The indigenous knowledge of the local community towards weeds and alien invasive plants in the Dinokana area, North-West Province, South Africa

THE INDIGENOUS KNOWLEDGE OF THE

LOCAL COMMUNITY TOWARDS WEEDS AND

ALIEN INVASIVE PLANTS IN THE DINOKANA

AREA, NORTH-WEST PROVINCE, SOUTH

AFRICA.

By

KEBALEPILE BENEDICT ITHOLENG,

Dissertation submitted in fulfilment of the requirements for

the degree in M. Environmental Science in the School of

Environmental Science and Development: North-West

University (Potchefstroom Campus).

Supervisor: PROF. KLAUS KELLNER Co-Supervisor: DR. LUKE SANDHAM

POTCHEFSTROOM

ABSTRACT

The study was u n d e r t a k e n to determine the indigenous knowledge of the local community of the Dinokana Area, including t h e perception a n d attitude towards the declared weeds a n d alien invasive p l a n t s (WIP). The study w a s conducted in the following villages in the Dinokana Area, namely: Dinokana, Borothamadi, Mantsie, Maramage, Ntsweletsoku, Madutle, Matlhase, Ikageleng a n d Khunotswana. These villages are situated in the district of Lehurutshe within the Ramotshere Moiloa Local Municipality of the North West Province in the Republic of South Africa. The following two m e t h o d s were used, namely: a questionnaire a n d a vegetation survey. There were 100 questionnaires, which were divided on the basis of the size of the population per village. Vegetation surveys were done at Maramage a n d D i n o k a n a Villages. Belt t r a n s e c t s of 160m2 a n d 80m2 were u s e d

to carry out the vegetation sampling. The woody components were recorded according to species type, height classes a n d Tree Equivalent (TE) were calculated through predetermined factors for each height class. The other seven villages were m a p p e d mainly for the individual tree species. The results of the questionnaire indicated a fair knowledge of the occurrences of the declared weeds a n d alien invasive species in the area with some u s e s of these plants, s u c h a s roof construction. Approximately 56% of the r e s p o n d e n t s were females a n d the rests were males. Most of the participants were y o u t h (31%), who were less t h a n 25 years old a n d 27% were of the age between 26 a n d 36 years a n d only 4% of the people were older t h a n 70 years. 4 5 % of the r e s p o n d e n t s h a d Grade 8 to 12 while only 9% have higher education qualifications, s u c h a s Diploma or a degree. The majority of the people were unemployed (69%). The vegetation survey indicated t h a t there were more Populus canescens t h a n other plant species. Approximately 9.4 h a of the land in Maramage Village were invaded by Populus canescens. The predominant height classes in t e r m s of Tree Equivalent per hectare (TE/ha) w a s 2 to 3 meters with a density of 3 4 0 7 3 T E / h a , followed by trees of more t h a n 4 m e t e r s with a density of 6 1 6 8 7 T E / h a .

In the Dinokana Village, the most prominent species w a s mainly Opuntia imbricata. Other species identified were Melia azedarach a n d Lantana camara. These r e s u l t s were compared with the outcome of the questionnaire. The indigenous knowledge rated most of the p l a n t s a s moderate to heavy infestation (Figure 5.5). Capacity building, awareness raising a n d co-ordination amongst different Government D e p a r t m e n t s should be e n h a n c e d in order to encourage government efforts.

OPSOMMING

Die studie w a s uitgevoer om die inheemse k e n n i s van die plaaslike gemeenskap van die Dinokana gebied te bepaal ten opsigte van onkruid en indringerplante, asook hulle persepsie en houding in die verband. Die studie w a s in nege gemeenskappe uitgevoer, nl., Dinokana, Borothamadi, Mantsi, Maramage. Ntsweletsoku, Madutle, Matlhase, Ikageleng, en Khunotswana. Twee metodes naamlik, 'n vraelys en 'n plantegroeiopname is gebruik. Honderd vraelyste is gebruik wat volgens die grootte van die inwoners per gemeenskap verdeel is. Die plantegroeiopname was in Maramage en Dinokana gemeenskappe gedoen. 'n

Lyntransek van 160m2 en 80m2 was gebruik vir die neem van

plantegroeimonsters. Die houtagtige spesies w a s volgens spesie, hoogte en bos-ekwivalent m e t 'n voorafbepaalde faktor vir elke hoogteklas gedoen. In die ander sewe gemeenskappe was 'n k a a r t opgestel wat hoofsaaklik die individuele boomspesies a a n d u i . Die uitslag van die vraelyste het aangedui d a t d a a r 'n "redelike" k e n n i s van die voorkoms van onkruid en indringerplante in die gebied b e s t a a n , wat ook enkele gebruike soos d a k k o n s t r u k s i e s ingesluit het. Ongeveer 56% van die respondente was vroulike en die res manlik. Die meerderheid (31%) van die vraelyste is deur persone jonger a s 25 j a a r voltooi, terwyl 27% t u s s e n 26 en 36 j a a r oud was. Slegs 4% van die inwoners wat die vraelys voltooi het was bo die ouderdom van 70 jaar. Van die respondente inwoners w a s slegs 9% in besit van 'n hoer onderwys kwalifikasie, soos byvoorbeeld 'n diploma of 'n graad. Vyf en veertig p e r s e n t (45%) van die inwoners w a s slegs in besit van 'n graad 8 tot graad 12 kwalifikasie. Die meerdereheid (69%) van die r e s p o n e n t s w a s werkloos. Die plantegroeiopname het aangedui d a t Populus canescens die mees dominante spesies is en het 9.4 h a van die veld in die Maramage gemeenskap ingeneem het. Die mees prominente hoogteklasse w a s 2 tot 3 meter (34073 B E / h a ) en ook tot 4 meter (61687 B E / h a ) in terme van die Boom Ekwivalent per hektaar (BE/ha). Opuntia imbricata w a s die mees opvallende spesies in Dinokana. Ander plant spesies naamlik Melia azedarach en Lantana camara is ook geidentifiseer.

Die resultate is vergelyk met die uitslag van die vraelys. Volgens inheemse kennis is die meeste van die plantgroei van gemiddeld tot dig gegradeer (Figuur 5.5). Die samewerking, gewaarwording en koordinasie t u s s e n verskillende regeringsdepartemente moet verbeter word.

Sleutelwoorde: Waarneming, verklaarde onkruide en vreemde indringerplante

(Dedication.

I would li^e to dedicate this study to the two most important people in my life, Being my mother, Mrs. IthoLeng Merriam. Mother, you have never had time to learn as much I did But you never deny me the opportunity to learn, even though you did not have anything to assist me with to go thus far. Secondly, this study is dedicated to my one and only daughter, <Reatlegile IthoLeng. (Rea, this I would like it to serve as an example of what your father would wishyou to Become in life, someone out of nothing!'.!

A c k n o w l e d g e m e n t s

I w o u l d like to e x p r e s s m y s i n c e r e g r a t i t u d e and a p p r e c i a t i o n s to the f o l l o w i n g p e r s o n s :

P r o f e s s o r K l a u s K e l l n e r and D r . Luke S a n d h a m , b e i n g m y study l e a d e r s , y o u h e l p e d m e v e r y m u c h and g u i d e d m e all the w a y . A l t h o u g h the road w a s n o t that easy b u t y o u took m e far and n o w I c a n see the road c l e a r l y .

P r o f e s s o r F a a n s S t e y n , y o u b e c a m e m y h e l p e r in d a t a i n t e r p r e t a t i o n and a n a l y s i s , y o u w e r e a l w a y s t h e r e w h e n I w a s in n e e d of y o u .

I t a k e the o p p o r t u n i t y t o thank the D e p a r t m e n t of A g r i c u l t u r e for t h e i r time and f i n a n c i a l s u p p o r t , as w e l l as its p o l i c i e s on e m p o w e r i n g e m p l o y e e s .

