Jo Atherton's Anthropocene Prints

Jo Atherton makes beautiful prints (below) from plastic flotsam and jetsam gathered from the shore. The first time that I saw them I was reminded of natural aggregates within water bodies, perhaps because these were a research interest of mine [1].

Marine aggregates vary in size, from the minute (a few micrometres across – the scale bar in the micrographs below shows 2 micrometres [with acknowledgement to Ransom et al., 2]) to masses that are visible to the naked eye and which can coalesce to cover water bodies. The aggregates are bound by organic matter produced by algae and bacteria [1] and many sink through the water column and end up on the bed of oceans, especially after storms. Waves generate many billions of bubbles and these enhance the aggregation process, although it also occurs within the water column from collisions brought about by currents, turbulence, and biological processes. 

Jo's Anthropocene Prints complement her Flotsam Weaving [3] that uses plastic rope, Lego figures and many other anthropogenic materials that float around the oceans and drift on currents before coming ashore or being washed up by waves from the shallow continental shelf. Anyone making a sea crossing will be familiar with flotsam; large-scale ocean currents gather this material and transport it very large distances. Recently, we have been made aware of this by the findings in the western Indian Ocean of fragments of Flight MH370 that crashed into the sea near Australia and impressive amounts of material from the Japanese tsunami of 2011 have also been washed ashore along the west coast of North America. This is movement of plastics and other anthropogenic materials on a large scale and much will have sunk to the sea bed, a process aided, for tiny fragments, by the aggregation process I mentioned earlier.

The transfer of matter to the ocean floor from the water column is a continuous process that has occurred over very long periods of time; sediments being laminated and eventually transforming into rock. We are familiar with massive chalk deposits like the White Cliffs of Dover, but less familiar with how they were formed. Much of the chalk comes from calcium salts present in quantity in ancient oceans, much as they are today. However, the chemical was deposited having been extracted by organisms that use(d) it to form protective coatings, the most important being the single-celled coccolithophores (above). It is hard to imagine the number of "shells" falling to the ocean floor, and for how long deposition took place, to accumulate the large deposits of chalk found around the world. All this calcium would have been transferred from the water column in the form of aggregates containing the "shells" of these minute creatures. As many gardeners know, chalk deposits contain flints and we think that these have a quite different origin, being rich in silicon and probably originating from the casing of diatoms (single-celled algae that build these extraordinary glass-like frustules, below), or from siliceous spines, or webs, produced by some animals. After death of the algae, their coats become enmeshed in aggregates and slowly sink to the ocean floor where they become concentrated in some areas and mix with the other silicon-based biogenic materials. The process by which these concentrated masses are transformed into flints is poorly understood.

Limestone is even more abundant than chalk and consists of calcium salts, but with origins in marine shells, corals and the calcareous structures created by a whole range of creatures. Most of these were bottom-dwelling, although some lived in the water column and sank after the death of the animals that produced them. Imagine a shell beach being compacted over time and you get some idea of how limestone was formed, and the model becomes even more realistic if one includes all the other fragments that become washed up. This process occurs underwater as well as at the ocean margins.

Future chalk and limestone deposits will be rather different to those of the past. Those being laid down during the Anthropocene, will not only contain natural materials, but much that is anthropogenic. On the substratum, organic matter is broken down and re-utilised through the microbial community and onwards up a food chain, but plastics are much more resistant to breakdown. If humans, or their evolutionary successors, survive to investigate the geology of Anthropocene rock deposits they will be surprised at their content and at the origins of some of the components. It is also possible that the effects of heat and pressure over very long time periods will transform some of the plastics into oil - returning them from whence they came...

Please take a look at Jo's work [3] and I am sure that it will inspire you as it has me.

[1] Roger S. Wotton (2005) The essential role of exopolymers (EPS) in aquatic systems. Oceanography and Marine Biology: An Annual Review 42: 57-94.

[2] Barbara Ransom, Kevin F. Shea, Patti Jo Burkett, Richard H. Bennett and Roy Baerwald (1998) Comparison of pelagic and nepheloid layer marine snow: implications for carbon cycling. Marine Geology 150: 39-50.

