With its unprecedented changes in the earth’s geo-and biosphere, the fundamental and irreversible human imprint and impact on natural systems and processes has turned humankind into a geological agent, which has led to term this epoch and state of affairs, the ‘Anthropocene’. Under the techno human condition, anthropogenic-induced environmental change and the domination of the Earth’s ecosystems have reached a global scope and a permanent geological time-scale. Humanity has become the most successful parasite of any invasive species, a hominiscence appropriating the entire planet—taking without giving and engaging in continual (terrorizingly) territorialization. Conceptual disconnection and practical alienation from materialities and nature, life, the appropriation of (capitalist) desires, and fantasies of constant growth and repeatable progress have gained increasingly ideological traction and power. The earth bio-spherical and socio-ecological metabolism cannot ‘digest’ human interferences, interventions and outputs.
The Earth System is usually defined as a single, planetary-level complex system, with a multitude of interacting biotic and abiotic components, evolved over 4.54 billion years and which has existed in well-defined, planetary-level states with transitions between them. A state is a distinct mode of operation persisting for tens of thousands to millions of years within some envelope of intrinsic variability. The Earth System is driven primarily by solar radiation and is influenced by other extrinsic factors, including changes in orbital parameters and occasional bolide strikes, as well as by its own internal dynamics in which the biosphere is a critical component.
Earth’s mean temperature is determined primarily by its energy balance, including the key variables of solar insolation (increasing during Earth history), greenhouse gas forcing (broadly decreasing during Earth history) and albedo. The distribution of heat at the Earth’s surface is modified by orbital variations and paleogeographic patterns driven by tectonics, which in turn can drive feedbacks that lead to whole-Earth changes in albedo or greenhouse gas forcing. Thus, over multi-million-year timescales, Earth’s climate shifts in response to gradual changes in continental configuration, the opening or closing of ocean gateways, and the plate tectonic, which, together, drive long-term changes to the carbon cycle and the biosphere. These long, slow changes modify the effects of solar forcing, not least by changing the balance between sources of CO2 (from volcanic activity) and its sinks (starting with chemical weathering and progressing through sequestration in sediments).
A REMINDER OF WHERE WE ARE IN THE IMMENSITY OF SPACE, THE EONS OF TIME, AND THE MAJESTIC EVOLUTION OF EXISTENCE.
The Universe is immense, estimates suggest at least two trillion galaxies. Our galaxy holds 100 to 400 billion stars. One of those stars, our sun, has eight planets orbiting it. One of those, planet Earth, has a biosphere, a complex web of life, at its surface. The thickness of this layer is about twenty kilometers. This layer, our biosphere, is the only place where we know life exists. The broadest of perspectives can locate the shift underway on planet Earth as the most recent scene in a vast pageant of cosmic emergence. A cosmological panorama takes us beyond the ambit of daily life and beyond even the larger compass of human history, offering a vantage point for pondering the contemporary predicament. About 3.8 billion years ago, life appeared on Earth, opening a new chapter in the story of the universe. Biological evolution has been a wondrous adventure of tenacity and inventiveness through titanic episodes of extinction and proliferation. We humans emerged and evolved within the biosphere. Our economies, societies, and cultures are part of it. Across the ocean and the continents, the biosphere integrates all living beings, their diversity, and their relationships. There is a dynamic connection between the living biosphere and the broader Earth system, with the atmosphere, the hydrosphere, the lithosphere, the cryosphere, and the climate system. Life in the biosphere is shaped by the global atmospheric circulation, jet streams, atmospheric rivers, water vapor and precipitation patterns, the spread of ice sheets and glaciers, soil formation, upwelling currents of coastlines, the ocean’s global conveyer belt, the distribution of the ozone layer, movements of the tectonic plates, earthquakes, and volcanic eruptions. Water serves as the bloodstream of the biosphere, and the carbon, nitrogen, and other biogeochemical cycles are essential for all life on Earth.
It is the complex adaptive interplay between living organisms, the climate, and broader Earth system processes that has evolved into a resilient biosphere.
The biosphere has existed for about 3.5 billion years. Modern humans (Homo sapiens) have effectively been around in the biosphere for some 250 000 years. Powered by the sun, the biosphere and the Earth system coevolve with human actions as an integral part of this coevolution.
Short-term abrupt changes are imposed by sudden aperiodic volcanic activity that may be as brief as a single volcanic eruption or as long as the life of a Large Igneous Province of the kind that gave rise to the Siberian Traps and the end-Permian extinction. These are aside from natural fluctuations of minor amplitude driven by orbital change or internal oscillations within the ocean–atmosphere system, such as El Niño events or the Pacific Decadal Oscillation.
