# The Carbon Sequestration Potential of Degraded Agricultural Land in the Amhara Region of Ethiopia
## Results
### Identification of Potential Reforestation Areas
#### 3.1.3 Aridity Index  
We applied the aridity index (AI) as calculated according to Equations (1) and (2) (Section 2.3.2) Figure 2a) as numerical indicators for each grid point to classify the climatic zones [68]. Areas with an aridity index AI < 0.65 are excluded from reforestation, because they do not support dense forests but only more xeric vegetation types [23].  
Combining our selection criteria (1) land use suitability; (2) potential elevation/vegetation belt; and (3) an AI > 0.65, for selecting potential reforestation areas for the Amhara region, suggests that 3.4 Mha or 22% of the total land area are ecologically suitable for reforestation. This includes 0.7 Mha of bare land, 1.2 Mha of grass land, and 1.5 Mha of shrub land. Summary statistics are given in Table 1, the spatial patterns are provided in Figure 2b. Most of the bare land and shrub land is located in the central, eastern, and north-eastern part of the Amhara region (Figure 2b), areas often rugged and mountainous. Grass land is predominantly located in flat and crop dominated areas, especially in the southern and western part of Amhara.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Land Use** & **Agro-Ecology** & **Elevation (m)** & **P\({}_{\text{mean}}\) (mm)** & **Area (Mha)** & **Points** & **NPP (t C ha\({}^{-1}\) year\({}^{-1}\))** \\ \hline \multirow{6}{*}{Bare land} & Highland-dry & 2300–3200 & \textless{}900 & 0.10 & 11 & 1.8 \\  & Highland-moist & 2300–3200 & 900–1400 & 0.19 & 22 & 2.3 \\  & Highland-wet & 2300–3200 & \textgreater{}1400 & 0.10 & 11 & 3.1 \\  & Midland-dry & 1800–2300 & \textless{}900 & 0.10 & 12 & 1.8 \\  & Midland-moist & 1800–2300 & 900–1400 & 0.14 & 16 & 2.2 \\  & Midland-wet & 1800–2300 & \textgreater{}1400 & 0.08 & 9 & 2.6 \\ \hline \multirow{6}{*}{Grass land} & Highland-dry & 2300–3200 & \textless{}900 & 0.06 & 7 & 2.1 \\  & Highland-moist & 2300–3200 & 900–1400 & 0.28 & 31 & 3.3 \\  & Highland-wet & 2300–3200 & \textgreater{}1400 & 0.23 & 26 & 4.7 \\  & Midland-dry & 1800–2300 & \textless{}900 & 0.09 & 10 & 2.0 \\  & Midland-moist & 1800–2300 & 900–1400 & 0.22 & 25 & 3.0 \\  & Midland-wet & 1800–2300 & \textgreater{}1400 & 0.32 & 36 & 4.2 \\ \hline \multirow{6}{*}{Shrub land} & Highland-dry & 2300–3200 & \textless{}900 & 0.08 & 8 & 2.7 \\  & Highland-moist & 2300–3200 & 900–1400 & 0.25 & 27 & 3.5 \\ \cline{1-1}  & Highland-wet & 2300–3200 & \textgreater{}1400 & 0.07 & 7 & 4.4 \\ \cline{1-1}  & Midland-dry & 1800–2300 & \textless{}900 & 0.28 & 30 & 2.2 \\ \cline{1-1}  & Midland-moist & 1800–2300 & 900–1400 & 0.61 & 65 & 3.1 \\ \cline{1-1}  & Midland-wet & 1800–2300 & \textgreater{}1400 & 0.22 & 23 & 3.7 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Agro-ecological zones (Agro-ecology), Elevation ranges (Elevation), and Annual precipitation ranges (P\({}_{\text{mean}}\)), area size of each agro-ecological zone in million hectare (Area), number of simulation points (Points), and annual NPP (10-year mean, years 91–100 after reforestation) from Biome-BGC simulations (unthinned) averaged over the simulation points.