I w o u l d like to thank m y w i f e for u n d e r s t a n d i n g w h i l e I w a s sharing m y t i m e b e t w e e n w o r k and s t u d i e s , and n o t h i n g for h e r . Say t h a n k s to m y f r i e n d s for s t a n d i n g b y m y side for t h e i r support and m o t i v a t i o n s as well as g u i d a n c e , and e s p e c i a l l y to M r . M a m p h o l o , w h o m o t i v a t e d m e to p u r s u e w h e n I t h o u g h t I c o u l d n ' t m a k e it.

H o w c a n I forget m y m o t h e r and the e n t i r e f a m i l y . M o t h e r , y o u m a y n o t h a v e b e e n to a n y formal e d u c a t i o n , b u t y o u g o t c o u r a g e to e n c o u r a g e m e and b e b y m y side all the w a y . W e d i d n ' t h a v e m u c h b u t y o u m a n a g e to p u l l t h r o u g h for u s . . Let m e a l s o thank m y late c o u s i n , T s h i p a D a v i d M o n t s h i o a g a e , I w i s h y o u w e r e h e r e to see m e f i n i s h i n g w h a t w e b o t h s t a r t e d . T h e y e a r 1985 u n t i l 1989 w e r e n o t e a s y , b u t y o u took m e as y o u r c h i l d , t h a n k s and G o d w i t h his a n g l e s b e w i t h y o u w h e r e v e r y o u a r e .

TABLE OF CONTENTS PAGES Abstract i Opsomming iii Dedication v Acknowledgement vi Table of c o n t e n t s vii List of Figures xii List of Tables xvi Appendices xvii

CHAPTER 1: INTRODUCTION AND PROBLEM STATEMENT

1.1 Declared weeds a n d alien invasive p l a n t s 1

1.2 Government intervention 2 1.3 Community r e s p o n s e s to government intervention 3

1.4 Preliminary study 5 1.5 Aim of t h e study 6 1.6 Layout of dissertation 6

CHAPTER 2: LITERATURE REVIEW

2.1 Conservation of Agricultural Resources Act (No 4 3 of 1983) 8 2.2 Invasion process of declared weeds a n d alien invasive p l a n t s (WIP) 10

2.3 Results of the d i s t u r b a n c e of declared weeds a n d alien invasive p l a n t s

(WIP) 12 2.3.1 Impacts on the functioning of riparian a r e a s 15

2.3.2 Economic loss 16 2.3.3 Biodiversity loss 18 2.3.4 Land degradation 21

2.3.4.1 Natural c a u s e s of land degradation 21 2.3.4.2 Direct c a u s e s of land degradation 2 3

(a) Overgrazing 23 (b) Soil degradation 26 (c) Deforestation 27 (d) Over-exploitation 28

(e) Fire 29 2.3.4.3 Indirect c a u s e s of land degradation 30

(a) Land t e n u r e 30 (b) Poverty a n d population growth 30

2.3.4.4 Fragmentation of the l a n d s c a p e 35 2.3.5 Indigenous knowledge system, perception a n d attitudes of the local

people 37

2.4 Management of declared weeds a n d alien invasive p l a n t s (WIP) 40

2.5 S u m m a r y for literature review 4 5

CHAPTER 3 : THE STUDY AREA

3.1 Location of the s t u d y area 46

3.2 Natural Vegetation 49 3.3 Geology a n d soil of t h e area 52

3.4 Climatic condition 54 3.5 Infrastructure a n d development in the study area 56

CHAPTER 4: MATERIALS AND METHODS

4.1 Indigenous knowledge sampling 57

4.2 Vegetation sampling 59 4.3 Data analysis 61

4.3.1 Indigenous knowledge, perception a n d attitudes of the people

interviewed 6 1 4.3.2 Vegetation d a t a analysis 62

CHAPTER 5: RESULTS AND DISCUSSION

5.1 Introduction 6 3 5.2 Population demography 6 3

5.2.1 Age classes 6 3 5.2.2 Level of education 64

5.2.3 Occupation 65 5.3 Indigenous knowledge of the declared weeds a n d alien invasive p l a n t s (WIP)

in the local community 67

5.4 Problems with plant identification 74 5.5 Attitude of the local community towards the control of the declared weeds

a n d alien invasive p l a n t s (WIP) ...75

5.5.1 Use of land .76 5.5.2 Control of WIP 76 5.6 Support by the Department of Agriculture for the control of WIP.... 78

5.6.1 D e p a r t m e n t of Agriculture subsidy scheme 79

5.6.2 Government WIP programs 8 1 5.7 The density of WIP in the study a r e a 84

5.7.1 Introduction 84 5.7.2 Maramage Village 84

5.7.3 DinokanaVillage ....88 5.8 Comparison between qualitative a n d quantitative d a t a 92

5.9 S u m m a r y 94

CHAPTER 6: CONCLUSION AND RECOMMENDATIONS

6.1 Introduction 96 6.2 Perception a n d attitudes of t h e indigenous knowledge 96

6.3 Comparison of vegetation survey with perception a n d attitudes of the

indigenous knowledge 99 6.4 Recommendation 99

LIST OF FIGURES

PAGES

Figure 2 . 1 : An example of a category one plant, Opuntia imbricata in Dinokana

Area 9

Figure 3 . 1 : A m a p indicating t h e location of t h e North West Province in South

Africa (ArcView/GIS, 2007) 46

Figure 3 . 2 : The location of the Dinokana Area in the Ramotshere Moiloa Local

Municipality of t h e North West Province (ArcView/GIS, 2007) 47

Figure 3 . 3 : Population distribution for Dinokana Area per village (Statistics

South Africa, 2001) 48

Figure 3.4: Number of h o u s e h o l d s per community studied in the different

villages (Statistics South Africa, 2001) 49

Figure 3 . 5 : Sourish mixed bushveld (Veld Type 19; Acocks, 1988) in t h e

Dinokana Area 50

Figure 3.6: Geology a n d soil for the s t u d y a r e a (ArcView/GIS,

2007) 53

Figure 3.7: Average monthly rainfall a n d s t a n d a r d deviation for Ramotshere

Moiloa Local Municipality from 1960 until 2007 (ARC,

2007) 55

Figure 4 . 1 : The problem of Lantana camara (a) a n d Eucalyptus species (b) at the

school in the Dinokana Village 59

Figure 5 . 1 : Age distribution of r e s p o n d e n t s in Dinokana Area on knowledge of

declared weeds a n d alien invasive p l a n t s 64

Figure 5.2: Education s t a t u s of t h e r e s p o n d e n t s interviewed (%) on their

knowledge of declared weeds a n d alien invader p l a n t s in t h e

D i n o k a n a Area 6 5

Figure 5 . 3 : Different occupations of t h e local community interviewed (%) on

their knowledge of declared weeds a n d alien invader p l a n t s in the

Dinokana Area 66

Figure 5.4: The indigenous knowledge of the local community (%) regarding

different species of p l a n t s u s e d in the study 68

Figure 5.5: Ratings of the degree of occurrences of the declared weeds a n d alien

invasive species by the local community (% of respondents) in the

Dinokana Area 70

Figure 5.6: People from the village of Borothamadi fetching Populus canescens

for roof constructions 75

Figure 5.7: Factors t h a t contribute to lack of commitment by the local

community in controlling t h e declared weeds a n d alien invasive

Figure 5.8: Response of t h e local community regarding the u s e of different

control m e t h o d s for declared weeds a n d alien invasive

p l a n t s 78

Figure 5.9: The r e s p o n s e regarding the a m o u n t of money t h a t the people are

willing to contribute for the p u r c h a s i n g of the herbicide 79

Figure 5.10: Respondents willingness to volunteer in the control of declared

weeds a n d alien invader p l a n t s 80

Figure 5 . 1 1 : Respondents perception towards the roles of the three s p h e r e s of

