by subsistence agriculture and nomadic herding move to towns and cities.  The freed-up land can potentially be repurposed in part or whole for wildlife conservation.  An underlying assumption is that agricultural intensification can take up any slack in food production and keep everyone fed. 

Urban greenbelt areas, parks, and gardens may serve directly as another assist to biodiversity conservation.  They support native and alien species and could serve as refuges for plant and animal species that are extirpated regionally by climate change and land use change.  Urban rivers and streams can likewise be managed to protect and support wildlife.

4.  Strategically Increase Ecotourism

In theory, the local economic benefits of nature-based tourism inspire local conservation efforts.  However, high tourist demand produces pressure to increase supply.  More local economic development (e.g. hotels and restaurants) plus more intensive visitor utilization of natural resources may end up degrading local ecosystems.  The research literature contains ecotourism case studies of successes, as well as failures.

Ecotourism narrowly defined refers to tourism that allows visitors to experience local wildlife and landscapes, creates incentives to protect those organisms and landscapes, and supports local communities.  More ecotourism is probably not appropriate in many places where it already exists because capacity is limited.  Rather, it is needed where wildlife is under threat and conservation incentives might be effective.      

Building socio-ecological systems is an emerging route to local sustainability.  These stakeholder groups optimally self-regulate to conserve the economic health and ecological health of the local environment.  Nobel Prize winner Elinor Ostrom has developed principles for structuring and operating these groups.  Monitoring the social, economic, and ecological dimensions of sustainability is a key requirement for successful ecotourism management.

Ecotourism, and tourism more generally, cannot be discussed in the context of biodiversity conservation without considering their global scale impacts.  As noted, climate change is a threat to biodiversity, and the carbon footprint of tourism is estimated to be 8% of total greenhouse gas emissions. 

Air travel is the foundation for much tourism, but it is especially difficult to decarbonize.  Short hop electric airplanes and long-haul flights powered by renewable energy based liquid fuels are technically feasible.  They could replace fossil fuel powered flights, but more government supported research is needed, and air travelers must be willing to pay an increased fare as these fuels are brought online.  Airline-associated carbon offset programs − although varying in effectiveness and not a permanent solution − contribute significantly to biodiversity conservation.  They help expand protected area and, by sequestering carbon, help slow climate change.

Conclusion

The human capacity to extinguish other species on this planet, and to pervasively alter wildlife habitat, means that we are in many ways responsible for which species and ecosystems will survive.  As we move through peak human population this century and begin to more purposefully manage our impacts on Earth’s biota, let’s keep the biodiversity bottleneck of our own making as wide open as possible.  Progress towards that goal would be both pragmatic and gratifying.

Recommended Audio/Video

To the Last Whale

Redesigning Technosphere Metabolism

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David P. Turner / April 7, 2020

When I was 20 years old, I picked up a paperback version of “Life and Energy” by Isaac Asimov.  This lucid scientific description of the chemical basis for life was very compelling, indeed, it helped inspire me to pursue a career in biology and ecology.  The time around its publication in the mid 1960s was quite exciting in biology because the fields of biochemistry and cell biology were in full flower; scientists had worked out the role of DNA in regulating cellular metabolism and had achieved a good understanding of the chemistry of photosynthesis and respiration.

Metabolism is broadly defined as the chemical machinery of life, the networked sequences of chemical reactions that build and maintain living matter.  Biologists think of living matter in terms of levels of organization – from cells, through organisms, communities, and the biosphere.

In Asimov’s days, the concept of metabolism was mostly applied at the level of the cell or organism.  However, ecologists in recent years have also applied it in the context of ecosystems and the Earth system as a whole.  Here I would like to consider metabolism at the scale of the technosphere. 

An ecosystem is a biogeochemical cycling entity, e.g. a pond or a patch of forest.  Like an organism, it requires a source of energy and it cycles nutrients such as nitrogen from one chemical form to another.  Strictly speaking, it is the biota (the set of all organisms) that in a sense has a metabolism.  Component organisms are classified into nutrient cycling guilds — most simply as producers (photosynthesizes), consumers, and decomposers. 

