Rapid Population Growth as Foremost Cause of Land Degradation in Ethiopia: A Review

Ethiopia is the second most populous country in Sub-Saharan Africa countries. The rapid population growth in country leads to land degradation; it includes soil degradation, vegetation degradation and water degradation, and natural resources degradation as whole. Diverse scholars indicated, decreasing tendency of forest cover in Ethiopia over time with the population increment. In Ethiopia, the high population growth leads to soil erosion and soil fertility loss; it accelerates soil erosion due to foot path, overgrazing and others, which is meanly estimated 12 tons/ ha/ yr. and, People are using animal dung and crop residue for household fuel rather than being added to the soil to improve soil fertility, which leads to soil quality declination. And, the population pressure leads the water courses to dry up, reduced the volumes of surface water, depletion of aquifers and pollution. If this rapid population growth of Ethiopia continues like the current situation, the land degradation problem is likely to be even more challengeable in the future. Therefore, this paper aims to explore rapid population growth as foremost cause land degradation in Ethiopia by taking typical evidence from different parts of the country and to suggest solutions.


Population growth nexus land degradation
The relationship between population growth and land degradation has been a matter of argument for eras (Bekele and Stein 2003).The debate has been between those who consider population growth as the main offending factor affecting the environment , and those who have shown that population growth does not always result in land degradation (Teklu 2016).
For example, studies by Amara et al. (2011) in Eastern of Wollo (Ethiopia) and Munro et al. (2008) in Tigray highlands revealed that vegetation cover enhanced through rehabilitation by the community efforts. While, Muluneh (2003) conveyed that population growth in west Gurage (Ethiopia) is both a cause of land degradation in the practice of soil erosion and an issue for environmental enrichment in the form of conservation activities.
There are studies which stated that population growth was the original cause for land degradation in Ethiopia. For instance, Paulos (2001) discussed that the rapid growing population of Ethiopia was playing major role in Speeding up land degradation in a manner that due to growing population injured land by deforestation and overgrazing. Likewise, Fitsum et al. (1999) argued that the foremost causes of land degradation in Ethiopian are occasioned from the rising population which is displayed in positions of overgrazing, deforestation and using crop residues and dung for fuel. Berry (2003) also stated that the damage of land resource productivity in Ethiopia is due to the constant population growth. Similar to the above point of views, Desta et al. (2000) maintained that the severe land degradation problems in the Ethiopian highlands are originating from the loads of the rapid growing human populations. Tilahun et al. (2001) also argued that deteriorating vegetative cover and amplified levels of farming on steep slopes in Ethiopian highlands is linked with high population growth. Similarly, Temesgen et al. (2014a) reported that rapid population growth was the major powerful forces for the enlargement of cultivated lands on the forest area in Dera District (Ethiopia).
Typically, studies at large scales and long term have shown that rapid population growth has enormously major cause of land degradation (Lambin et al. 2003). Generally, the rapid population growth in Ethiopia made the land to be 9.24% very high degraded,17.44% high degraded and24.83% medium degraded of the total coverage of the country (Hurni et al. 2010) (Figure 2). Journal of Environment and Earth Science www.iiste.org ISSN 2224-3216 (Paper) ISSN 2225-0948 (Online) Vol.11, No.8, 2021 Figure 2: Land degradation status in Ethiopia (Hurni et al. 2010)

Exploring land degradation forms due to population growth in Ethiopia
Land degradation takes place in the forms of vegetation degradation, soil degradation and water degradation (Temesgen 2015). In Ethiopia, the dependence of the rapid population growth on unmannerly types of existence agriculture and natural resources use are the key reason for the those land degradation forms(forest, soil and water degradations) (Gebreyesus and Kirubel 2009).

Vegetation degradation
Vegetation degradation represents decrease of plant species in biomass, species diversity, or in value in terms of the nutrition (George 2002).Population growth is most factoring that reason to tropical deforestation (Geist and Lambin 2002). Population growth and poverty interrelate with a congregation of daily human consumption factors, which are fuel wood, timber and agricultural products to result land-cover change (Lambin et al. 2003). Similarly to the other tropical countries, the rapid population growth in Ethiopia raises the forest resources consumption (Gurmessa 2015).
Diverse scholars indicated, decreasing tendency of forest cover in Ethiopia over time (Gurmessa 2015). In 1960s, the forest coverage of the country was about 37% (Brieten 1961). MoA (1984) also estimated that at the start of 20th century it was about 35.4%, and it was reduced to 15% in1955 (IUCN,1955),and then the country's current forest coverage to be less than 5% (Gurmessa 2015 This high annual deforestation area is due to the rapid population growth in the country, which leads to growing demand for more agricultural land, fuel wood, construction material and other forest products (Gete 2002) (Figure 3).

Soil degradation
Soil degradation indicates to the deterioration in soil qualities and quantity which includes soil erosion, low organic matter of the soil, loss of soil structure, and salinization and soil acidity problems (Wall et al. 2003). Ethiopia is one of the most severe soils degraded country in the world (Temesgen, 2015). Soil degradation in the form of soil erosion and soil fertility loss are the severe encounters in the country (Paulos 2001).

