Bush encroachment under three contrasting land-use practices in a mesic South African savanna B. J. Wigley*, W. J. Bond and M. T. Hoffman Botany Department, University of Cape Town, Private Bag. Rondebosch, 7700, Cape Town, South Africa Abstract This study determined the effects of land-use practice had on the rate and extent of bush encroachment in a mesic savanna in KwaZulu-Natal, South Africa. Changes in woody cover were measured for 1 km2 sites in areas under communal, commercial and conservation land-use sys- tems for the period between 1937 and 2000. Land users from each area were interviewed to gain the histories of each area and to determine how the changes in woody cover had impacted them and whether anything was being done to counteract the spread of trees and shrubs on their land. Bush encroachment occurred across all three of the land-use types in the 67-year period between 1937 and 2000. The results showed that land-use practice had enormous impacts on the process of bush encroachment. The communal site showed a decrease in grass (21%) and tree (5%) cover and an increase in shrub cover (13%). At the commercial site, there was a considerable decrease in grass cover (46%) and moderate increase in shrub cover (10%) and a massive increase in tree cover (36%). The area under conservation showed a substantial decrease in grass cover (47%), a slight decrease in shrub cover (19%) and a massive increase in tree cover (66%). The perceived causes of these changes were fairly similar amongst the different land users. The changes were mostly not per- ceived to be a problem for the communal land users. The main advantages mentioned were increased woody resources for building and firewood and increased browse availability. The commercial and conservation land users perceived the changes to have significant negative con- notations including the loss of grazing land and biodiver- sity and secondary invasion of encroached areas by alien plant species. Despite these perceptions, very little has been done to combat bush encroachment in the commercial and conservation land use systems. Key words: bush encroachment, consequences, land use, perceptions Introduction Woody plant proliferation in grasslands and savannas has long been a concern of land managers because it adversely affects herbaceous productivity and livestock handling, thus threatening the sustainability of pastoral, subsistence and commercial livestock farming (Rappole et al., 1986). The loss of grassland and savanna habitat to encroaching woody species is also a major concern for conservation managers as the conservation of biodiver- sity is normally a high priority for conservation orga- nizations around the world (e.g. Ezemvelo KZN Wildlife���s Mission Statement). Woody plant encroachment is the slow proliferation of woody plants at the expense of grasses in savannas and grasslands. Encroaching woody species may be trees or shrubs, collectively referred to as bush in the South African literature (Hudak & Wessman, 2001). Recent trends towards increased bush encroachment in savannas have been documented in North America (Archer, 1995 Asner et al. (2003), South America (Adamoli et al., 1990 Silva, Zambrano & Farinas, 2001), Australia (Burrows et al., 1990 Fensham & Fairfax, 2003 Fensham, Fairfax & Archer, 2005) and India (Singh & Joshi, 1979). In Southern Africa, numerous studies have shown significant increases in bush encroachment over approximately the last 50 years. Increases in woody plant cover have been documented for KwaZulu-Natal���s grass- lands (O���Connor, 2003), Eastern Cape savanna and grassland (O���Connor & Crow, 1999), open savanna (Dougill & Trodd, 1999), miombo woodland (Chidumayo, 2002), semi-arid savanna (Hudak & Wessman, 1998, 2001 Higgins, Shackleton & Robinson, 1999 Moleele *Correspondence: E-mail: benjamin.wigley@uct.ac.za 62 �� 2009 The Authors. Journal compilation �� 2009 Blackwell Publishing Ltd, Afr. J. Ecol., 47 (Suppl. 1), 62���70

et al., 2002) and mesic savanna (Hoffman & O���Connor, 1999). In South Africa alone, it has been estimated that 13 million hectares of savanna have been subject to thorn bush encroachment (Trollope et al., 1989). However, de- spite the wide extent of this occurrence, little is known about the dynamics and causes of encroachment (Archer, 1995). During the past century, the balance between plant life forms has shifted to favour trees and shrubs in many savannas (e.g. Fensham et al., 2005) and drylands (Ar- cher, 1994, 2002). Factors contributing to these lifeform transitions are subject to debate and include human alterations of fire frequency, grazing intensity, atmospheric CO2 concentration and nitrogen deposition (Grover & Musick, 1990 Archer, Schimel & Holland, 1995 Van Auken, 2000 Asner et al., 2003). Climate change has been cited as the impetus for directional shifts between grass and woody plant domination, but evidence in sup- port of this contention is mixed (Fensham et al., 2005). The pattern of and relative abundance of herbaceous and woody life forms in semi arid and mesic savannas result from interactions between climatic variables (e.g. rainfall amount and seasonality), topo-edaphic properties (e.g. texture depth, fertility and run-off) and disturbance regimes (e.g. grazing, browsing and fire) (Scholes & Archer, 1997 Asner et al., 2003). Land-use practices can change the structure and func- tioning of savanna ecosystems and hence the type of and quantity of ecosystem services provided. A predictive knowledge of the relationships among land-use practices, the composition, structure and function of vegetation, and the supply of ecosystem services is thus required (Higgins et al., 1999). Variants of three broad forms of land use, namely sub- sistence, wildlife and commercial livestock farming are widely practiced in the savanna regions of Africa (Gross- man & Gandar, 1989). Studies on the social, environ- mental conservation and economic value of these forms of land use have failed to achieve consensus on the optimal management system for African savanna ecosystems (Higgins et al., 1999). This may be because many land-use studies concentrate on the effects of a single aspect of a management system such as bush clearing (e.g. R.I. Scholes, unpublished data), fuel wood harvesting (e.g. Shackleton, 1993) or grazing (e.g. Skarpe, 1986, 1990) consequently, they do not account for the effects and interactive effects of the management activities that con- stitute a land use option (Higgins et al., 1999). The objectives of this study are twofold first, we set out to determine what effect the three main land use practices practiced in South African savannas (communal, com- mercial and conservation) have on the process of bush encroachment. This was measured by using aerial pho- tography, which dates back to 1937 for our study site. In this way, we measured and compared changes in woody cover for areas under the different land-use practices over the period 1937���2000. The second objective set out to determine what the observed changes in woody plant cover under each of the three land-use practices mean to the actual land users or land owners. This information was obtained by conducting semi-structured interviews with the different land users and land owners under each land-use type. Previous studies have neglected to determine how bush encroach- ment has affected the actual land users. This study is therefore novel in that it has set out to determine what the changes in woody cover actually mean to the land users and how the changes have affected them. The combination of the two objectives should contribute to a comprehensive understanding of how land-use prac- tice affects the process of bush encroachment in a mesic South African savanna. This understanding is crucial for management strategies addressed at combating or con- trolling further invasions of woody plants into grassland and woodland habitats. The study sites were selected as close to each other as possible to control for climatic and edaphic differences between sites. The differences in rates of woody plant encroachment across the different land-use systems can therefore be attributed to differences in land-use and management practices. Methods Study site The study was undertaken in the Hluhluwe area of the Hlabisa district of KwaZulu-Natal, South Africa (28.00��S to 28.25��S and 32.00��E to 32.58��E) (Fig. 1). The mean average rainfall for the area is ca. 980 mm per annum with most of the rainfall falling in the summer months of September to March. Temperatures in the area are warm to hot, particularly during the summer months (Whateley & Porter, 1983). The two main veld types in the area are Coastal Tropical Forest type (type 6) and the Tropical Bush and Savanna (type 10) (Acocks, 1988). Most of the area Bush encroachment and land-use practices 63 �� 2009 The Authors. Journal compilation �� 2009 Blackwell Publishing Ltd, Afr. J. Ecol., 47 (Suppl. 1), 62���70