USING BIODIVERSITY PLANS TO GUIDE MITIGATION AND OFFSETS FOR A ZINC
MINE IN NORTHERN CAPE, SOUTH AFRICA
Introduction
Black Mountain Mining (BMM), a subsidiary of Vedanta, proposed a new Zinc mine (hereafter
referred to as the ‘Gamsberg Project’) in a semi-desert area located in the heart of the Bushmanland
Inselberg Region in the Northern Cape, South Africa. The area covers 6300km2 and is home to
unique succulent flora and is a national priority for protected area expansion (DEA, 2010). Several
inselbergs had already been identified as “Critical Biodiversity Areas” (CBAs) in the Namakwa
Bioregional Plan (Desmet et al, 2011), based on fine-scale vegetation mapping (Desmet et al 2005).
ERM was commissioned to conduct an Environmental and Social Impact Assessment (ESIA) for
the project in parallel with a separate Biodiversity Offset Study (Botha et al 2013). This was based
on prior knowledge of the area’s biodiversity importance and recommendations by the Northern
Cape’s Department of Environment and Nature Conservation (DENC). This approach accords
with Vedanta’s sustainability framework which is aligned with IFC Performance Standards. The
process followed by the ESIA and Offset Study recognised that an offset is a ‘last resort’ and every
effort must be made to avoid and minimize potential impacts. The need to avoid irreplaceable(1)
habitat was thus considered in the early planning phases of the project.
This paper describes the approach followed to optimise application of the mitigation hierarchy
through the ESIA and biodiversity offset planning process. It further outlines the advantages of the
availability of fine scale vegetation mapping and spatial plans that identify Regional Critical
Biodiversity Areas (CBAs) with conservation targets.
Site Setting and Biodiversity Importance
The Bushmanland landscape comprises mostly flat to gently undulating grassy, sand covered plains
that slope gently northwards down towards the Gariep (or Orange) River and forms the border of
South Africa and Namibia (Figure 1). Scattered rocky inselbergs lie between 1100 and 1200 masl.
Climate in this semi-desert region is typified by sparse and variable rainfall averaging around
98mm a year - reaching 200mm in some years - while maximum summer temperatures range
between 30-35oC (Desmet 2000).
The Gamsberg Project is located in the Succulent Karoo Global Biodiversity Hotspot and is
identified as the Gamsberg Centre of Endemism within the broader Eastern Gariep Centre (Desmet
2000). The region is rich in succulent flora. A total of 397 plant species are recorded from
Gamsberg (excluding annuals and monocots), of which 16 are of conservation concern i.e. endemic
or rare of which four two are restricted (Desmet 2000). The Gamsberg inselberg is considered the
most botanically diverse and important with priority plant habitats being gravel quartzite patches.
The presence of permanent water in a ‘kloof’ on the northern side of the Gamsberg inselberg close
to the mine deposit is one of three permanent water sources in the Bushmanland region.
(1) “Irreplaceable habitat” is equivalent to the IFC PS6 definition of those biodiversity values that trigger "critical habitat" determination,
while “constrained and flexible habitat” are equivalent to the “natural habitat” definition.
1
Figure 1. Gamsberg StudyArea Within Bushmanland Inselberg Region, Showing Gariep River
Source: Desmet et al 2005
The Mine Project and Alternatives
The deposit comprises a steep sided inselberg in a crater-like structure measuring 7 km x 5km with
a life of mine estimated at 19 years. Open pit mining would yield 190 million tons of concentrate
while underground mining would produce 125 million tons in the same period. The ESIA
compared trade-offs between underground and open pit mining: the latter having a larger impact on
biodiversity. However, given technical constraints, sterilisation of >40% of available ore reserve,
and low financial returns underground mining was not considered viable. The emphasis thus shifted
to evaluating whether open pit mining, with all required mitigation (including offsets) could be
viable. Alternatives for the development of the open-pit mine design plans included various
designs for the open pit, and locations for support infrastructure such as access roads, waste rock
dumps, tailings facilities, and processing facilities.