Ecosystem metabolism can be described in terms of energy fluxes, as well as the stocks and fluxes of key chemical elements. The element carbon plays a central role in ecosystem metabolism.  Its cycle extends from the atmosphere, through plants, to animals, and to decomposers, then back to the atmosphere.

The ecosystem carbon cycle. Image credit, Figure 4.1, The Green Marble, David Turner, 2018, Columbia University Press.

At the scale of the Earth system, we can likewise talk about biogeochemical cycling guilds and the associated biogeochemical cycles.  Biosphere metabolism is based on photosynthesis on the land and in the ocean.  Biosphere driven element fluxes help regulate the atmospheric chemistry, ocean chemistry, and global climate. 

Despite repeated intervals in the geologic record of Hothouse Earth and Icehouse Earth, the metabolism of the biosphere has run steadily for over 3 billion years.  

Quite recently in geologic time, a new sphere has emerged within the Earth system.  This “technosphere” is the cloak of technological devices and associated human constructs that has come to cover the Earth.  Like the biosphere, it has a metabolism.

We can think about technosphere metabolism in terms of three key factors: energy flows, materials cycling, and information processing. 

Humans are a part of the technosphere and mostly benefit from its metabolism.  The technosphere produces a vast array of goods and services that support billions of people.  However, the metabolism of the technosphere has begun to disrupt the formerly background global biogeochemical cycles.  It is effectively now a geological force and the changes it has precipitated are not necessarily favorable to advanced technological civilization.  Notably, the delivery of vast amounts of CO2 into the atmosphere is destabilizing the global climate.  A course correction in the evolution of the technosphere is required.

Energy flow into the technosphere is predominantly from the combustion of fossil fuels (coal, oil, and natural gas).  The problem is that the resulting source of carbon to the atmosphere is orders of magnitude greater than the background source from volcanoes.  The background geologic sink for CO2 by way of mineral formation in the ocean depths is likewise small.

Some of the technosphere-generated CO2 is sequestered by land plants and in the ocean, but most of it is accumulating in the atmosphere and causing the planet to rapidly warm.  The technosphere has begun to disrupt the entire Earth system. 

The solution, as is well known, is conversion of the global energy infrastructure to renewable energy sources (solar, wind, hydro, geothermal, biomass, and renewable natural gas).  That conversion is a daunting task but technically it can be accomplished.  The challenge is as much to economists and politicians as it is to engineers.

Converting from fossil fuel-based energy sources to renewable energy sources.
Image credit for power plant and wind turbines.

The materials cycling factor in technosphere metabolism is problematic because the technosphere as currently configured is not effective at recycling its components.  Unlike the biosphere, in which nutrients are cycled, there is often a one-way flow of key chemical elements in the technosphere − from a mineral phase, to a manufactured product, to a landfill.

The problem is that sources of the technosphere components are not infinite.  Building the next mega-mine to extract aluminum degrades the biosphere, a key component of the global life support system. 

Again, this is a largely solvable problem using advanced industrial practices.  We now speak of the emerging circular economy and of dematerializing the technosphere.  More comprehensive recycling may require more energy than dumping something into a landfill, but the potential for renewable energy sources is large.

The information processing aspect of technosphere metabolism refers to its regulatory framework.  Regulation requires information flow, a receiver of that information, and a mechanism to act on it.   

Homeostasis at the level of an organism is a clear case of regulation.  Homeostasis of internal chemistry, such as the blood sugar level in mammals, depends on factors including signals based on chemical concentrations, DNA-based algorithms to formulate a response, and organs that implement a response.

Ecosystems also self-regulate in a sense.  Disturbances (e.g. a forest fire) are followed by vigorous regrowth.  As a result, nutrients that are released in the process of the disturbance are captured and prevented from loss by leaching.  Damaged ecosystems, say that lack species specialized for the early successional environment, may deteriorate after a disturbance.

