**2. Material and methods**

### **2.1. Study area**

or depressions with herbaceous vegetation, mainly grasses and sedges, and devoid of trees [3]. About 60% of wetlands are found in communal and resettlement areas [1], and are predominantly used for cultivation and livestock grazing [4]. Several researches in Zimbabwe have been focusing on communal and resettlement areas to understand the impact of the aforementioned agricultural practices on various wetland ecosystem components such as vegetation,

Estimates show that more than 50% of the original wetlands have been lost world over [7]. In Zimbabwe, estimates show that wetlands declined by almost 50% over the past three decades. In the 1980s, wetlands covered 3.6% of the total country area [3] compared to 1.8% in 2015 [1]. Despite previous research on severe wetland degradation in communal, resettlement and urban areas of Zimbabwe [2, 8], there is a dearth of information on how wetlands located in demarcated or state-protected forests (which accounts for part of 40% of wetlands in Zimbabwe) are affected by the existing land uses that are different to those of well-studied communal and resettlement areas, dominated by agriculture. Lack of information on wetlands condition may compromise effective management of these ecosystems in

In Zimbabwe, demarcated forests are primarily established to manage catchment areas located on fragile Kalahari soils [9]. These forests are managed by a statutory body, the Forest Commission. The major focus of this statutory body is to ensure protection of the forests; hence, there is no deliberate policy to manage wetlands found in the demarcated forests. Wetland ecosystems in protected forests are managed as part of the forest ecosystem, with the primary objective being to protect the forest. However, these wetlands have different human threats to that of forests, a situation that may result in unnoticed wetland degradation and loss. Therefore, there is need to understand the ecological as well as the geomorphological conditions of wetlands in protected areas in light of the presence of potential degrading agents such as high number of tourists and wildlife densities. Some studies have shown that wetland degradation in game reserves is possible, although the rate and causes may vary spatially [10–13]. Dete vlei is primarily used for photographic safaris since it is adjacent to Zimbabwe's largest wildlife sanctuary, Hwange National Park. As a result, different wildlife species graze and drink water in the vlei during the dry season. Wetlands are known to provide forage for herbivores in the African savannah ecosystem over the dry season and during droughts [11, 14]. However, lack of wildlife management within the carrying capacity can lead to high grazing pressure and ultimately wetland degradation [11, 14, 15]. On the other hand, the population of wild herbivores may be threatened by widespread degradation of wetlands [11, 12]; hence need to explore ways of sustainably managing wetlands with different

Meanwhile, salt licks and watering points were established to attract wildlife for game viewing in Dete vlei. The importance of salt licks and watering points as attractants for game viewing has been studied [10, 16]. However, the link between wildlife-based tourism activities and wetland conditions has not been well studied in Zimbabwe regardless of the fact that wildlife pressure is known to have the most damaging outcomes to the world's natural environment, including wetlands [17]. This study, therefore, assesses the potential impact of wild animals

hydrology, geomorphology, soils and water quality [5, 6].

170 Wetlands Management - Assessing Risk and Sustainable Solutions

protected forest areas.

drivers of change.

Sikumi forest has several depressions, with Dete and Zingeni vleis forming the main drainage system of the forest. The study was carried out in Dete vlei found in Sikumi forest (27°10′E; 18°45′S), located in Hwange district of Zimbabwe (**Figure 1**). Sikumi forest is a demarcated forest area that occupies about 55,700 ha [18]. Dete vlei occupies about 903.1 ha, that is, approximately 1.6% of the total forest area. The forest shares boundaries with communal areas, large commercial farms and Hwange National Park (**Figure 1**).

Rainfall in the area is low, variable and unpredictable. The average rainfall for the past 5 years is 500 mm [9]. The rain season normally stretches from October to April. The average minimum

**Figure 1.** Map showing the location of Dete vlei in Sikumi Forest, Hwange district of Zimbabwe.

and maximum temperatures are 13 and 29°C, respectively, with occasional frost experienced in the depressions [9]. The forest reserve provides commercial timber and wildlife. The dominant soil type is the Kalahari sand associated with the endemic dominant *Baikiaea* genus tree species [18]. The depressions and gentle areas in the forest area are associated with pale sands.

