Environmental Engineering Reference
In-Depth Information
one to more than a thousand vouchers collected), at least some 150 others have
never been explored; some of these sites may have already been totally des-
troyed. Since 2005, an important plant collecting initiative has taken place.
Some 5 000 voucher specimens have been collected in less than 4 years, about
39% of the total collected since 1914. However, these collections presently need
to be carefully checked for naming and classified regarding Cu-Co metallo-
phyte biodiversity. At least 15% of previous collections are in the same situ-
ation, awaiting assignment of correct scientific names. It has been estimated
that more than 700 higher plant species exist on the Katangan Cu-Co outcrops,
but the real figure could in fact be much higher. How many species new
to science are in these collections? To what extent are they copper-cobalt
endemics? Leteinturier (
2002
) already highlighted the time extending between
a collection and the description of a new taxon, a few years even up to 50.
Several families and genera of the flora of southcentral Africa (Flore d'Afrique
centrale, Flora Zambesiaca, Flora of Tropical East Africa) are in need of revision,
and this adds a further complication. A good example is given by the genus
Basananthe Peyr. (Passifloraceae). Revision of the material hosted in the National
Botanic Garden of Belgium (BR) has allowed the description of six new species,
all from Katanga, including two species restricted to Cu-Co sites (Robyns
1995
;
Malaisse & Bamps
2005
). On the other hand, a re-evaluation of the copper
indicator Haumaniastrum katangense (Lamiaceae) comes to the conclusion that
this species is more widespread on soils with low Cu levels than on those
with high ones (Choo et al.
1996
). The Zambian copper flower Becium homblei
(Lamiaceae) has lost specific rank; it is now considered nothing more than a
Cu-tolerant ecotype of Becium centrali-africanum (Sebald
1988
), the species mostly
occurring on low-Cu soils.
Data concerning heavy-metal tolerance and accumulation in the Cu-Co flora
have also to be reviewed thoroughly. Very few experimental studies under
controlled conditions have been performed to date (see, e.g., Baker et al.
1983
),
and there is an urgent need to confirm the putative status of the 35 Cu-, and
36 Co-hyperaccumulators listed by Reeves and Baker (
2000
). Fine superficial dusts
tightly adhering to dried herbarium specimens may account for the variable and
possibly spurious apparent hyperaccumulation values published in early biogeo-
chemical studies (Brooks et al.
1987
). Several experimental studies on metal
uptake and localization in the metallophytes of Katanga are currently under way.
Conservation and management of the Cu-Co metallophyte flora
Conservation of the Co-Cu metallophyte diversity in relation to current and
future mining activities is a major challenge. A few mining groups have,
however, recognised the issues and developed excellent scientifically based
conservation strategies. The operations at Luiswishi and Tilwezembe mines