Government in t h e control of the declared weeds a n d alien invader

p l a n t s 8 1

Figure 5 . 1 2 : R e s p o n d e n t s (%) knowledge with regard to the different programs

u s e d to control declared weeds a n d alien invader p l a n t s 82

Figure 5 . 1 3 : Two plots at Maramage Village where vegetation sampling of Populus

canescens w a s carried out 85

Figure 5 . 1 4 : Densities (TE/ha) of Populus canescens a n d Melia azedarach for

different height classes (m) for Sample No 2 in the Maramage Village

(right h a n d side of the road) 86

Figure 5.15: Densities (TE/ha) of Populus canescens for different height classes

(m) for Sample No 1 at Maramage Village (left h a n d side of the

road) 87

Figure 5 . 1 6 : Map showing ten (10) sites where vegetation monitoring was carried

out a n d WIP identified within t h e Dinokana Village 88

Figure 5.17: Map showing two (2) sites where the densities of only the d o m i n a n t

WIP species were established (survey 5 a n d 6) in the Dinokana

Village 90

Figure 5:18: The density of Populus canescens a n d Lantana camara (TE/ha) for

different height classes for survey site 5 in the Dinokana

Village 91

Figure 5 . 1 9 : The density of Populus canescens for different height classes for

survey site 6 in the Dinokana Village 92

LIST OF TABLES

PAGES

Table 3 . 1 : The principal trees a n d grass species of the sourish mixed bushveld

type No 19 (Acocks, 1988) 51

Table 4 . 1 : An example of a Table u s e d to record the density at different height

classes of the trees in the study a r e a 61

Table 5 . 1 : Ratings of t h e degree of occurrences of different species of WIP by the

local community in the Dinokana Area 69

Table 5.2: The rate of infestation of all WIP species at the different sites sampled

in t h e Dinokana Village 8 9

APPENDICES

APPENDIX A: QUESTIONNAIRE FOR THE INDIGENOUS KNOWLEDGE OF

THE LOCAL COMMUNITY TOWARDS WEEDS AND ALIEN INVASIVE PLANTS IN THE DINOKANA AREA, NORTH-WEST

PROVINCE, SOUTH AFRICA ...110

APPENDIX B: SAMPLES OF THE PICTURES OF SOME OF THE WIP

IDENTIFIED IN THE STUDY AREA 122

APPENDIX C: NAMES OF DECLARED WEEDS AND ALIEN INVADERS WITH

THEIR CATEGORIES, Henderson (2001) 125

CHAPTER 1

INTRODUCTION AND PROBLEM STATEMENT

1.1 Declared w e e d s and alien invasive plants

Declared weeds a n d alien invasive p l a n t s (WIP) are regarded a s non-natives or exotic p l a n t s whose introduction c a u s e or is likely to cause h a r m to the economy, the environment or to h u m a n health (Abrahams, 2 0 0 3 ; Evans, 2003). They are introduced intentionally or accidentally by h u m a n activities into regions in which they did not evolve (Abrahams, 2003).

These p l a n t s have become a world-threatening problem regarding the sustainability of the ecosystem, biodiversity a n d the integrity of species, water availability a n d the aesthetic value of n a t u r a l a r e a s (Barnard & Newby, 2003). According to B a r n a r d a n d Newby (2003), the occurrence of WIP in the country h a s serious implications for water availability a s these p l a n t s u s e u p to 7% of the available soil water annually.

It also reduces the a m o u n t of runoff towards s t r e a m s a n d rivers, a n d contributes to the reduction in diversity a n d cover of indigenous plant species. Animal diversity is also altered significantly (Meyer et al. 2002). Some WIP have dominated a r e a s to the extent t h a t n a t u r a l vegetation h a s almost been lost (Meyer et al. 2002). While the government a n d scientists warn t h a t the invasive p l a n t s pose a multibillion r a n d threat to the local economy m a n y South Africans are still ignorant towards the problem (Richards, 2003). In the North-West Province, WIP have invaded a b o u t 400 000 h a of land, which is 0.005% of the total of 7991 million ha. This r e p r e s e n t s only 3.9% of the total a r e a of land in South Africa invaded with WIP, b u t Meyer et al. (2002), warned t h a t although WIP are presently not perceived a s a priority in the North-West Province, they are being perceived a s a greater problem in the commercial t h a n in the c o m m u n a l a r e a s . WIP are also reported to be the major contributor to land degradation (Meyer et al. 2002).

1.2 Government i n t e r v e n t i o n

The government introduced legislation to regulate control a n d m a n a g e m e n t of these plants. The responsibility for the implementation of this legislation is scattered through various Government Departments, which sometimes m a k e s it difficult for the laws to be enforced. In dealing with the problem of controlling declared weeds a n d alien invasive p l a n t s (WIP), the important laws include, a m o n g others: t h e Conservation of Agricultural Resources Act (No 4 3 of 1983) or CARA, (South Africa, 1984) the National Water Act (No 36 of 1998) (South Africa, 1998), the National Environmental Management Act or NEMA (No 107 of 1998) (South Africa, 1998), a s well a s the Environment Conservation Act (No 7 3 of 1989) (South Africa, 1998) or ECA.

These acts stipulate t h a t the occurrences of these p l a n t s in any area in the Republic of South Africa are to be controlled a n d that, whenever a development is considered, it is important to indicate the occurrence of WIP and to take the necessary action to prevent t h e m from spreading. In this study, CARA is u s e d more often, a s it deals directly with ensuring the proper m a n a g e m e n t of the n a t u r a l agricultural r e s o u r c e s where the impacts of the WIP are most prevalent.

CARA requires t h a t every landowner should control the declared weeds a n d alien invaders (WIP) on h i s / h e r farmlands. In order to support a n d make it possible for this objective to be achieved, the government introduced some intervention m e c h a n i s m s such a s the Working for Water (WfW) program of the Department of Water Affairs a n d Forestry (DWAF), a s well a s the weed scheme and the Land Care program of the National Department of Agriculture (2001). These programs are there to e n s u r e t h a t there is a plan to m a n a g e the problem of declared weeds a n d alien invasive p l a n t s .

1.3 C o m m u n i t y r e s p o n s e s t o government intervention

Despite the government intervention through the Acts a n d the programs a s outlined above, it a p p e a r s t h a t various communities are not taking sufficient ownership of the problem. This is t h e biggest challenge for various d e p a r t m e n t s , especially the D e p a r t m e n t s of Agriculture a n d Water Affairs a n d Forestry a s they have different focuses. The a t t i t u d e s a n d perception of the people prevent t h e m from becoming p a r t of the solution to t h e problem. According to Schermerhorn et

al. (2000) perception is referred to a process whereby the people select, organise, interpret, retrieve a n d respond to the information from the world a r o u n d them. It can also be regarded a s a w a r e n e s s a n d concern (Dembele, 2006). Attitude is said to be more universal a n d therefore the perception formed within one's mind is more on a personal, cultural disempowerment level t h a n on a level of t e m p e r a m e n t or style (Huysemen, 1994). The local community is blamed for poor m a n a g e m e n t of the n a t u r a l r e s o u r c e s leading to degradation of the land which eventually exacerbates the invasion of WIP.

This blaming of the people, especially by outsiders, is b a s e d on beliefs a n d not on long-term empirical d a t a (Dembele, 2006). Richards a n d Dean (1998) indicated t h a t the c a u s e s of conflicting behaviour include lack of knowledge of p l a n t s of the local community, inadequate enforcement of the existing policies a s well a s the inability to predict which p l a n t s will be invasive.

According to McNeely (2003) ecologists have recently brought the problems of WIP

to the world's attention while Evans (2003) indicated t h a t this problem h a s intensified within the last few years, making it a serious challenge to global trade. Despite the fact t h a t the problem of declared weeds a n d alien invader p l a n t species is regarded to be a s serious, with negative implications for the environment, a n d also despite the legislation a n d the programs t h a t the government h a s introduced, t h e problem of WIP still exists on tribal, commercial a s well a s municipal lands.

