PLANTATION FORESTRY AND INVASIVE ALIEN PLANTS: SEEKING
SOLUTIONS TO THE MUTUAL BENEFIT OF THE ENVIRONMENT.
M. Mondlane*, BW van Wilgen+, and Michael Shuttleworth#
*Working for Water Programme
Private Bag X4390
Cape Town
8000, South Africa
+ CSIR Division of Water, Environment and Forestry Technology
PO Box 320, Stellenbosch, 7599, South Africa
# Working for Water Programme
Private Bag X4390
Cape Town
8000, South Africa
Abstract
About 750 tree and 8 000 other plant species have been introduced to South Africa. At
least 161 species are regarded as invasive, and they impact on 10 million hectares (8%) of
the country. Water use increases where short vegetation is invaded by alien trees, which
use an estimated 7% of the country’s runoff. Fuel loads at invaded sites are increased
tenfold, increasing fire intensities and causing soil damage, increased erosion and
decreased germination from indigenous seed pools. South Africa has unusually high
levels of biodiversity, and alien plants could eliminate several thousand species of plants
if spread is not controlled, seriously affecting the delivery of ecosystem services.
Economic impacts have not been well studied, but the impact of alien plants on water use
alone justifies intervention. South Africa has been fortunate in being able to raise
significant funding for control programmes through a combination of economic argument
and strong political support, but conflicts of interest with the forest industry and other
users of plant products need to be resolved.
Some of the possible approaches to avoid conflict include recognising the value of a
vibrant forest industry and actively managing the spread of plantation trees; using noninvasive species wherever possible, or ensuring that biocontrol is introduced at the start
of new agroforestry projects; using biocontrol to reduce the invasive potential of
otherwise useful species without killing them (for example, by reducing the number of
seeds they produce); recognizing potential invaders early and taking precautionary
measures; and educating people as to the dangers and costs of invasive species.
Plantation forestry is an important part of the South African economy, contributing
US$300 million, or 2%, to the GDP and employing over 100 000 people. Downstream
industries, based on forestry, produce timber products worth a further US$1.6 billion,
much of which is exported, earning valuable foreign exchange. Clearly, these activities
are significant. However, a large proportion (38%) of the area invaded in South Africa is
occupied by species used in commercial forestry (especially Pinus and Acacia species).
It is thus clear that forestry has been one of the country's major sources of alien
infestation.
This apparent conflict should be avoided through a responsible approach to forestry. The
forest industry is committed to an environmental code of conduct that includes the
management of the spread of alien plants on their estates and beyond, and that seeks to
minimise the negative impacts of their activities on the environment. Modern and more
recent forestry developments have been carried out in a very responsible way. However,
there is a backlog in older established areas that is going to require dedicated attention if
the problem is to be solved.
The Working for Water Programme has recently concluded an agreement for
collaborating in order to address these issues. This paper outlines the history of the
approach, which was initially characterised by suspicion, but has reached a level of
collaboration that should work to the mutual benefit of all parties concerned.
Introduction
Natural forests in southern Africa are surprisingly limited in their extent. Areas that
receive in excess of 800 mm of rainfall annually, at altitudes below 2000 m, are covered
by grasslands or shrublands, while similar areas in other parts of the world would support
natural forests (Holdridge et al., 1971; Schulze and McGee, 1978). One of the main
reasons for this disparity is repeated fires which prevent the establishment of forest
species (Moll et al., 1980; Manders, 1990; Manders and Richardson, 1992). In areas
which are sheltered from regular fires, forests can and do develop (Geldenhuys, 1994),
and forests tend to have fuel properties that do not promote fire (van Wilgen et al., 1990),
ensuring their survival in the fire-prone landscape. Nonetheless, natural forests in
southern Africa cover less than 0.25% of the landscape (Low and Rebelo, 1996; Midgley
et al., 1997).
The lack of a natural source of fast growing timber trees led to the establishment of
plantations of alien (introduced) species, beginning in the late 19th century (King, 1943;
Le Maitre, 1998a). Plantations of alien trees, primarily pines and eucalypts, now cover
1.52 million ha in South Africa (FOA, 1998). These plantations have brought many
benefits. Plantation forestry contributes US$300 million, or 2%, to the GDP and employs
over 100 000 people. Downstream industries, based on forestry, produce products worth
a further US$1.6 billion, much of which is exported, earning valuable foreign exchange
(FOA, 1998).
However, the establishment of these plantations has not been without cost. The negative
impacts of afforestation include significant reductions in surface streamflow (Van Lill et
al., 1980; Bosch and Hewlett, 1982; Bosch and von Gadow, 1990). Commercial
plantations are estimated to have reduced surface runoff by about 1.4 billion m 3 per year
or 3.2%, at a national scale (Le Maitre et al., 1997; Scott et al., 1998a). These reductions
are important because South Africa has a mean annual rainfall of only 490 mm and less
than 10% of this becomes surface runoff (Alexander, 1985). Commercial plantation
forestry is the only land-use which is restricted because its impacts of afforestation on
streamflow (van der Zel, 1995). Plantations also have substantial impacts on biodiversity
and the functioning of natural ecosystems (Armstrong and van Hensbergen, 1996; Allen
et al., 1997).
