# The Carbon Sequestration Potential of Degraded Agricultural Land in the Amhara Region of Ethiopia
## 1 Introduction
According to these political goals, in 2011 the Ethiopian government developed a Climate Resilient and Green Economy (CRGE) strategy to transform the economy by 2025 [25; 26]. The plan aims for protection of the environment and to decrease the CO2 emissions. In Ethiopia, about one third of the emissions come from forestry (55 Mt CO2e of the total 150 Mt CO2e in 2010) [26] and 50% are the result of deforestation. Under CRGE, the government has set a target to reforest 7 million ha by the year 2030. The National Forest Sector Development Program of the recent national REDD+ Strategy [27] has set a target of 16.1 Mha reforested land by 2030, which would double the current forest area in Ethiopia. Land use conflicts (crop production, grazing, infrastructure etc.) and uncertainties in user rights [28] may impose serious limitations for successful reforestation activities. Planting activities may compete with food security [29]. Many Ethiopian farmers convert their crop land to plantations due to the growing market for construction and fuelwood [30]. Today, _Eucalyptus_ sp. L'Her. accounts for about 90% of Ethiopian plantations and studies show that these _Eucalyptus_ sp. plantations strongly affect the soil conditions, the ground water, the wetland areas, and the biological diversity [31; 32; 33]. Thus, experts are increasingly pushing the government to ratify rules that ban Eucalyptpt plantations on cropland, along rivers, lakes, and in wetland areas. As a result, the current Ethiopian REDD+ implementation strategies focus on (i) the reforestation of grass and shrub land areas; (ii) the enhancement of agroforestry practices with indigenous species; and (iii) sustainable forest management of the remaining natural forests [26; 34]. The remaining natural forest areas, even though they are often degraded, are banned from human intervention [11; 16; 35] as they are highly important for implementing the CRGE strategy of the Ethiopian government. Information from available studies in Ethiopia focuses on the aboveground and soil carbon stock of current forests using plot level information [14; 15]. However, only a few studies [25; 26; 34; 36] address the carbon sequestration potential due to reforestation and sustainable forest management in Ethiopia. The purpose of this study is to estimate the reforestation potential and carbon storage options of degraded dry tropical Afromontane landscapes in the Amhara region of Ethiopia. Since forests are an important source of fuel and construction material for the local population, we include (a) three different thinning scenarios and (b) five different rotation lengths (10, 30, 50, 100, and 150 years), assuming a so called 'Normal-forest' system (equal representation of every age class). No climate change scenarios are considered, though, because of the high additional uncertainty different climate change trajectories would cause over such long simulation periods, when one purpose of this study is to compare the impact of different rotation lengths. As a diagnostic tool, we chose the process-based biogeochemical (BGC) ecosystem-flux model Biome-BGC to estimate the carbon sequestration potential of reforestations in different agro-ecological zones, for different current land uses, and under different forest management options. The model was chosen because it simulates forest growth and soil development by simulating major carbon, nitrogen, and water pools in fluxes in response to climatic and soil variables and different forest management options. In a previous study, the model had been tested and evaluated with measured vegetation carbon, soil carbon, and net primary production (NPP) data across different agro-ecological zones (across elevation, temperature, and precipitation gradients) within the Amhara region [10]. The main working steps can be summarized as follows.