The evolution of the biosphere can be divided into two fundamental stages. Between ∼4 to 0.8 billion years ago, the biosphere comprised mostly of unicellular organisms occurring either individually or in colonies. This initial stage featured several important developments in biospheric functioning, such as the appearance of sulfur-reducing bacteria and the development of photosynthetic metabolic pathways.
From ∼0,8 billion years ago molecular (genetic), fossil, trace fossil, and biomarker evidence supports the evolution of a biosphere with metazoans (animals). This led to the Cambrian adaptive radiation (or Cambrian explosion), in which skeletonized organisms become preserved in rock successions worldwide. The rich fossil record of the past 600 million years provides additional evidence of major innovations in the Earth’s biota and their interaction with the abiotic components of the Earth System. Neoproterozoic and Cambrian sedimentary strata provide the first evidence of motile bilaterian organisms as part of an evolutionary continuum that produced the complex trophic structures of the marine ecosystems of the Phanerozoic.
The Ordovician to Devonian stratigraphic records show the rise of a complex terrestrial biosphere, first with nonvascular plants and later with vascular plants that produced only spores followed by the rise of seed plants along with more complex seedless vascular plants and the growth of extensive forests. Regime shifts in the Earth’s biosphere are reflected by mass extinction events, after which major alterations in the trajectory of evolution occurred, and in the relatively rapid transitions between the three evolutionary faunas recognized by paleontologists as the Cambrian Fauna, the Paleozoic Fauna, and the Modern Fauna.
A reminder of where we are in the immensity of space, the eons of time, and the majestic evolution of existence, this wide vista cultivates a sense of awe and humility, stirring resolve to renew the vitality of our precious island of life. Such reflections bring into focus a transcendent challenge: to navigate toward a new order of complexity in our corner of the universe, a flourishing and resilient global society.
EVOLUTION OF THE CLIMATE SYSTEM
The climate system is integral to all other components of the Earth system, through heat exchange in the ocean, albedo dynamics of the ice sheets, carbon sinks in terrestrial ecosystems, cycles of nutrients and pollutants, and climate forcing through evapotranspiration flows in the hydrological cycle and greenhouse pollutants. Together these interactions in the Earth system interplay with the heat exchange from the sun and the return flow back to space, but also in significant ways with biosphere-climate feedbacks that either mitigate or amplify global warming. These global dynamics interact with regional environmental systems (like El Niño–Southern Oscillation or the monsoon system) that have innate patterns of climate variability and also interact with one another via teleconnections. The living organisms of the planet’s ecosystems play a significant role in these complex dynamics.
Earth has been oscillating between colder and warmer periods over a million years (the entire Pleistocene), but the average mean temperature has never exceeded 2o C (interglacial) above or 6oC below (deep ice age) the preindustrial temperature on Earth (14oC), reflecting the importance of feedbacks from the living biosphere as part of regulating the temperature dynamics of the Earth.
The stratigraphic record, based on a wide variety of geological, paleontological, and geochemical proxies also provides the evidence needed to infer changes in the climate. From the Archean to the present, homeostatic processes have forced Earth’s climate to remain within rather narrow temperature limits. That constraint has allowed the three phases of water—liquid, vapor, and solid—to coexist on the surface of the planet, providing a key precondition for the appearance and evolution of life.
The evolution of the climate system shows its highly systemic nature. This includes;
- the alternation between so-called greenhouse states (warm times when the poles were ice-free) and icehouse states (cold times with permanent polar and lower latitude sea ice and/or glacier ice), evident from late Archean times onward.
- the evolution of the global carbon cycle that provides a critical link between the physical climate and the biosphere.
- the Earth System’s intrinsic negative feedback processes, coupled with lithosphere evolution (e.g., CO2 release from within the Earth), that enable it to absorb and recover over the long term from marked temperature changes that cause severe glaciation (e.g., in the early and late Proterozoic).
The stratigraphic record provides important clues to key positive and negative feedback mechanisms, such as the influence of ice cover on albedo or changes in atmospheric greenhouse gas composition (principally CO2, methane (CH4), and water vapor). These feedbacks can, under appropriate conditions, either amplify or dampen external forcing, such as orbital variation and solar insolation, to drive or suppress transitions between states of the climate. In addition to providing essential knowledge on the evolution of the Earth System in the past, the stratigraphic record, coupled with mechanistic insights derived from Earth System science, can also provide insights into how the system might evolve in the future.
EMPHASIZING THE COEVOLUTION OF THE GEOSPHERE AND BIOSPHERE.
The climate and the biosphere are two highly intertwined, aggregate components of the whole-Earth System—a single complex system—even though the evolution of those two components can be inferred somewhat independently from each other. In this very era of the Anthropos, natural forces and human forces are so intertwined (across temporal and spatial scales) that the fate of one determines the fate of the other. Such entwinement of human and non-human spheres and socio-natural entangled hybridization in a climate-changed world has led to what has been called a post-natural ontology of the Anthropocene. The stratigraphic record provides the means by which a systematic integration of climate and biosphere evolution can be attempted—the evolution of the Earth as a system. Complex-systems approaches have been applied by ecologists to track coevolution of the biosphere and geosphere as a series of states and transitions, especially through the metazoan stage.