Application of the Mitigation Hierarchy
Avoidance
Application of the mitigation hierarchy considered the viability of underground versus open cast
mining. However, once it was understood that it was not economically viable, the assessment
focused on alternative pit designs and locations for mine infrastructure and waste dumps in relation
to impacts on sensitive habitats, hydrogeology, visual and archaeological sensitivity. A series of
sensitivity maps were compiled and later integrated into an overall sensitivity map. The habitat
sensitivity map was a primary driver for influencing mine layout changes. This map defined habitat
areas (based on species rarity, endemicity and threat) and defined three categories reflecting degree
of flexibility for locating infrastructure, as follows:

Flexible areas impacting <5% of the regional extent of a habitat feature and where a complete
like for like offset is possible;
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

Constrained areas impacting 5-20% of regional extent of a habitat feature, where offset likely
to be possible; and
Irreplaceable areas impacting >20% of the regional extent of a habitat where features of
conservation concern are only known from 5 or less locations, and where no offset is
considered possible.
The sensitivity maps were overlain onto the original mine layout plan and used by the engineering
team to shift infrastructure to avoid irreplaceable and sensitive vegetation. The southern and southwestern side of the Gamsberg inselberg has the highest ecological value.
Avoidance measures were achieved through:
i) Siting tailings, waste rock dump and processing facilities to avoid impacts on irreplaceable
habitats; and
ii) Moving the access road, crusher and workshop to the north to avoid the southern slopes with
irreplaceable succulent habitat.
Minimisation
Once the mine layout had been optimised to avoid sensitive areas as far as possible, additional
minimisation measures were considered to further reduce residual impacts on biodiversity.
Minimisation measures were achieved through:
i) selecting least impact options for tailings, waste rock dump and processing facilities to
minimise impacts on sensitive or important habitats;
ii) increasing the set-back distance between edge of open pit and the permanent water body
(kloof), and reshaping the slopes of the pit for greater stability and to avoid risks of
contamination;
iii) designing sprinkler systems for dust suppression within the open pit; and
iv) appropriate management of water to reduce the risk of contamination of habitats.
Restoration and rehabilitation of disturbed areas was not considered to be an option in these arid
environments.
Biodiversity Offsetting
The approach to biodiversity offsetting for the Gamsberg project was underpinned by the principles
in the Business and Biodiversity Offset Policy (BBOP); IFC Standards; the South African National
Biodiversity Offsets Policy (SANBI/DEA 2012) and the Draft Guideline on Wetland Offsets
(SANBI 2012). In South Africa, the aim of biodiversity offsets is ‘no net loss in relation to
conservation targets’, rather than the internationally accepted goal of an absolute ‘no net loss’.
Scientifically determined conservation targets are used as the basis for calculating offset
requirements.
Residual adverse impacts of the Gamsberg Project on biodiversity were quantified as the basis for
determining offset needs, by:
i)
Calculating the area of different habitats lost, including a buffer zone to allow for dust and
water contamination. Note: the potential impacts of mine-related black dust on succulent
species which typical occurring in white quartzite gravel patches are uncertain, and therefore a
precautionary approach was taken in quantifying the offset requirement and identifying
mitigation measures for dust. The residual impact totalled 2785ha of habitat in the project
footprint.
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ii)
Calculating the percentage habitat loss at a regional level. Habitats with the greatest regional
loss were kloof, headwater seeps and wetlands, all scarce and localised in the landscape but
which were predicted to be impacted due to groundwater lowering from pit dewatering.
iii) Calculating offset ratios for each impacted habitat derived from the conservation targets set for
each recognised vegetation type in the National Biodiversity Strategy and Action Plan
(NBSAP) (Driver et al 2004), taking into account the proportion of the total remaining extent
of that habitat that would be lost as a result of mining.
iv) Adjusting the offset ratio by applying three types of multipliers to cater for risks and
uncertainties, habitat condition, and biodiversity priority (i.e. CBA).
v) Multiplying the adjusted offset ratio by the size of the impacted area to give the required offset
area of each habitat type in hectares. The highest ratio of 16X was applied to calcrete gravel
plains as an Endangered habitat type.