At the global scale, Earth system scientists have long debated the issue of planetary homeostasis.  James Lovelock famously hypothesized that indeed the Earth system (Gaia) is homeostatic with respect to conditions that favor life.  His idea inspired much research, and many significant biophysical feedbacks to global change have been identified.  The biosphere clearly exerts a strong influence on global climate by way of its impacts on greenhouse gas concentrations, specifically through its role as an amplifier in the rock weathering thermostat.

A new research question concerns the degree to which the technosphere is homeostatic.  Continued exponential growth in many of the indices of technosphere metabolism is suggestive of inadequate regulation.  To begin with, the regulatory capability of the technosphere is obviously diffuse and underdeveloped. 

Monitoring is a necessary component of effective management systems but the self-monitoring capability of the technosphere barely existed until quite recently.  An anomalous growth in the atmospheric CO2 concentration was measured in the late 1950s by atmospheric chemist Charles David Keeling.  This observation was the first clear signal of technosphere impact on the Earth system.

The Landsat series of satellite-borne sensors that monitor land cover change, e.g. deforestation and urbanization, was initially launched in 1972.  These satellites have since tracked the explosive spatial expansion of the technosphere.  A fleet of other satellites now monitors many other features of the global environment.

From synthesis efforts by agencies such as the United Nations Food and Agriculture Organization, we have good observational data on the growth of key technosphere variables like global population size and energy use. 

As far as a decision-making organ for the technosphere, one barely exists at present.  You might say that market-based capitalism is the organizing principle of the current technosphere.  Everyone wants cheap, plentiful energy (the demand side) and the global fossil fuel industry has managed to keep ramping up the supply.  Under the current neoliberal economic regime, the environmental costs are externalized, and no global oversight is imposed.

However, a new constraint has arisen.  The scientific community has built Earth system models to refine our understanding of Earth’s biophysical regulatory mechanisms and to simulate effects of various greenhouse gas concentration scenarios.  These simulations make clear that uncontrolled emissions of CO2 from fossil fuel combustion must cease or advanced technological civilization will be imperiled.  The 2015 Paris Agreement on Climate Change was a step towards reining in the technosphere, but the influence of that international agreement is not commensurate with the challenges of current global environmental change.

An essential feature of a needed paradigm shift regarding technosphere regulation is the development of a global environmental governance infrastructure.  The technosphere is having global scale impacts on the environment and must correspondingly be evaluated and regulated at the global scale.

A proposed World Environment Organization would not necessarily supersede the traditional nation-state-based architecture of global governance, but it could go a long way towards the required scale of integration needed to address global environmental change issues.

A revamped technosphere metabolism must be built over the course of the 21st Century in which the energy sources are renewable, the material flows are cyclic, and the regulatory framework is rooted in an understanding of limits.  Societies are more likely to change under extreme circumstances, and the economic shock of the 2020 coronavirus pandemic will certainly qualify as extreme.  As the global economy recovers, there will be significant opportunities to change technosphere metabolism.  Let’s hope they are not wasted.

Can Humanity be a “We”?

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David P. Turner / February 16, 2020

The peer-reviewed literature and the popular media today abound with concern about human-induced global environmental change.  Articles often argue that global scale problems require global scale solutions: humanity is causing the problem and “we” must rapidly implement solutions.  Environmental psychologists have found that people who sympathize with or identify with a group are energized to support its cause.  Can a majority of human beings identify with humanity in a way that motivates collective change towards global sustainability?      

Let’s consider several key constraining factors and unifying factors relevant to making humanity a “we” with respect to global environmental change.

Constraining Factors

Notable sociopolitical factors that impede global solidarity include the following.

