Monitoring rehabilitation success on Namakwa Sands heavy minerals mining operations, Namaqualand, South Africa
Date
2006-12
Authors
Blood, Jeremy Russell
Journal Title
Journal ISSN
Volume Title
Publisher
Stellenbosch : University of Stellenbosch
Abstract
Anglo American Corporation’s Namakwa Sands heavy minerals mining and beneficiation operation has
been strip-mining a heavy mineral deposit, rich in the commercially valuable minerals ilmenite, rutile and
zircon, since September 1994. The mine is located in the vicinity of Brand-se-Baai on the west coast of
South Africa, approximately 385 km north of Cape Town. Strip-mining causes total destruction of natural
ecosystems through the removal of vegetation and soil in the area where mining is being undertaken.
Namakwa Sands has been rehabilitating mined out areas as the mining front moves forward. Due to the
difficulty of rehabilitating mined out areas as a result of harsh environmental factors, Namakwa Sands has
initiated various research projects to gain an understanding of the baseline conditions and ecosystem
function in order to increase plant cover and biodiversity on post-mined areas. This on-going research
and the development of rehabilitation and mining techniques have resulted in the implementation of four
rehabilitation techniques varying in investment of topsoil replacement, seeding and plant translocation.
This study assesses the success and effectiveness of these techniques in terms of various vegetation
and soil parameters. In addition, those parameters that are considered useful for monitoring are identified.
This study indicated that topsoil replacement and plant translocation facilitate the return of similarity,
species richness, species diversity and vegetation cover to post-mined areas. The rehabilitation site that
had the greatest amount of biological input (topsoil replacement and plant translocation) appeared to be
the most successful technique in facilitating vegetation recovery similar to reference sites. In comparison,
the site that had the least amount of biological input performed the worst and requires adaptive
management, e.g. reseeding and / or plant translocation. Namakwa Sands should continue to replace
topsoil in all future rehabilitation efforts and, when possible (e.g. after sufficient winter rain), continue to
translocate species in multi-species clumps.
In terms of species selected for translocation, Othonna cylindrica, Ruschia versicolor and Lampranthus
suavissimus should be considered for future large-scale translocation projects. Zygophyllum morgsana
appears to be more difficult to re-establish under the current climatic conditions (below average rainfall).
The long-term viability of rehabilitated Z. morgsana populations needs to be determined before
considering this species for any future large-scale translocation purposes. No translocated Asparagus
spp. individuals survived and should therefore not be considered for any further translocation purposes.
The grass Ehrharta calycina, which is dominant in the site seeded, should continue to be considered for
future seeding.
Species and functional diversity appear to be the most limiting factors within all the rehabilitation sites and
Namakwa Sands will not be able to meet their long-term objective of small-stock farming if diversity and
the number of palatable species do not increase significantly. Adaptive management should seriously be
considered in order to speed up this process. Alternatively, an appropriate grazing strategy, which is
related to the Tetragonia fruticosa dominated vegetation within rehabilitation sites, would need to be
determined and adopted.More time is needed to ameliorate the rehabilitated soil profiles to the same level as in reference sites,
especially with regard to carbon, pH and sodium levels. In order to increase organic matter within
rehabilitation areas, Namakwa Sands should consider creating clumps with cleared vegetation from the
mining front.
Since the long-term rehabilitation goal has not been achieved, Namakwa Sands will need to continue to
monitor plant and soil changes until it has been achieved. The objectives of the current rehabilitation
programme are limited and Namakwa Sands should develop additional objectives relating to the structure
and function of the natural vegetation. This will give a better indication of whether rehabilitation sites are
progressing towards the desired end point and if adaptive management is required. In addition, the
current monitoring programme (vegetation survey) implemented at Namakwa Sands could be improved
by increasing the vegetation parameters to be monitored. It is recommended that the following vegetation
parameters be monitored as part of the long-term monitoring programme: species composition and
similarity, species richness, species diversity, vegetation cover, species dominance, vertical structure and
functional diversity of the vegetation (clumps and inter-clumps). It is also recommended that carbon, pH
and sodium of soil profiles be monitored as part of the long-term monitoring programme. These
parameters should not be seen as exhaustive as this study only considered various vegetation
parameters and soil chemistry between rehabilitation and reference sites. The results of other studies on
the fauna, mycorrhiza, insects, etc. should also be taken into consideration and the monitoring
parameters expanded accordingly.
Description
Thesis (MScConsEcol(Conservation Ecology and Entomology)--University of Stellenbosch, 2006.
Keywords
Dissertations -- Conservation ecology and entomology, Theses -- Conservation ecology and entomology, Abandoned mined lands reclamation -- South Africa -- Namaqualand, Strip mining -- Environmental aspects -- South Africa -- Namaqualand, Heavy minerals -- Prospecting -- Environmental aspects -- South Africa -- Namaqualand, Restoration ecology -- South Africa -- Namaqualand, Revegetation -- South Africa -- Namaqualand, Plant conservation -- South Africa -- Namaqualand