Biol Invasions (2014) 16:499–512
DOI 10.1007/s10530-013-0601-1
ORIGINAL PAPER
Model invasions and the development of national concerns
over invasive introduced trees: insights from South African
history
Brett M. Bennett
Received: 13 December 2012 / Accepted: 25 August 2013 / Published online: 4 December 2013
Springer Science+Business Media Dordrecht 2013
Abstract
This article examines how invasions
within a discrete geographic, cultural, and ecological
context disproportionately shaped awareness of invasions in other places. Such ‘‘model invasions’’ have
been valuable for catalyzing national and international
interest in biological invasion since the 1980s.
Specifically, this article traces how scientific and
public perspectives of invasive introduced trees
evolved in South Africa during the twentieth century.
It argues that concerns about the impact of invasive
introduced trees first developed in the Mediterraneanclimate region of the southwestern Cape Province
during the 1940s and 1950s before emerging elsewhere in South Africa during the 1970s and early
1980s. Though there has been a nation-wide convergence in scientific and public views of invasive trees
since the 1980s, there are still stark geographic and
cultural knowledge divergences that hinder the effectiveness of contemporary invasive tree management
efforts. This study suggests that geographical knowledge imbalances between regions should not be
B. M. Bennett (&)
School of Humanities and Communication Arts,
University of Western Sydney, Bankstown Campus,
Building 7, Locked Bag 1797, Penrith, NSW 2751,
Australia
e-mail: [email protected]
B. M. Bennett
Department of Historical Studies, University of Cape
Town, Private Bag, Rondebosch 7701, South Africa
overlooked when historicizing or planning environmental management schemes at national scales.
Keywords Citizen science Environmental
history Fynbos South Africa Tree invasions
Introduction
Invasive alien plants are one of South Africa’s most
pressing environmental problems. South Africa’s
Department of Water Affairs and Forestry proclaims
that invasive introduced species—non-native plants
with self-perpetuating and expanding populations—
are: ‘‘the biggest threat to the country’s biological
biodiversity’’ (dwaf.gov.za/wfw/, accessed 2 May
2013). The most studied (Musil and Macdonald
2007: 9) and ecologically significant (Henderson
2007: 220; van Wilgen et al. 2012: 31) invasive plants
in South Africa are trees and shrubs. The Department
of Water Affairs and Forestry devotes significant
funding for the Working for Water (WFW) program,
which manages invasive plants, primarily trees, such
as species of Australian Acacia and Hakea. WFW has
received approximately $432 million USD to clear
invasive plants since its origin in 1995 (McConnachie
et al. 2012: 129). Policies to control introduced trees
are frequently (and often heatedly) discussed in
newspapers, town, and environmental planning
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meetings, and a variety of other forums (Comaroff and
Comaroff 2001; van Wilgen 2012).
The intensity of concerns over introduced invasive
trees has stimulated social scientists to study when and
why South Africans become concerned about the
impacts of invasive introduced plants, especially trees.
There is a developed literature focusing on how fears
of invasive alien plants expressed South African
nationalism in its apartheid and post-apartheid forms.
Carruthers et al. (2011: 813) suggest that ‘‘The
discourse of the ‘danger’ of introduced invasive
species in South Africa gained momentum in the late
1950s and early 1960s’’. They argue: ‘‘nationalism…provided justification for eradicating these [i.e.
introduced Australian Acacia] species’’. Peretti (2010:
33) takes this argument one step further by linking
South African interest in biological invasions in the
1980s with ideologies of apartheid that were ‘‘concerned with separating the pure from impure’’. Taking
up the thread after the end of apartheid, Comaroff and
Comaroff (2001) argue that the frenzied criticisms of
invasive introduced trees that followed the 2000 Cape
Peninsula fires were expressions of a new postcolonial South African nationalism that sought to
naturalise the territorial boundaries of the South
African nation-state by drawing a clear line between
‘‘aliens’’—including plants and people—and ‘‘natural’’ South Africans. One of the common features of all
three analyses mentioned above is their use of
historical examples from the southwestern Cape to
make a larger point about the nation of South Africa
and nationalism as a phenomenon.
There is another body of historical literature that
suggests that the Cape was not always an accurate
reflection of wider South African identities or history.
Van Sittert (2003: 113) suggests that the rise of floral
preservationism in the southwestern Cape during the
late nineteenth and early twentieth centuries, which
included the formation of the ‘‘national’’ Kirstenbosch
Botanic Gardens in 1913, reinforced a distinctly
patrician and Anglo Cape regional identity and
culture. He argues that at ‘‘the eve of the Second
World War, identification with the indigenous Cape
flora had become a mark of class, ethnic and regional
identity for the old imperial urban, English-speaking
middle class marooned in a new nation state governed
by rural, Afrikaans republicanism’’. British-born and
trained botanists who dominated Cape botany prior to
the 1950s consistently used the rhetoric of the
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‘‘nation’’ to support a specifically Cape-oriented
botanical agenda (Pooley 2010: 601). Pooley suggests
that ecologists, botanists, and foresters in the southwestern Cape were the first scientists who attempted
‘‘to preserve ‘virgin’ indigenous vegetation against
invasion by ‘alien’ interlopers’’ before the 1960s
(Pooley 2010: 605).
Two distinct approaches to the Cape’s position in
South African environmental history have thus developed: one focuses on the Cape (particularly its
southwestern and southern regions with a Mediterranean-type climate). The second focuses on South
African history and nationalism through the lens of the
Cape. This article suggests that both perspectives can
be used justifiably so long as scholars explicitly
recognize that both regions and national identities and
histories existed simultaneously and did not always
causally overlap. Rather than criticizing scholars for
focusing on the Cape at the expense of other regions,
such as the Transvaal (Carruthers 2011: 263), scholars
should remember that nation-states are constructed
and not constitutive of all of their elements. Ironically,
the trend to write transnational and comparative
histories—which were meant as a way to look beyond
the nation—can reinforce the category of nation-state
and constructions of nationalism by leading scholars
to overlook important regional distinctions. A more
nuanced understanding of the nation and nationalism
taking into account regional differences is required.
