It is the fifth largest forest country in the world and the African country has the largest area of forest, with 47% of Africa’s forest formations. From a regional point of view, there are more than 60% of all forests in the Congo Basin. In addition, forests cover 67% of the national territory. Dense wet forests occupy nearly 99 million hectares, of which just over 83 million are low-lying. It is estimated that 60 million hectares of these forests would be suitable for timber production, roughly equivalent to all other forest countries in Central Africa. These forests are located mainly in the central basin .Through to the analyzed data we obtained the results presented in Table 2. This development points to a risk of the country slipping in the forest transition curve, which would result in a very strong acceleration of the dynamics of loss of forest cover in the coming years, like other tropical countries . The result of the forest cover estimate in 1990 and the detection of negative change in 2018 give an annual deforestation rate relative to forest area of 2.12% ± 0.07%. Poverty, population growth, weak local governance and scarcity of infrastructure and energy, fuel rural exodus, and are the indirect causes of deforestation. Agriculture and charcoal production: Currently, the main drivers of deforestation and forest degradation in the Democratic Republic of Congo are food agriculture and charcoal production, which alone destroy more than 90% of the Democratic Republic of Congo’s forests. Firewood collection and logging and mining operations also have an impact. Democratic Republic of Congo’s deforestation rates are closely linked to population growth, with nearly two-thirds of the population living in rural areas and producing nearly half of their own food. Small-scale agriculture appears to be the main driver of deforestation in the Democratic Republic of Congo and other countries in the Congolese basin.
However, researchers warn that a “new wave” of industrial deforestation could emerge. If the Congolese basin does nothing to reduce deforestation rates, all forest cover is likely to pass through. Illegal logging is the second largest factor in deforestation in the Democratic Republic of Congo. It is mainly fuelled by small-scale logging for national and regional markets, and has played a key role in financing the current conflict. Although itinerant cultivation does not necessarily indicate expansion in the primary forest,stackable flower pots growing populations can intensify agricultural practices, reducing fallow periods when trees naturally regrow. In 2017, 3% of the total loss of tree cover occurred in protected areas and 10% in forest concessions. Watershed degradation in the developing countries due to anthropogenic activities is increasingly becoming a threat to the natural water resources . As a result, most rural areas are undergoing rapid and far reaching land use changes. Many researchers including Olson and Matina concur that most of the changes are mainly associated with intensification of agriculture and expansion of mixed-crop livestock systems into former grazing land and other natural areas. In addition there is increased deforestation and encroachment of the forests hence reduced forest cover . Changes in land use patterns in Kenya are linked to a rapidly increasing population in rural areas . This growth rate translates to an increased pressure and demand for land resources especially in the watershed regions such as Mau Forest Complex. As a result, there is continuing watershed degradation reflected through diminishing forest cover, reduced water quality, soil productivity, loss of riparian vegetation and wetland areas leading to a decline in the ecological stability of these systems .
SWMFC is considered the most important of the five main watershed areas in Kenya because of its immense economic, social and environmental contributions to the country . It is the main source of Chemosit and Kipsonoi rivers among other major rivers that drain into the Lake Victoria Basin. Despite the critical role in supporting environmental, socio-economic and biological processes, South West Mau Forest Complex has been greatly deforested through excision and encroachment for settlement and farmland . This high rate of vegetation loss has led to decline in the ecological and hydrological changes that may threaten the sustainable future of areas downstream, biodiversity conservation and livelihood support systems . Riparian areas are essential for diminishing negative impacts of land use activities on rivers . However, the riparian areas in SWMFC are experiencing diverse development initiatives likely to have also considerably reduced the biodiversity and increased threats to these river systems . This study set out to determine how land use activities have affected riparian structure, water and soil qualities along Chemosit and Kipsonoi rivers in South West Mau Forest Complex. Adjacent land use activities were obtained through direct observation and photographs. Information on major crops was collected using a structured questionnaire administered to the sampled households living in the immediate vicinity and within 1 km on either side of the river bank. Local land use in every sampling site was recorded. Physical parameters , chemical parameters and heavy metals was done according to the standard procedures as described in APHA . These are as follows: Total suspended solids were estimated gravimetrically, water pH using a pH meter, Total Nitrogen determined by Kjeldahl digestion. Total phosphorous was determined using the ascorbic acid method while analysis for potassium, copper, cadmium and lead was carried out using Atomic Absorption Spectrophotometer . Before analysis, calibration standards of different concentrations were prepared. In this particular analysis, each replica representing samples from the middle and the two edges were mixed separately to form a composite sample.
