Environmental Management: Principles and practice

Dealing with cumulative impacts
The systematic and comprehensive identification and assessment of cumulative
impacts—cumulative effects assessment (CEA) (cumulative impacts assessment) is
increasingly attracting the attention of researchers and practitioners. Mostly the focus
has been on negative cumulative impacts. However, it can assess positive impacts as
well. The USA, Canada, New Zealand and a number of other nations now have
regulations requiring assessment of cumulative impacts (in the USA, it has been part
of EIA legislation since 1979, but in practice progress has been slow).
Spaling (1994:243) observed that environmental changes accumulate through
many different processes or pathways:
♦
incremental (additive) processes (repeated additions of a similar nature
a+a+a+a . . .);
♦
interactive processes (a+b+c+n . . .);
♦
sequential effects;
♦
complex causation;
♦
synergistic impacts;
♦
impact which occurs when a threshold is passed as a consequence of some
trigger effect (e.g. chemical timebomb or biological timebomb);
♦
irregular surprise effects;
♦
impacts triggered by a feedback process (antagonistic—positive feedback which
reinforces a trend, as opposed to ameliorative—negative feedback which
counters a trend).
In practice CEA is difficult. Nevertheless, there are methods which are at least
partially effective, for example the component interaction matrix and the minimum
link matrix. There are also specific CEA methods (see Spaling and Smit, 1993; Smit
and Spaling, 1995). Some have tried to assess cumulative impacts by adopting a
regional or strategic stance (see earlier discussion of SEA), and others have tried
CEA at the project level.

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ENVIRONMENTAL IMPACT, HAZARD AND RISK MANAGEMENT
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There are signs that global stability and even some of the Earth’s life-support
systems are increasingly shaped by cumulative impacts and global impacts can affect
local and regional systems. Cumulative impacts may result in a runaway process
which exceeds some critical threshold and may be difficult to remedy (e.g. global
warming leads to uncontrollable releases of greenhouse gases from various sinks
resulting in uncontrollable warming)—impact assessment has the potential to warn
environmental managers of these.