Plant communities along rivers are commonly referred to as the river bank vegetation. River banks are some of the most ecologically productive places on earth. The first 10‐15 meters of land that surround rivers are responsible for 90% of river life. These areas are up to 500% more diverse than other areas upland rivers (Liu, Liu, & Zhang, 2014). In addition, they support a lot biodiversity which include plants, insects, amphibians, birds, and mammals. The vegetation along rivers helps in maintaining clean water/water quality since it is vital in filtering, retaining and treating surface runoffs before they can reach the water (Liu et al., 2014). As Safari D et al. (2012) stated it, run offs contain pollutants for example pesticides, fertilizers, sediment, manure and motor fluids. These have negative effects on river water since fertilizers can stimulate algae and plant growth; sediments can affect fish habitat and nursery areas; and pathogens can contaminate the water. The vegetation reduces flooding since it acts as barriers against moving water by reducing the force, height, and volume of floodwaters (Teresa et al., 2010). It also controls soil erosion by keeping soil in place with their underground root systems which prevent topsoil from being exposed and washed away into the river. Thermal cover and temperature moderation: The vegetation also shields the river from summer temperature extremes, thus moderating the water body temperature. The cover of leaves and branches provides shade that provides a cooler area for aquatic life since cooler areas hold more dissolved oxygen (Liu et al., 2014).It also acts as source of food and habitat to wild life. It protects wildlife from weather and predators.Thus, due to the importance of the river bank vegetation stated above, its diversity, abundance and distribution patterns will be assessed along R. Chambura.1.2.3 Various human activities and how they affect the vegetation along the river.Despite the benefits of the river bank vegetation, it is currently under threat majorly due to increasing human activities (Safari D et al., 2012). These degrade the vegetation, altering the plant community assemblage along rivers which consequently affect the ecological integrity of the river. Some of these activities include;Hydro power/ dam construction: – Dams are constructed on the rivers to meet the varying requirements of power, flood control, irrigation and drinking water. Dam construction on the river changes the ecological and biological conditions of river (Gupta, Vishwakarma, & Rawtani, 2009). Alteration occurs in the faunal and floral characteristics near the dammed site. In the upstream of a river, increased water level is the main effect of damming. The hydro-geomorphic changes of the rivers strongly affect the population, structure and distribution of the upstream riparian plant communities. This consequently leads to loss of the vegetation of the surrounding riparian areas (Tombolini, Caneva, Cancellieri, Abati, & Ceschin, 2014).Studies on the impact of dam construction on the upstream riparian vegetation have become a topic of scientific interest, mainly over the last decades (NILSSON & BERGGREN, 2000). Many studies assessed the main factors affecting the plant colonization of the riverbanks, such as the water level fluctuation and the instability of the new shorelines (e.g. (Johnson, 2002)). However, the knowledge about the effect of damming on the riparian vegetation is very poor in communities along R. Chambura since dam construction on this river just started in 2017. Therefore, mankind intervention towards hydropower development on this river is the major concern for maintaining the river bank vegetation and the overall ecological integrity of the river. Thus, dam construction will be considered in this study.Eucalyptus growing: – Eucalyptus plants are grown mainly because they are fast growing tree species, require minimum care, they can grow in wide ranges of environments including poor environments and they are as well as resistant to environmental diseases and stress (Poore & Fries, 1985) & (FAO, 2009). In addition, eucalyptus is a source of timber, electric poles and firewood to humans. However, negative impacts of eucalyptus on the environment have raised worries about planting the species. The alleged negative environmental impacts of eucalyptus have become a global narration. According to Teklu (2009), major effects of eucalyptus along the rivers include; – they drain water resources; suppress undergrowth river bank vegetation and enhance river bank erosion.. This makes the study relevant since eucalyptus growing will also be considered as an example of human activities that affect the vegetation along R. Kyambura.Brick laying: – Brick laying is usually carried out along river banks since it requires a lot of water in mixing clay. According to Mohamed & Abdalla (2015), red brick manufacturing on the river banks has several effects on vegetation along rivers. Herbaceous plants are usually affected through clearance since brick laying needs a clear place free from plants, where bricks are placed. Wood is the main material used in the burning red bricks, because at least 50% of energy used for burning the bricks is from it (A. Shakir & Ahmed Mohammed, 2013). This affects most of the woody plants that grow along river banks. Along R. Chambura, red brick manufacturing is carried out, however, there’s insufficient information about the effect of brick laying on the plant community composition along this river. This makes the research pertinent since brick lying will be considered as one of the human activities that affect the vegetation along this river.Agriculture (especially banana growing): – Banana is considered as the most important fruit crop in East Africa in terms of volume of production and export earnings. According to Nyombi (2013), banana growing is usually carried out because it is a major staple food and provides a good source of carbohydrates, minerals and vitamins; the surplus can be sold to generate income for further house hold use; in addition, harvesting can occur continuously throughout the year once the crop is established, rather than over a short season and it can as well as outperform many other crops in terms of yield under optimum conditions. However, according to Svensson, Bellamy, Van den Brink, Tedengren, & Gunnarsson (2018), banana production carried out along the rivers has the following effects on the river bank vegetation: it leads to deforestation and biodiversity loss especially due to clearance of the vegetation to grow bananas. In most banana plantations, application of pesticides and manure is usually carried out. Pesticides degrade the vegetation by altering their reproduction. It also leads to sediment production which affects the vegetation if the sediments become too much. However, there is little information about effect of banana plantations on the river bank vegetation thus, making this research relevant since banana growing will be considered as one of the human activities that affect the vegetation along this river. Most of the human activities described above threaten the important vegetation along the river by modifying the plant species’ communities and characteristics (Ibarra-manrı, 2014). It is clear that the impact of these human activities on the river bank vegetation is still inadequately understood by communities along R. Chambura, and very few studies have been carried out in this area. This makes this research relevant since it will focus on effect of human activities on the vegetation along R. Chambura in a bid to develop strategies to restore and conserve this vegetation.
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