The community h a d limited knowledge a b o u t the programs (i.e. Working for Water a n d Land Care) programs, which are available to assist communities in managing WIP problems. There is a clear indication t h a t these programs are not easily accessible to the communities. One of t h e r e a s o n s for not implementing the programs is t h a t there is no ownership of the land, a s indicated during a personal conversation with J o r d a a n1 (2004). Another reason from WfW a s highlighted

during a personal conversation with Roodt2 (2003), is t h a t there w a s some

interference from t h e tribal authority a s they w a n t t h e local people to be employed by the WfW program.

Roodt (2003) indicated that, a p a r t from interference by the tribal authority, there was no warm welcome to the tribal land. The reason for the interference w a s mainly d u e to t h e fact t h a t the community wanted the WfW to adopt its own procedures by indicating specific n u m b e r of people to be employed by the project. The WfW program w a s introduced in the Dinokana area, which d e p e n d s on contractors, some of which are not from the Dinokana area. This c a u s e d the people to resent the WfW plan to control WIP in their area. This resistance led to the withdrawal of t h e program (Roodt, 2003).

In the context of a participatory rural approach, some c a u s e s of failure include inappropriate development, poor u n d e r s t a n d i n g of the social a n d cultural context of the development a s well a s lack of participation, Anon (2005). According to Critchley a n d Netshikovhela (1998), there is a serious ignorance of t h e indigenous knowledge a b o u t the problems of WIP a n d there is a perception by scientists t h a t traditional people do not know a b o u t or realise the r e s u l t s of their actions on their lands. This misconception c a u s e s p l a n n e r s a n d policy m a k e r s to implement programs without consulting the local people (Critchley & Netshikovhela, 1998).

4

1 J o r d a a n , D. 2004. The Land Care Coordinator-Southern region within the Provincial

Department of Agriculture, contact details (018) 2 9 7 5 3 3 0 .

The so called "experts" are u s u a l l y from a different cultural a n d social background a n d a d d r e s s those problems of the local community which they perceive to be important, without consulting the community to find out where the real problem exists. The priorities a n d the need of the supposed "beneficiaries", who were rarely consulted during the planning p h a s e of the National programs s u c h a s Land Care a n d Working for Water, are not considered, Anon (2005).

1.4 Preliminary s t u d y

Before this study w a s u n d e r t a k e n , a preliminary study w a s conducted in the a r e a in 2 0 0 4 . The study was done on a small scale with a population size of 30 people from the villages of Goo-Mokgatla a n d Ikageleng only. The outcome of the study w a s t h a t all the r e s p o n d e n t s (100%) were aware of the problem of declared weeds a n d alien invasive plants. The r e s p o n d e n t s indicated t h a t they were not going to take part in the control program, since they are not the ones who introduced the p l a n t s to the area. The local people have the perception t h a t the Government, t h r o u g h the D e p a r t m e n t s of Agriculture, both Provincial a n d National, h a s a n important role to play t h r o u g h a w a r e n e s s raising a n d financing the control m e t h o d s .

In t e r m s of attitude towards the control of these p l a n t s , unemployment w a s mentioned a s a reason for the resistance against participation in the government's existing WIP control strategies. These programs did not employ the local community. Most of the people did not know anything a b o u t the different p r o g r a m s referred to in the study, s u c h a s Working for Water, the Government Subsidy Scheme a n d Land Care. They were aware of "Namola Leuba", which include any project a s long a s it created job opportunities. The people were also not aware of any policy dealing with the control of weeds a n d alien invader plant species.

As a result of this preliminary study, it w a s considered t h a t it w a s important to investigate in more detail the problem of a t t i t u d e s a n d perceptions of the local community. It is necessary to determine the influence t h a t the local indigenous knowledge h a s on the occurrence of WIP in the area, a n d the extent to which the study can rely on the local knowledge to influence decision making in dealing with the control thereof.

The s t u d y includes vegetation survey to determine t h e extent of t h e area infested with WIP. The two methods, namely t h e perception survey a n d vegetation survey, were compared to determine the extent to which the respondent's knowledge relates with the vegetation survey.

1.5 Aim of t h e s t u d y

The purpose of the study w a s to achieve the following aims:

> To a s s e s s perception a n d a t t i t u d e s of the indigenous knowledge of the local community towards declared weeds a n d alien invasive p l a n t s (WIP).

> To carry out a vegetation survey to quantify the a b u n d a n c e of the different WIP species a n d compare the perception a n d attitudes of the indigenous knowledge by the community of Dinokana Area with the r e s u l t s of vegetation survey.

> To formulate recommendations for the existing programs of WIP control.

1.6 Layout of dissertation.

The study consists of six chapters, where Chapter One introduces the study background a n d the problem statement. Chapter Two r e p r e s e n t s a critical review of relevant literature. Possibilities of how t h e problem can be m a n a g e d a s well a s their impacts on the environment a n d t h e lives of the local communities are also considered.

Chapter Three describes the location of the study area, including the n a t u r a l vegetation, the geology a n d the soil aspect, the climatic conditions a s well a s infrastructure of development of the area.

Chapter Four explains t h e materials u s e d a n d the m e t h o d s followed in conducting the study, which include using the questionnaires a s well a s a qualitative vegetative sampling of the affected areas. Chapter Five discusses the r e s u l t s a n d t h e outcome of t h e studies conducted in Chapter Four, while Chapter Six gives the conclusion of t h e study a s well a s r e c o m m e n d a t i o n s resulting from the study.

In the following Chapter, the state of WIP's, a s well a s the impacts a n d processes t h a t lead to the invasion of alien p l a n t s is briefly discussed.

CHAPTER 2

LITERATURE REVIEW

2.1 Conservation of Agricultural Resources Act (No 4 3 of 1983)

According to Henderson (2001), there are approximately 198 declared weeds a n d alien invasive p l a n t s (WIP) in South Africa, which are all covered by the Conservation of the Agricultural Resource Act, Act 4 3 of 1983 (CARA). The newly introduced a m e n d e d sections 15 a n d 16 of the CARA legislation mention t h a t these p l a n t s are classified into three different categories (National Department of Agriculture. 2001). These categories are:

Category 1: These are weeds, which are prohibited a n d m u s t be controlled. They

are not allowed to occur anywhere in South Africa, except in biologically controlled reserves. An example of one of these species is given in Figure 2 . 1 . (A list of the entire category 1 p l a n t s is presented a s Appendix C).

Category 2: These are invader p l a n t s , which can be grown in demarcated a r e a s

providing t h a t there is a permit a n d t h a t steps are t a k e n to prevent their spreading. They are p l a n t s mainly u s e d for economic p u r p o s e s (commercial forestry a n d community woodlots) a n d are only allowed to grow in South Africa in a r e a s t h a t are specifically d e m a r c a t e d for t h e m a n d in biologically controlled reserves. (A list of the entire category 2 species is presented a s Appendix C).

Category 3 includes ornamentally u s e d plants. They may no longer be planted

b u t existing p l a n t s may remain, except within the flood line of watercourses a n d wetlands, a s long a s all reasonable s t e p s are taken to prevent the spreading thereof, (Henderson, 2001). (A list of the entire list of category 3 p l a n t s is presented a s Appendix C).

There are also 36 plant species identified to have the potential for invasion (Henderson. 2001). All these three categories will be dealt with in this study.

Figure 2.1: An example of a category one invader plant, Opuntia imbricata in

Dinokana Area.

Some WIP have been historically regarded as ideal rock garden plants and enthusiasts and collectors are responsible for the rapid dispersal of these species (Ranger, 2003). Many of the declared weeds and alien invasive plants have been introduced intentionally by h u m a n s , mainly by nurturing species that are helpful or needed by people, such a s for agricultural, ornamental, forestry or even for psychological purposes (McNeely, 2003). The introduction of these species is an

integral part of h u m a n welfare and local culture. Throughout the world there is danger that additional species will continue to invade the ecosystems, as the people purposefully or accidentally introduce species a s a result of the growing global trade.