1.  Climate Injustice among Nations 

In the process of their development, the most developed countries burned through a vast amount of fossil fuel and harvested a large proportion of their primary forests, hence causing most of the observed rise in atmospheric CO2 concentration.  But these countries are now asking the developing countries to share equally in the effort to curtail global fossil fuel emissions and deforestation to prevent further climate change.  At the same time, the impacts of climate change will tend to fall most heavily on the developing countries because of their lower capacity for adaptation.  The developing countries are pushing back on the basis of fairness, e.g. the outcome of the Kyoto protocol (albeit now obsolete) was that only the developed countries made commitments to reduce greenhouse gas emissions.

2. Rising Nationalism

Economists generally agree that economic globalization has spurred the global economy and helped lift hundreds of millions of people out of extreme poverty.  However, globalization of the labor market beginning around 1990 has also meant a large transfer of manufacturing from the developed to the developing world – and with it many jobs.

Likewise, immigration is helping millions of people a year find a better life by leaving behind political corruption, resource scarcity, and environmental disasters. 

Unfortunately, one effect of economic globalization and mass immigration has been political backlash within developed countries in the form of populism and nationalism.  Hypersensitivity to loss of national sovereignty is not conducive to international agreements to address global environmental change issues.

3.  Climate Science Skeptics

Although the global scientific community is broadly in consensus about the human causes of climate warming and other global environmental change problems, the rest of the world is more divided.  Most people in the U.S. accept that the global climate is changing, but only about half accept the scientific consensus that climate warming is caused by human actions.  Sources of skepticism about climate science include religious beliefs and vested interests. 

4.  Economic Inequality

Wealth inequality, both within nations and among them, is a pervasive feature of the global economy.  The rich end of the wealth distribution contributes to the vested interests problem as just noted.  At the poor end of the wealth distribution, the hierarchy of needs discourages concern for the environment; solidarity with the fight against climate change is a luxury when you are starving.

These four constraining factors are deeply rooted and are only the head of a list that would also include competition for limited natural resources and geopolitical conflict.  It is daunting to think about overcoming these obstacles to a “we” that includes all of humanity.  There are substantive ongoing research and applied efforts (not documented here) to overcome them, but in a general way let’s consider some equally significant factors that may help foster a global “we”.

Unifying Factors

The following rather disparate set of factors supply some hope for human unification under the banner of environmental concern.

1.  Our Genetic Heritage

Humans are social creatures.  Sociobiologists, such as Harvard Professor E.O. Wilson, have argued that many of our social impulses are genetically based.  We have an instinctual propensity to identify with a particular social group, and to draw a distinction between that group (us) and outsiders (them).  The average ingroup size during the hunter/gatherer phase of human evolution, which largely shaped our social instincts, is believed to have been about 30 people.  Remarkably, the size of the social group that humans identify with has vastly expanded over historical time − from the level of tribe, to the level of village, empire, and the modern nation-state.  Conceivably, that capacity could be extended to the global scale:  we might all eventually consider ourselves citizens of a planetary civilization.

The historical expansion of social group size was driven in part by military considerations  − the need to have a larger army than your neighbor.  Obviously, this rationale breaks down at the global scale, but a distinct possibility for inspiring global solidarity is the looming threat of global environmental change. 

Note that being a citizen of the world does not require rejecting one’s local or national culture.  Multiple sources of identity could include being an autonomous individual, being a member of various ingroups, and being a member of humanity in its entirety.

2.  The Advance of Earth System Science

A conspicuous general trend favorable to achieving a collective sense of responsibility for managing human impacts on the Earth system is growth in our scientific understanding of the Earth system.  From studies of the geologic record, scientists know that Earth’s climate has varied widely, from cool “snowball” Earth phases to relatively warm “hothouse” Earth phases.  Greenhouse gas concentrations have consistently been an important driver of global climate change, which gives scientists confidence that as greenhouse gas concentrations rise, Earth’s climate will warm. 

The scientific community also has expansive monitoring networks that reveal the exponentially rising curves for metrics such as the atmospheric CO2 concentration.  Earth system models that simulate Earth’s future show the dangers of Business-as-Usual scenarios of resource use, as well as the benefits of specific mitigation measures.  At the request of the United Nations, the global scientific community periodically assembles the most recent research about climate change, the prospects for mitigation (i.e. reduction of greenhouse gas concentrations), and the possibilities for adaptation. 

