country (Thuiller et al. 2006; Donaldson et al. 2014). It is not surprising, therefore,
that the earliest records of invasion are from species that were introduced for
utilitarian purposes, and that most of the new records of invasive plants have been
taxa used in horticulture that were intentionally introduced and widely planted.
The most widespread alien plant species in South Africa today, Opuntia ficusindica (Mission Prickly Pear; found in 35% of all quarter-degree grid cells in
South Africa), started expanding its range around planting sites in the 1770s and
“had become a serious and troublesome weed” by about 1890 (Annecke and Moran
1978). There are no records of major incursions of other alien plant species into
natural vegetation in the 18th or early 19th centuries. Widespread invasions of alien
plant species in natural ecosystems in South Africa were reported in the mid-1800s
when invasive pines introduced for forestry [Pinus pinaster and possibly
P. halepensis (Aleppo Pine)] began spreading into fynbos in the Western Cape
(Richardson et al. 1994; Richardson and Higgins 1998). Other species that were
already clearly invasive in the second half of the nineteenth century were
O. aurantiaca (Jointed Cactus) and X. spinosum. In some cases, the enactment of
policies and legislation provides clues on the emergence of major invasions. For
example, although early distribution records for X. spinosum are scarce, the promulgation in 1861 of the Xanthium spinosum Act points to a major increase in the
abundance, distribution and nuisance value of this species in preceding decades (see
Lukey and Hall 2020, Chap. 18). Several reports of widespread invasions of Acacia,
Hakea and Pinus species appeared in the 1920s and 1930s; by the 1940s large-scale
invasions of these taxa occurred in many parts of the Fynbos Biome (reviewed in van
Wilgen et al. 2016).
Widespread invasions began later in other parts of South Africa, but there are few
detailed reports of the first invasions in the eastern and northern parts of the country.
Among species that are currently widespread invaders in the northeastern parts of the
country, Lantana camara (Lantana) and Solanum mauritianum (Bugweed), both of
which were planted as ornamentals, were widespread in the 1930s and both were
listed on the National Weeds Act of 1937. Henderson and Wells (1986) provide the
earliest records of naturalisation for a range of species that are now widespread
invaders in the Grassland and Savanna Biomes; dates range from the 1770s for
O. ficus-indica, the 1870s for Acacia dealbata (Silver Wattle) and A. mearnsii
(Black Wattle), to 1907 for Lantana camara and the 1940s for Chromolaena
odorata.
Several examples illustrate the very rapid and recent emergence of invasions over
large parts of the eastern, northern and interior parts of South Africa by species that
are now among the country’s most widespread and damaging invasive species.
Chromolaena odorata was first recorded in Durban in 1945 and was present in
Hluhluwe–iMfolozi game reserve by 1961 (Macdonald and Frame 1988). Goodall
and Erasmus (1996) document the spread of this species over large parts of eastern
South Africa within 50 years of its arrival in the country. The first records of Lantana
camara were from Durban and Cape Town, management efforts were reported as
72
D. M. Richardson et al.
that the earliest records of invasion are from species that were introduced for
utilitarian purposes, and that most of the new records of invasive plants have been
taxa used in horticulture that were intentionally introduced and widely planted.
The most widespread alien plant species in South Africa today, Opuntia ficusindica (Mission Prickly Pear; found in 35% of all quarter-degree grid cells in
South Africa), started expanding its range around planting sites in the 1770s and
“had become a serious and troublesome weed” by about 1890 (Annecke and Moran
1978). There are no records of major incursions of other alien plant species into
natural vegetation in the 18th or early 19th centuries. Widespread invasions of alien
plant species in natural ecosystems in South Africa were reported in the mid-1800s
when invasive pines introduced for forestry [Pinus pinaster and possibly
P. halepensis (Aleppo Pine)] began spreading into fynbos in the Western Cape
(Richardson et al. 1994; Richardson and Higgins 1998). Other species that were
already clearly invasive in the second half of the nineteenth century were
O. aurantiaca (Jointed Cactus) and X. spinosum. In some cases, the enactment of
policies and legislation provides clues on the emergence of major invasions. For
example, although early distribution records for X. spinosum are scarce, the promulgation in 1861 of the Xanthium spinosum Act points to a major increase in the
abundance, distribution and nuisance value of this species in preceding decades (see
Lukey and Hall 2020, Chap. 18). Several reports of widespread invasions of Acacia,
Hakea and Pinus species appeared in the 1920s and 1930s; by the 1940s large-scale
invasions of these taxa occurred in many parts of the Fynbos Biome (reviewed in van
Wilgen et al. 2016).
Widespread invasions began later in other parts of South Africa, but there are few
detailed reports of the first invasions in the eastern and northern parts of the country.
Among species that are currently widespread invaders in the northeastern parts of the
country, Lantana camara (Lantana) and Solanum mauritianum (Bugweed), both of
which were planted as ornamentals, were widespread in the 1930s and both were
listed on the National Weeds Act of 1937. Henderson and Wells (1986) provide the
earliest records of naturalisation for a range of species that are now widespread
invaders in the Grassland and Savanna Biomes; dates range from the 1770s for
O. ficus-indica, the 1870s for Acacia dealbata (Silver Wattle) and A. mearnsii
(Black Wattle), to 1907 for Lantana camara and the 1940s for Chromolaena
odorata.
Several examples illustrate the very rapid and recent emergence of invasions over
large parts of the eastern, northern and interior parts of South Africa by species that
are now among the country’s most widespread and damaging invasive species.
Chromolaena odorata was first recorded in Durban in 1945 and was present in
Hluhluwe–iMfolozi game reserve by 1961 (Macdonald and Frame 1988). Goodall
and Erasmus (1996) document the spread of this species over large parts of eastern
South Africa within 50 years of its arrival in the country. The first records of Lantana
camara were from Durban and Cape Town, management efforts were reported as
72
D. M. Richardson et al.