Environmental Assessment
Volume A-7
Introduction
EA Methods and Study Area
of responses to habitat fragmentation depending upon the specific combination of
life history traits and dispersal capabilities (With and King 1997). Species with
limited reproductive potential go extinct sooner than predicted by Lande’s model.
Therefore, based on the bulk of available literature, the 20% criterion is the base
case used in the Ambatovy EA, unless additional data suggest a higher or lower
value.
Geographic extent:
refers to the area affected by the impact and is classified as
local, regional or beyond regional. A method of defining impacts within a study
area, in terms of the percentage of a certain resource affected, is influenced by
the size of the study areas. As such, quantitative values of impacts must be
tempered with an overall qualitative approach that considers the project impacts
on the overall viability and diversity of ecological units.
Duration:
refers to the length of time over which an environmental impact
occurs. Short-term is defined as less than the construction phase (< 3 yr);
medium-term as longer than short-term and up to the operational duration of the
project (3 to 30 yrs); long-term is greater than medium term (> 30 yrs).
Reversibility
: is an indicator of the potential for recovery following the impact.
Frequency:
describes how often the effect occurs within a given time period and
is classified as low, medium or high in occurrence. Seasonal considerations are
discussed when they are important in the evaluation of the impact.
Impact description criteria have been made for all project components based on
professional judgment of the EA team and the considerations of the issues that
were identified as particularly significant to stakeholders. The precise use of the
above system will be varied as appropriate for certain disciplines.
The overall residual impact for each effect, or environmental or social
consequence, will be classified to one of: negligible, low, moderate or high by
evaluation of the rankings for magnitude, geographic extent and duration
(Table 7.1). For example, an impact with a moderate magnitude, local extent,
and short duration would be classified as having a low overall impact
classification. This system is used to ensure that the final classification is
consistent among EA disciplines.
Ambatovy Project
62
January 2006
