Metallophytes: the unique biological resource, its ecology and conservational status in Europe, central Africa and Latin America - Ecology of Industrial Pollution - page 22

but historical interest can add value to anthropogenic sites. Discussion as to
whether sites are natural or anthropogenic has centred less on ecology than
on the demands of legislation, which designate heritage status based upon
industrial archaeological values.
Heavy-metal vegetation in Central Africa
In Central Africa, there are a lot of sites enriched with cobalt (Duvigneaud
1959 ), copper (Duvigneaud & Denaeyer-De Smet 1963 ; Wild 1968 ; Brooks et al.
1992a ) and nickel (Wild 1970 ) and only a few soils have high levels of lead and
zinc (Ernst 1972 ). The greatest interest has concentrated on the flora on the
cobalt and copper outcrops in Katanga (Brooks et al. 1985 ).
The copper-cobalt metallophytes of Katanga
The copper-cobalt flora of Katanga (Democratic Republic of Congo) is without
doubt the richest described to date globally in terms of numbers of endemic
metallophytes. Our knowledge of this flora has emerged from alternating
periods of active exploration with periods of total inactivity. This progression
has been, and still is, linked to efforts on several fronts but primarily from a
knowledge of the existence of Cu-Co outcrops and site accessibility. Subsequent
collection of plant materials (and later also soils), taxonomic works, a few
systematic studies and biogeochemical investigations have followed.
Historical perspective
Five broad periods of progress may be recognised (Leteinturier 2002 ; Leteinturier &
Malaisse 2002 ). Although local mining activities in Katanga commenced as
early as the fourteenth century (De Plaen et al. 1982 ), the first plant collections
from Cu-Co sites were made by Rogers probably around 1910, and certainly in
1914 at the ´ toile du Congo mine. Other collections in this first period were
made by Burt-Davy (1919), Rogers (1920), Robert (1921), Robyns (1926), Quarr´
(1937, 1939) and by priests from Saint Fran¸ois-de-Sales (1939). Only one paper
(Robyns 1932 ) was published in this period; it provides a list of the first
45 Katangan copper metallophytes recorded. From 1940 to 1953 further
collections were few and erratic, and included those by Hoffman (1946) and
Duvigneaud (1948). A second period extended from 1954 to 1963 with inde-
pendent plant collections from the Cu-Co outcrops by Duvigneaud and his
collaborators and by Schmitz. Duvigneaud collected at least 3704 voucher speci-
mens, and the number of Cu-Co metallophytes was raised from 72 (Duvigneaud
1958 ) to 218 (Duvigneaud & Denaeyer-De Smet 1963 ). Other collections during
this period are rare, but include those of Symoens (1956 1963), Plancke (1958),
Bamps (1960) and Ledocte (1960). From 1963 until 1978, few occasional collec-
tions were made (Evrard & L´onard in 1968, Lisowski 1968 1971, Bercovitz 1971,
Breyne 1977 and Pauwels 1978). A third period of botanical exploration started