Soil erosion
Soil erosion refers to wearing a way of soil from one point on the earth surface to be deposited elsewhere by anthropogenic agents or natural factors (Mitiku et al. 2006).
In Ethiopia, the condensed reliance of growing population on a rigorous kind of agriculture with traditional approaches of invention has superior influence for soil erosion (Temesgen 2015). The population has increased very rapidly on the restricted land and each parcel of land is placed into farming, to produce food without proper management and later which outcomes soil erosion (Temesgen et al. 2014a).
Soil erosion is taking place in all corner of the country, but in northern and central highlands are highly severed, due to the effect of high population on the land that are steep and mountainous (Paulos 2001). Some highland areas of the country, which speedily occurs soil erosion are Tigray highlands, Amhara region, Hararge highlands, North and East Shewa, and Wollega and Arsi Zone (Bezuayehu et al. 2002). FAO (1986) stated that, in the mid of1980's 27 million hectare, 14 million hectare and above 2 million hectare of the highland area of Ethiopia were moderate eroded, highly eroded and very highly eroded respectively. Amhara region one of the Ethiopian highlands, soil erosion arrays 9 to 300 tons/ha/ year. Of the total area of the region,30%, 31%, 29% and 10%, of the region practices slight, moderate, high and very high erosion risk, respectively (Temesgen 2015) ( Table 2). The mean yearly rate of soil erosion in country is expected to be 12 tons/ha/yr., and it can radically outstrip this on steep slopes with soil loss 300 tons/ha/year (USAID CRSPT 2000).Of which, the 1.5 billon tons annual soil loss from Ethiopia is due to population growth (Muluneh, 2003).Population growth accelerates soil erosion due to foot path, overgrazing (Mitiku et al. 2006) (Figure 4) and cultivating steep lands (Bezuayehu et al. 2002).

Soil fertility declination
Escalation of agriculture in Sub-Saharan Africa without adding of plant nutrients has caused in wide nutrient running down and subsequent soil fertility declination (Breman and Swift 1997). In Ethiopia, the high population growth and the subsequent land-use intensity causing higher nutrient disturbance through crop removal (Drechs et al. 2001).Similarly, Fantaw (2007) stated that firewood and forest products are scares in Ethiopia due to deforestation. As a result, people are using animal dung and crop residue for household fuel rather than being added to the soil to improve soil fertility, which leads to soil quality declination. Likewise, study in Southeastern highlands of Ethiopia indicated that deforestation and their following change into farmland reduces the soil carbon content (Fantaw 2007).
Alike, the impression of population change on landholder size in Tigray region has led to descent in practice of fallowing which consequences reduce soil nutrients (Corbeels et al. 2002). Correspondingly, study by Tilahun et al. (2001) indicated that burden from the growing population leads, the farmers to cultivate marginal lands, and withdraw fallow. Similarly, Mitiku et al. (2003) reported that the soil nutrients in Tigray region are very deficient, which are 94% of the land had very low level organic carbon, 21% had very low levels of nitrogen content and 98% low phosphorus content. Similarly, Hailu (2010) estimated 1605 kg.ha -1 , 60 kg.ha -1 and 590 kg.ha -1 for nitrogen (N), Phosphorus (P), and potassium (K) stock at plough layer in Tahtay Maichew (Table3). This showed that the soils are attainment the lowest restrictions of productivity (World Bank 2007).

Water degradation
Water degradation refers the declines of water quality and quantity (Temesgen 2015). Human actions lead the water to degraded (Owa 2013). In Ethiopia, the high population pressure leads the water courses to dry up, reduced the volumes of surface water, depletion of aquifers and pollution (Berry 2003). Teklu (2016) stated that, the application of chemical fertilizers and insecticides by high population of Ethiopia lead surface and ground contamination. In Ethiopia, freshwater has deteriorated by pollutants, due to anthropogenic activities like urbanization, industrialization and agricultural practices (Maschal and Truye 2018). For instance, in Addis Ababa, there are a number of pollutant sources that continuously deteriorate the quality of surface and groundwater (Maschal and Truye 2018). About 90% of industries which are found in Addis Ababa have simply discharged their sewage into nearby water bodies, streams, open land without any form of treatment (Maschal and Truye 2018).

Conclusion
In Ethiopia, the concern of rapid population growth rates is an increasing pressure on natural resources, consequently land degradation. It drives gradually hard to satisfy the basic needs of rising population as the each one intake of resources increases. The amount of population increase will rise the demand of the present which leads to land degradation severity and global insufficiency of land resources for future.
The outcomes of high population growth rates are increasing number of people below poverty line, an increasing population density, and pressure on natural resources. This review paper reveals that the country's population growth is imposing an increasing burden on the country's limited and continually degrading natural resources. So, society should be aware on family planning, natural resource conservation, land resource management and environmental protection to sustain the proportion of population growth of the country with its land resource capacity.