Accordingly, this paper situates the Cape within the
context of twentieth-century South African history. It
demonstrates that concerns about the impact of
invasive introduced trees only developed outside of
the Cape in the 1980s, approximately 30 years after
the development of similar concerns in the Cape
Province. The formation of a national discourse on
tree invasion built on and was influenced by a
sustained movement to study and control invasive
introduced trees in the southwestern Cape Province
that began in earnest during the 1940s and 1950s.
Fears about invasive trees developed as an expression
of the desire to protect indigenous flora from destruction rather than as an extension of earlier concerns
about the economic impact of agricultural weeds and
pests. Scientific, public, and government actors
located in the greater Cape Town metropolitan area
established a coordinated program to educate the
public about the ecological threats posed by invasive
introduced trees. These anxieties reflected distinct
Insights from South African history
regional environmental concerns and identities that
were located within the Cape and only broadly
reflected South African nationalism or identity. Residents of the southwestern Cape were unique amongst
South Africans for expressing and acting on their
concerns about the ecological impact of invasive
introduced trees before the 1980s.
In spite of the considerable attention that invasive
introduced trees received in the southwestern Cape,
there was little widespread or sustained concern about
invasive introduced trees (as opposed to other types of
weeds) elsewhere in South Africa. It was only during
the 1980s and early 1990s when scientific researchers
outside of the Cape Province began to express serious
and persistent worries about the negative hydrological,
ecological, and economic impacts caused by invasive
introduced trees. Though major post-apartheid programs, such as Working for Water, originated from a
groundswell of national interest during the 1980s and
early 1990s, they were largely justified based on Cape
research and concerns. Despite considerable funding
and publicity efforts, attempts to control invasive
introduced trees outside of a Cape fynbos context have
presented numerous challenges that have been hindered by the shortage of professional experts outside
of the Cape and lower levels of awareness about the
threat posed by invasive introduced trees.
This article offers two points that are signficant for
scientists, environmental managers, and social scientists researching invasive species worldwide.
First, it offers an important case study explaining
how and why scientific and public perceptions of
invasive alien species developed in one of the
world’s leading centres for the study of invasive
species. This helps to explain why people became
concerned about the ecological impact of invasive
trees during the last half of the twentieth century.
Despite the growth of historical studies of perceptions of alien and indigenous vegetation, this specific
question remains unanswered.
Second, the article clarifies how scientific understanding of particular types of invasion that developed
within specific geographic, cultural, and ecological
contexts have inspired research about invasions in
other geographies and ecologies (for a broader
discussion of how science ‘‘moves’’, see Livingstone
2003). This explains how and why concerns about
invasion in one place—such as the Mediterraneanclimate Cape or other Mediterranean-climate
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ecosystems—shaped national and global awareness
of invasive species. The article concludes by suggesting that more attention should be focused on finding
ways to overcome geographic knowledge and power
imbalances in regions where recognitions of invasion
have more recently developed.
Tree invasions in South Africa
Environmental and colonial contexts
Much of Southern Africa is naturally tree-less or
forest-less but has environmental conditions that could
allow for the growth of trees (Richardson and Cowling
1992; Rundel et al. 2014). This is a significant factor
that has determined much of the dynamics of the
ecological history of Southern Africa since the mid
seventeenth century. With a few exceptions, southern
Africa has in the recent past been devoid of closedcanopy forests, which today account for less than
0.3 % of South Africa’s biomes (Mucina and Rutherford 2006: 37). The lack of forests that characterises
three of South Africa’s biggest ‘fire driven ecosystems’—savanna (32.5 %), grassland (27.9 %), and
fynbos (6.6 %)—is caused by the prominence of
recurring fires that kill trees or tree-like vegetation
before they can grow tall enough to survive fires
(Mucina and Rutherford 2006: 32, 37). Without the
recurrence of fire, forests might have evolved in these
biomes because in many localities there is suitable
rainfall, climate, and soil types for tree growth.
Starting in 1652 with the Dutch East India
Company (VOC) settlement at Cape Town, European colonists imported and planted a wide variety
of introduced trees in the southwestern and southern
Cape (Pooley 2009: 11–14). For the next 150 years
settlers planted trees for aesthetic and utilitarian
reasons, such as providing windbreaks, shelter,
shade, fruit production, and wood fuel (Showers
2010: 296). The intensity and scale of tree-planting
increased dramatically throughout the nineteenth
century as a result of the expansion of European
settlement across Southern Africa, the introduction
of a greater variety of introduced tree genera and
species (especially Australian species of Acacia and
Eucalyptus), and the growing demand for timber,
forest-cover and species to stabilise soils. The first
commercial plantation of Pinus pinaster was planted
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at Genadendal Valley in the Riviersonderend Mountains of the southwestern Cape during the last half of
the 1820s (Showers 2010: 299). Settlers started
establishing commercial Acacia plantations in the
Midlands of Natal during the 1860s (Witt 2005:
110–4). The creation of a state forestry department in
the Cape in the early 1880s led to the formation of the
first systematic program of timber planting throughout the Cape. Foresters experimented widely with
introduced species in arboreta and plantations (Bennett 2011: 272–77). Foresters from the Cape established forestry departments in Natal, Transvaal and
Free State during the early 1900s (Bennett 2011:
274–5). At the dawn of the twentieth century the
largest established state plantations were located in
the Cape Colony. Natal had large commercial Acacia
plantations (Witt 2005) and private growers in the
Transvaal were beginning to establish eucalyptus
plantations (Bennett 2010: 33–6). Introduced trees
were thus spread, with some unevenness, throughout
the whole of southern Africa (Richardson et al.
2003).
Prevailing ideas of late-Victorian biogeography,
hydrology, and climatology led European settlers to
see introduced trees as a necessary botanical addition
to Southern Africa’s indigenous vegetation types.
