Apart from the odd sacrificial burning and the invoking of Olympian lightning strikes, the ancient Mediterranean people lived in harmony with nature – the ancient Egyptians worshipped cats, for Pete’s sake! (although in the age of the internet, it can be argued that we do too).

But did they really? A group of scientists from France and the UK has been digging (literally) to find out what effect the ancient harbours of Phonecia had on their local environments.

The rock in the harbour seabed is formed from layers of sediment that settle in the harbour and are eventually squashed into rock by the weight of layers above them. The rock itself, as well as animals and plants (and other debris) preserved within it can give us clues about how the local area was affected as the harbour was developed over the ages.

So, what’s the point?

The authors highlight man-made harbours as having wide-ranging impacts on the local marine environment. Of course, bronze-age man is unlikely to have caused as much chemical pollution as we do today – canoes and galleys are less of a problem in this respect than speedboats and tankers – but the impact a harbour has goes beyond pollution into areas that most people won’t even think about.

Fundamentally, a harbour is an area of coast where ships are somewhat sheltered from stormy weather. Natural harbours exist where outcrops of land act as a barrier to the large waves that can be generated in the open sea. Te sea inside the harbour is generally calm, as the waves and currents of the open sea are kept largely separate from it by the land barriers and so only have a limited influence on it.

Artificial harbours are where we have built our own barriers, using sediment, rocks or (nowadays) concrete to construct jetties and breakwaters. But in building these barriers, we are attempting to change the nature of the local environment – we’re turning an area of (sometimes) choppy sea into one which is calm all of the time.

This affects environmental processes such as local currents, erosion, sediment deposition and as a result of these, the ecosystem too. Ancient people are unlikely to have employed environmental consultants when constructing their harbours, but they would have resulted in the same sorts of environmental impacts that we have today.

Understanding how our ancestors affected the environment will hopefully help us to better understand and contextualise our own impact. While building a few harbours might seem small-fry compared to global-scale pollution and climate change, it is worth seeing that there are all sorts of other impacts that human activity has on the environment.

What did they do?

The researchers focused their study of the modern-day Lebanese ports of Sidon, Beirut and Tyre, all major ports of the ancient Phoenicians – a famous maritime trading power.

By looking at cores (a cylindrical sample of rock taken by drilling vertically down), the researchers could analyse the different layers of rock that had formed in and around the harbours over time. Rock on the sea bed is formed as layers of sediment build up over time, and are crushed together by the weight of the sediment layers above.

The core allows scientists to see what kind of sediment has built up in the region over time (and consequently been turned into rock), which can indicate how calm the sea was kept by the harbour. They can also look for signatures of animals and plants as well as signs of human activity such as fragments of wood, pottery and seeds all buried in the sediment and now preserved in the rock.

Did they prove anything?

The scientists’ analysis, taken along with previous archaeological evidence, led them to suggest 4 phases of harbour development that have occurred from before the Bronze-age to the height of the harbours during the Roman-Byzantine era, and their associated environmental impacts:

Phase I: Before direct human interference (8,000 – 6,000 years ago) – little evidence of human activity. Natural phenomena identified include ‘ponding of freshwater runoff’ and ecosystem ‘dominated by species of lagoonal affinities’.

Phase II: Proto-harbour (Bronze age): Archaeological evidence suggests human-built harbours existed around this time, but only in the Sidon core were the scientists able to see a difference in the sediment (‘moderate shift from medium to finer-grained sedimentary conditions’).

Phase III: Artificial harbour (Iron age): Archaeological evidence ‘attests to a pattern of expanding Mediterranean trade’, and new iron technology meant ‘much larger shipping vessels could be constructed’. The scientists discovered ‘fine-grained silts and clays’ in the rock corresponding to this period, which indicates ‘increased human alteration of the natural environment.’

‘Hiatuses’ and ‘dating inversions’ (older sediment appearing above newer sediment), over this period suggests ‘port overhauls’ including the dredging of built-up sediment. Around this time, the Romans were known to be ‘refashioning’ many harbours within their empire.

Phase IV: Harbour peak (Roman-Byzantine era): The Lebanese seaboard was known to be economically important during this period, and the rock again changes accordingly: ‘Plastic (meaning mouldable) harbour clay’ at Beirut and Sidon and fine-grained silts and sands at Tyre.

The researchers also observed a ‘sharp increase’ in the signatures of ‘lagoonal species’, which they say indicates that the water was hyposaline (less salty than normal sea water).After the harbours’ heyday they fall into relative decline, and by the 6th – 7thC CE, with ‘coarse-grained sand attest(ing) to a semi-abandonment’.

So, what does it mean?

Comparison of the layer in the era before direct human interference (Phase I) and later eras, gives a good indication of humanity’s impact, and matching the data to what we know about changes in technology and society at around the same time gives us a good idea of how the harbour developments altered the local environment.

In particular, we can see how the composition of the sediment changed, as well as the impact on the local ecosystem (turning the harbour water hyposaline, for instance). This shows that even ancient civilisations affected the environment, even if these changes might pale in comparison to what we do today.

It would be interesting to see more clearly the difference that humans have had – comparing sediments in the same area, but from different times can tell us how it has changed, but not necessarily the cause of that change.

I’m not trying to sound like a climate change sceptic, but it is important to consider natural contributions to any change too – for instance, the authors mention the Mediterranean sea-level stabilised around 6,000 years ago (due to glacial melting at the end of the last ice age).

So while we can point to certain human activities affecting the environment (especially when placed in the context of other archeological evidence, such as other human developments in the same region at the same time), natural changes also need to be considered.

A neat way to do this would be the use of control samples – cores of rock from nearby (relatively) undeveloped natural harbours. This may, of course, be impossible (they may be no natural harbours nearby that have remained undeveloped), but if it could be done, scientists could directly compare the sediment layers found inside the developed harbours with those in undeveloped harbours, thereby getting a better idea of what would have happened to the rock in the harbour had humans not interfered at all.

In The Ascent of Man, Jacob Bronowski talks about how other animals adapt to their respective environments, and what sets man apart is the ability to change our environment to suit us. So many of ancient man’s important technological advancements – fire, farming, domestication and breeding of animals, are based on manipulating the environment and changing nature in ways the planet had never previously experienced.

Even though the impact of ancient people might appear to us to be inconsequential, it should make us think a bit more about our own impact. Practically everything that we do, no matter how mundane it may seem to us, is a result of humanity changing the environment to suit our needs.

We travel to work along ground that has been covered with tarmac or laid with steel tracks. We eat food that is grown on modified land (farms) then shipped across the world. Even this article is written by and accessed through technology built from materials taken from the ground and physically and chemically processed using yet more stuff taken from the ground.

I like the fact that this research provides a perspective that arguably humanity’s greatest achievement, our technology, has been developed by altering the environment in which we live, even from our earliest days.

Hopefully, it will help us to realise that our impact on the environment, upon which we rely, is not a product of our modern, industrialised society (although this greatly exacerbates it), but an inherent part of our development and use of technology – the factor that sets us apart from other animals and has ensured our survival and success as a species.

We need to understand that our impact on the environment is, and has always been, unavoidable, but this means we need to be more considered in managing the effects we have on the world around us, rather than necessarily simply minimising them: creating artificial reefs, breeding endangered species in zoos and planting trees are all methods in which we can use our unique ability to transform and manipulate nature in order to manage the problems that we cause.

Original article in Scientific Reports Jul 2014

All images are open-source/Creative Commons licence.Credit: Exekias (First); US Forest Service (Second); N Marriner et al. (Third); EDSITEment (Fourth); J Lendering (Fifth).

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