**4. Discussion**

Results of this study indicated negative changes in the area occupied by the lower section of the wetland by a magnitude of 38 ha between 1984 and 2007 and by about 11 ha between 1984 and 2013. Meanwhile, the upper section incurred significant increase of about 32 ha between 1984 and 2007 and 130 ha between 1984 and 2013. The significant decreases in the area occupied by the lower section of the wetland could be attributed to the high concentrations of wild animals in the salt pans and water points as well as the high intensities of anthropogenic activities. On the other hand, the limited number of wildlife concentrations in the upper section could explain the intact and increases in the areal extent of the wetland covered by grass. Our results are supported by those of a study carried out in South Africa which also indicated that the creation of artificial water points in Kruger national park on the upland section of the park caused a high concentration of wild animals [23].

A gravel road stretching along the northern fringe of the vlei is likely to disrupt normal sediment mobility and deposition in the wetland area, a situation also observed by [23]. Erosion in the wetland is initiated from concentrated flow starting from culverts established to divert runoff from the road. This has resulted in rills and gullies in some parts of the lower wetland section where water is discharged into unplanned roads (**Figure 8**). Therefore, the effect of road construction through culverts on the vlei's erosion is evident. This result concurs with observations that roads tend to disrupts wetlands functioning through erosion and sedimentation [24].

Salt licking was observed as one of the main wildlife-related causes of wetland landscape alteration as indicated by existence of open pits surrounded by bare areas (**Figure 2**). This concurs with previous studies that salt lick areas are mostly devoid of vegetation as a result of heavy trampling from large herbivore which including those elephants and sables [10, 24]. This explains why in countries like Malaysia salt licks and land in its immediate vicinity are protected against disturbance of soil and vegetation [10]. Loss of vegetation cover generally exposes soil to erosion by either water or wind [25]. Despite the fact that the total amount of rainfall received per season has been declining over the past four decades as shown by linear regression results (y = −2.932x + 672.8; r2 = 0.033), the occasional high rainfall occurrences noted in this study could also be attributed to excessive erosion activities. Arid conditions worsened by increasing minimum and maximum temperature also may expose the bare areas around salt licks to wind erosion. Therefore, the wetland is susceptible to both water and wind erosion given the changing climate in the area. Wind speed in the vlei may be high since the depression is predominantly grassland surrounded by forests, which could make it a trough for wind passage.

for concentrated flow, a condition that enhances geomorphic process such as water erosion linked to surface runoff. The most pronounced developing gully is on average 3 m wide,

There are also unplanned roads that are used for game drive by tourists into the forest area surrounding the vlei. Some of the roads are developed following fairly steep gradients (on average 6% slopes) on the margins of forest area that forms the catchment area of the vlei into the wetland. Despite the fact that the predominant soil type is Kalahari sand (with high infiltration capacity), there is evidence of soil erosion on these roads as runoff is enhanced by the steep slope and channelized flow. Some of the sediment ultimately gets into the vlei, a situation likely to alter the ecological characteristics of the wetland due to enhanced sediment

Results of this study indicated negative changes in the area occupied by the lower section of the wetland by a magnitude of 38 ha between 1984 and 2007 and by about 11 ha between 1984 and 2013. Meanwhile, the upper section incurred significant increase of about 32 ha between 1984 and 2007 and 130 ha between 1984 and 2013. The significant decreases in the area occupied by the lower section of the wetland could be attributed to the high concentrations of wild animals in the salt pans and water points as well as the high intensities of anthropogenic activities. On the other hand, the limited number of wildlife concentrations in the upper section could explain the intact and increases in the areal extent of the wetland covered by grass. Our results are supported by those of a study carried out in South Africa which also indicated that the creation of artificial water points in Kruger national park on the upland section of the

A gravel road stretching along the northern fringe of the vlei is likely to disrupt normal sediment mobility and deposition in the wetland area, a situation also observed by [23]. Erosion in the wetland is initiated from concentrated flow starting from culverts established to divert runoff from the road. This has resulted in rills and gullies in some parts of the lower wetland section where water is discharged into unplanned roads (**Figure 8**). Therefore, the effect of road construction through culverts on the vlei's erosion is evident. This result concurs with observations that roads tend to disrupts wetlands functioning through erosion and sedimen-

Salt licking was observed as one of the main wildlife-related causes of wetland landscape alteration as indicated by existence of open pits surrounded by bare areas (**Figure 2**). This concurs with previous studies that salt lick areas are mostly devoid of vegetation as a result of heavy trampling from large herbivore which including those elephants and sables [10, 24]. This explains why in countries like Malaysia salt licks and land in its immediate vicinity are protected against disturbance of soil and vegetation [10]. Loss of vegetation cover generally exposes soil to erosion by either water or wind [25]. Despite the fact that the total amount of rainfall received

park caused a high concentration of wild animals [23].

24 cm deep and 45 m long.

180 Wetlands Management - Assessing Risk and Sustainable Solutions

delivery.

tation [24].

**4. Discussion**

Wildlife grazing is also influencing the alteration of the wetland's landscape. High grazing intensities by plain game species were mostly observed around watering points and were almost devoid of vegetation. The pressure on grazing has the potential to enhance soil erosion by exposing the soil facilitating surface runoff. Some previous studies revealed that the effect of cattle grazing around watering points is low [15] whereas that of wildlife was found to be high, characterised by absence of vegetation [10, 16, 17]. This explains why large-scale commercial farmers which occupied vleis in the early days limited the use of the vlei to late dry season grazing to avoid heavy grazing which resulted in erosion throughout the year [2]. In the case of the lower section of Dete vlei, pressure of wild grazing is high since grazing is continuous during the dry season while wild animals are attracted by watering points and salt licks to a central point. Therefore, strategies should be considered to regulate grazing around watering points and salt licks in order to mitigate soil erosion considering that bare conditions were not a common phenomenon in the upper section of the vlei which has no watering points and salt licks.