Colonial forestry advocates in all four colonies
assumed that the largely tree-less fynbos and grassland
biomes of Southern Africa were forested prior to
human habitation (Powell 2007: 869). The lack of
forest cover was used to explain why much of
Southern Africa had such variable rain patterns, high
summer temperatures, and was prone to aridity and
drought. Tree planting was therefore seen as a way to
‘‘improve’’ Southern Africa’s climate to facilitate
European settlement (Bennett 2010: 30–33). It was an
economic imperative to plant trees in order to produce
timber for growing population and the burgeoning
mining industry during the last three decades of the
nineteenth century. With these ecological and economic imperatives interlinked, forestry enthusiasts
believed that the sub-continent should be clothed with
forests.
These attitudes, combined with late-Victorian ideas
of natural selection, led some colonial foresters to
view self-propagating introduced tree populations as
positive and unstoppable processes. In 1902, David E.
Hutchins approved of an example where ‘‘the Clusterpine has spread, self-sown, up the rocky face of the
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mountain, and into the rugged Genadendal valley’’
because it created a ‘‘picturesque’’ appearance (Hutchins 1904: 1). Hutchins believed that introduced trees
(North American, Eurasian, and Australian) would
eventually colonize much of the Cape flora because
trees from the Northern Hemisphere and Australia
were younger, more aggressive and fitter than the Cape
flora (Bennett 2011: 269). This belief was based on
Alfred Russell Wallace’s widely cited biogeographic
argument that the Cape flora1 (e.g. what is today
classified as fynbos) was ‘‘comparatively impotent and
weak’’ (Wallace 1880: 495) when compared to more
aggressive Northern Hemisphere and Australian
floras.
Studying and conserving fynbos
The late-Victorian belief that the Cape flora was
‘‘comparatively impotent and weak’’ also influenced
the rise of an indigenous flora preservation movement
in the southwestern Mediterranean-climate region of
the Cape Colony. Fears that individual species as well
as the Cape flora could become extinct played a key
role in mobilizing floral preservation efforts during the
early twentieth century. These two concerns preceded
worries about the impact of invasive introduced trees.
Biogeographical studies of the southwestern Cape’s
flora completed during the 1880s and 1890s by the
amateur botanists Harry Bolus and Rudolph Marloth
broadly confirmed Wallace’s theory that the Cape
flora was ‘‘ancient,’’ ‘‘weak,’’ and vulnerable to
destruction by people, plants, and floras (Van Sittert
2003: 116–7). They warned that many species that
botanists had collected as recently as the late-eighteenth and early-nineteenth centuries might have
already gone extinct as a result of human activities.
They specifically singled out flower pickers as key
drivers of extinction (Van Sittert 2003: 119–20). The
Mountain Club of South Africa (MCSA) was established in Cape Town in 1891 partly to encourage
people to see flowers in situ on Table Mountain rather
than buying them at the Adderley Street flower market
for display at home (Van Sittert 2003: 118). From its
origin, the MCSA was a vehicle of citizen science
1
This paper often uses the term fynbos, but prior to the 1960s
and 1970s it was more frequently called the ‘‘Cape flora.’’
Botanists believed that the Cape flora included renosterveld and
fynbos but not succulent Karoo or forest thickets.
Insights from South African history
(Miller-Rushing et al. 2012): its members included
leading amateur botanists (Marloth), and the Club
catalyzed regular citizens to document the botanical
geography of the Cape, collect specimens and lobby
for the preservation of the Cape flora. The MCSA’s
foundations were, like other Cape-based ‘‘national’’
South African institutions (such as the national botanic
garden established at Kirstenbosch), tied intimately
within an Anglo-imperial, Cape Fold Mountain, and
fynbos—rather than wider Southern African—context
(Van Sittert 2003: 119–20).
As a result of lobbying by botanists and Mountain
Club members, the Cape Colony’s Parliament implemented the colony’s (and Southern Africa’s) first
wildflower preservation legislation, the Wildflower
Protection Act of 1905, which mandated the preservation of listed indigenous species and banned flower
picking on crown land. Though the law was at first
considered to be un-successful, at the response of the
citizen-led Wild Flower Protection Committee (created in 1912), elected provincial governments
amended the law to make it more restrictive and
punitive (Van Sittert 2003: 124). By the second half of
the century Cape-based indigenous floral preservationists viewed it as a successful legal intervention. In
1960 the Department of Nature Conservation in the
Cape Province praised the success of the Wildflower
Protection Act because: ‘‘Indiscriminate flower picking for commercial purposes was an important factor
contributing to the disappearance of our Flora, but this
practice has now been largely checked’’ (Department
of Nature Conservation of the Cape of Good Hope
1960: 11).
Botanists were equally troubled by the perceived
expansion of the drier Karoo flora, which they
believed was slowly colonizing fynbos. This theory
was also justified by Victorian biogeographic ideas:
fynbos was seen to be ancient and weaker than the
supposedly youthful and more vigorous Karoo (Van
Sittert 2003: 116–7). The fear that the Karoo was
expanding (Hoffman et al. 1995: 159–61) remained an
important theme in South African botanical and
agricultural debates throughout the twentieth century.
Concern about the southwestwardly advance of
Karoo recurred in Cape botanical discourse until the
1950s when Margaret Levyns quelled fears by
declaring in her presidential speech to the botanical
section at the 1952 South African Association for the
Advancement of Science that fynbos was safe from
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destruction from invading floras: ‘‘the sad picture of
the Cape flora being slowly but surely pushed off the
African continent by the aggressive tactics of newer
and more drought-resistance floras pushing down on it
from the north is far from accurate’’ (Levyns 1952:
163). Levyns’ also challenged the ‘‘ancient’’ Cape
flora thesis, which underpinned pessimistic fears, by
showing its more ‘‘recent’’ evolution as a result of the
establishment of the Benguela current and the subsequence drying and cooling of the southwestern Cape
(Levyns 1962). Concerns about the expansion of the
Karoo declined in importance partly as a result of
Levyns’ research, which paved the way for modern
theories of the origins of the Cape flora.