A new time interval in Earth history can be defined only when globally synchronous stratigraphic signals related to the structure and functioning of the Earth System are clearly outside the Holocene norm, a new time interval in Earth history can be defined. There is an overwhelming amount of stratigraphic evidence that the Earth System is indeed now structurally and functionally outside the Holocene norm. This evidence includes novel materials such as elemental aluminum, concrete, plastics, and geochemicals; carbonaceous particles from fossil fuel combustion; widespread human-driven changes to sediment deposits; artificial radionuclides; marked rises in greenhouse gas concentrations in ice cores; and trans-global alteration of biological species assemblages.
The Earth’s biosphere may be approaching a third fundamental stage of evolution the first two, as noted above, being a microbial stage from ∼4 to 0.8 billion years ago and thereafter a metazoan stage], and the climate is in an interval of rapid, and possibly, irreversible change. With the amount of CO2 currently in the atmosphere, the planet will continue to warm, driving a long-term rise in sea level even if emissions of CO2 ceased immediately. Past rises in sea level have taken considerably longer to reach equilibrium than the rise in surface air temperature.
The Earth system contains several biophysical sub-systems that can exist in multiple states and which contribute to the regulation of the state of the planet as a whole. These so-called tipping elements, or sleeping giants, have been identified as critical in maintaining the planet in favorable Holocene-like conditions. These are now challenged by global warming and human actions, threatening to trigger self-reinforcing feedbacks and cascading effects.
Tipping elements central in regulating the state of the planet, and identified interactions among them that, for humanity, that could cause serious cascading effects and even challenge planetary stability
- Boreal forest
- Greenland Ice sheet
- Arctic sea ice
- Permafrost
- Jet stream
- Alpine glaciers
- Atlantic circulation
- Sahel
- Indian summer monsoon
- Amazon rainforest
- El Nino / La Nina Oscillation
- Coral Reefs
In addition, ocean acidification, deoxygenation, tropical cyclones, ocean heat waves, and sea level rise are challenging human wellbeing.
The Earth System is still in a phase of rapid change and the outcome is not yet clear; there is no sign that the system is anywhere near a stable or quasi-stable state. The trajectory is influenced strongly by human agency in addition to natural processes and feedbacks inherent in the Earth System, and so cannot be predicted with any confidence. Furthermore, it is not clear whether a scenario characterized by a transition from one well-defined state of the Earth System, the Holocene, to another well-defined state is plausible, given that the geological climate record shows a broad range of dynamics, such as transitions, aberrations, perturbations, singular events, and a great deal of variability overall.
Regarding the biosphere, as aforementioned, the Earth may be approaching a third fundamental stage of evolution because of a wide range of human pressures. The contemporary biosphere differs significantly from previous stages of evolution due to many anthropogenic modifications and perturbations. These include global homogenization of flora and fauna; human appropriation of 25–40% of net primary production (likely to increase along with population growth); extensive use of fossil fuels to break through photosynthetic energy barriers; human-directed evolution of other species; and increasing interaction of the biosphere with technological systems.
Ontologically, epistemologically and practically, the Anthropocene challenges the traditional distinctions that are separating nature from culture that is from cultural structures, and the order of approaches and knowledge about the world and social practices. Nature has been and is domesticated, technologized and capitalized in a way that it even cannot any longer be considered as what was used to be called ‘natural’. Whereas nature is ‘humanized’ in the sense of anthropo- and socio-genic practices, these same practices are normalized or ‘naturalized’ and thus understood as part of ‘natural’ occurrences. Realizing humanity’s material dependence, embodiment, and the fragility of beings including human ones calls for rethinking and reimagining those traditional assumptions and myth about the autonomy-based self-contained and rational subject that commences and terminates with itself. The challenge will be developing a different alternative approach. This would be one that processes differences sensitively, and simultaneously is more inclusive concerning the very status of the entangled material-based and the human-mediated spheres seen in a newly understood and enacted continuum of the natural and cultural life and its worlds. The degree of stabilization of biospheric change equivalent to that needed to stabilize the climate system would require ecosystem restoration and careful stewardship, a rapid reduction in the extinction rate, innovative approaches to agricultural production, full recycling of nutrients such as nitrogen and phosphorus and other materials, the spread of living (green) infrastructure in urban areas, and so on.
It requires a fundamental change in the nature of the anthroposphere, so that its dynamics become more synergistic with those of the biosphere. Yet even this dramatic shift could not undo the past alteration of the biosphere relative to the Holocene, an alteration that already represents a regime shift in the Earth System.