Bare Area Detection in Botswana

Abstract

This paper estimates bare areas gain detected using a Landsat 7 (ETM+) and Landsat 8 (OLI) in Botswana. From 2002 to 2020, agricultural fields shrunk by 76.4%, while build-up increased by 49.2%, and bare areas increased from 3.32% to 7.03% (or 111.7%). There is a lot of seasonal changes in bare areas reaching maximum during the long and dry season when there is very little or no ground cover. In this study, this effect was normalized by only considering as true bare ground if the pixel being considered is bare during both winter and summer months. The probability of bare area detection was 75.0% and probability of false detection was 13.3% respectively, this means that a detected bare area has a 75% chance of being an actual bare area and there is a 13% chance that a detected bare area is not an actual bare area on the ground. This 13% tended to be buildup areas which have a lot of bare pixels. For other studies such as soil erosion, it might be advisable to consider bare ground detected during the winter months since most soil is lost during the first rains after the long dry winter. The changes in LULC and accelerated increase in bare area is attributed to the population growth rate of 3.4%. From 2001 to 2017, the population of the study area has increased by 34% and now accounts for 47% of the population of Botswana.

Keywords: bare area, LULC, population, soil erosion