3.2. Soil erosion change (2005 - 2015)
The annual rate of soil erosion was estimated at 1 km spatial resolution for 2005 and 2015 using the RUSLE (Figure 4). The soil erosion ranges from <1 ton/ha/year to >20 ton/ha/year. In the sloppy highlands areas of Gilgit-Baltistan, Azad Jammu & Kashmir, Khyber Pakhtunkhwa and Balochistan high (5-20 ton/ha/year) and very high (>20 ton/ha/year) annual rate of soil erosion were detected while from medium (1-5 ton/ha/year) to low (<1 ton/ha/year) values were noticed in the flattened areas of the Punjab and Sindh provinces. The estimated average soil erosion at the national scale in 2005 was 1.79 ± 11.52 ton/ha/year (mean ± standard deviation at 95% confidence interval) which increased to 2.47 ± 18.14 ton/ha/year in 2015. In the Azad Jammu & Kashmir administrative unit 14.44 ± 35.70 ton/ha/year soil erosion was detected in 2005 which increased to 28.03 ± 68.24 ton/ha/year in 2015. In the Balochistan, Islamabad Capital Territory, Punjab, and Sindh, <1 ton/ha/year average soil erosion was perceived in 2005 and 2015. In 2005, average 7.54 ± 20.25 ton/ha/year soil erosion was in Gilgit-Baltistan, which increased to 9.06 ± 29.69 ton/ha/year in 2015. Similarly, in Khyber Pakhtunkhwa province average 8.73 ± 25.55 ton/ha/year soil erosion was 2005 increased to 12.84 ± 39.88 ton/ha/year in 2015 (Table 3). Among all the administrative units, only in Azad Jammu & Kashmir average soil erosion doubled from 14.44 ± 35.70 ton/ha/year in 2005 to 28.03 ± 68.24 ton/ha/year in 2015. In Khyber Pakhtunkhwa province average soil was 8.73 ± 25.55 ton/ha/year in 2005, which increased to 12.84 ± 39.88 ton/ha/year in 2015. Similarly, in the Gilgit-Baltistan administrative unit of Pakistan in 2005 mean soil erosion was 7.54 ± 20.25 ton/ha/year which increased to 9.06 ± 29.69 ton/ha/year in 2015. In Balochistan, Punjab, and Sindh administrative units, the negligible average increase was observed in ten years (2005 - 2015). In Islamabad Capital Territory, mean soil erosion was 0.77 ± 2.22 ton/ha/year in 2005, which rose to 1.57 ± 4.56 ton/ha/year in 2015 (Table 3).
Figure 5 presents latitude wise mean soil erosion in 2005 and 2015. Between 24º - 29.5º latitude as such no soil erosion was observed, from 29.5º (dotted blue line) until 33º (dotted yellow line) latitude very slight erosion detected in 2005 and 2015. Between 33º-37º latitude, a parabolic shape was observed which reflects soil erosion in 2005 and 2015. At 35.5º N latitude (dotted red line), in 2005 mean soil erosion was nearly 17 ton/ha/year, which climbed up to 30 ton/ha/year in 2015.
Through cross tabular or change matrix method, in ten years (2005 - 2015) at the national scale, 35,252 km2 (4%) area observed under negative change (commission) of soil erosion and 12,108 km2 (1.37%) area covered under positive change (omission). Out of total area of Pakistan (881,913 km2), in 834,553 km2 (94.6%) area no change of soil erosion observed between 2005 and 2015 (Table 4). From 2005 to 2015, 731,863 km2 (~83%) area remained intact under the low (<1 ton/ha/year) soil erosion while less than six ton/ha/year remained unchanged under the three soil erosion classes (i.e. medium, high and very high). Between 2005 to 2015, total 451 km2 (0.05%) area converted from very high (> 20 ton/ha/year) to low (<1 ton/ha/year) soil erosion class following only 43 km2 area transformed from very high (> 20 ton/ha/year) to medium (1-5 ton/ha/year) and 1,012 km2 (0.11%) area shifter from very high (> 20 ton/ha/year) to high (5-205 ton/ha/year) soil erosion class. From 2005 to 2015, total 11,734 km2 (1.33%) area moved from medium (1-5 ton/ha/year) to high (5-20 ton/ha/year) soil erosion. Similarly, 9,730 km2 (1.10%) soil erosion area moved from high (5-20 ton/ha/year) to very high (> 20 ton/ha/year) soil erosion in ten years (2005–2015) (Table 4).