If improved understanding of the human environmental predicament can filter down to the global billions, we might hope for a strengthening support for collective action.

3.  The Evolution of the Technosphere

The technosphere is a new global-scale part of the Earth system.  It joins the pre-existing geosphere, atmosphere, hydrosphere, and biosphere.  However, just as the evolution of the biosphere was a major disturbance to the early Earth system, the evolution of the technosphere is proving to be disruptive to the contemporary Earth system.  

Around 2.3 billion years ago, cyanobacteria evolved that could split water molecules (H2O) in the process of photosynthesis.  The resulting oxygen (O2) began to accumulate in the atmosphere, radically changing atmospheric chemistry.  Oxygen was toxic to many existing life forms, but eventually micro-organisms capable of using oxygen in the process of respiration evolved, which in time led to the evolution of multicellular organisms (and eventually to us). 

In the case of technosphere evolution, a process that emits excessive amounts of CO2 (combustion of fossil fuels) has arisen, which is altering the global climate and ocean chemistry in a way than may be toxic to many existing life forms.  One potential solution is that the technosphere can further evolve (by way of cultural evolution) to subsist on renewable energy rather than combustion of fossil fuels, thus moderating its influence on the atmosphere, hydrosphere, and biosphere.

A characteristic feature of technosphere evolution is ever more elaborate means of transportation and telecommunications.  These capabilities – especially the on-going buildout of the Internet – allow for increased integration across the technosphere and tighter coupling of the technosphere with the rest of the Earth system.  Sharing results of environmental monitoring in its many dimensions over the telecommunications network can help with creating and maintaining sustainable natural resource management schemes.   

Through the popular news and social media, nearly everyone in the world can learn about events such as regional droughts and catastrophic forest fires that are associated with climate change.  It is thus becoming easier to have a common frame of reference among all humans about the state of the planet.

There is not yet anything like a global consciousness that coordinates across the whole technosphere.  However, the Internet is facilitating the emergence of a global brain type entity.  One indication of what the nascent global brain is thinking about is the relative frequencies of different search terms on Google.  Interestingly, in the algorithms that determine the response to search engine queries, a high frequency of previous usage for a relevant web site makes that site more likely to reach the top of the response list.  That process is evocative of learning, i.e. reinforcement through repetition.  Similarly, the Amygdala Project monitors Twitter hashtags.  They are classified according to emotional tone, and a running visual summation gives a sense of the collective emotional state (of the Twitterers).  Advances in artificial intelligence and quantum computing may soon improve the module in the global brain that simulates the future of the Earth system.

4.  The Expanding Domain of Human Moral Concern

In “The Slow Creation of Humanity”, psychologist Sam McFarland recounts the history of the human rights movement.  Writer H.G. Wells, humanitarian Eleanor Roosevelt, and others have helped develop the rationale and legal basis for including all human beings in our “circles of compassion” (Einstein’s term).  The concept of rights has now begun to be legally extended to Nature (in Ecuador) and specifically to Earth (in Bolivia).  Since protecting the rights of Earth (e.g. to be free of pollution) clearly requires that humans work collectively, we come to an incentive for global human solidarity.

Again, these four unifying factors are only the start of a list that might also include global improvements in education, as well as growth in the activities of global non-governmental environmental organizations. 

Conclusions

The field of Earth system science is producing an increasingly clear understanding of the human predicament with respect to global environmental change.  Scientist know what is happening to the global environment, what is likely to happen in the future under Business-as-Usual assumptions, and to some degree, what must change to avert an environmental catastrophe.

The process of changing the trajectory of the Earth system cannot be done unilaterally.  From the top down, an important step will be genesis or reform of the institutions of global governance – including institutions concerned with the political, economic, and environmental dimensions of governance.  This is a task for a generation of researchers, political leaders, and diplomats.  From the bottom up, individuals must be brought around as adults, and brought up as children, to adopt an identity that includes global citizenship and associated responsibilities for the global environment.  This is a task for a generation of educators, religious leaders, and business leaders.

