ABSTRACT
Ancient rubbish dumps, mine workings, soil disturbances and old building foundations are combed through by archaeologists seeking evidence of the activities of our ancestors. What are now interesting artefacts may be obscured by natural processes, but they were not deliberately destroyed, except incidentally, as in the reuse of favourable building sites and scavenging of materials. Societies moved on, from one phase or activity to the next, with little or no attention to what was (or was not) left behind. Population expansion has gradually led to recognition that this cannot continue indefinitely because the Earth and its resources are finite. Given a clear measure of the scale of effects of human activity on the environment, an assessment of their reversibility is possible using evidence of consequential changes in the activity. This feedback loop has attracted increasing attention because of climatic effects. Earth scientists with an interest in the geology of the last 10,000 years, the period referred to as the Quaternary (Figure 18.1), shared with archaeologists one of the targets of their studies, the control exerted by climate and changes in it, on human activity. A new recognition of the significance of these studies has arisen with the realisation that human modifications of the environment are not restricted to local effects but that we are modifying the global climate. Other activities in this feedback loop include land clearing, mining developments, industrial and city expansions, waste disposal, intensive fishing and resource exhaustion generally, with global effects that are effectively instantaneous when viewed on the time scale of Earth history.
