# The Carbon Sequestration Potential of Degraded Agricultural Land in the Amhara Region of Ethiopia
## 4 Discussion  
The Amhara region in Ethiopia has an estimated area potentially suitable for reforestation of about 3.4 million ha or 22% of the total land area (Figure 2). Considering the current forest coverage of about 250,000 ha, which is less than 2% of the Amhara region [14], the potential is great and reforestation in the region could substantially contribute to the suggested REDD activities within Ethiopia. Note that Amhara represents 14% of Ethiopia's land area but could contribute around 20% of Ethiopia's 2030 target for afforestation with 16.1 Mha [27]. Any successful implementation of the proposed potential reforestation areas will depend on a practical implementation plan. We suggest the implementation of the Normal-forest approach (e.g., equal share of area by age according to a pre-defined rotation period) and improvements of the forest management regulations and a clarification of the forest user rights [28]. Furthermore, important factors determining forest productivity and thus carbon sequestration potential are (i) site elevation and the associated climatic conditions; (ii) initial land use as an indicator for soil degradation; as well as (iii) forest management [69; 70; 71; 72]. In Amhara, the Midlands (elevation range from 1800 m to 2300 m) and especially the Highlands (2300 m to 3200 m) are the most productive, but also highly populated areas, versus the sparsely populated Lowlands (500 m to 1800 m) and Alpine areas (>3200 m). Our recommendations in focusing on reforestation activities at elevations between 1800 m and 3200 m is in line with common practices since already established forest plantations are mainly in the Midlands and Highlands [11; 73]. Aridity and frequent fires limit forest growth in the 'Combretum-Terminalia woodland and wooded grassland' of the Lowlands (see Figure 2 and Equations (1) and (2) for Aridity index, a measure for water stress). Forest plantations in this Lowland vegetation belt would be jeopardized by severe water stress, followed by salinity problems, by free livestock grazing [74] and a dense layer of tall grasses. Drought together with a dense grass layer promotes forest fires in the Lowlands, which may occur several times per year [38]. Thus, only so called 'exclosures' [15; 75], which are fenced and guarded areas with natural regeneration and no or reduced grazing may help to restore the woodland areas in the Lowlands [76]. Unfortunately, it is especially the Combretum-Terminalia woodlands that are suffering from recent deforestations [27]. Within the determined suitable elevation belt for reforestation in Amhara region, the Highlands show higher NPP and aboveground as well as soil carbon stocks versus the Midlands (Tables 2-4). These productivity variables are also higher on wet versus dry sites, for example, agro-ecology 'wet' vs. agro-ecology 'dry'. This indicates that the climatic condition in the Highland-wet zone induces less drought stress and favors vegetation growth [77]. Another observed effect is the trend in the contribution of soil carbon storage to the total storage across the moisture gradient. Both in Midlands and Highlands, and similarly for all initial land use types, the contribution of net soil carbon stock to the total net carbon stock is highest in dry conditions (compare Tables 3 and 4). Dry conditions result in a reduction of forest growth and the decomposition processes, the former leading to lower aboveground carbon storage, the latter to higher carbon accumulation in the soil. The estimated 3.4 Mha of ecologically suitable reforestation areas include different current land use types, namely, 0.7 Mha (Million hectares) of bare land, 1.2 Mha of grass land, and 1.5 Mha of shrub land (Figure 2). The land use distribution follows regional topographic conditions and climatic patterns (Figure 1). This confirms previous findings from several studies [38; 78; 79; 80], which demonstrated that the crop production and other farming activities (grazing etc.) follow vegetation patterns and thus are a constraint by ecological growing conditions.