Wildlife trampling which is well pronounced within a 15 m radius of watering points also results in top soil loosening and loss of vegetation cover, making the soil susceptible to erosion and possibly siltation of the existing water points. This finding concurs with [10] who acknowledged that the visibility of wild herbivores trampling around watering points results in vegetation cover reduction. According to [13], the continuous trampling by wild animals in a forage land accelerates the reduction of vegetation cover and ultimately exposes the soil to erosion agents.

Wildlife vegetation destruction, especially *Acacia* trees by elephants, exposes soil to water erosion along the wetland fringes, facilitating increased sediment input into the wetland given its fairly steep gradient (**Table 2**). The effect of high elephant densities on vegetation and the environment in general is well documented [26]. This was complemented by findings by [27] that high elephant population results in severe environmental damage, loss of biodiversity and increased competition for scarce resources. In the case of Dete vlei, the elephant density is estimated at 0.01/km<sup>2</sup> in the whole of Sikumi forest (and 0.52/km<sup>2</sup> in the wetland area). According to the Ecologist and Forester, the current elephant population is beyond the optimum carrying capacity of the area. Considering that there are various wildlife species frequenting the vlei as well as a result of the presence of water during the dry season (**Figure 4**), the ecological carrying capacity of the vlei could have been severely exceeded as different wild animals compete for grazing; hence vegetation loss and the potential of soil erosion being accelerated in the vicinity of watering holes.

Furthermore, artificial salt licks attract more wildlife for photographic safaris, resulting in more tourists visiting the area at the detriment of the wetland. In this case, safari operators, by applying salt, are more concerned with the economic gains associated with the influx of game viewers at the expense of the vlei's ecological condition which is the basis for the existence of these economic activities. The tourists have also been contributing to soil erosion as evidenced by erosional features such as rills and gullies developing along footpaths around watering points in the lower section of the wetland. Therefore, instead of simultaneously harmonising environmental and economic considerations to achieve wise use of the wetland, these two objectives are treated as discrete entities by safari operators, a situation with potential to cause vlei degradation and loss and ultimately loss of business in the long run for the safari operators.

**Acknowledgements**

**Conflict of interest**

No conflict to declare.

Thomas Marambanyika1

marambanyikat@staff.msu.ac.zw

**Author details**

Zimbabwe

**References**

123-150

We would like to thank Mr. Tendai Serima, Forester—Sikumi Forest for assisting in field data collection and the Forest Protection Unit guards for providing security during the field survey. We would also like to thank the Research Board, Midlands State University, for funding the fieldwork.

Assessing the Drivers of Wetland Changes in Areas Associated with Wildlife-Based Tourism…

http://dx.doi.org/10.5772/intechopen.80513

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1 Department of Geography and Environmental Studies, Midlands State University, Gweru,

[1] Government of Zimbabwe. Zimbabwe's Fifth National Report to the Convention on Biodiversity. Harare: Ministry of Environment, Water and Climate; 2015. 18 p

[2] Whitlow R. A review of dambo gullying in South-Central Africa. Zambezia. 1989;**16**(ii):

[3] Whitlow R. Survey of dambos in Zimbabwe [intensive conservation areas]. Zimbabwe

[4] Fenken K, Mharapara I. Wetland Development and Management in SADC Countries: Proceedings of a Sub-Regional Workshop. Harare: FAO and SAFR; 2002. pp. 64-85 [5] Marambanyika T, Beckedahl H, Ngetar NS, Dube T. Assessing the environmental sustainability of cultivation systems in wetlands using the WET-health framework in Zimbabwe.

[6] Madebwe V, Madebwe C. An exploratory analysis of the social, economic and environmental impacts on wetlands: The case of Shurugwi District, Midlands Province.

Zimbabwe. Journal of Applied Sciences Research. 2005;**1**(2):228-233

2 Discipline of Environmental Sciences, School of Agricultural, Earth and Environmental

\* and Mbulisi Sibanda2

\*Address all correspondence to: tmarambanyikat@yahoo.co.uk;

Sciences, University of KwaZulu Natal, Scottsville, South Africa

Agricultural Journal. 1984;**18**(4):129-138

Physical Geography. 2017;**38**(1):62-82

Unplanned and poorly designed drive ways have potential to worsen the rate of erosion despite the reduction in rainfall amounts received in the area. This is more evident where some roads from the catchment surrounding the vlei were established following fairly steep gradients, a situation likely to accelerate the rate of soil erosion due to the effect of concentrated flow and possibly increased sediment yield. This may suggest that vehicle movements if not well planned and monitored have great potential to cause soil erosion in the wetland and tourist areas.

Although the gullies noted in this study are relatively small (a depth of 24 cm) when compared with those reported in other studies [2] which exceed 50 cm in depth, they are still of major concern. This implies that intervention strategies to mitigate soil erosion should be considered so that the vlei does not develop big gullies as those noted by Whitlow in the communal areas of Zimbabwe. These gullies are a growing threat to the socio-economic benefits linked to wetland utilisation. This is grounded on the findings of this study which illustrated that there is a temporal increase in the spatial extent of bare areas in the lower section of the wetland and overall reduction in the wetland size. In contrast, the upper section of the wetland without watering points and salt licks is increasing in size (**Table 1**). This suggests that if photographic safari activities, watering points and salt licks, in particular, are not well regulated, degradation of the wetland is likely to be more pronounced.
