The Anthropocene is not just about gases.

I started this blog with a restatement of the Ruddiman hypothesis that forest clearances during the Neolithic to create room for farming started the anomalous upward trend in greenhouse gases. I set that in contrast with the accepted hypothesis that industrialisation during the last 200 years was the cause. The research and reading since that post has made me reappraise my thinking. Now I realise that this is not about accepting or rejecting the Ruddiman position, it is about understanding the complete picture, including what happened to other environmental components between 8,000 BP and 200 BP.

Early agriculture spread from the Fertile Crescent across Europe between 9000 BP and 5000 BP (Isern et al, 2012). The coastal expansion is known as the Impressed Ware trajectory, from the delightful habit of the culture of decorating ceramics with patterns made with cockle (Cardium sp.)shells (Cunliffe, 2011, 115-6), which makes it readily identifiable. The following case study briefly explores an example, starting around 7,400 BP.


Computer-generated model of the Neolithic expansion into Europe based on radiocarbon dates (Isern et al, 2012, e51106)

Anthracological analysis of charcoal fragments from forest clearance in Alicante, south-eastern Spain (Badal et al, 1994) showed that there was a sequence of changes in the prevailing vegetation that paralleled the changes in the Neolithic and Bronze Age cultural horizons. The archaeological evidence showed that agriculture intensified with the introduction of mixed crop rotation and animal traction for ploughing. At the same time black pines (Pinus nigra) and evergreen oak (Quercus ilex) are replaced by olives (Olea europaea) mastic (Pistacia lentiscus) and heather (Erica multiflora) along with the appearance of domesticates such as cereals and beans and the Aleppo pine (Pinus halepensis). Similar changes are observed in many sites around the Mediterranean leading to the prevalence of the now familiar scrubby landscapes. This occurred during a period of generally stable rainfall and temperature.

A significant secondary product of livestock husbandry is dung. The use of dung and manure for agricultural soil enhancement spread across Europe following the Neolithic expansion (Baakels, 1997). Plaggens are slabs of grassy or heather turf used as bedding material in ruminant byres and so soaked in animal waste; across northern Europe, evidence has shown that farmers have been creating deep anthrosols, by the addition of composted plaggens to sandy soils, since the Bronze Age (Blume and Leinweber, 2004).

Soil enhancement is not solely a European phenomenon, the pre-Columbian Amazonian Formative period has also left a legacy of anthropogenic soils, known as terra platas and terras mulatas, that have their origins in Early and Mid Holocene anthropogenic activity (Arroyo-Kalin, 2010, 483-4; 490).

Continuous tillage and soil enhancement has a long term environmental effect. The addition of organic material to soil, by manuring or from forest clearance and burning, significantly elevates carbon levels. This effect can last significantly longer than the duration of the agriculture, depending on the climate and farming systems (Johnston, 1986, 98-9; McLauchlan, 2006, 1369-70), suggesting that ecosystems may be able to retain carbon after agriculture stops.

The ability to detect a global stratigraphic marker in soils and sediments is a geological pre-requisite for an epoch, as we saw in this post. The studies discussed here are examples of markers left in the soil as a result of agricultural intensification. They support the pre-industrial start date for the Anthropocene,for which Certini and Scalenghe (2011) argue, though they precede their preferred date of 2000 BP.

The empirical geoarchaeological evidence discussed here provides a convincing argument for farming to be an initiating factor of the Anthropocene.


References cited that are not available online:

Cunliffe, B. W., 2011. Europe between the oceans: themes and variations: 9000 BC to AD 1000. Yale University Press.