Using existing fine scale vegetation mapping available at the time of the ESIA, land within the core
Bushmanland Inselberg Region was assessed for its ability to meet offset requirements. Land units
were identified and selected in an incremental process based on the following criteria: ability to
best meet the conservation targets for impacted vegetation types, location in adjoining areas for
optimal management; least potential land use conflicts (eg with other proposed developments), and
were smallest in extent to reduce purchase and management costs. Priority was given to selecting
plateaux tops and south-facing slopes as climate refugia; corridors linking the inselberg units and
all available kloof and seep type habitats. Set asides of mine property unaffected by mining were
also included to contribute to the biodiversity offset.
Outcome of Biodiversity Offset Selection and Approval Process
Most habitat targets could be met through securing the optimal selection of properties as a
protected area in perpetuity except Quartz and Calcrete Gravel types if and only if ‘worst case’ dust
impacts were to occur; and kloofs, headwater seeps and springs. Net gain could be achieved for a
further two habitat types. Importantly, the freshwater habitats are not highly threatened or
irreplaceable in terms of national conservation targets, but are considered to be significant features
for the Bushmanland Inselberg Region. For these habitats, protection of kloofs and wetlands in the
neighbouring Eastern Gariep Centre of Endemism was recommended as compensation. For loss of
Quartz and Calcrete Gravel habitats compensation could be achieved by securing regional
representations of unique succulent communities.
Following confirmation of the potential to secure a biodiversity offset for the project, an
Environmental License was awarded subject to implementation of a biodiversity offset. As required
of the license, a Biodiversity Offset Agreement was signed in late 2014 between the mine and the
provincial conservation authority (DENC). This agreement specified that IUCN’s Biodiversity and
Livelihood Committee shall oversee and audit the offset implementation for a period of at least five
years, subject to renewal. The agreement requires the mining company to secure, fence, manage
and protect the biodiversity offset, extending to a period ten years beyond submission of
application of a closure certificate. The land is to be transferred to the provincial conservation
authority (DENC), and prescribed amounts for its management paid to a Trust.
Lessons Learned
Key lessons learned include:
1. The availability of regional spatial data of habitats and species and suitable experts provided
the basis for a well-informed evaluation of biodiversity impacts in a regional context, and
confirmed the potential to achieve biodiversity offsets.
2.
Team approach to the ESIA enabled the linkages between different disciplines to be explored
as the basis for understanding potential risks between aspects such as increased dust and
groundwater lowering on habitats.
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3.
Overlap between the ESIA and biodiversity offset process optimised the potential for the mine
design to avoid impacts through design re-planning and minimise the residual adverse impacts
prior to calculating the offset requirements.
4.
Uncertainty of the potential links between groundwater lowering and dust dispersion on
habitat and species survival led to inclusion of additional land area requirements for offsetting.
In following the precautionary principle, these uncertainties may have over-estimated the
offset area requirement and monitoring is needed to confirm the actual impacts.
5.
The alignment of the offset planning and ESIA processes in parallel served to increase the
trust of conservation stakeholders in the process and outcome. Engagement with key
conservation stakeholders during the offset identification and planning process improved the
level of stakeholder support for the outcome. This has led to the successful agreement between
the mining company and the provincial conservation regulatory authority to implement and
manage the biodiversity offset.
6.
That despite the best efforts to secure an offset area for conservation, mining rights could take
precedence over the surface land rights. It is possible that the long term security of the offset
could be compromised by approved mining rights in offset areas.
Despite the uncertainties and risks indicated above, the Gamsberg Project is one of the few real
examples where a practical and achievable offset has been identified, confirmed and approved
based on an expert-driven process, and subject to a tight agreement between the mining company
and regulatory authority within the bounds of legal frameworks. As a result of the legal agreement,
the offset has a high potential for being implemented successfully.
Figure 2. Gamsberg Sensitivity Map Showing Mine Layout
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References
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Business and Biodiversity Offsets Programme (BBOP) (2009). Biodiversity Offset Design
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Department of Environmental Affairs (2010). The National Protected Areas Expansion Strategy.
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Department of Environmental Affairs and Development Planning (DEA&DP). (2011). Information
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Cape
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