A total of 18 composite samples were obtained for the entire water samples collected. Soil samples were separately air-dried at room temperature, crushed, homogenized and passed through a 2 mm sieve. Soil organic carbon content was determined by the Walkey Black titration method . Total Nitrogen was determined using the Kjeldahl distillation method . Potassium, Sulphur, Phosphorous, Cadmium, Copper, and Lead were analyzed using inductivity couple plasma spectrophotometer . Soil pH was determined using a pH meter. Chemosit and Kipsonoi rivers traverses through different land use types. In this case, six distinct land use activities were identified along based on their dominant land uses and characteristics. Generally there is a variation in land use activities from upstream to downstream. Upstream is dominated by indigenous forest characterized by dense network of trees and bushes with little human disturbance. From the edge of the forests towards midstream, the land opens up to a rich upland agricultural area of extensive and intensive farming characterized by tea plantation and few human settlements. Moving downstream, grazing and mixed agricultural farming predominate with more permanently settled small scale farmers and urban set-up with high population and economic activities. From our results, farming plays an important role in South West Mau catchment and is in agreement with findings by Calamari et al., 1995; Jaetzold and Schmidt, 2009. Figure 2 reports the overall riparian biodiversity disturbance in South West Mau catchment. Upstream riparian vegetation was least disturbed with native vegetation present on both sides of the river, intact canopy and with continuous woody vegetation along the riparian zone, dense ground cover and river banks in natural condition. Midstream riparian vegetation is in poor condition characterized by isolated woody vegetation, limited ground cover and disturbed banks. In addition there is a high disturbance of the riparian zone by stock or through the intrusion of exotic species, although some native species remain. Valley vegetation is clearly agriculture with native vegetation clearly disturbed and with a high percentage of introduced species present. Downstream riparian vegetation is severely disturbed on both sides as indicated by reduced and absence of riparian vegetation.During the study period, significant differences were observed in Water pH and Total Nitrogen between sampling sites. Tukey’s test showed that the mean water pH at upstream sampling site differed significantly from that recorded at downstream of Chemosit river. Along Kipsonoi river, the mean water pH differed significantly between midstream and Downstream sampling sites. In both rivers, the mean value for water pH ranged from 6.9 to 7.2 . However these values fall within the pH range associated with most natural waters of 6.5 to 8.5 . Most ecosystems are sensitive to changes in pH while certain organisms prefer different ranges of pH . The reported land use activities in SWMF do not seem to modify the pH of the water. On the other hand, along Chemosit river significant differences were observed in total nitrogen between upstream and midstream sampling sites and between upstream and downstream along Kipsonoi river, respectively. The high Total Nitrogen concentrations of 6.7 mg/l and 5.7 mg/l observed midstream of the two rivers could be associated with adjacent urban and agricultural land use activities.
According to agricultural activities can lead to an increased flux of nitrogen into water bodies while use of fertilizers on agricultural land has been associated to high nutrient levels at such sites . Further, total suspended solids, potassium, flower pots for sale total phosphorous, cadmium, lead and copper did not however show any significant differences. Total Suspended Solids were highest midstream on both rivers. This variation could be associated to the different land use activities reported for these sites, run-off from agriculture, soil erosion as well as in- stream activities such as car washing. Presence of indigenous forests, absence of agricultural activities, intact riparian zones characterized by dense vegetation explain the low levels of Total Suspended Solids in the upstream of the two rivers . However total suspended solids in SWMF ranged from 24 – 84 mg/l which is below WHO limits of 1000 mg/l of suspended solids of drinking water. Total phosphorous concentrations increased downstream with the highest concentration recorded at midstream and lowest at upstream on both rivers. Natural concentrations of phosphorous in surface waters usually range from 0.005 to 0.02 mg/l, while the Environmental Protection Agency recommends a 0.1 mg/l for aquatic systems to prevent accelerated eutrophication . Low concentrations of total phosphorus recorded upstream of Chemosit and Kipsonoi rivers is linked to the undisturbed dense network of trees. In undisturbed forested areas, streams are believed to have good water quality with low concentration of nutrients . The dense riparian vegetation within the forest land use are effective buffers in filtering out most of the nutrients from the surface run-off . These findings mirror previous studies that concluded that water quality is greatly linked to land use in a catchment and confirms several studies that have shown agriculture and urban land use as a primary predictor for nitrogen and phosphorous in stream water . The amount of heavy metals represented by Cd, Cu and Pb did not differ significantly across sites and their concentration did not follow any trend from upstream to downstream. These results agree with previous study that metal concentrations at sites located relatively high up in the catchment were comparable to, or higher than concentrations of these metals downstream. These values are linked to effluent discharge, agricultural and urban run-off, washing and bathing activities by local inhabitants and livestock access to the rivers. In addition degradation of the forest cover and other anthropogenic activities going on inside the forest, atmospheric deposition and geology weathering are potential sources of these metal ions . The mean values and standard deviation of soil physico-chemical variables at different sampling sites along the two rivers of Chemosit and Kipsonoi are presented in Table 3 below. The low soil pH upstream might be due to the presence of slightly higher organic carbon content in the soil. Variability in total organic carbon along the two river systems is linked to the reduction in organic material being returned to the soil system due to decreasing vegetation cover downstream and oxidation of soil organic matter as a result of continuous cultivation along the riverbanks, uncontrolled grazing and browsing, loss of organic matter by water erosion and removal of green materials. These results are in agreement with other studies that reported that the soil organic content differed with different land use types .