The common grass species in the vlei are *Aristida*, *Sporobolus*, *Eragrostis*, *Pogonarrhia, Perotis and Hyperrhenia* as well as sedges such as *Cyperus*. Due to the forest's proximity to Hwange National Park, the vlei has abundant and wide diversity of game. The common wildlife during the dry season includes elephants, buffaloes and different type of plains game. About 7500 ha of forest land, including the vlei, is leased to private operators for photographic safari business. Therefore, the vlei provides grazing and water to wildlife during the wet and dry seasons and at the same time sustains photographic safari activities. This means the impact of these wildlife-tourism-based business ventures on the vlei needs to be understood in order to come up with appropriate wetland use and management strategies as promoted by [19].

### **2.2. Hydrogeomorphic characteristics of the vlei**

The study compares land cover changes in the upper and lower sections of Dete vlei. The lower section is primarily used for photographic safaris, whereas the upper section has been set aside for uncontrolled wild animal grazing. The whole vlei resembles the features of an unchanneled valley bottom [20]. The vlei has a gentle, longitudinal slope (approximately 1.5%), and no clearly defined stream. The wetland is located at the head waters of a stream that drains into Gwaai River. The predominant source of water for the vlei is direct precipitation, although subsurface inflows can be experienced from the protected forest area that occupies the entire upstream catchment area of the wetland due to the presence of dense vegetation and Kalahari sand soils with a high hydraulic conductivity and infiltration capacity. The use of the wetland for wildlife-based photographic safaris influenced by artificial watering points and salt licks has potential to change wetland cover and possibly degradation of the resource.

computed in GIS environment. Image characteristics such as tone, texture, shape, colour and contextual traits as well as locations noted during the field surveys were used in characteris-

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A field survey was carried out during the dry period between November and December 2016. Field observations were carried out to identify evidence of erosion in the form of rills and gullies, sediment deposition and grass cover loss within the vlei. The locations of these erosional sites were noted and used to facilitate their characterisation during the on-screen digitising procedure. Observations were further done, through transect walks, to ascertain if movement of wild animals and associated tourist activities was influencing vegetation cover changes and soil erosion within the vlei. Wildlife paths, pressure on grazing, gravel roads condition, salt

The slopes of the vlei depression were measured at 500 m intervals, from the main road going eastwards (**Figure 2**; **Table 1**). The slope was measured since it influences water erosion, although the rate of erosivity depends on a combination of factors including rainfall amount and intensity, soil type, to mention a few [21]. The identified erosional features such as gullies' slope, depth, width and length were measured. Gully depth and width were measured using a tape measure, whereas the length was measured using a measuring wheel (Bosch GWM 32

The diameter and depth of the observed salt licks pits near watering points in different parts of the wetland were also measured to determine how the wetland morphology or landscape was altered by salt licking. Annual rainfall data (1962–2016) and annual mean daily minimum and maximum temperatures data (1962–2010) were obtained from the Meteorological

ing the land cover types within the vlei.

**Figure 2.** Slope sampling points on the lower section of the wetland.

licks and watering points were observed, noted and described.

Professional). Slope was measured and expressed in percentages.