[3] https://flotsamweaving.com/

The beginning and the end of the Anthropocene

Is there an Anthropocene? This question is being debated currently and a report is to be published in 2016 on whether a geological epoch created by the transformative activities of Homo sapiens should be defined, and what should mark its beginning. According to Richard Monastersky [1]:

A committee of researchers is currently hashing out whether to codify the Anthropocene as a formal geological unit, and when to define its starting point.. .. The push to formalize the Anthropocene upsets some stratigraphers.. ..One major question is whether there really are significant records of the Anthropocene in global stratigraphy.. ..Some researchers argue that it is too soon to make a decision – it will take centuries or longer to know what lasting impact humans are having on the planet.

Monastersky then quotes from Erle Ellis, a Geographer at the University of Maryland:

"We should set a time, perhaps 1000 years from now, in which we would officially investigate this.. ..Making a decision before then would be premature."

Discussion about the Anthropocene thus reflects a typical debate among scientists and other academics having different views of what marks a definable stratigraphic boundary.

As Monastersky points out, markers could be from the Industrial Revolution, or from the radioisotope signatures resulting from atmospheric testing of nuclear weapons that ceased in the 1960s. While supporting the case for 1964 as the beginning of the Anthropocene, Lewis and Maslin [2] also put forward a strong argument for using the measurable decrease in atmospheric carbon dioxide between 1570 and 1620 (with a minimum in 1610), something that they relate to the effects of New World colonisation and dramatic changes in human population density, changes in diet and agricultural practices brought by new foods, and the development of increased trade based on industrial production. Their selection of 1610 adds another part to the Anthropocene debate, but their paper also contains an interesting review of human impacts in the very short time that Homo sapiens has been the dominant species on the Earth.

In conclusion, Lewis and Maslin write [2]:

Past scientific discoveries have tended to shift perceptions away from a view of humanity as occupying the centre of the Universe. In 1543 Copernicus's observation of the Earth revolving around the Sun demonstrated that this is not the case. The implications of Darwin's 1859 discoveries then established that Homo sapiens is simply part of the tree of life with no special origin. Adopting the Anthropocene may reverse this trend by asserting that humans are not passive observers of Earth's functioning. To a large extent the future of the only place where life is known to exist is being determined by the actions of humans. Yet, the power that humans wield is unlike any other force of nature, because it is reflexive and therefore can be used, withdrawn or modified. More widespread recognition that human actions are driving far-reaching changes to the life-supporting infrastructure of Earth may well have increasing philosophical, social, economic and political implications over the coming decades.

Whether the Anthropocene should be defined, and what its definition should be, seem trifling issues compared with those raised in that last paragraph. Whether the Anthropocene began in 1610 or 1964, it has the potential to be one of the shortest epochs thus far. The end of a geological time period is usually marked by large-scale events such as asteroid impacts, widespread upheavals in the Earth’s crust, or dramatic changes in climate. We don’t know how the Anthropocene will end and it may be from one of these causes and thus be outside human control. Alternatively, the epoch may end as a direct result of human actions. We know how destructive we have already been, and continue to be; with wars, global warming, widespread removal of forests, extinction of populations, introduction of poisons and antibiotics, etc. all being major impacts. There are those who feel that we should be able to overcome the many difficulties we face using technological solutions but, while I admire human invention, I do not feel optimistic about the future. The dominant economic system is based on growth and growth cannot be sustained indefinitely, so those of us in the Developed World will no longer be able to cocoon ourselves in warmed (or cooled) buildings and we may need to hunt and forage to obtain food. The social crises that result from a catastrophic fall in living standards can be imagined.

This is preachy, but our way of life, and its characteristic complacency, is highly damaging for other organisms on Earth and, like all the others, our epoch will end. The Anthropocene will be followed by another epoch, but what organisms will dominate? After our controlling influence is no longer present, the environment will again be the main vehicle for selection of changes in genes (a natural mechanism that we override). Bacteria and other unicellular organisms are sure to survive the cataclysmic events at the end of the Anthropocene, but what about other organisms? Will evolution result inevitably in a dominant form that makes drastic changes to its surroundings, or will there be a less destructive solution to the relationship between organisms and their environment?

[1] Richard Monastersky (2015) The human age. Nature 519: 144-147.

[2] Simon L. Lewis and Mark A. Maslin (2015) Defining the Anthropocene. Nature 519: 171-180.