If “we” human dwellers on Earth don’t gain a collective identity and begin to better manage the course of technosphere evolution, then we may no longer thrive on this planet.

Recommended Audio/Video, Mother Earth, Neil Young

Land Photosynthesis is Increasing

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January 20, 2020/David P. Turner

An image of the global biosphere in which depth of greenness on land represents annual photosynthesis.  Wikimedia Commons

Natural Processes are Slowing the Accumulation of Carbon Dioxide in the Atmosphere − Strategic Land Management Could Boost That Trend

As global climate warms in response to rising greenhouse gas concentrations, various components of the Earth system are responding in ways that amplify or suppress the rate of change.  Most of these feedbacks are positive (amplify warming).  However, a natural negative feedback (suppresses warming) exists and it could be augmented by human actions.

Scientists generally agree that an increase in the concentration of carbon dioxide (CO2) in the atmosphere, precipitated by human activities, is a major driver of climate change.  Hence, any process induced by rising CO2 and climate change in which less CO2 is added to the atmosphere, or more CO2 is removed from the atmosphere and sequestered, constitutes a negative feedback to climate change. 

The most obvious and necessary negative feedback is a rapid reduction in fossil fuel emissions.  The 2015 Paris Agreement on Climate Change points to progress in that direction.  Unfortunately, fossil fuel emissions continue to rise. 

Research in Earth system science is examining the operation of another significant, but naturally occurring, negative feedback to climate change.  Observations suggest that the rising atmospheric CO2 concentration and associated climate change is spurring carbon sequestration by the terrestrial biosphere. 

Earth system scientists speak of the “carbon metabolism” of the terrestrial biosphere, referring to the uptake of carbon by way of photosynthesis and its release back to the atmosphere by way of respiration of plants, animals, and microbes (Figure 1).  When photosynthesis exceeds respiration, carbon is sequestered from the atmosphere.  A critical question concerns the degree to which humanity can purposefully augment this negative feedback and help slow climate change.

Figure 1.  The atmospheric CO2 concentration is a function of uptake by processes such as plant photosynthesis, and release by processes such as respiration and combustion of fossil fuels.  Wikimedia Commons.

The Terrestrial Biosphere is Speeding Up

Laboratory and chamber studies show that plant photosynthesis is generally sped up, and drought stress is alleviated, as CO2 concentration increases.  At the global scale, long-term observations are finding a trend of increasing global photosynthesis in recent decades as the CO2 concentration in the atmosphere rises.  The estimated increase is on the order of 30% based on four independent lines of evidence.

Terrestrial respiration (see Figure 1) also appears to be increasing, but at a slower rate.  The carbon mass difference between global photosynthesis and respiration is accumulating in the biosphere and helping restrain growth of the atmospheric CO2 concentration. 

The dominant reservoir for sequestered carbon is most likely wood.  Note that forests accumulate wood as they recover from disturbances.  Thus, the terrestrial biosphere uptake or “sink” for carbon is a function of both the disturbance history of global forests and the stimulation of wood production by high CO2.

One indication of an invigorated biosphere comes from observations of the atmospheric CO2 concentration at Mauna Loa Hawaii.  The iconic “Keeling curve” (Figure 2) shows an upward trend attributable mostly to fossil fuel emissions, and an annual oscillation, which is attributable to terrestrial biosphere metabolism.  The annual drawdown in concentration is driven by an excess of photosynthesis over respiration in the northern hemisphere spring, and observations of CO2 in recent decades find a strengthening of that drawdown.  Contributing factors include a longer growing season, deposition of nitrogen from polluted skies (= fertilization), and CO2 stimulation of growth.

Figure 2.  Monthly mean atmospheric carbon dioxide at Mauna Loa Observatory, Hawaii (in red).  The black curve represents the seasonally corrected data. NOAA.