**2.4. Field data collection methods**

#### **2.3. Wetland mapping procedures**

Spatial and temporal changes of wetland ecological conditions in relation to erosion and vegetation cover changes were assessed by comparing SPOT satellite imagery for years 1984, 2007 and 2013 to determine the spatial extent of impact of various photographic safari activities. The upper section of the vlei has no artificial watering points and salt licks; hence was compared with the lower section characterised by watering points and salt licks established to influence game viewing. In this study, the upper section of the vlei, across the road to the western side (**Figure 2**), was used as a baseline condition to show an area grazed by wild animals without the influence of watering points and salt licks. Selection of the years for satellite imagery analysis was influenced by availability of high spatial resolution imagery. The image acquired in 1984 image was used as a baseline imagery since it pre-dates the establishment of artificial watering points and salt licks in the entire vlei. The areas that have no grass due to wildlife grazing, salt licking and watering points, which facilitate a high concentration of wild animals on the same spot more frequently, were digitised on screen and classified as bare areas. The spatial extent occupied by bare areas, water and grass within the vlei was Assessing the Drivers of Wetland Changes in Areas Associated with Wildlife-Based Tourism… http://dx.doi.org/10.5772/intechopen.80513 173

**Figure 2.** Slope sampling points on the lower section of the wetland.

computed in GIS environment. Image characteristics such as tone, texture, shape, colour and contextual traits as well as locations noted during the field surveys were used in characterising the land cover types within the vlei.

### **2.4. Field data collection methods**

and maximum temperatures are 13 and 29°C, respectively, with occasional frost experienced in the depressions [9]. The forest reserve provides commercial timber and wildlife. The dominant soil type is the Kalahari sand associated with the endemic dominant *Baikiaea* genus tree species [18]. The depressions and gentle areas in the forest area are associated with pale sands. The common grass species in the vlei are *Aristida*, *Sporobolus*, *Eragrostis*, *Pogonarrhia, Perotis and Hyperrhenia* as well as sedges such as *Cyperus*. Due to the forest's proximity to Hwange National Park, the vlei has abundant and wide diversity of game. The common wildlife during the dry season includes elephants, buffaloes and different type of plains game. About 7500 ha of forest land, including the vlei, is leased to private operators for photographic safari business. Therefore, the vlei provides grazing and water to wildlife during the wet and dry seasons and at the same time sustains photographic safari activities. This means the impact of these wildlife-tourism-based business ventures on the vlei needs to be understood in order to come up with appropriate wetland use and management strategies as promoted by [19].

The study compares land cover changes in the upper and lower sections of Dete vlei. The lower section is primarily used for photographic safaris, whereas the upper section has been set aside for uncontrolled wild animal grazing. The whole vlei resembles the features of an unchanneled valley bottom [20]. The vlei has a gentle, longitudinal slope (approximately 1.5%), and no clearly defined stream. The wetland is located at the head waters of a stream that drains into Gwaai River. The predominant source of water for the vlei is direct precipitation, although subsurface inflows can be experienced from the protected forest area that occupies the entire upstream catchment area of the wetland due to the presence of dense vegetation and Kalahari sand soils with a high hydraulic conductivity and infiltration capacity. The use of the wetland for wildlife-based photographic safaris influenced by artificial watering points and salt licks has potential to change wetland cover and possibly degradation of the resource.

Spatial and temporal changes of wetland ecological conditions in relation to erosion and vegetation cover changes were assessed by comparing SPOT satellite imagery for years 1984, 2007 and 2013 to determine the spatial extent of impact of various photographic safari activities. The upper section of the vlei has no artificial watering points and salt licks; hence was compared with the lower section characterised by watering points and salt licks established to influence game viewing. In this study, the upper section of the vlei, across the road to the western side (**Figure 2**), was used as a baseline condition to show an area grazed by wild animals without the influence of watering points and salt licks. Selection of the years for satellite imagery analysis was influenced by availability of high spatial resolution imagery. The image acquired in 1984 image was used as a baseline imagery since it pre-dates the establishment of artificial watering points and salt licks in the entire vlei. The areas that have no grass due to wildlife grazing, salt licking and watering points, which facilitate a high concentration of wild animals on the same spot more frequently, were digitised on screen and classified as bare areas. The spatial extent occupied by bare areas, water and grass within the vlei was

**2.2. Hydrogeomorphic characteristics of the vlei**

172 Wetlands Management - Assessing Risk and Sustainable Solutions

**2.3. Wetland mapping procedures**

A field survey was carried out during the dry period between November and December 2016. Field observations were carried out to identify evidence of erosion in the form of rills and gullies, sediment deposition and grass cover loss within the vlei. The locations of these erosional sites were noted and used to facilitate their characterisation during the on-screen digitising procedure. Observations were further done, through transect walks, to ascertain if movement of wild animals and associated tourist activities was influencing vegetation cover changes and soil erosion within the vlei. Wildlife paths, pressure on grazing, gravel roads condition, salt licks and watering points were observed, noted and described.