The National Water Act recognises that a portion of the available water needs to be
reserved for basic human needs and to sustain natural ecosystems; this places additional
constraints on the water available for other uses (Anon, 1970; DWAF, 1986; Walmsley
and Davies, 1991; DWAF, 1996). Water is the primary resource that will ultimately limit
development in South Africa and efficient management and allocation of water resources
is a national imperative (DWAF, 1996).
Unfortunately, many of the plantation species have become major invaders, spreading the
negative impacts far beyond the afforested areas. Foremost amongst these are several
species of pine (Pinus) and wattle (Acacia). The forestry industry recognises these
problems and subscribes to a code of conduct which, among other things, requires that
riparian zones and non-afforested areas within the forest estates are kept clear of invading
alien plant species (FIEC, 1995). The forest industry has also recognised that the impacts
of plantation trees on streamflow are far greater in the riparian zone than outside it (Scott
and Lesch, 1995; Scott, 1999a), and follow a policy of non-afforestation of such zones
(FIEC, 1995). The industry also actively supports the government’s alien plant control
programmes by funding control operations, providing expertise and forming partnerships
with Working for Water.
Commercial forestry based on alien trees is a well-established feature of the South
African landscape and economy, but the invasions that are associated with it are going to
have to be managed to minimise conflicts around scarce resources, especially water.
Studies to quantify the relative benefits of clearing have been carried out in the Western
Cape Province, where mountain catchment areas covered with fynbos shrublands have
been invaded by pines and wattles (Le Maitre et al., 1996; van Wilgen et al., 1996, 1997).
These areas are subjected to fires at about 15-year intervals; the fires trigger the spread of
alien trees, initially from adjacent plantation areas, and subsequently from invaded areas
in the catchment.
As the problem of invasive alien trees and their impacts was not restricted to the Western
Cape Province (Henderson, 1995; Dye and Poulter, 1995), a study was commissioned to
estimate the predicted impact on a national level. This study found that about 10.1 million
hectares, or 6.8% of South Africa has been invaded to some degree (Versfeld et al.,
1998). These invasions were estimated to be using almost 6.7% of the country’s runoff,
and would cost an estimated US$ 0.86 billion to clear over 20 years (Le Maitre et al.
2000). While these results were based on very crude estimates of the extent of invasion
they were nonetheless convincing enough for the national government to launch an
extensive and ambitious control programme (the Working for Water programme) aimed
at minimising the effects on water resources (van Wilgen et al., 1998).
In this paper, we review the sources of conflict between forestry and the environmental
impacts of invasive plants, and explore possible solutions to the problems. We present
information from South Africa to illustrate how the conflicts, which were acrimonious to
begin with, have been resolved through agreement on a partnership to the mutual benefit
of both parties. We also explore future challenges to this approach.
Sources Of Conflict
Plantation forestry in South Africa is a form of landuse that replaces pristine ecosystems
and impacts on biodiversity and streamflow; it is also a source of invasive trees that
spread and cause impacts beyond the borders of plantations. Both of these aspects lead to
conflicts of interest (Johns 1993; Celliers 1994). In the first place, the fact that forestry
plantations use significant amounts of water have been used by government to restrict
planting, in order to save water. The forest industry often feels that it has been singled out
for “special” treatment, as other forms of land use have not been subject to the same
restrictions, mainly because their impact on water resources is not that clearly
understood. Added to this, the fact that many of the species used by forestry are invasive
has added a new source of potential conflict. Regulations are currently being drafted to
hold growers responsible for containing the spread of invasive species, while growers
themselves point out that they are not the only source of invasive trees (which have been
and still are planted in many areas by people with other interests, including the
government itself).
These conflicts have to be dealt with in a sensitive manner if progress is to be made in
reducing the significant negative impacts of invading alien plants. Some of the possible
approaches to avoid conflict in South Africa include recognising the value of a vibrant
forest industry and actively managing the spread of plantation trees; making allowance
for well-managed woodlots in areas where fuelwood is scarce, using non-invasive species
wherever possible, or ensuring that biological control is introduced at the start of new
agroforestry projects; using biological control to reduce the invasive potential of
otherwise useful species without killing them (for example, by reducing the number of
seeds they produce); recognizing potential invaders early and taking precautionary
measures; educating people as to the dangers and costs of invasive species; and
encouraging the use of alternative, non-invasive species for ornamental and utilitarian
purposes.
