Environmental Assessment
Volume C-4.1
Slurry Pipeline
Flora
Ambatovy Project
88
January 2006
Table 4.1-4 Impact Description Criteria for Exotic and Unwanted Plant Species
Direction
Magnitude
Geographic
Extent
Duration
Reversibility
Frequency
neutral:
no change
in exotic and
unwanted species
negative:
a change
in exotic and
unwanted species
negligible:
no measurable
effect on exotic and
unwanted species
low:
low amounts of exotic
and unwanted species
moderate:
moderate
amounts of exotic and
unwanted species
high:
high amounts of exotic
and unwanted species
local:
effect
restricted to the
LSA
regional:
effect
extends beyond
the LSA
short term:
<3 years
medium term:
3 to 30 years
long term:
>30 years
reversible or
irreversible
low:
occurs once
medium:
occurs
intermittently
high:
occurs
continuously
4.1.6.3 Mitigation
The primary mitigation to reduce or eliminate the invasion of exotic or unwanted
plant species due to project-related effects is through the implementation of an
invasive species control program. This invasive species control program will be
made operational only along targeted sections of the pipeline route, where the
conservation of adjacent native habitats is desired by Malagasy society.
4.1.6.4 Results
There is a high potential for the spread of weeds or unwanted species along the
slurry pipeline corridor. Currently the risk has already been observed within the
Mantadia-Zahamena Conservation Corridor with the presence of Eucalyptus trees
and other exotics (13 species identified during the field surveys), which can pose
a threat to the area’s ecological integrity. Increasing the amount of edge along
the perimeter of primary forest stands will also support and increase the
probability of invasion by heliophytic (sun-adapted) vines like lianas. These
vines may permanently alter forest stand succession by spreading into primary
forest stands as vegetation is cleared during the construction phase under
increased sun conditions and where there are few competitors. The numbers of
vehicles and machinery will increase sharply as pipeline construction is initiated.
Vehicles provide a vector to transport weeds from areas on- and off-site into new
areas as they are become cleared.