Increasing carbon sequestration by the biosphere is evident from the observation that the proportion of human generated carbon emissions that stays in the atmosphere (the airborne fraction) has fallen in the last decade, despite the large upward trend in fossil fuel emissions.  The airborne fraction was 44% for the 2008-2017 period, with the remainder of emissions accumulating on the land (29%) or in the ocean (22%).

Human Augmentation of Terrestrial Biosphere Carbon Sequestration

So, we have a natural brake on the rising CO2 concentration.  And it is one that could potentially be augmented by human intention. 

Thus far, human land use impacts such as deforestation and agriculture have tended to decrease biosphere carbon storage.  However, there is a large potential to deliberately sequester carbon in terrestrial ecosystems by way of several approaches.   

1.  Expansion of the UN-REDD Programme (United Nations Reducing Emissions from Deforestation and Forest Degradation).  REDD consists of intergovernmental agreements that pay developing countries to protect forests.  The carbon benefit is both in terms of reducing carbon emissions and maintaining carbon sinks.  Remote sensing is increasingly effective in monitoring carbon stocks.  Norway has begun to make payments to Indonesia for reducing rates of deforestation.

2.  Making land management decisions in the context of the whole suite of ecosystem services.  Carbon sequestration in biomass and soil is a climate related service that compliments other services such as conservation of biodiversity.  Management of both public and private land could be shifted towards this comprehensive perspective.

3.  Planting trees − something that can be done at the scale of a suburban back yard, whole urban areas, or regions (Figure 3).  Satellite-observed greening in China is attributed in part to large scale tree planting.  Trees affect the absorption and reflection of solar radiation as well as the carbon balance, so care must be taken about planning large scale plantings.

Figure 3.  Forests accumulate large stocks of carbon relative to other vegetation cover types.  Wikimedia Commons.

These human-mediated carbon sinks will all benefit from high CO2 impacts on biosphere metabolism.  In contrast, the impacts of continuing climate change − independent of CO2 impacts − on these carbon sinks and on biosphere metabolism generally are difficult to anticipate.  At high latitudes, climate warming appears to be associated with vegetation greening.  In contrast, increased rates of disturbance in mid-latitudes − such as climate warming induced forest fire − may offset the strength of biosphere carbon sequestration.

In an optimistic scenario, radically reduced fossil fuel emissions along with increased carbon uptake by the land and ocean will cause the atmospheric CO2 concentration to peak within this century, leading to a gradual decline that is powered by biosphere sequestration (natural and augmented). 

Since we are already committed to significant climate change, that CO2 trajectory would still leave us with major − but hopefully manageable − adaptation challenges.  A stabilized CO2 concentration, would also reduce the possibility that the Earth system will cascade through of series of positive feedback tipping points.  That scenario would take hundreds to thousands of years to play out but it could push Earth into a state threatening to even a well-organized, high-technology, global civilization.

Peak Carbon Dioxide Emissions and Peak Carbon Dioxide Concentration

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David P. Turner / January 11, 2024 (update)

Figure 1.  Projections of CO2 emissions and concentration.  Image Credit NOAA

In 2020, a remarkable speculation circulated in the cybersphere to the effect that global emissions of carbon dioxide (CO2) from fossil fuel combustion may have peaked in 2019.  Considering that recent formal projections generally indicated increasing emissions through 2030 or longer, this assertion was striking.  It matters because CO2 emissions determine the growth in the atmospheric CO2 concentration, which in turn influences the magnitude of global warming.

The atmospheric CO2 concentration is currently around 420 ppm (up from a preindustrial value of around 280 ppm) and is rising at a rate of 2-3 ppm per year.  The consensus among climate scientists is that rapid greenhouse-gas-driven climate change will be harmful to the human enterprise on Earth.  It would be good news indeed if CO2 emissions were on the way down.