Though public and scientific apprehensions about
flower picking and the expanding Karoo abated in the
southwestern Cape during the second half of the
twentieth century, many white Cape residents sought to
protect the Cape’s flora against threats, be they people
or plants. This vigilance was supported by a motivated
group of amateur bushwalkers and conservationists
who had already been taught to believe that fynbos was
fragile and required human protection. The strong
cultural connections that people in the southwestern
Cape formed with indigenous plants, and pre-existing
concerns about extinction, shaped concerns about
invasive introduced trees from the 1950s and after.
The rise and decline of Clementsian paradigms
of invasion
The recognition that self-propagating introduced tree
populations threatened indigenous plants and vegetation types was delayed until the mid twentieth century
as a result of the arrival of Clementsian ecology into
South Africa during the 1910s–1920s (Pooley 2010:
602–6). Clementsian ecological theory encouraged
ecologists to downplay the late-Victorian ‘‘survivalof-the-fittest’’ perspective that colonial foresters used
to explain the dynamics of introduced tree invasions.
A more benign view on invasion emerged in the 1910s
that lasted until the late 1930s and early 1940s.
The first generation of trained ecologists who began
working in South Africa during the 1910s and 1920s
were profoundly shaped by the American ecologist
Frederic Clements. Clements argued that ‘‘climax
communities’’ of vegetation, which were the culmination of progressive evolutionary stages, would
remain in equilibrium unless disturbed by an outside
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force, such as deforestation, land clearing, or fire
(Worster 1994: 205–220). Clementsian advocates in
South Africa used this theory to argue that climax
communities would naturally resist introduced plant
invasions because foreign species could not outcompete indigenous species that were better adapted to
local edaphic and ecological conditions.
Ecologists in South Africa recorded and analyzed
tree invasions in the Cape and Natal during the 1910s
and 1920s. These studies argued that, without disturbance, introduced tree populations would not invade
or radically modify South Africa’s indigenous vegetative communities. That is because ecologists
believed that the reproductive powers of introduced
plants were alone insufficient to extinguish indigenous
plants or change vegetation types. For instance, the
professor of botany at the University of Cape Town,
Robert S. Adamson, believed that (supposedly)
anthropogenic-induced fire caused the spread of
invasive Hakea and Acacia in the southwestern Cape
(Pooley 2010: 611). Studies from ecologists in Knysna
and Natal came to similar conclusions. In Natal, John
Bews observed that Acacia mearnsii invasions had led
to the local suppression of indigenous plants. But he
concluded that Natal’s vegetative communities were
‘‘resistant to invaders’’ on the whole (Bews 1916: 157
from Pooley 2010). John Phillips agreed. He witnessed
the invasive tendencies of Acacia melanoxylon along
the edges, rivers, and cuttings near the Knysna forest.
Yet Phillips concluded that wattle invasions were
unlikely to spread beyond a few clearings and along
some rivers because ‘‘native floras are not seriously
influenced by introduced species unless agents of
disturbance—principally the activities of man—assist
the advances of the latter’’ (Phillips 1928: 42).
Orthodox Clementsian views, such as those
expressed by Phillips above, began to soften in the
southwestern Cape during the late 1930s and early
1940s. Botanists, foresters, and ecologists there began
to observe rapid plant invasions and fear that introduced trees could destroy the habitat of rare flowers,
beliefs that were ‘‘dissonant’’ with Cape ecologists and
botanists’ dominant Clementsian paradigm (Pooley
2010: 617). Adamson noted in his 1938 survey of
South African flora that, ‘‘The planting of these exotics
[trees] often has a very great effect on the native
vegetation, in extreme cases even leading to its
extinction’’ (Adamson 1938: 228). Though he most
likely referred to trees planted by humans (as opposed
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to self-propagating trees), this marked one of the
earliest instances when trees were implicated with the
extinction of indigenous plants.
In 1945 a panel of esteemed scientists expressed
concerted alarm for the first time about the impact of
invasive vegetation in disturbed and undisturbed sites
in the southwestern Cape. The publication of the
landmark Report of the Committee on the Preservation
of the Vegetation of the South Western Cape cautioned
that ‘‘exotic and undesirable species’’ were spreading
at a disquieting rate. Chaired by Christiaan L. Wicht, a
forester and director of the Jonkershoek Forest
Research Station, the report alerted: ‘‘One of the
greatest, if not the greatest, threats to which the Cape
vegetation is exposed, is suppression through the
spread of vigorous exotic plant species. These exotics
are extremely difficult to control and possibly are
already out of hand’’ (Wicht 1945: 34).
By the 1950s, few botanists, ecologists, or
foresters who had worked in the southwestern Cape
still maintained the Clementsian theory that introduced plants could not invade in undisturbed indigenous vegetation types. Ironically, the forester
Richard J. Poynton’s statement in 1957 that, ‘‘[P.
pinaster] shows very marked aggressive tendencies
and forms natural woods on [winter rainfall] sites
previously occupied by undisturbed natural vegetation,’’ merely confirmed what Hutchins had observed
in 1902 before the rise of Clementsian ecological
perspectives (Poynton 1957: 83).
Forestry researchers in the Cape began to recognize
that self-propagating introduced trees could undermine attempts to preserve indigenous vegetation and
to conserve water in the arid Cape. By the mid 1950s
foresters working for the Department of Forestry in the
Cape Province started to describe some invasive
introduced trees as ‘‘weeds’’ (Pooley 2012: 72).
Around the same time, researchers from the forest
hydrology research station at Jonkershoek demonstrated that exotic trees transpired more water than
indigenous fynbos, lowering streamflow (Showers
2010: 311). In spite of research that showed that
introduced trees could have negative ecological and
hydrological impacts, the Department of Forestry
continued to afforest the Cape with introduced pines in
the 1960s and 1970s. This created ideal conditions to
promote tree invasions at the same time that it inspired
researchers and the public to become increasingly
concerned about these invasions.
