The Offset Design Process
35
BBOP Pilot Project Case Study – Ambatovy Project
7.3.5 Step 5: Choose methods to calculate loss / gain and quantify residual losses
The Project is using methodologies described in the BBOP Biodiversity Offset Design Handbook to assess the
Project’s impact on biodiversity, to identify appropriate activities and sites for the biodiversity offset, and to
determine the scale of the offset needed to achieve the
CONSERVATION GAINS
that will achieve
NO NET LOSS
.
The methodologies combine consideration of biodiversity of equivalent or higher value and site selection to
ensure that all key biodiversity components are represented at the offset and have two key features:
‘benchmarks’ and ‘
HABITAT HECTARES
’:
BBOP defines a ‘benchmark’ as reference point against which the losses of biodiversity due to the Project
and gains through the proposed offset can be quantified and compared consistently and transparently. A
benchmark usually comprises a number of representative and characteristic ‘
ATTRIBUTES
’ used to represent
the type, amount and quality of biodiversity which will be lost / gained. Comparison of the observed level
(or ‘score’) of each
BENCHMARK ATTRIBUTE
at the impact site (before and as predicted after the impact)
against the level at the benchmark can help to quantify the loss of biodiversity to be caused by the Project.
Similarly, comparing the observed level (or ‘score’) of each benchmark attribute at the offset site (before
the offset and as predicted after the offset intervention) against the level at the benchmark can help to
quantify the gain in biodiversity caused by the offset. A benchmark can be based on an area of land that
provides a representative example, in a good condition, of the type of biodiversity that will be affected by
the proposed development project.
‘Habitat hectares’ are units of measurement that take into account the area affected and the quality or
CONDITION
of the biodiversity impacted (determined by the quantities of a number of chosen attributes
related to the structure, composition and function of that habitat). The habitat hectares
METRIC
was
originally developed in Victoria, Australia to focus on
HABITAT STRUCTURE
, particularly native vegetation,
and thus to provide proxies for composition and function. It has since been adapted by BBOP to cover both
flora and fauna, and to include some aspects of composition and function as benchmark attributes. The
habitat hectares approach is described in more detail in Section 7.3.5.1 below.
The Project’s proposed benchmark meets specific predetermined criteria with respect to surface area, habitat
quality and connectivity (see below). It is ideally located as it is in the mine area conservation zones, thus
ensuring its long term protection. The long-term presence of the benchmark is important as it will enable
background environmental degradation arising from external factors (such as climate change) to be quantified
and subsequently addressed at the offset site.
Lists of key biodiversity components were identified in the impact area; these include species and habitat
types (structural). Complementary faunal data will be collected by the Project in 2009 to integrate more
species attributes into the habitat hectares loss calculation, as current calculations are limited to quantitative
information for only three priority lemur species.
The Project has calculated its habitat hectares loss values for forest habitats. Scores for streams and
ephemeral pools were calculated in April 2008, but have been temporarily excluded subject to re-assessment
during the next iteration of the loss calculations.
Two habitat hectares calculation scenarios were assessed in April 2008: without and with post-impact
MITIGATION
. It is important to note that both potentially relate to real situations since restoration performance
is not well documented for Madagascar or the Ambatovy region. ‘Post-impact mitigation’ significantly
decreases the habitat hectares loss value and will ultimately be included in the final (definitive) offset
calculations. However, care is necessary to avoid overestimating the potential for rehabilitation success as
this can result in the underestimation of the number of habitat hectares that the offset must deliver. Only the
‘without post-impact mitigation’ scenario is reported here as further analysis (modelling) is required to
accurately calculate losses based on the ‘with post-impact mitigation’ scenario.