Estimates for annual global CO2 emissions are produced by assembling data on consumption of coal, oil, and natural gas, as well as data on production of cement and effects of land use.  The sum of fossil fuel and cement emissions is termed Fossil Fuel & Industry emissions (FF&I).  Land use, land use change, and forestry (LULUCF) is mostly the net effect of carbon emissions from deforestation and carbon sequestration from afforestation/reforestation.  Total anthropogenic emissions are the net of FF&I and LULUCF.  Two independent estimates of CO2 sources and sinks (GCP and IEA) differ slightly.

The suggestion that peak fossil fuel emissions occurred in 2019 held true in 2020 and again in 2021 and 2022, but 2023 saw a 1.1% increase over 2019. 

Intriguingly, a decline in LULUCF compensated for the increase in fossil emissions such that total anthropogenic emissions remained the same in 2023 as 2022 (11.1 GtC yr-1).  That result may hold in 2024 as well if President Lula of Brazil continues to succeed in reducing deforestation, and global fossil fuel emissions grow only modestly (if at all).

Several specific observations points towards lower emissions in the near-term future.

1.  Global coal emissions declined from 2012 to 2019 but have risen above 2012 in recent years, primarily due to increases in India and China.  However, coal emissions declined 18.3% in the USA and  18.8% in the EU in 2023.  Aging coal powered electricity plants in the U.S. are being replaced with plants powered by natural gas (more efficient that coal) or renewable energy.  Some coal plants have been prematurely retired.  A gradual phase out in global coal consumption is being driven by the price advantage of renewable energy, impacts of coal emissions on human health, and the reluctance of insurance companies to cover new coal power plant construction.  China has agreed to stop financing the construction of coal power plants in developing nations and India has pledged to stop approving new domestic coal plants.

2.  Peak oil use may have occurred in 2019.  Global demand in 2020 fell 7.6% because of Covid-19. It partially recovered in 2021 and 2022 and 2023 but remains below the level in 2019.  Structural changes such as reduced commuting and business-related flying mean that some of the demand reductions associated with Covid-19 have persisted.  Vehicles powered by electricity and hydrogen rather than gasoline are on the ascendancy, sparked in part by governmental mandates to phase in zero emissions vehicles.

3.  Even a near-term peak in natural gas consumption is being discussed.  The GCP budget for 2022 showed a 0.2% decline in gas emissions and for 2023 a 0.5% increase.  Again, the price advantage of renewable sources will increasingly weigh against fossil-fuel-based power plants.  The growing importance of energy security at the national level also argues against dependence on imported fossil fuels.  Ramped up production of renewable natural gas could substitute for fossil natural gas in some applications.

It is likely that the approaching peak in total fossil fuel use will be driven by diminishment of demand rather than lack of supply.

Currently about half of FF&Iemissions remain in the atmosphere, with the remainder sequestered on the land (e.g. in vegetation and soil) and in the ocean.  The land sink is increasing in response to 1) high CO2 enhancement of photosynthesis and plant water use efficiency, and 2) policy driven impacts on land management (e.g. more reforestation and afforestation).

Once fossil fuel emissions begin decreasing and fall by half − and assuming the net effect of increasing CO2 and climate warming is still substantial carbon uptake by the land and ocean − the atmospheric CO2 concentration will peak and begin to decrease.  The year of peak CO2 concentration could be as early as 2040 (see carbon cycle projection tool below).

On the other hand, there is plenty that might go wrong with this optimistic scenario.  As climate change intensifies, the net effect on land and ocean sequestration could be a decline in carbon uptake.  On land, carbon sources such as permafrost melting and forest fires will be stimulated by climate warming.  In the ocean, warming will intensify stratification, thereby reducing carbon removal to the ocean interior.  The steady increase in the ocean carbon sink since around 2000 has stalled in recent years, for poorly understood reasons.  If fossil fuel emissions are not significantly abated in the coming decades, the CO2 concentration could still be rising in 2100 (Figure 1).

Recommended:  Interactive CO2 Emissions and Concentration Projection Tool.