Although biodiversity is understood as a key factor for the sustainability of life, biodiversity loss is one of the greatest environmental crises. The growing human population and the demand for natural resources have put great pressure on the biodiversity wealth of the world through deforestation, habitat fragmentation, and overexploitation of species [1, 2].
Habitat loss and change, over-harvesting, pollution, and climate change have been the direct causes of global biodiversity loss [3], while population growth, changes in economic activities, socio-political factors, cultural factors, and technological change are indirect drivers [4]. Besides, these global factors, lack of technical knowledge and awareness, and political instability have exacerbated the problem in many developing countries [5].
The definition of forest given in two important studies of East-African vegetation [6, 7] has been adapted: "Forest is a continuous stand of woody individuals, at least 5 m in height, with crowns touching or intermingling".
However, Ethiopia adopted a new forest definition as follows: “Land spanning at least 0.5 ha covered by trees and bamboo), attaining a height of at least 2 m and a canopy cover of at least 20% or trees with the potential to reach these thresholds in situ in due course” [8]. This forest definition differs from the definition used for international reporting to the Global Forest Resources Assessment (FAO) and from the forest definition used in the National Forest Inventory which both applied the FAO forest definition with the thresholds of 10% canopy cover, a 0.5 ha area and a 5 m height. The reason for Ethiopia to change its national forest definition is to better capture dry and lowland-moist vegetation resources. In specific, the reason for lowering the tree height from 5 to 2 m is to capture Terminalia - Combretum dense woodlands found in Gambella and Benishangul Gumuz Regional States which in its primary state consists of trees reaching a height of around 2–3 m and above [8].
Forest degradation in Sub-Saharan Africa, for instance, has widely taken place because people gain immediate economic benefits from the forest -related economic activities [9].
Ethiopia is one of the top 25 biodiversity-rich countries in the world, and two of the world’s 34 biodiversity hotspots, namely: the Eastern Afromontane and the Horn of Africa hotspots [10]. It is also among the countries in the Horn of Africa regarded as major center of diversity and endemism for several plants. The diverse topography gave rise to a wide range of altitude and other environmental factors. This has resulted in wide variations in rainfall, humidity, and temperature because of which the country comprises ten ecosystems that range from Afro-alpine at the highest elevations to desert and semi-desert ecosystems at the lowest elevations. Owing to the combined effects of topographic and climatic factors, the country is endowed with diverse ecosystems. The Ethiopian flora is estimated to be home for 6000 species of higher plants of which 10% are considered to be endemic. Woody plants constitute about 1000 species [11].
Currently, natural forests in Ethiopia mainly occur in the south-western part of the country, while the forests that originally existed in central and northern Ethiopia have almost disappeared [12, 13, 14].
Accelerated deforestation and habitat fragmentation that arise largely due to the conversion of forests to other agricultural land-use types and the overutilization of forest resources to satisfy the food and energy requirements of the increasing population are major environmental concerns in Ethiopia [15, 16, 17].
Tigray is one of the most environmentally degraded regions in Ethiopia left with remnant natural vegetation. According to pollen and charcoal studies in northern Ethiopia, forest disturbance has a 3000-year history [18], and soil erosion following vegetation clearance in Tigray occurred in the middle Holocene [19].
Around 500 BC, the pre-disturbance Podocarpus-Juniperus forest was converted into a secondary vegetation of Dodonaea scrub and grasslands that dominated the northern Ethiopia for 1800 years while Juniperus, Olea and Celtis spread around AD 1400 to 1700 [18]. The travertine deposition in the plateau of Tigray indicates the dense forest cover that once covered northern Ethiopia during the middle Holocene [19].
At present, the original vegetation is confined around religious and worship areas where religion and culture forbid cutting trees and removal of plants and in limited other isolated and protected areas [20]. [21] stated that misuse of natural resources has resulted in very serious land degradation in most places. It can be said that environmental degradation, drought and socioeconomic instability are common in contemporary Tigray.
In 2003, the natural forest cover in Tigray was only 0.2% of the total land mass of the region [4], indicating the severe forest degradation in the region. Currently, the western escarpment of the Great Rift Valley is the only site with an intact Afromontane forest cover in northern Ethiopia.
To my knowledge, no work has been published to date on the plant communities of Embahasti remnant forest that is found in the western escarpment and one of the National priority areas for restoration in Ethiopia.
1.2.3 Objectives
1.2.3.1 Major objective
1.2.3.2 Specific objectives