Insights from South African history
Becoming anti-exotic
Starting in the 1950s, a growing number of white
residents in the southwestern Cape began expressing
strong concerns that invasive introduced trees were
negatively impacting the Cape’s indigenous plants.
Whereas scientists pointed this out in the 1930s and
1940s, these concerns did not initially cause widespread public anxiety. But by the 1950s professional
scientific observations became instilled in the minds of
white middle class residents in the Cape as a result of
highly coordinated educational effort between public
institutions, government departments and professional
and amateur scientists and conservationists. Indigenous floral advocates working at a variety of key
institutions—Kirstenbosch, the Department of Nature
and Environmental Conservation of the Cape Province, University of Cape Town, Stellenbosch University, and the Jonkershoek Forestry Research Station—
worked together to inculcate a sense of reverence of
fynbos, at the same time that they warned against its
destruction. The legacy of these coordinated efforts to
educate white Cape residents about fynbos shaped the
study of invasive introduced trees throughout South
Africa from the 1980s onward.
Kirstenbosch Botanic Gardens, established in 1913
on the southern slopes of Table Mountain, played a
significant role in generating awareness about the
threats invasive introduced trees posed to the Cape’s
indigenous flora. The establishment of the University
of Cape Town in the neighbouring suburb of Rondebosch in 1918 created a powerful corridor linking
scientific researchers, botany students at the University of Cape Town, amateur botanists, and wealthy
white patrons who lived in the southern suburbs.
Kirstenbosch maintained an active research program,
undertook breeding efforts (to promote indigenous
gardening), and ran a popular educational program for
white students who lived near or around Cape Town
(Van Sittert 2003: 123). Students took school fieldtrips
to Kirstenbosch where they were shown beautiful
plants, told that the Cape was a ‘‘flower paradise’’
(Rycroft 1963), and informed by staff about ‘‘green
cancers’’ of invasive species (Hey 1995: 185).
The participation of engaged activists expanded
awareness of the problem through media and amateur
groups. Key individuals distributed professional scientific research to the public. These included the populariser D.H. Wood, who ‘‘tirelessly’’ penned articles for
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Cape Town newspapers and Cape-based magazines
about the threat of invasive plants (Stirton 1978: 149);
Conrad Lighton, author of the popular Cape Floral
Kingdom (Lighton 1960); and female botanists, such as
Levyns, who served as liaisons between professional
botanists and ecologists and nature conservation groups.
Cape Province officials diffused and popularized
scientific knowledge about the threat of invasive
introduced trees. The Department of Nature and
Environmental Conservation of the Cape Province
played an important role in promoting the interests of
professional and amateur floral enthusiasts. Founded
in 1952, the Department of Nature and Environmental
Conservation advised on legislation, ran research
stations, and undertook educational activities, such
as publishing and distributing books on wildflower
protection and dangerous weeds written by university
and state botanists, ecologists, and agriculturists.
These ‘‘attractive publications’’ were designed purposefully to build ‘‘awareness of the beauty and
value’’ of fynbos because officials sought to cultivate a
sense of reverence for indigenous flora in order to
inspire fear of invasion: ‘‘public awareness both of the
invaders, and what they threaten—is an integral part of
the control effort’’ (Stirton 1978: 150). Department
publications such as A Nature Conservation Handbook (Hey 1957), Nature Conservation in the Province of the Cape of Good Hope (Dept. of Nature
Conservation of the Cape Provincial Administration
1960), and Plant Invaders: Beautiful but Dangerous
(Stirton 1978) informed the public about the Cape’s
invasive plant problem.
Cape residents founded what was probably South
Africa’s first introduced tree eradication movement.
Scientists and concerned citizens formed the Control
of Alien Vegetation Committee in 1958 as a section of
the Wild Flower Protection Society Committee
(Botanical Society of South Africa 1960). The committee commissioned and published, Green Cancers
in South Africa: The Menace of Alien Vegetation
(Control of Alien Vegetation Committee 1959), to
warn the public about the negative impacts of invasive
introduced plants, especially trees. The misleadingly
titled book actually only focused on invasive introduced trees in the Cape, not throughout all of South
Africa (not unlike the Botanical Society of South
Africa focused more on the Cape than elsewhere). The
Committee, along with members of other Cape
volunteer societies, formed the first ‘‘hack parties’’
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that trekked across the Cape destroying introduced
trees on mountains.
The combination of an active citizenry, concerned
scientists, and government support entrenched the
view that invasive introduced trees threatened the
existence and diversity of fynbos. After being established in the 1950s, this view continued to direct
scientific research and educational programs in the
Cape for the rest of the century. Yet only in the Cape
did this view take hold so quickly and firmly. In other
regions of South Africa the belief that introduced trees
threatened indigenous vegetation developed decades
later.
Cape regionalism or South African nationalism?
There is little evidence to suggest the Cape’s high
level of public and scientific concern about the
ecological impact of invasive introduced trees was
found elsewhere in South Africa prior to the 1980s.
From 1950 to 1980 there was little sustained attention
given to the perceived negative impacts of invasive
introduced trees outside of a Cape, and more specifically, fynbos context. There was indeed awareness of
invasive plants (e.g. herbaceous, shrubby, aquatic, or
creeping invasive introduced plants or weeds) in South
Africa, but on the whole these observations and
interests were not linked with introduced trees or fears
about the extinction of indigenous flora. There is, for
instance, scant evidence to suggest that Cape-oriented
publications such as Green Menace (1959) and Plant
Invaders: Beautiful but Dangerous (Stirton 1978)
‘‘gained momentum in the late 1950s and early 1960s’’
outside of the Cape (Carruthers et al. 2011: 813).