2 . 2 Invasion process of declared w e e d s and alien invasive plants (WIP)

Schwartz (1997) suggested t h a t one of the first objectives in making decisions a b o u t managing a potentially problematic species invasion is to determine whether t h a t species is a n a t u r a l component of, or is indigenous to the community in question. There are several ways in which the distribution of species can change (Schwartz, 1997; C h a p m a n & Le Maitre, 2001):

• Suitable climatic conditions, such a s humidity a n d temperature, which can influence the n a t u r a l distribution process of species (i.e. independent of h u m a n factors), by the dispersal a n d colonization of new habitats.

• As a result of a change in h a b i t a t s c a u s e d by h u m a n land u s e or disturbance regimes.

• Fragmentation of the landscape, which creates extensive ecotones a n d corridors for invasions.

• Changes in the availability of the limiting factors, e.g. temperature a n d rainfall.

• Persistent seed b a n k s in situ or the ability to colonise via effective dispersal a n d the ability to recover through vegetative m e a n s .

• The ability to establish immediately after d i s t u r b a n c e s or between d i s t u r b a n c e s .

• Timing of reproductive maturity, lifespan a n d longevity of seed b a n k s relative to the timing of disturbances.

• High tolerance against environmental extremes a n d greater adaptability in a wide range of environmental conditions s u c h a s a n increase in moisture availability, light a n d n u t r i e n t u s e efficiencies, zero or very short dormancy periods, high productivity a n d high reproductive potential (Raghubanshi et al. 2005).

These a n d other factors t h a t influence the distribution of species a n d contribute to vegetation change are discussed below. Initially, species have to be transported into a new region, which in the case of declared weeds a n d alien invasive p l a n t s is usually supported deliberately or unknowingly by h u m a n activities (Brock et al.

1997). Often the transport of p l a n t species is across geographic barriers t h a t separate t h e m . In the n a t u r a l system, propagule dispersal is restricted to a distance of 10 to 30 meters a n d the n u m b e r of propagules decreases rapidly a n d non-linearly with increasing distance from the source (Chapman & Le Maitre, 2001). Even if only a few individuals of invasive species succeed in the n a t u r a l system, they could radically transform t h e system they invade.

According to C h a p m a n a n d Le Maitre (2001), there are approximately 750 introduced tree species in South Africa, b u t only 70 of these are considered major invaders. The role of anthropogenic factors in the introduction of new propagules m a k e s the impact of invasions difficult to predict. H u m a n activities are influenced by a political system, state of the economy, a s well a s international relations, since goods a n d p r o d u c t s are being exchanged between, for example, Botswana a n d South African m a r k e t s . The invader p l a n t s in Botswana are not considered to be proclaimed invader p l a n t s . According to (personal subjective observation), it seems t h a t the Government of Botswana h a s done very little since the 1980's to control these p l a n t s . In the former homeland of B o p h u t h a t s w a n a , which s h a r e s the border with Botswana, people were working u n d e r the drought relief s c h e m e s (Namola leuba) to get rid of the plants.

The degree of utilization a n d manipulation of the environment for n a t u r a l resources, s u c h a s firewood a n d food, d e p e n d s on the degree of poverty, access to agricultural equipment or finances, stock management, a s well a s the grazing p a t t e r n s . Many alien species are incapable of becoming established a s in some cases seedlings fail to develop into m a t u r e plants. Many species may remain sterile, or if they flower, they do not develop fruit, or the seeds are not viable.

Those species t h a t failed to become established are mainly ephemerophytes (Chapman & Le Maitre, 2001). These p l a n t s are characterized not so m u c h by their rate of establishment, which is likely to be very low, b u t by the ability of the species to maintain itself at a few locations over a n u m b e r of years. In South Africa, the invasiveness of p l a n t s is categorised according to Provinces (National Department of Agriculture, 2001).

A p l a n t can be regarded a s a n invader in one Province a n d regarded a s a weed in another Province (Henderson, 2001). It is i m p o r t a n t that, to prevent a potentially invasive species from developing further, action should be taken during the so called lag p h a s e in the plant's life cycle a n d development (Brock et al. 1997). However, given t h a t the species is not always known, identification is likely to be very difficult in m o s t administrative areas. According to personal communication with 3Modungwa (2003), another problem t h a t occurs in most sites of the study

area, is t h a t there is a lack of knowledge regarding the impact of WIP on the n a t u r a l agricultural resources, especially by the local agricultural practitioners. She indicated t h a t there is problem of Lantana camara (Lantana or Cherry pie) in Dinokana, which poses a serious t h r e a t to livestock production d u e to its toxicity. The North West Provincial Department of Agriculture (NWPDA) h a s , however, taken no action to a d d r e s s the problem a s m o s t people are u n a w a r e t h a t L. camara poses a problem to the livestock production system.

2 . 3 Results of t h e disturbance of declared w e e d s and alien invasive plants (WIP)

The primary d e t e r m i n a n t s of plant community "invasibilities" is the n u m b e r of safe sites for seed germination in the community.

12

This m e a n s t h a t non-indigenous plant species are most likely to invade sites t h a t experience disturbance t h a t differ in type or frequency from their n a t u r a l d i s t u r b a n c e regime (Belsky & Gelbard, 2000). Areas with disturbed soil provide a n optimal habitat for t h e development of declared weeds a n d alien invasive plants.

Most of the "problems" with WIP in the Dinokana a r e a have evolved from m i s m a n a g e m e n t practices, s u c h a s overgrazing a n d c o n t i n u o u s veld burning, which c a u s e s disturbance a n d soil erosion (Sheley et al. 1995). The influence a n d spatial spread of species in a n environment is a result of a combination of intrinsic a n d extrinsic factors t h a t govern the species population dynamics.

As indicated by Pyke a n d Knick (2003) "intrinsic" factors include the dispersal, growth, survival a n d reproduction constraints dictated by the species' physiological a n d morphological capabilities, w h e r e a s extrinsic factors include the spatial a n d temporal availability of suitable habitat for survival, growth a n d reproduction a n d suitable corridors a n d vectors for dispersal". Declared weeds a n d alien invasive species m a y respond to h u m a n induced environmental changes or they may initiate environmental changes through their dominance of t h e landscape. High intensity d i s t u r b a n c e s t h a t transform the landscape often occur at a local spatial scale. Land transformation from rangeland to h u m a n habitation, s u c h a s village expansions, are concentrated n e a r the fringe of h u m a n population centers. Low intensity d i s t u r b a n c e s t h a t result in degradation are often more diffusely distributed t h r o u g h o u t the landscape. Invasive species may directly benefit from the land transformations a n d degradation (Pyke & Knick, 2003). Transformation often r e s u l t s in large land d i s t u r b a n c e s . Disturbances are characterised by extended p a t c h sizes, fragmentation distribution, a n d the dispersal ability which interact to influence invasions a n d spread. Invasive species have a n equal probability of spread regardless of t h e distribution of the d i s t u r b a n c e , even when the extent exceeds the threshold area.

"When t h e proportion of the landscape disturbed is below a certain threshold level, the distributions of d i s t u r b a n c e a n d the dispersal ability interact to affect the probability of the spread for invasive organisms" (Pyke & Knick, 2003). Changing disturbance frequency or intensity may c a u s e ecosystem modifications. Invasive p l a n t s may contribute to modifications, for example in the n a t u r a l fire cycles, providing a positive feedback which e n h a n c e s their spread. Pysek et al. (2005), indicated t h a t "man-made" habitats, especially in settlements, are prone to invasions by alien species, which is attributable to h a b i t a t heterogeneity, frequent a n d diverse d i s t u r b a n c e a n d intensive propagule p r e s s u r e . Arable land, a h u m a n - m a d e habitat with a high representation of alien species, is a n environment with a specific d i s t u r b a n c e regime.