The slopes of the vlei depression were measured at 500 m intervals, from the main road going eastwards (**Figure 2**; **Table 1**). The slope was measured since it influences water erosion, although the rate of erosivity depends on a combination of factors including rainfall amount and intensity, soil type, to mention a few [21]. The identified erosional features such as gullies' slope, depth, width and length were measured. Gully depth and width were measured using a tape measure, whereas the length was measured using a measuring wheel (Bosch GWM 32 Professional). Slope was measured and expressed in percentages.

The diameter and depth of the observed salt licks pits near watering points in different parts of the wetland were also measured to determine how the wetland morphology or landscape was altered by salt licking. Annual rainfall data (1962–2016) and annual mean daily minimum and maximum temperatures data (1962–2010) were obtained from the Meteorological


**Table 1.** Location of the selected slope sampling points.

Services Department of Zimbabwe. Local climate data were used to assess the possible effect of local climate variability on wetland vegetation condition and geomorphic processes such as erosion and deposition.

Historical information of the wetland's geomorphic condition was obtained from purposively sampled key informants targeted for semi-structured interviews. In this case, a template with open-ended questions was prepared to guide face-to-face discussions. The key informants were selected from organisations that are involved in photographic safari ventures, management of the forest areas located in the catchment area of the vlei or individuals who had knowledge of the area stretching over several decades. The key informants were the Safari Operators, former Forest Commission Divisional Manager for Indigenous Forests, Matabeleland North Forestry Commission Provincial Manager, Sikumi Forester and the Parks and Wildlife Management Authority Ecologist. Records of wildlife population changes and number of tourists were also obtained and reviewed.

### **2.5. Data analysis**

Rainfall and temperature data obtained from the Meteorological Services Department of Zimbabwe used for determining trends were subjected to regression analysis performed in Microsoft Office Excel 2007. Trend analysis was done to determine if there was change in mean annual temperature (minimum and maximum) and annual rainfall totals, since temperature and rainfall amount influences vegetation cover and geomorphic processes such as erosion and deposition. Qualitative data generated through semi-structured interviews (on perceived changes in wildlife numbers, vlei's condition and climate trends) were analysed using thematic analysis method [22]. Wildlife population density was calculated basing on average game counts done by Forestry Commission in 2016 and the vlei size measured in ha.

2016 (y = −2.932x + 672.800; r2 = 0.033). The highest (975.9 mm) and lowest (311.9 mm) amount of rainfall were received in 1973 and 2000, respectively. In contrast, mean maximum yearly temperature (y = 0.035x + 28.350; r2 = 0.219) and the mean minimum yearly temperature (y = 0.019x + 12.910; r2 = 0.059) have been increasing between 1962 and 2010. The mean maximum yearly temperature is 29.1°C, whereas the mean minimum yearly temperature is 13.3°C (**Figure 4**). The former Forest Commission Divisional Manager for Indigenous Forests attributes the reduction in rainfall to

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The common wildlife species found in the vlei are elephants, buffaloes, baboons, sables, impalas, kudu and warthogs (**Figure 5**). Generally, small and large predators account for relatively

changing climate accompanied by frequent droughts that intensified from the year 2000.

**Figure 4.** Annual minimum and maximum temperature for Dete Vlei, Hwange district.

**3.2. Wildlife population changes**

**Figure 3.** Annual rainfall totals for Dete Vlei, Hwange district (1962–2016).