The biological control of species with commercial potential warrants special mention
when considering potential conflicts of interest. Historically, 103 biological control
agents have been released in South Africa against 46 weed species (almost all of them
non-commercial species). Of these, 22 weed species are now under complete or
substantial biological control (Olckers and Hill 1999). It is hoped to build on these
successes, and South Africa’s biological control research programme has been expanded
to include some species (e.g. Acacia and Pinus spp.) that were previously excluded from
research because of their commercial value (Stubbings 1977; Pieterse and Boucher 1997).
In such cases, the approach would be to introduce control agents that reduce seed output
(and therefore invasive potential) without impacting on the growth potential of the plant.
This has been done for several species already, notably Australian Acacia species. The
total cost of the biological control research initiative between 1997 and 2000 was US$ 3
million. Indications are that these activities represent unprecedented returns on
investment.
Possible solutions and approaches.
The forest industry is committed to an environmental code of conduct that includes a
commitment to sustainable timber production, and protection of the environment. In
addition, some companies in the South African forest industry have obtained certification
of their products by the Forestry Stewardship Council (FSC). FSC certification is
necessary when selling forestry products into certain markets, but it requires that the
environmental practices of the companies concerned are certified by independent
evaluators. Modern and more recent forestry developments have been carried out in a
very responsible way, as a result of external pressures for environmental responsibility,
the need for certification, and the need to comply with the law. However, while more
recent plantings have been done in accordance with regulations requiring riparian zones
to be kept clear of trees in order to reduce the negative impacts on streamflow, there is a
backlog in older established areas that is going to require clearing if the minimum
standards are to be met. The clearing of a backlog of riparian areas planted to alien trees
will mean a sacrifice of timber and additional costs, and these need to be covered.
FSC certification also requires that companies comply with FSC principles. Principle
10.8 states that “…no species should be planted on a large scale until local trials … have
shown that they are ecologically well-adapted to the site, are not invasive (our italics),
and do not have significant negative ecological impacts on other ecosystems. The fact
that South African forestry companies have obtained certification despite the clearly
invasive characteristics of the trees that they plant indicates that evaluators have taken a
very accommodating view of this principle. Nonetheless, the pressure from
environmental groups for forestry companies to deal with invasive trees will mean that
means for dealing with this issue will need to be found.
The South African government is considering legislation which will allow growers to
continue to plant invasive trees in order to produce timber, but which will require them to
share in the costs of clearing invasions of the species concerned on neighbouring
properties. Biological control, which reduces the invasive potential of the trees
concerned, may be one way of dealing with this problem (as mentioned above).
Introducing biocontrol at the same time as new plantation or woodlot species, would also
be a way of reducing the risk of unwanted invasions. Nonetheless, practical solutions to
the actual implementation of theses options, and to the equitable sharing of costs, still
need to be explored.
Case study: a partnership between Working for Water and the Forest Industry
The potential for conflicts of interest to develop between the forest industry on the one
hand, and those charged with nature conservation and alien plant clearing programmes on
the other, is obvious in the South African context. However, these conflicts have largely
been avoided through a common commitment to finding lasting solutions to the problems
of forestry and invasive alien plants. The forest industry have formed a partnership with
the government’s Working for Water programme, with the stated intention of developing
a relationship, based on collaboration, integrity, and a shared vision to enhance (i) the
control of invading alien species; (ii) the utilization of local communities in such
activities; (iii) the sustainable management of the country’s natural resources; and (iv)
best management practices.
In terms of the agreement, the forest industry has seconded a senior forester to the
Working for Water programme, to provide additional capacity in the evaluation of safety
standards, clearing standards, and planning with a view to improving efficiency. In
addition, the forest industry will assist with training of Working for Water personnel, and
with mapping and data capture onto GIS. In addition, the forest companies will make
various facilities or services (such as storage facilities, sporting, crèche or clinic facilities,
transport or supervision capacity) available to Working for Water teams in the field. In
return, the Working for Water programme has undertaken to fund the clearing of
demarcated areas (including riparian zones planted up prior to legal requirements that
outlawed such plantings). It will also ensure that the forest industry’s efforts with regard
to clearing invading alien plants are publicized, and that it will work closely with industry
to develop equitable legislation to govern the forest industry.
The agreement marks a significant repositioning away from earlier stances which had the
potential to develop into protracted conflicts over management approaches. It also
represents a significant commitment by both industry and government to finding lasting
solutions to serious environmental problems associated with forestry practices.
Future challenges.
The above approaches are still in their infancy in South Africa, and will need to be
developed in order to find sustainable and practical solutions to the problems of invading
alien plants that often accompany large-scale afforestation using alien trees. These
problems are often not recognised when the pressing need for economic development is
addressed by initiating new afforestation schemes, both in South Africa and elsewhere on
the continent of Africa or even further abroad. The success of the partnership between
industry and government should be closely watched. Should it succeed, it could provide a
role model for similar approaches elsewhere in the world.
Acknowledgements
We thank Mondi Forests, and the Department of Water Affairs and Forestry (through the
Working for Water programme, for funding this paper.
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