The second half of the 20th Century is unique in the history of human existence. The last 60 years have without doubt seen the most profound transformation of the human relationship with the natural world in the history of humankind.
Human activity, predominantly the global economic system, is now the prime driver of change in the “Earth System” (the sum of our planet’s interacting physical, chemical, biological and human processes), according to a set of 24 global indicators, or “planetary dashboard”.
A decade on, IGBP in collaboration with the Stockholm Resilience Centre has reassessed and updated the Great Acceleration indicators, first published in the IGBP synthesis, Global Change and the Earth System in 2004. “After 1950 you can see that major Earth System changes became directly linked to changes largely related to the global economic system. This is a new phenomenon and indicates that humanity has a new responsibility at a global level for the planet” said Professor Will Steffen, a researcher at the Australian National University and the Stockholm Resilience Centre and lead author of the new research paper “The trajectory of the Anthropocene: The Great Acceleration”published in Anthropocene Review journal (16 January 2015).
Co-author IGBP Deputy Director, Dr Wendy Broadgate said, “The Great Acceleration indicators allow us to distinguish the signal from the noise. Earth is in a quantifiably different state than before. Several significant Earth System processes are now driven by human consumption and production.”
The new research charts the “Great Acceleration” in human activity from the start of the industrial revolution in 1750 to 2010, and the subsequent changes in the Earth System – greenhouse gas levels, ocean acidification, deforestation and biodiversity deterioration.
Take a look at Great Acceleration.
“It is difficult to overestimate the scale and speed of change. In a single lifetime humanity has become a planetary-scale geological force,” says Professor Will Steffen, who led the joint project between the International Geosphere-Biosphere Programme (IGBP) and the Stockholm Resilience Centre.
The human imprint influences all components of the global environment – oceans, coastal zone, atmosphere, and land.
Dramatic though these human-driven impacts appear to be, to begin to understand their significance their rates and magnitudes must be compared to the natural patterns of variability in the Earth system. The increase in atmospheric carbon dioxide concentration provides a useful measure to evaluate the rate and magnitude of human-driven change compared to natural variability. The human imprint on carbon dioxide is unmistakable. In December 2014, atmospheric carbon dioxide concentration stood at 399 parts per million by volume (ppmV), over 100 ppmV above the previous maximum level of around 280 ppmV recorded in the Vostok ice core. Within the current limits of resolution of the ice-core records, the present concentration has been reached at a rate at least 10 and possibly 100 times faster than carbon dioxide increases at any other time during the previous 420 000 years. Thus, in this case human-driven changes are well outside the range of natural variability exhibited by the Earth system for the last half-million years at least.
The domino effect
A single type of human-driven change triggers a large number of responses in the Earth system, which themselves cascade through the system, often merging with patterns of natural variability.
The responses seldom follow linear chains, but more often interact with each other, sometimes damping the effects of the original human forcing and at other times amplifying them.
The nature of the Earth system’s responses to the increasing anthropogenic forcing is more complex than simple cause-effect relationships, such as greenhouse gas emissions causing global warming.
Fossil-fuel combustion produces a range of gases that have a large number of cascading effects. For example, carbon dioxide not only affects climate but directly affects how vegetation grows. It changes the carbonate chemistry in the ocean – the oceans are becoming more acidic, which in turn affects marine organisms. Changing carbonate chemistry is a factor in the widespread decline of coral reefs around the world.
Fossil-fuel combustion also produces oxidising gases such as nitric oxide and sulphur dioxide that have well-known effects such as acidification and eutrophication of ecosystems.
However, these gases can eventually contribute to changes in fundamental Earth system functioning because of their indirect effects on the radiative properties of the atmosphere, and hence climate. The mechanisms are through reactions with other gases plus their impacts on the ability of the atmosphere to cleanse itself through oxidation and other processes.
Aerosols produced by fossil-fuel combustion can fertilise or reduce plant growth, depending on the circumstances, and directly affect human health. They also lead to large-scale direct or indirect modifications of climate. We can trace even more subtle effects back to fossil-fuel combustion. Increasing carbon dioxide levels affect the stomatal opening of terrestrial vegetation, reducing water vapour loss through the stomates. This results in higher water-use efficiency. This effect is especially pronounced in semi-arid vegetation, and can lead to increased productivity through enhanced soil moisture.