Pysek et al. (2005) indicated t h a t studies to analyze the d e t e r m i n a n t s of weed species r i c h n e s s are rare a n d hardly any have focused on detecting general p a t t e r n s of alien species invasions. The difference in diversity of the weed flora is mainly attributed to lack of specific type of m a n a g e m e n t a n d partly to crop specific agricultural practices, a s well a s to the general intensification of m a n a g e m e n t of arable land in the p a s t (Pysek et al. 2005). According to Sheley et al. (1999), disturbance creates available sites, t h u s succession can be controlled by altering the size, severity, frequency a n d p a t c h i n e s s of disturbance in a m a n n e r favourable to desirable plant species. Historically the d i s t u r b a n c e s were designed by experts through cultivation, grazing a n d burning. The usefulness of any d i s t u r b a n c e for invasions will depend on the range site, plant community type, invading weed species, history of the site a s well a s "other environmental conditions". As indicated by Sheley et al. (1999), a site vulnerable to invasion, m u s t be occupied by the desirable indigenous plant species to prevent WIP to establish. This is termed 'controlled colonization' which intentionally affect succession. Controlled species performance includes u s i n g m e t h o d s to alter growth a n d reproduction of specific plants, thereby contributing to a desirable shift in the plant community.

This requires u n d e r s t a n d i n g of the factors t h a t influence the competitive balance s u c h a s grazing, disease, resource availability, allelopathy (the inhibition of growth in one species by chemicals from another species), predators, growth rates a n d their complex ecological interactions.

Since t h e process of WIP invasion w a s discussed a n d the r e s u l t s of WIP invasion outlined, the following section will deal with the impacts of WIP on different environmental variances.

2 . 3 . 1 Impacts on t h e functioning of riparian areas

Riparian a r e a s are the greener zones along rivers a n d s t r e a m s , a r o u n d potholes, springs, bogs, lakes a n d p o n d s (Sheley et al. 2001). Healthy riparian systems purify water by removing sediments a s they move t h r o u g h the vegetation. WIP can be extremely competitive in a riparian system. Riparian systems are prone to WIP invasions b e c a u s e of their dynamic n a t u r e a n d high n u t r i e n t level. They overcrowd valuable native species by forming solid s t a n d s a n d they can also alter the hydrological cycles of the riparian areas. WIP also lower water tables and, in some areas, eliminate surface water a n d native vegetation needed by wildlife, a n d also affect the carrying capacity of the flooding cycles (Sheley et al. 2001).

According to Smith a n d P a n e t t a (2002), riparian ecosystems are important for maintaining biodiversity a n d ecosystem functioning within landscapes. Riparian systems are prone to WIP invasions b e c a u s e of their dynamic n a t u r e a n d high n u t r i e n t level. Some of the invasive species, called "transformer species", are capable of markedly changing ecosystem s t r u c t u r e a n d functioning. When the functional values of a riparian system are compromised, downstream ecosystems may be negatively affected. This may occur via reduced water quality a n d increased n u t r i e n t a n d sediment flows. Once invaded, the riparian vegetation can act a s a source of weed propagules for downstream a n d u p s t r e a m habitats.

As landscape corridors, they present major foci for long distance dispersal a n d range expansion of invasive weeds (Smith 85 Panetta, 2002). More restricted stock access along waterways h a s led to reduced grazing p r e s s u r e on riparian weeds. F a r m e r s from villages situated along the river, s u c h a s Maramage, depend on the river to graze a n d water their livestock.

If WIP alter the infiltration process d u e to different canopy architecture, or contribute to the production of more hydrophobic litter layers, they may significantly influence soil water balance a s they become increasingly d o m i n a n t in the community. This p h e n o m e n o n , according to Schwartz (1997), h a s been estimated to reduce winter soil moisture recharge by more t h a n 50% in dense s t a n d s . If invasive species result in greater surface disturbances, this may have a negative impact on surface water balance a s the runoff water after large a n d heavy rainfalls is thereby increased.

2 . 3 . 2 E c o n o m i c l o s s

The development of an u n d e r s t a n d i n g of the environmental i m p a c t s a n d consequences of declared weeds a n d alien invasive plant species would be extremely useful for the quantification of their economic impact. Unfortunately no s t a n d a r d system exists for the objective quantification of the m a n y a n d varied environmental i m p a c t s of WIP worldwide (Van Wilgen et al. 2001). Currently there is, unfortunately, no agreed criterion for the m i n i m u m damage, spread or even the size of the population needed for alien species to be considered invasive (Mc

Neely et al. 2004). The effect of the invasion of p l a n t s can either be negative, neutral or even positive. Negative or n e u t r a l impacts of an invading p l a n t species occur if the invader grows slower t h a n , or at similar rate to the species it replaces (Lawrence et al. 1997). Invasive species m a y c a u s e major financial losses to the national economy. The loss could be the result of direct problems c a u s e d by invasive species, loss of living resources, a n d losses d u e to any pest brought with the invasive species.

In South Africa, figures are not readily available b u t it is estimated t h a t the control of plant invasions cost RIO.5 billion each year (Howard, s.a). The potential loss of biodiversity is difficult to quantify or translate into monetary terms, b e c a u s e the value of m a n y species or ecosystems is unexplored, for instance the loss of potentially productive land, the loss of grazing a n d the increased costs of fire protection a n d damage by wildfires. Declared weeds a n d alien p l a n t s also c a u s e major economic impacts t h r o u g h the non-productive u s e of water. These p l a n t s are also responsible for reducing stream flow from c a t c h m e n t a r e a s a n d for reducing ground water supplies. These reductions impact the economy in two ways (Howard, s.a):

Firstly, they reduce the ability of existing water supply schemes to deliver sufficient water to meet d e m a n d s , especially in the dry periods. This necessitates the building of new or bigger supply schemes at considerable expenses in order to meet the d e m a n d s . Secondly, they reduce the total a m o u n t of water available for h u m a n u s e . Because water is a limiting resource for economic development, removing water from t h e hydrological cycle m e a n s t h a t t h e scope for development is reduced significantly (Howard, s.a).

In t e r m s of the economic dimension, the invasive species can be seen from two perspectives: t h a t economics is central to the c a u s e of biological invasiveness, a n d the r e s u l t s of pest incursions go far beyond direct d a m a g e or control costs. Most cases of invasions can be linked to the intended or u n i n t e n d e d consequences of economic activities and, a s a result, knowledge of economic applications is essential in order to u n d e r s t a n d the problem a n d to provide more accurate a n d comprehensive a s s e s s m e n t s of the benefits a n d costs of control alternatives. The a s s e s s m e n t of the costs a n d benefits of the control of WIP is essential in order to increase the effectiveness a n d efficiency of public funded programs s u c h a s Working for Water a n d Land Care (Howard, s.a). Furthermore, modeling the economic a n d trade i m p a c t s of technical t r a d e barriers is becoming more important (Evans, 2003).

Common a m o n g such barriers are those dealing with trade restrictions t h a t can be imposed by a country in an a t t e m p t to prevent entry of invasive species (Evans, 2003). According to the Global Invasive Species Program (GISP. 2006), a n n u a l losses to p e s t s were estimated at US$6.24 billion in Australia, US$42.60 billion in Brazil, US$78.50 billion in USA, US$5.56 billion in the UK, US$91.02 billion in India a n d US$4.30 billion in South Africa.

Globally t h e costs of damage c a u s e d by WIP have been p u t at US$1.4 trillion per year - nearly 5% of the global Gross Domestic Product (GDP). These figures provide a n interesting comparison between developing a n d developed countries. The estimated damage caused by WIP in developed countries w a s 5 3 % of agricultural GDP in the USA, 3 1 % in t h e UK a n d 4 8 % in Australia. By contrast, the damage in developing countries, s u c h a s South Africa, India a n d Brazil a m o u n t e d to 96%, 78% a n d 112% of the agricultural GDP, respectively (GISP, 2006).

2 . 3 . 3 Biodiversity l o s s

The term "biodiversity" is described a s the diversity of life on earth, encompassing all genes, species, populations, l a n d s c a p e s , and ecosystems, ecological a n d evolutionary processes t h a t allow these elements of biodiversity to persist over time (GISP, 2006). It is essential for the functioning of a healthy ecosystem, which in t u r n provides a variety of services vital for h u m a n wellbeing (Van Ruijven, 2005). The diversity of life on earth is affected by h u m a n alteration of ecosystem (Diaz, 2006). These ecosystem services include resources s u c h a s food, water, building materials a n d traditional medicines, processes regulating water purification, soil formation, flood attenuation, erosion control, crop pollination a n d n u t r i e n t cycling, a s well a s cultural aspects s u c h a s recreational opportunities a n d spiritual fulfilments (GISP, 2006).

