Identifying and Evaluating Impacts - Mining and the Environment: From Ore to Metal - page 404

Spatial crowding includes overlapping effects from separate activities (e.g. downstream
conl uence of efl uent plumes from multiple discharge points). Temporal crowding is
when impacts from different actions overlap or occur before the receiving environment
has had time to recover (e.g. family stress due to continuous l y-in/l y-out employment).
(4) Each impact can induce further effects, sometimes called growth-inducing potential.
The effects of these spin-off impacts (e.g. increase in hunting or trade of endangered spe-
cies due to improved access to areas) may add to the cumulative effects in the vicinity of
the mine. The magnitude of cumulative effects, or the impact propagation between causes
and effects, can equal the sum of each individual effect (additive effects) or can result in an
increased effect (synergistic effect).
There are many other examples of cumulative impacts - incremental noise from inde-
pendent activities (either from one or several projects) or the cumulative effect of individ-
ual impacts on a particular receptor, such as human stress due to combined noise and dust
exposure, or visual impacts. Impact interactions, a subset of cumulative impacts, can occur
either between the impacts of one project or between the impacts of several projects. A
mineral processing plant, for example, may produce two waste water streams that indi-
vidually meet relevant water quality standards, but that react in combination resulting in
signii cant pollution levels.
The opposite to cumulative impacts are cancelling, offsetting or compensating impacts.
These are also quite common. Examples include water abstraction that is offset by water
discharges, or increases in trafi c, offset by improvements in capacity of local roads. Clearly
one of the objectives of environmental management is to generate impacts that will offset
the signii cant adverse impacts.
While categorizing impacts is helpful in identifying impacts, the fundamental question
remains 'Is the impact signii cant?' Dei ning impact signii cance is generally based on evalu-
ations of a number of signii cance attributes. These attributes have gained common accept-
ance (although dei nitions may vary) as a means of identifying and measuring various aspects
of an impact, and collectively assist in evaluating impact signii cance ( Table 9.3 ) .
Direction or nature. The categorization of impacts into positive or negative (adverse)
impacts is not necessarily simple as project impacts may have both positive and negative
effects, for example because one group may benei t while another is disadvantaged or the
impact may be positive socio-economically but not ecologically. Take household income
as an example. One of the main positive impacts of mine development is the creation of
signii cant income opportunities. Some community members however, may lose their cur-
rent source of income due to displacement. In the early days of environmental assessments,
study focus was mostly directed towards understanding and mitigating negative project
impacts. The main question was 'How can we minimize impacts?' Even today many peo-
ple may initially associate project impacts with negative project outcomes (or environmen-
tal damage). This of course does not do justice to development. If all the impacts of mining
were negative, it would not exist. Fortunately the focus of environmental assessment has
now shifted to maximizing positive project impacts, predominantly socioeconomic benei ts
for local communities and the host region, while minimizing negative impacts. The main
question today is or at least should be 'How can we maximize benei ts?'
Magnitude of impact. Magnitude measures the severity of environmental effects. Effects
range from minor or inconsequential with little signii cance to major or catastrophic with
signii cant adverse environmental effects, which may be unacceptable. The number of
project-affected people is often selected as a criterion to determine impact magnitude. ADB
(1998) dei nes resettlement as signii cant if more than 200 households are displaced. When
considering the magnitude of potential impacts, it is important to consider mine develop-
ment within the context of regional development and the extent to which the project could

'Is the impact signifi cant?'

The categorization of impacts
into positive or negative
(adverse) impacts is not
necessarily simple as project
impacts may have both positive
and negative effects.

The main question today is or
at least should be 'How can we
maximize benefi ts?'