This comment piece looks at the Anthropocene as a political construct and a tool to constrain the concept of ‘Earth System Governance’ within the social sciences. To quote the author ‘the Anthropocene is political’ and this is indeed the case when attempting to organise disparate and often conflicting bodies into a global community that can guide society to a way of working within nature, but it is also a biological, ecological and geological term and as such a scientific rational to understanding our Anthropocene is required not just a political one.
The writer succinctly demonstrates the interdependence of countries, social groups and global organisations within the modern era along with the intergenerational aspect of a range of social and environmental issues. However it places the Anthropocene as a marketing tool targeted at a political audience rather than a scientific term that denotes a currently unverified chronostratigraphic unit.
It is in no doubt that humans are a significant driving force behind changes to the biosphere and the concept of ‘Earth System Governance’ as described within this paper demonstrates the wide ranging global issues that require consensus.
Regardless of whether it’s worthwhile designating the “Anthropocene” as a new geological epoch (I have my doubts), determining the trajectory of human impact upon the Earth system is important. It provides context for how people see their relationship with natural systems and resources, and can help shape environmental policy and its acceptance by the public. But where to put the onset of this impact – where does the Anthropocene start? The authors of this paper belong to the Institute of Social Ecology at Klagenfurt University, Austria, and take a social sciences approach to the problem. Rather than focusing on physical evidence in the environment, as a geologist might do to delimit a geological epoch, Fischer-Kowalski et al. use a model where human impact is measured as the product of population size, affluence (= energy available per person) and technology, summed over three modes of subsistence: hunter-gatherers, agrarian and industrial. This avoids problems of time lags between human activity and the signature it leaves, and allows the authors to pull apart different driving factors across different societal types.
Using this approach shows a definite shift at around AD 1500: human impact was gradually increasing prior to this, but there is a sharp upturn at ~AD 1500, energy use becomes more important for amplifying the impact of population growth, and a shift from biomass to fossil fuel driven energies enhances this further. While there are problems with this approach – determining energy throughput for long-dead societies will always involve a lot of extrapolation from modern patterns – the authors are careful in stating their assumptions, and going through possible issues with the model itself. It would have been nice to see a comparison between the model output and the empirical evidence though, to help bridge the gap between these two different takes on the same question.
An interesting research article introducing a stratigraphy (technostratigraphy) for and within the Anthropocene, stratigraphic markers are defined as “fossils” left behind by humans (technofossils); for example Iron Age tools from around 1000 BC. The article is driven by the need to:
characterise the deposits, and
date and correlate strata,
of (and within) the Anthropocene in a similar manner to other periods of geological time. By using technofossils from the different stages of homonid technological development Zalasiewicz et al. argue that a chronology can be developed and applied to the Anthropocene concept. Furthermore, Zalasiewicz et al. provide examples of how technofossils, such as pottery and mobile phones, could be used to produce a high resolution (sub-centennial) dating and correlation of strata; so far an unreachable target for other periods of geological time. The paper provides a thought provoking insight the definition of strata throughout geological time, and a novel technique into how this could be done in the Anthropocene.
The Anthropocene Review is a new journal focusing on the impact of humans on planet Earth through time; information on the latest publications can be found on the associated blog.
Given that much of the research we are interested in relates human-environment interactions in the past we decided to take a closer look at the range of articles being covered by this journal. Our thoughts on seven articles published in the first issue of The Anthropocene Review will appear in a series of blog posts soon. To get started here are a list of the papers we will be covering:
Human modification of the landscape in the Andes (Peru)
Whilst working on intergrating palaeoecological and archaeological data for a recent publication (Gosling & Williams, 2013) I was struck by the range of sources I had to go to to obtain data from the two different disciplines. The paper focuses on the how societies in the high Andes have developed over the last 5000 years and the role, if any, that changes in natural resource (ecosystem service) avaliability might have played in pacing any societal changes. However, when I got the first set of review comments back I was left considering my (academic) resource base, how I accessed this, and how that influenced my ability to conduct research; especially when moving slightly outside the area of my specialism.
Trecking with sediment corer in the high Andes of Peru
When it comes to collecting sediments from lakes its all about having the right tools for the job. Working in remote areas of the tropics we tend to favour the Colinvaux-Vohnout corer; supplied by Vince Vohnout at Geo-core). The advantages of this system are:
its light-weight nature (can be backpacked or donkeyed into field sites), and
the cam system (which allows hammering to penetrate tough sediments).
Eric Martinez carrying an Avon Redstart back out from Laguna Khomer Kotcha (Williams et al., 2011a)
With the right platform (two banana boats and an A-frame) we have manged to retrive c. 20 m of sediment from 20 m of water (c. 40 m of drill rod extended); Lake Pacucha, Peru (Hillyer et al., 2009). More typically we use two Avon Redstart inflatables and a platform following the design of Colinvaux et al. (1999).
CHIRONOMIDAE AS A PALAEO-ECOLOGICAL TOOL
Chironomidae is a family of two-winged flies more commonly referred to as non biting midges. This diverse group of insects have been known for a long time to be sensitive environmental indicators. Early research in the field showed that the trophic status of lakes could be classified according to the characteristic chironomid assemblages found within them (Thienemann, 1922). Furthermore the head capsules of the larvae are well preserved within the sedimentary record. As a result palaeolimnological researchers became increasingly interested in the potential for using Chironomids to track the trophic development of a lake through time by examining the changing assemblages within the accumulated sediments. With geographically close lakes displaying significantly different midge faunas the potential for the insects being used as climatic indicators was dismissed and the following hypothesis became established: Chironomid assemblage composition reflects in-lake variables, e.g. lake depth, pH, dissolved oxygen, trophic status and substrate. However work by Walker and Matthews (1989) demonstrated that temperature was by far the most significant variable in controlling the broad scale distribution and abundance of midge fauna.
Walker and Matthews realised the potential for the non biting midge to be used as a palaeoclimatic indicator from two initial observations. Firstly within the fossil records, as climate began warming following the deglaciation of the northern hemisphere, the relative abundance of taxa associated with cold oligotrophic lakes (Heterotrissocladius) abruptly declined. Secondly they noticed the best analogues for late glacial assemblages were found in modern day arctic and alpine settings. Overall Walker and Matthews concluded that the northern limit of temperate taxon was controlled by cold summer air and/or water temperatures. The southern limit of Arctic species was instead driven by cold oxygenated refugia in the profundal zone of deep, temperate lakes. These temperatures were significant with respect to the insect’s life cycles as many species require critical temperature thresholds to complete pupation and emergence stages.
Since the pioneering work of Walker and Matthews (1989) and others the debate linking Chironomids to temperature has raged. Debate has centred upon what controls chironomid distribution and how suitable, if at all, the insects are in the context of palaeoecological studies. Recently Velle et al. (2010) discussed some key factors which must be considered when working on chironomid based temperature resonstructions.
Below I present some of the debate around the midge-environment-temperature debate; focusing on both midge distribution and identification and the potential of this proxy as a indicator of past environmental and climatic change.