This statement is demonstrated by the paucity of
published and unpublished scientific literature focused
on trees as invaders and weeds outside of the Cape
prior to the 1980s. There was not, for instance, a single
study referenced focusing on tree invasions in the
Transvaal or Natal in a comprehensive bibliography of
ecological research ongoing in 1979 (Committee for
Terrestrial Ecosystems 1981); and only a handful of
scattered studies that focused on these regions before
1980 were listed in Moran and Moran’s bibliography
of invasive plants since 1830 (1982). Scientists noted
that there was no sustained attempt to study the
extensiveness and impact of invasive introduced trees
in the Transvaal before 1979 and in Natal before 1980
(Farrar and Kruger 1983: 12).
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B. M. Bennett
Conservation scientists working in other regions
recognized from the 1950s and on that introduced trees
were highly invasive in fynbos, but expressed little
concern about introduced tree invasions in other
biomes. For instance, in 1958 T.J. Steyn, the Director
of Transvaal government’s Nature Conservation Division, declared in the department’s official publication
Fauna and Flora: ‘‘The threat to indigenous flora [by
invasive plants in the Transvaal] thus far experienced
in the Transvaal is negligible in comparison with the
position in the Western Province, for example’’ (Steyn
1958: 21). In the same article, Steyn listed the
Transvaal’s worst weeds—not a single introduced
tree was mentioned. Expansion of native woody
vegetation—bush encroachment—was a more significant problem because South Africa’s cattle industry
and its large game reserves (e.g. Kruger National Park)
were located predominately in the savanna biome in
the northern and eastern Transvaal (Feinstein 2005:
267). Unlike introduced tree invasions, which since
the 1940s had been recognized to occur in undisturbed
fynbos, the expansion of encroaching native trees in
savanna was explained more simply as a consequence
of improper land management, especially overgrazing
(see Walter 1971).
There was a lag in the appreciation of the biological
uniqueness and diversity of South Africa’s extensive
grasslands and coastal forests, a factor that may have
delayed appreciation of the extent and impact of
invasive trees. Compared with fynbos or savanna,
there was less of an appreciation for the aesthetics and
biodiversity of grasses (Bond and Parr 2010) and some
indigenous coastal forest types in Natal (Sundnes
2013) prior to the 1980s. Johannesburg, Bloemfontein,
and Pretoria are located in grassland, one of the least
protected and most threatened biomes in South Africa.
Durban is located in Coastal Thicket, a highly
fragmented and degraded biome. Farming and urban
expansion, particularly around Johannesburg and
Durban (Ellis 2002), caused the widespread destruction of indigenous flora.
The relative economic importance and ownership
structure of timber plantations also distinguished the
southwestern Cape from other parts of the country.
After Union in 1910 the Forestry Department shifted
its focus away from the Cape and towards higher
rainfall areas in the east and north (Bennett 2011:
277–8). The majority of South Africa’s new plantation
expansion occurred in Natal, Zululand, and the
Insights from South African history
Transvaal. Private plantations accounted for over
70 % of the plantation estate during the second half
of the century (Bennett 2010: 36). Private sector
linkages changed the dynamic of forest-based research
outside of the southwestern Cape. Forest researchers at
the Wattle Research Institute, established in 1947 at
Natal University in Pietermaritzburg, were mandated
to work closely with private wattle plantation owners.
In one instance, attempts by WRI officials to negotiate
with private owners to pursue biological control for
Acacia in the 1970s failed because owners felt it would
limit profits (Impson et al. 2009: 43). There were fewer
privately owned timber plantations in the southwestern Cape because the region’s aridity was less
conducive to fast-growing tree species. Most timber
plantations (mainly Pinus radiata) were government
owned. This fact explains why government foresters
could take the lead in studying and managing invasive
trees on government land in the southwestern Cape.
Invasive introduced trees go national
A groundswell of interest in biological invasions
blossomed in South Africa during in the late 1970s and
early 1980s as a result of the intersection of key
scientific, environmental, and cultural trends. There
was a greater nation-wide awareness that the problem
of invasive and weedy plants (native and introduced
species) seemed to be getting out of hand. For the first
time, the negative ecological impacts caused by
invasive introduced trees were seen as a national
problem rather than something that was isolated to the
Cape. Scientists met at interdisciplinary conferences
and national and international research conferences to
discuss regional problems and to theorise the ecological and biological dynamics of invasion. These
concerns reflected not only the fact that South Africa’s
environment had been reshaped by self-propogating
populations of introduced species, but also indicated a
rising tide of environmentalism and ecological consciousness that sought to stop pollution and maintain
South Africa’s biomes in pristine and wild forms.
South Africans in the 1970s and 1980s expressed
unique local variants of broader global environmental
anxieties over pollution, the destruction of rare and
fragile ecosystems, and extinction. The South African
botanists A.V. Hall and C.H. Boucher drew parallels
in 1977 between ‘‘industrial air pollution’’ and invasive Australian wattles which ‘‘polluted our vegetation
507
and our landscapes’’ (Low 2001: 165) Concerns about
pollution led many to seek to preserve South Africa’s
environment in pristine forms. The concept of ‘‘wilderness’’ permeated South African discussions of
conservation management after the First World Wilderness Conference was held in Johannesburg in 1977
(Player 1977; Hey 1995: 242–3). Conservation groups
in KwaZulu-Natal began to focus on preserving
indigenous ecosystems in their ‘‘pristine’’ indigenous
form during the early 1980s (Sundnes 2013).
A more coherent understanding of the scale of
South Africa’s invasive plant problem emerged as a
result of meetings between agricultural, forestry,
ecological, and botanical researchers at a series of
national weeds conferences held in Pretoria in 1974,
Stellenbosch in 1977, and Pretoria in 1979 and 1981.
These meetings encouraged weed researchers, who
often focused on agricultural pests and biological
control, to collaborate with researchers concerned
about invasive species in state forests, parks, and
reserves. The WEEDS conferences preceded and
informed the drafting South Africa’s Conservation of
Agricultural Resources Act, 1983 (Act No. 43). The
Act listed numerous species of Australian Acacia,
Hakea and Pinus into two categories, ‘‘declared
weeds’’ or ‘‘invader plants,’’ depending on their
impact. This was the first time many introduced tree
genera and species gained standing as national weeds.
