Abrupt Geological Changes: Causes, effects and public issues.
by
Berger, Antony
Co-Director, IUGS Geoindicator Initiative, Woody Point, Bonne Bay, Newfoundland A0K 1P0, Canada

This paper deals with some of the broader questions and issues regarding rapid environmental change. What causes landforms, and rocks, soils, and water to change fast enough for ordinary people to be aware of the effects - beneficial or harmful - on their lives? What kinds of changes are possible? What broad effects do these have on societies and settlements, and how have such impacts affected the way people think about the natural (non-human) world? As the Earth moves, so it seems, into a period of accelerated environmental change, through climate warming and a variety of human-induced stresses, what lessons can be learned from the past and how can the resilience of contemporary societies be strengthened?

When dealing with abiotic geological change, the time frame of most importance is that of a normal human lifetime or less - decades, years, seasons, days, and even less in the case of earthquakes. The impacts on people and ecosystems may be immediate, as when a volcano erupts or a slope fails, or they may be much longer, as in the drought-induced collapse of the Mayan civilization (Fig.1) where the impacts of short-term environmental changes were played out over several centuries. The spatial scale can vary from the continental and regional to the local and individual landscapes. Abrupt changes are especially harmful to long-lived and relatively immobile societies and ecosystems (coral reefs and highly-developed societies). For example, when Viking settlements failed in Greenland during the Little Ice Age cooling, hunter-gatherer Inuit societies in the same region continued to survive.

Abrupt change can be related to climate (e.g. droughts, dust storms, weather extremes, glacier retreat), though exactly what pushed the temperatures preserved by proxy in the ice of Greenland and Antarctica through annual averages of as much as 70C over a decade or so is not understood. Indeed, regional climate changes of 8-160C have occurred repeatedly in as little as a decade or less. Rapid environmental changes can also be generated by non-climatic events such as volcanic eruptions (Pompeii), earthquakes (Lisbon, San Francisco, Kobe), neo-tectonics, and heat flow, some of which may influence climate locally and even globally, as when volcanic emissions induce a temporary cooling. Regular behaviour and stable structures can emerge out of chaos as certain natural systems organize themselves without external forcing - streamflow patterns, shoreline position, patterned ground, stream channel morphology (meanders). Using the IUGS geoindicator approach, Table 1 shows possible causes of some important rapid abiotic (geological) changes in terrestrial areas.

It is essential, insofar as possible, to distinguish human-induced change, which can probably be managed, from natural changes, which may or may not be manageable. This is, however, a difficult task. For example, a particular change in the shape and dimensions of stream channels or the capacity of rivers to store and discharge sediments might be a result of dams and reservoirs, irrigation systems, and river diversions. Or it could be the result of rainfall and flash floods, failure of watershed slopes, variations in the supply of source sediments or a consequence of self-organization and the internal dynamics of fluvial flow. Ground subsidence, seismicity, and slope failure are all natural processes that can also be triggered directly or indirectly by human action. Indeed, volcanism may be the only rapid geological process that cannot be induced directly or indirectly by human activities.

The distinction of human from non-human causes of landscape change is fundamental to environmental management and decision-making. Trying to stop natural processes may be both futile and harmful to ecosystem well being —as in the former North American public campaign to eradicate the forest fires that are now known to be essential to natural forest renewal. Policies and declarations that aim to change human behaviour may also be misguided when they assume that nature left alone is inherently stable, in equilibrium and "benevolent" to life. As the 2001 Amsterdam Declaration on Global Change (IGBP) put it, "The Earth System behaves as a single, self-regulating system comprised of physical, chemical, biological and human components. Critical thresholds and abrupt changes characterize Earth System dynamics. Global change cannot be understood in terms of a simple cause-effect paradigm." The difficulty in separating human-induced from natural environmental change does not make any easier the management of landscapes and urban areas, but ignoring natural forces in policy and practice, would seem to guarantee failure.

These points will be illustrated by case histories from the western Canadian prairies (Fig. 2), and the river systems of northern India (Fig. 3). Major abrupt changes in each of these examples had profound effects on people, settlements and economies. Since history is replete with other examples where societies and settlements were harmed or failed in the face of abrupt environmental change, it is rather surprising that public attitudes today, especially in Europe and North America, seem to regard nature as inherently benevolent, with the only “downside” coming from human activities. Indeed, it is rather difficult to detect in some of the major foundational belief-systems the reality of “dark nature.” Recognizing more clearly the role of non-human inputs to abrupt environmental change could make a difference in the way people think about the world around them and the kinds of policies that might be adopted in the search for some kind of sustainability.

Date received: January 27, 2004