Chap. 6, Sect. 6.2), and hatcheries were established at Jonkershoek (Western Cape)
and Boschfontein (KwaZulu-Natal) to breed and distribute trout for recreational
fishing. The establishment of hatcheries facilitated stocking of angling species such
as Largemouth Bass (Micropterus salmoides), Smallmouth Bass (M. dolomieu),
Common Carp (Cyprinus carpio), Brown Trout (Salmo trutta) and O. mykiss,
initially by government agencies and later by angling societies and private individuals. These fish have subsequently become invasive, and their management is
complicated and sometimes highly contentious because of differences in how people
view the benefits they provide and the negative impacts they cause (Woodford et al.
2016; Ellender et al. 2014; Zengeya et al. 2017). While certain pines (Pinus species)
were introduced as early as 1690, it was not until the 1930s that extensive planting in
formal plantations began, to grow a viable forest industry. Pines subsequently
become invasive, particularly in the Fynbos Biome (van Wilgen and Richardson
2014). In the 1950s, farmers were actively encouraged by government, through
subsidies and extension programmes, to plant Prosopis trees on their farms to
provide for shade and fodder (Wise et al. 2012). These trees are now the most
serious invaders of arid landscapes in South Africa. These few examples of early
deliberate introductions and propagation were typical of our history until relatively
recently. Currently, almost 1500 alien species are known to have established in
South Africa, many of which have become invasive (see Sect. 1.3). The rate at which
new taxa are recorded as introduced and established has been increasing over the
past decades, and by the 1980s over 50 new species were recorded as established per
decade, rising to 70 recently (van Wilgen and Wilson 2018). Of the invasive species
that were assessed by experts, 107 have either severe or major negative impacts:
80 of these are plants, 11 terrestrial invertebrates, eight mammals, seven freshwater
fish species, and one marine invertebrate (van Wilgen and Wilson 2018). Data on
how invasions have changed over time are not available for most taxa, but, based on
the Southern African Plant Invaders Atlas (SAPIA), it is clear that both the number
and extent of plant invasions has increased markedly in recent years [as of May
2016, SAPIA had records for 773 alien plant taxa, an increase of 172 since 2006; and
between 2000 and 2016, the number of quarter degree grid cells occupied by alien
plants has increased by ~50% (Henderson and Wilson, 2017)]. While many early
introductions were deliberate, accidental introductions are becoming more common
(Fig. 1.1c; Faulkner et al. 2020, Chap. 12). One recent and potentially very damaging
example is the Polyphagous Shot Hole Borer (Euwallacea fornicatus), an ambrosia
beetle native to Asia, that together with its fungal symbiont Fusarium euwallaceae
poses substantial threats to both native and alien trees in South Africa (Paap et al.
2018; Potgieter et al. 2020, Chap. 11, Box 11.3).
Particular features of South Africa’s biomes and biota have resulted in a demand
for particular alien species, thereby shaping introduction pathways (Richardson et al.
2003; Faulkner et al. 2020, Chap. 12). For example, the paucity of native trees
suitable for timber production resulted in major efforts to introduce trees from many
other parts of the world. Although such introductions created much-needed ecosystem services to support growing human populations, they also sowed the seeds,
literally and figuratively, for rampant invasions decades or centuries later. No other
1 Biological Invasions in South Africa: An Overview
11
and Boschfontein (KwaZulu-Natal) to breed and distribute trout for recreational
fishing. The establishment of hatcheries facilitated stocking of angling species such
as Largemouth Bass (Micropterus salmoides), Smallmouth Bass (M. dolomieu),
Common Carp (Cyprinus carpio), Brown Trout (Salmo trutta) and O. mykiss,
initially by government agencies and later by angling societies and private individuals. These fish have subsequently become invasive, and their management is
complicated and sometimes highly contentious because of differences in how people
view the benefits they provide and the negative impacts they cause (Woodford et al.
2016; Ellender et al. 2014; Zengeya et al. 2017). While certain pines (Pinus species)
were introduced as early as 1690, it was not until the 1930s that extensive planting in
formal plantations began, to grow a viable forest industry. Pines subsequently
become invasive, particularly in the Fynbos Biome (van Wilgen and Richardson
2014). In the 1950s, farmers were actively encouraged by government, through
subsidies and extension programmes, to plant Prosopis trees on their farms to
provide for shade and fodder (Wise et al. 2012). These trees are now the most
serious invaders of arid landscapes in South Africa. These few examples of early
deliberate introductions and propagation were typical of our history until relatively
recently. Currently, almost 1500 alien species are known to have established in
South Africa, many of which have become invasive (see Sect. 1.3). The rate at which
new taxa are recorded as introduced and established has been increasing over the
past decades, and by the 1980s over 50 new species were recorded as established per
decade, rising to 70 recently (van Wilgen and Wilson 2018). Of the invasive species
that were assessed by experts, 107 have either severe or major negative impacts:
80 of these are plants, 11 terrestrial invertebrates, eight mammals, seven freshwater
fish species, and one marine invertebrate (van Wilgen and Wilson 2018). Data on
how invasions have changed over time are not available for most taxa, but, based on
the Southern African Plant Invaders Atlas (SAPIA), it is clear that both the number
and extent of plant invasions has increased markedly in recent years [as of May
2016, SAPIA had records for 773 alien plant taxa, an increase of 172 since 2006; and
between 2000 and 2016, the number of quarter degree grid cells occupied by alien
plants has increased by ~50% (Henderson and Wilson, 2017)]. While many early
introductions were deliberate, accidental introductions are becoming more common
(Fig. 1.1c; Faulkner et al. 2020, Chap. 12). One recent and potentially very damaging
example is the Polyphagous Shot Hole Borer (Euwallacea fornicatus), an ambrosia
beetle native to Asia, that together with its fungal symbiont Fusarium euwallaceae
poses substantial threats to both native and alien trees in South Africa (Paap et al.
2018; Potgieter et al. 2020, Chap. 11, Box 11.3).
Particular features of South Africa’s biomes and biota have resulted in a demand
for particular alien species, thereby shaping introduction pathways (Richardson et al.
2003; Faulkner et al. 2020, Chap. 12). For example, the paucity of native trees
suitable for timber production resulted in major efforts to introduce trees from many
other parts of the world. Although such introductions created much-needed ecosystem services to support growing human populations, they also sowed the seeds,
literally and figuratively, for rampant invasions decades or centuries later. No other
1 Biological Invasions in South Africa: An Overview
11