Ecological researchers working with the Council for
Scientific and Industrial Research (CSIR) reinforced
the growing interest in South Africa’s ‘‘pristine’’
ecosystems by embarking on a major national project
to detail the essential ecological processes and structures of South Africa’s distinct vegetative biomes.
CSIR instigated the first biome-specific research
project during the 1970s in response to the IUCN’s
International Biological Program. The first multidisciplinary project, led by Brian Huntley, focused on
savanna. As a result of the success of this project, CSIR
started a fynbos project in 1977 and other projects on
grasslands (1982), forests (1985) and Karoo (1986).
From the outset, the Fynbos Biome Project paid
significant attention to how invasive plants, especially
trees, negatively impacted fynbos’ ecological functioning. The initial abstract for the Fynbos Biome
Project stated: ‘‘Particular emphasis is being devoted to
major environmental problems such as invasive plants
and the ecological effects of fire’’ (Kruger 1978: iv).
The Fynbos Biome Project sustained research on fire
123
508
and invasive introduced trees in fynbos that Frederick J
Kruger had initiated at the Jonkershoek Forest
Research Station in the late 1960s (Pooley 2012:
66–8). Researchers working at the South African
Forestry Research Institute, influenced for much of the
decade by its Deputy-Director for Conservation Forestry and then Director (1984–1990) Kruger, played a
particular important role in researching invasive species. Leading scholars of fynbos and invasion—
including William Bond, David Le Maitre, Jeremy
Midgley, Dave Richardson, and Brian van Wilgen—all
worked with SAFRI during the life of the Fynbos
Biome Project.
The Fynbos Biome Project ran parallel with a series
of Mediterranean-climate ecosystem conferences
(MEDECOS) founded by the eminent Stanford ecologist Hal Mooney in 1971. These meetings and the
comparative framework that arose from them
prompted researchers to become more concerned that
invasive species were becoming a major global
environmental problem in Mediterranean-climate
ecosystems. Interactions between Mooney and Kruger, who attended the second 1977 (Stanford) and third
1980 (Stellenbosch) meetings, helped lead to the
creation of a coherent international research program
on invasion biology. Researchers at the meeting were
struck by the density and extensiveness of pine
invasions in fynbos. As a result, Mooney and Kruger
decided to call for a ‘‘post-Elton global assessment of
the status of invasive species’’ in Mediterraneanclimate ecosystems at the upcoming 1982 Ottawa
meeting of the Scientific Committee on Problems of
the Environment (SCOPE) (Richardson 2011: xi;
Simberloff 2010: 16). At the Ottawa meeting their
proposal was ‘‘upgraded’’ to a full global investigation. This proposal was approved, and SCOPE’s
project began internationally and in South Africa in
1983. South African researchers produced a detailed
regional survey of invasion (Macdonald et al. 1986)
and contributed to the 1989 global synthesis on
invasion biology (Drake et al. 1989).
The SCOPE agenda provided a broader national
umbrella that linked together disparate provincial
research projects on weeds and invasive species,
especially trees, that started during the 1970s and early
1980s. Prior to the instigation of the SCOPE project,
researchers in Natal and the Transvaal began to survey
and map tree invasions to understand the extensiveness and impact of these invasions. In 1980, the Parks
123
B. M. Bennett
Board of Natal instigated a survey to find out the extent
to which woody vegetation had invaded Natal’s
reserves (Farrar and Kruger 1983: 12). A year earlier
researchers in the Botanical Research Institute (BRI)
began to survey invasive introduced trees in the
Transvaal. When they announced the results of their
first findings at the Third Annual Weeds Conference in
1980 they commended Cape researchers for ‘‘rightly’’
studying tree invasions in fynbos. They then noted
that, ‘‘relatively little notice has been taken of
introduced, woody invaders in other ecosystems
[outside of the Cape] in South Africa e.g. the bushveld
and grassland ecosystems of the Transvaal’’ (Wells
et al. 1979: 11).
Botanical Research Institute researchers led by
Henderson implemented the first Transvaal-wide and
nation-wide investigation into invasive plants. This
investigation was by its very design skewed towards
identifying invasive introduced trees because trees
could be more easily identified from the road than
other plant types. The BRI team completed their
survey of the Transvaal in 1982–1983. They then
surveyed Natal (Henderson 1989), the Orange Free
State (Henderson 1991a), and then the northern Cape
(Henderson 1991b), eastern Cape (Henderson 1992)
and the south and southwestern Cape (Henderson
1998) on an on-going project from 1986 to the mid
1990s. This roadside mapping eventually formed the
empirical basis for the African Plant Invaders Atlas,
created by Henderson and inaugurated in 1994 (Henderson 1995). The results of these surveys found that
fynbos was the most densely invaded biome in South
Africa, but that the savanna biome had the most
number of invasive species (in total) and grasslands
were also heavily invaded (Henderson 2007: 220).
The results of the Transvaal roadside surveys were
publicised by the government to warn Transvaal
residents about the growing threat of invasive introduced trees. In 1987, the Department of Agriculture
and Water published the public pamphlet Plant
Invaders of the Transvaal. This book was similar in
tone and content to Green Cancers (Control of Alien
Vegetation Committee 1959) and Plant Invaders:
Beautiful But Dangerous (Stirton 1978). It cautioned:
‘‘in all parts of South Africa, alien plants are gaining a
foothold of varying degrees’’ (Henderson and Musil
1987: 1) This included not only the more visible Cape
invasions, but also tree invasions in the Transvaal:
‘‘Woody alien invaders in the Transvaal, were recently
Insights from South African history
the subject of a research study which indicated that
some of the indigenous plant communities in the
northeast part of the country face invader threats
comparable to those of the more widely publicized
Cape fynbos’’ (Henderson and Musil 1987: 1–2).