More generally, no two species react in an identical way to elevated atmospheric carbon dioxide concentration.
Like fossil-fuel combustion, land-cover and land-use change also trigger widespread cascading effects at local, regional and global scales. Global change does not operate in isolation but rather interacts with an almost bewildering array of natural variability modes and also with other human-driven effects at many scales. Especially important are those cases where interacting stresses cause a threshold to be crossed and a rapid change in state or functioning to occur.
The Great Acceleration trends support the proposal that Earth has entered a new geological epoch, the Anthropocene, coined by researchers Paul Crutzen and Eugene Stoermer in 2000. Since then, the onset of the Anthropocene has been keenly contested by geologists, Earth System scientists and others, even though the term has not yet been formalised by the International Commission on Stratigraphy. Some say the dawn of agriculture 10,000 years ago – the Neolithic Age – is a likely candidate. Others say the industrial revolution, around the late 1700s.
The new paper argues that, “Of all the candidates for a start date for the Anthropocene, the beginning of the Great Acceleration is by far the most convincing from an Earth System science perspective. It is only beyond the mid-20th century that there is clear evidence for fundamental shifts in the state and functioning of the Earth System that are beyond the range of variability of the Holocene, and driven by human activities and not by natural variability.”
Co-author, Dr Lisa Deutsch, Senior Lecturer at the Stockholm Resilience Centre notes that: “Of all the socio-economic trends only construction of new large dams seems to show any sign of the bending of the curves – or a slowing of the Great Acceleration. Only one Earth System trend indicates a curve that may be the result of intentional human intervention – the success story of ozone depletion. The levelling off of marine fisheries capture since the 1980s is unfortunately not due to marine stewardship, but to overfishing.”
From Holocene to Anthropocene
Recent findings provide strong evidence that in recent decades key components of the Earth System have moved beyond the natural variability exhibited in the last 12,000 years, a period geologists call the Holocene. The Holocene, Latin for “entirely recent”, began at the end of the last ice age and provided the stability for agriculture to develop, leading eventually to townships and cities to flourish.
The beginning of Anthropocene
Furthermore, choosing the beginning of the Great Acceleration leads to a possible specific start date: when the first atomic bomb was detonated in the New Mexico desert on Monday 16 July 1945.
“Radioactive isotopes from this detonation were emitted to the atmosphere and spread worldwide entering the sedimentary record to provide a unique signal of the start of the Great Acceleration, a signal that is unequivocally attributable to human activities,” the paper reports.
The research explores the underlying drivers of the Great Acceleration: predominantly globalisation.
The bulk of economic activity, and of consumption, remain largely within the OECD countries, which in 2010 accounted for about 74% of global GDP but only 18% of the global population. This points to the profound scale of global inequality, which distorts the distribution of the benefits of the Great Acceleration and confounds international efforts, for example climate agreements, to deal with its impacts on the Earth System.
However, the paper shows that recently, global production, traditionally based within OECD countries, has shifted towards BRICS nations — Brazil, Russia, India, China and South Africa. Moreover, the mushrooming middle classes in BRICS nations are driving greater consumption here too.
About one half of the global population now lives in urban areas and about third of the global population has completed the transition from agrarian to industrial societies. This shift is evident in several indicators. Most of the post-2000 rise in fertilizer consumption, paper production and motor vehicles has occurred in the non-OECD world.
Coinciding with the publication of the Great Acceleration indicators, researchers also led by Professor Steffen have published a new assessment of the concept of “planetary boundaries” in the journal Science. The international team of 18 scientists identified two core planetary boundaries: climate change and “biosphere integrity”. Altering either could “drive the Earth System into a new state”.
The International Commission on Stratigraphy has set up a working group to analyse the validity of the Anthropocene claim. Professor Steffen is a member of this working group, which is due to report its conclusions in 2016.
Eusebio Loria -ONE
based on the material from IGBP International Geosphere Biosphere Programme