160 Poverty and Hunger
polarized between primarily human and totally physical; and adverse effects, polar-
ized between reversible and irreversible (as in Figure 6.1). In the north-east of the
figure are irreversible large-scale events beyond our control, most of the effects of
which are irreversible – earthquakes, meteor impacts and volcanic eruptions. In
the east are tsunamis and extreme weather events such as tornadoes, hurricanes,
floods and droughts that are uncontrollable, but where there is more scope for
mitigating adverse effects. In the south-east is seasonal weather, uncontrollable but
often with reversible adverse effects. In the south-west is renewable groundwater
extraction, and above it deforestation and fisheries depletion, which are less revers-
ible, at least in the shorter term.^29 While these are all vitally important, and so
often demand urgent and sustained intervention, it is the remaining areas that
merit the closest and most intense attention: the north-west with mining, oil and
gas extraction, quarrying and species extinction – controllable but irreversible; and
the north and centre with climate and ocean circulation change, and soil erosion
and siltation. These are areas where human agency is a major cause and adverse
effects are irreversible in the medium and long term or forever. It is in these areas
that long-term future options are closed off through human action, and that the
precautionary principle applies, and should be made to apply, with most force.
Source: Developed in discussions with Christopher Chambers and Jenny Chambers
Figure 6.1 Clusters of environmental change by types of cause and irreversibility