The loss of biodiversity a n d the degradation of ecosystems inevitably affect h u m a n well-being, contributing to lower food security, h a r s h e r living conditions, worsening health a n d reduced wealth. According to the GISP (2006), there h a s been an increased rate of species extinction over the p a s t few years of a s m u c h a s 1000 times, a n d t h a t amongst the higher taxa, the majority of species are in decline (GISP, 2006).

The South Africa's biodiversity provides a n i m p o r t a n t b a s i s for economic growth a n d development. The loss of biodiversity p u t s a s p e c t s of the economy a n d quality of life at risk a n d reduces socio-economic options for the future generation. This is one of the negative r e s u l t s of the introduction of declared weeds a n d alien invasive plant species t h a t could lead to marginalization or even elimination of native species. The declared weeds a n d alien invasive plant species are regarded a s the second largest threat to biodiversity, after direct h a b i t a t destructions (Feany, 2004; R a g h u b a n s h i et al. 2005).

The invasive species grow fast a s they do not have any n a t u r a l predators in the invaded a r e a s a n d a s s u c h draw more n u t r i e n t s a n d moisture from the ground. Due to the frequent presence of toxic metabolites, they also impair native species through allelopathy. Whenever declared weeds a n d alien invasive species invade a habitat, they also eliminate the n a t u r a l fauna, since fauna always d e p e n d s on n a t u r a l flora. The people are ultimately d e p e n d e n t on living, functioning ecosystems a n d the services they provide a n d therefore the loss of biodiversity leads to ecosystem degradation a n d s u b s e q u e n t loss of important services, which tend to h a r m the poor more directly (Raghubanshi et al. 2005).

The effective m a n a g e m e n t of biodiversity does not guarantee s u s t a i n a b l e development, b u t s u s t a i n a b l e development is not possible without it (Diaz, 2006). The principal negative i m p a c t s of these p l a n t s on biodiversity are displacement by direct competition, reduced structural diversity, increased biomass a n d disruption of the prevailing vegetation dynamics (Diaz, 2006).

Declared weeds a n d alien invasive p l a n t s may also change the structure a n d function of a n ecosystem completely, resulting in large scale changes in the environmental conditions of t h a t area. This occurs when the invasive species change the soil composition d u e to allelopathic s u b s t a n c e s released from their roots or leaf litter. The chemical n a t u r e a n d decomposition rate of their leaf litter a n d other dead p a r t s may also alter the n u t r i e n t cycle in a n ecosystem. When fast growing species invade a certain c a t c h m e n t area, they may drastically reduce t h e flow of s t r e a m s a n d rivers d u e to a high rate of evapo-transpiration a s well a s displacement of threatened a n d endangered species a n d soil n u t r i e n t s d u e to the invasion by WIP. Rare species are vulnerable to the environmental changes c a u s e d by infestations of WIP, Sheley et al. (2001).

According to the CSIR Division of water, environment a n d forestry technology, there is strong evidence t h a t c u r r e n t r a t e s of extinctions a n d loss of biodiversity are t h o u s a n d s of times higher t h a n the n a t u r a l r a t e s of extinctions (Howard, s.a.). Conservationists currently estimate a b o u t 2 7 0 0 0 a n n u a l losses of species globally. There are only a handful of proven cases where alien invasive p l a n t s have resulted in extinctions of species in South Africa. "However, almost 1900 of the 3 4 3 5 plant species listed in t h e 'red d a t a lists' for S o u t h Africa are threatened wholly or in part by alien invasive plant species (Howard, s.a)". According to Schwartz (1997), invasive p l a n t s may not have effects on levels of particular n u t r i e n t s if those n u t r i e n t s are not limiting.

Invasive p l a n t s can lower soil n u t r i e n t levels directly t h r o u g h competition, or indirectly through addition of n u t r i e n t poor litter, or via accumulation of salts which decrease the availability of n u t r i e n t s or dramatically alter the soil pH. Invaders t h a t increase fire frequency or severity can indirectly cause increased volatilisation of nitrogen, which may lead to a decline in soil nitrogen. Changes in n u t r i e n t levels in plant t i s s u e s d u e to invasive p l a n t s are therefore mediated t h r o u g h changes in soil n u t r i e n t levels (Schwartz, 1997).

Invasive p l a n t s can strongly impact on soil water content a n d landscape water balance of indigenous communities, with positive a n d negative effects. The most direct negative impact is t h a t invasive species u s e more water t h a n the indigenous species they are replacing (Schwartz, 1997). This is a result of the WIP species having intrinsically higher transpiration r a t e s per u n i t leaf area.

2 . 3 . 4 Land degradation

Invasive p l a n t s can influence l a n d s c a p e water balance by effectively changing the land surface characteristics of the h a b i t a t s . Land degradation is defined a s any form of deterioration of the n a t u r a l potential of land t h a t affects ecosystem integrity either in t e r m s of reducing its sustainable ecological productivity or in t e r m s of its native biological r i c h n e s s a n d m a i n t e n a n c e of resilience (GEF, 2003). The c a u s e s of land degradation are not only biophysical b u t also socio-economical (e.g. land t e n u r e , income a n d h u m a n health) a n d political factors (World Meteorological Organization, 2005). There are three c a u s e s of land degradation: n a t u r a l p h e n o m e n a , direct c a u s e s a s well a s underlying c a u s e s (Hoffman & Ashwell, 2001). These are discussed below in more details.

2 . 3 . 4 . 1 Natural c a u s e s of land degradation

Natural disasters s u c h a s droughts, floods a n d climate change contribute to land degradation (Morris, 1995). The land surface is a n important part of the climate system. C h a n g e s in vegetation type can modify the characteristics of the regional atmospheric circulation a n d the external moisture fluxes. Changes in surface energy b u d g e t s resulting from land surface c h a n g e s can have a profound influence on the e a r t h surface (World Meteorological Organization, 2005). Land transformation also h a s the potential to directly a n d indirectly influence climate change. Climate changes facilitate invasions where the invaders are more tolerant of or better able to exploit the altered conditions, s u c h a s increased frequency of droughts a n d increased nitrogen availability.

Climate changes, which may be very rapid also allowing invading exotic species to expand their ranges in a r e a s where climatic factors, s u c h a s t e m p e r a t u r e a n d rainfall allow their distribution (Chapman 85 Le Maitre, 2001). Drought stimulates land degradation b e c a u s e a lack of rainfall aggravates the effects of poor land m a n a g e m e n t (Hoffman 85 Ashwell, 2001). The rainfall a m o u n t s vary substantially from one region to a n o t h e r a n d from one year to another.

An increase in t e m p e r a t u r e affects the water cycle a n d c h a n g e s the water p a t t e r n which could have a serious impact on land degradation. This will give a n opportunity for declared weeds a n d alien invader species to encroach a s t h e environmental conditions change. These p l a n t s would not have any competition for t h e available n u t r i e n t s (Hoffman 8s Ashwell, 2001). The current global warming occurrences are u n u s u a l a n d are increased by h u m a n activities, especially the greenhouse gas emissions from t h e b u r n i n g of fossil fuels.

The loss of vegetation in t h e h e a d w a t e r s of dry land rivers a s a result of floods c a n increase sediment loads a n d lead to a dramatic change in the characters of the rivers to become less stable, more seasonal a n d characterised by rapidly shifting series of c h a n n e l s (World Meteorological Organization, 2005).