Ironically, at the same time when researchers across
South Africa became aware that invasive species were
a serious national environmental problem, the national
government devolved the management of invasive
plants in catchments, South Africa’s most significantly
invaded ecosystems. Since the late 1970s foresters in
the fynbos-dominated southern and western Cape
regions had used fire to control invasive species in
catchment areas (Pooley 2012: 72). This was part of a
larger integrated catchment management strategy to
increase stream flow and conserve fynbos diversity.
As a result of budget cuts, the President’s Minute 1109
in November 1986 devolved the management of
mountain catchments away from the national to
provincial governments on 1 April 1987 (Pooley
2012: 74). Provincial governments lacked the financial
or scientific capabilities to maintain the program. They
proved unable to continue fire-management policies in
catchments. South Africa lacked a management program for controlling invasive species in catchments
until after the end of apartheid.
The establishment of Working for Water in 1995
ushered in a new era that linked introduced invasive
plant eradication programs with South African nationalism. The idea for WFW—that introduced trees use
more water than indigenous vegetation—came largely
from the findings at Jonkershoek Forest Research
Station. When the government established WFW in
1995, it also abolished continuous funding for the
Jonkershoek Research Station after its last government
contracts ran out when SAFRI became part of CSIR
and was renamed Forestek (Pooley 2012: 74).
Whereas Jonkershoek was created in 1935 to apolitically solve a major scientific and public conflict,
WFW applied knowledge gained from Jonkershoek’s
research program to pursue an explicitly political
project that linked invasive plant control with economic growth, poverty relief, and national identity.
Rather than funding invasive species control efforts
through traditional departments (e.g. forestry), WFW
was created as a poverty-relief program that focused
on eradicating invasive plants that transpire limited
water supplies in catchment areas. One of the key
aspects of WFW is that it has sought to create a form of
509
post-apartheid South African nationalism spanning the
entire country. The program was created to bring:
community development and scientists together,
involving them jointly in invasive species control and encouraging a form of nationalism that
resonates with conserving an indigenous biodiversity and promoting sustainable development
and resilient ecosystems….an attitude that
Pauly…refers to as national ‘ecological independence’ (Carruthers et al. 2011: 815).
Working for Water has indeed sought to naturalise the
nation-state, as the Comaroffs suggested, by arguing
that ‘‘alien’’ plants negatively affect South Africa’s
economy, biodiversity, and water supply while
‘‘natives’’ promote sustainable economic growth and
create positive ecological services (Comaroff and
Comaroff 2001). In a sense, the Comaroffs are correct:
a new ecological nationalism has arisen after the end
of apartheid. Though this type of nationalism developed after apartheid, it draws heavily on older popular
concerns and Cape-based scientific research.
Though there has a been a growth in scientific and
public awareness of invasive introduced trees outside
of the Western Cape Province, Cape-based institutions
and researchers still predominately shape research on
invasive species policies and research directions in
South Africa. A survey published in 2007 showed that
55 % (89 people in total) of all experts on invasive
species who lived in South Africa worked in the
Western Cape, and 84 % of them (75 people) were
located in the greater Cape Town metropole (Musil
and Macdonald 2007: 4). The second greatest concentration of expertise was located in Gauteng, where
32 experts resided (20 % of South African experts)
with 21 experts living in Pretoria and 11 living in
Johannesburg, South Africa’s largest urban population. This geographic imbalance is indicative of the
distinct yet interconnected histories of regions
described in the paper.
Conclusions
The history of how perceptions of invasive introduced
trees first arose in the southwestern Cape and spread
throughout South Africa offers fundamental insights
into how scientists and the public became concerned
about the impact of invasive introduced trees. The
123
510
rapid growth of public concerns about invasive trees
around Cape Town beginning in the 1950s was built
on pre-existing scientific concerns that were sustained
by educational efforts directed towards the construction of emotional and cultural attachments with the
surrounding flora and landscapes. Anxieties about tree
invasions in fynbos later encouraged researchers in
other parts of the country to begin investigating the
ecological impact of invasive trees in the 1970s and
1980s.
With this history in mind, it may be sensible for the
South African government to spend more money on
education and biological control and less on menial
labour meant to control invasives. Currently, 92 %
cent of WFW’s budget goes to manual labour for
clearing plants with only 3 % each going to more costefficient biological control methods (van Wilgen et al.
2012: 35) and education programs for school children,
landowners, and the public (Staff Induction Manual
2008: 17). Awareness about the problem of invasive
species should also coincide with the cultivation of
knowledge about the uniqueness of indigenous flora
and fauna. A focus on regional natures, rather than
national ones, may alleviate some of the problems—
e.g. nationalism and xenophobia—associated with
imagined national natures. Such a region-based program would fit, rather than fight, the distinct regional
cultures and ecologies that have historically constituted the nation of South Africa.
The history of invasive introduced trees in South
Africa has wider relevance for international scholars
researching the history and science of invasive
species. This article suggests that certain model
invasions (in this case, invasive trees in the southwestern Cape) disproportionately influenced scientific
researchers around the world to become concerned
about invasion more generally. Further historical
research is required to understand what other model
invasions and places contributed to the global proliferation of interest in invasive species during the 1980s
and 1990s, the founding decades for the discipline of
invasion biology. Yet from this example it is clear that
the discipline and theoretical foundations of invasion
biology developed from particular examples of invasion that arose within ecologically, geographically and
culturally unique regions. The southwestern region of
South Africa was one of the most globally significant
localities that shaped the origin of the field of invasion
biology and led to the development of modern
123
B. M. Bennett
scientific and public concerns about introduced invasive species.
Acknowledgments BMB was supported financially by the
School of Humanities and Communication Arts at the
University of Western Sydney. This paper was greatly
improved by valuable criticism from Dave Richardson and
two anonymous reviewers; any mistakes or changes are entirely
my own. I benefited from discussions with participants during
the Tree Invasions Workshop held in Bariloche, Argentina,
September 3–5, 2012. I thank Brian van Wilgen, Marcel
Rejmánek, and Frederick J. Kruger for their comments on the
manuscript. Lance Van Sittert offered valuable insights on a
visit to Cape Town in March 2013.
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