Agriculture a n d land u s e changes, a s well a s other industrial processes t h a t release greenhouse gases, also contribute to climate change, a s the carbon dioxide (CO2) concentration in the lower atmosphere h a s increased dramatically. These c h a n g e s in the concentration of CO2 a n d other greenhouse gases have led to changes in the climate. The climate is warming in most p a r t s of the world, with an average increase of global t e m p e r a t u r e of u p to 0.7°C per a n n u m (Reid, 2006). According to Meyer et al. (2002), changing t e m p e r a t u r e a n d water availability conditions are likely to induce s t r e s s in vegetation a n d other plant species, which might encourage mobile o r g a n i s m s to alter their distribution.

Climatic change will possibly also c a u s e a gradual increased p r e s s u r e on the tolerance limits of native species a n d could thereby favour t h e s u c c e s s a n d spread of alien plant species (Meyer et al. 2002).

In contrast to the historical migration responses, species today m u s t move through a landscape t h a t is increasingly impassable d u e to the widespread loss a n d fragmentation of h a b i t a t s (Hugo et al. 1997). Some of t h e impacts of climatic c h a n g e s on biodiversity include species ranges a s a result of the changes in t e m p e r a t u r e , precipitation a n d phenology, causing shifts in the reproductive cycles a n d growing s e a s o n s of certain species. Changes in competitive ability may also emerge a s a result of changes in species interactions. For instance, early leafing trees will get a two-week h e a d start on their competitors in t e r m s of growth a n d thereby occupy an increasing proportion of the woodlands (Reid, 2006).

The dying back of trees would release carbon stored in those biomes a n d s u r r o u n d i n g soils a n d further accelerate global warming. Climatic change also relates to extreme events s u c h a s diseases, drought, fire or a n oscillation effect a n d can also seriously affect change in biodiversity (World Meteorological Organization, 2005). These extreme events will eventually affect organisms, populations a n d the ecosystem more t h a n gradual global or regional changes (Reid, 2006).

2 . 3 . 4 . 2 Direct c a u s e s of land degradation

(a) Overgrazing

Overgrazing affects land in two ways. It leads to the loss of the rangeland vegetation cover in a r e a s where the livestock density exceeds t h e carrying capacity

(GEF, 2003). High livestock densities result in soil compaction b e c a u s e of trampling. In both instances, the soil becomes more vulnerable to water or wind erosion (Hoffman & Ashwell, 2001).

Once the loss of vegetation t a k e s place, there is a change in plant species composition. The loss of vegetation cover a n d the changes in species composition are the first visible signs of land degradation, although it is often still difficult to distinguish between changes d u e to environmental factors, such a s a n n u a l rainfall a n d those d u e to m i s m a n a g e m e n t , s u c h a s overgrazing of the land (Meadows 85 Hoffman, 2002). Some animals have a varied diet a n d can feed on a wide n u m b e r of plant species, while o t h e r s are highly specialised a n d may be restricted to feeding on several or even a single p l a n t species.

Certain species of invading p l a n t s can have a positive effect on the environment a s they lead to a n increase in the Nitrogen (N) content of the soil with a symbiotic relationship with nitrogen fixing bacteria. Non-native plant species have a greater n u t r i e n t a n d water u p t a k e a n d retention r a t e s which lead to decreased species diversity a n d drier, more nutrient-poor h a b i t a t s . Livestock prefer to graze native plant species while avoiding most WIP, which are poor forage a n d have a low palatability d u e to toxins, spines a n d distasteful c o m p o u n d s (Meadows 85 Hoffman, 2002).

As a result, the size, density a n d competitive vigour of native species are reduced while WIP species are released from competition since their competitors are reduced. With c o n t i n u o u s livestock grazing, native g r a s s species decline in density a n d cover, leaving bare p a t c h e s t h a t are already colonized by weedy a n n u a l s (Belsky 85 Gelbard, 2000). Overgrazing is said to contribute to almost 50% of soil degradation in Africa (World Meteorological Organization, 2005), while Morris (1995) regarded water erosion a s being t h e most pervasive c a u s e of land degradation, contributing between 50-70% of all degraded land.

Cattle a n d sheep c a n reach all a r e a s including the steepest slopes a n d a r e a s furthest from the water. According to Belsky a n d Gelbard (2000), livestock are the most likely c a u s e s of weed introductions into non-recreational or remote a r e a s away from roads or trails.

The effectiveness of livestock a s WIP seed vectors is illustrated by their ability to t r a n s p o r t viable seeds in their hair, digestive track a n d m u d on their feet. Cattle are more important dispersers of WIP seeds t h a n sheep, b e c a u s e cattle are known to be more extensive grazers t h a n sheep a n d therefore are able to reach even t h e furthest places (Belsky 85 Gelbard, 2000).

The invasion of alien s h r u b s into grassland is also c a u s e d by the shifts in the types of livestock species kept. Many of the c h a n g e s occurring across t h e c o m m u n a l land are c o m p o n e n t s of degradation expressed a s h u m a n - i n d u c e d reduction in productivity, leading to degradation a n d loss of biodiversity. C o m m u n a l areas, especially those u n d e r grazing, a p p e a r to be particularly susceptible to decline in veld condition, so t h a t the former homelands, s u c h a s B o p h u t h a t s w a n a where this study w a s carried out, are highlighted a s problematic in this regard (Meadows & Hoffman, 2002).

B u s h encroachment is a n o t h e r form of land degradation t h a t results from overgrazing. It is characterised either by the invasion of g r a s s l a n d s by woody elements, or by an increase in the biomass of woody elements in s a v a n n a woodland a r e a s (Meadows 85 Hoffman, 2002). B u s h encroachment a n d b u s h thickening are problems affecting mainly cattle farming grassland areas, changing t h e m to s a v a n n a thickets. Both these processes reduce the relative a m o u n t of grass, a n d therefore cattle production (Hoffman & Ashwell, 2001).

The b u s h encroachment process is regarded a s serious a n d a rapid density of woody p l a n t s occurs, a n d h a s increased by a s m u c h a s 3 0 % in the last decades in some communally farmed a r e a s in respect to the local extinction of indigenous browsing herbivores a n d c h a n g e s in fire regimes (Meadows & Hoffman, 2001). Colonisation by declared weeds a n d alien p l a n t s would also c a u s e a major loss of biological diversity a n d significant c h a n g e s in c a t c h m e n t hydrology.

(b) Soil degradation

According to Puggle a n d Rabie (1992), Miller (1998) a n d Morris (1995), soil erosion is considered to be a n a t u r a l process a n d is regarded a s the movement of a soil component, especially surface litter a n d topsoil, from one place to another, mainly due to wind a n d the flowing of water. Wind a n d water move the eroded particles to new locations, where they are deposited a s sediments. During t h i s process, the soil particles take along seedlings of plants, including t h a t of WIP. After deposition of the soil, seeds start to germinate, bringing new types of WIP to the location where they did not occur before.

In South Africa, the rate of soil formation varies from 0.38 t o n s per hectare per year for light textured soil to 0.25 t o n s per hectare per year for heavy textured soils. Unfortunately, South African soils are susceptible to soil loss a n d this is due to a variety of physical factors (geology, steep slope and climate) a s well a s the h u m a n u s e of the land. The major c a u s e s of soil degradation include overgrazing, deforestation, agricultural activities a n d overexploitation of vegetation (Morris,

1995). Soil is one of the South Africa's most basic resources b u t it is being lost to erosion at a frightening rate, yet the South African population a p p e a r s to be complacent a b o u t it (Fuggle & Rabie, 1992).

The more topsoil t h a t is lost through erosion, the more the fertility of t h a t soil is affected a n d therefore sensitive g r a s s a n d other plant materials die off, making a new niche for WIP to establish. According to Miller (1998) a n d Hugo et al. (1997), there are three k i n d s of soil erosion. Sheet erosion occurs when surface water moves down a slope or across a field in a wide flow and peels off relatively uniform sheets or layers of soil. With rill erosion, the surface water forms fast flowing little rivulets t h a t cut small c h a n n e l s in the soil. The last form of soil erosion is gully erosion in which rivulets of fast flowing water join together a n d cut the c h a n n e l s wider a n d deeper with each succeeding rain until they become ditches or gullies.