Land Cover Changes in Wetlands and Surface Temperature Variation in the Wouri Estuary, Cameroon

Abstract

Wetlands play a major role in maintaining a stable climate. Nevertheless, their global decline driven by both natural and anthropogenic factors poses a serious threat to the environment. This research aims to investigate the impact of land cover changes in wetlands on Land Surface Temperature (LST) between 1985 and 2025 in Douala IV within the Wouri Estuary. Using Geographic Information Systems (GIS) and remote sensing, land surface biophysical properties were compared to sub-pixel thermal changes derived from Landsat imagery of 1985, 2005, and 2025. Pearson’s Product Moment Correlation Analysis was utilized to assess the association between urban expansion and wetland thermal variation. The results indicated a drastic reduction in wetlands to just 2.0 km², representing a 74% loss from 2005 and a 69% loss from 1985, averaging a loss of 0.28 sq. km annually. Wetland destruction in Douala occurred through multiple, distinct pathways. Built-up areas directly replaced 1.7 km², expanding water bodies converted 1.8 sq. km, and vegetated areas encroached upon 1.1 km². Exposed surfaces contributed essentially nothing (0.0 km²) to wetland loss. LST distribution revealed a significant warming trend, with overall values ranging from 21.1°C to 29.1°C. A strong negative correlation (R² = 0.8788) was observed, indicating that wetland cover explains 87.88% of the temperature variation. The linear regression model (y = -1.3377x + 35.777) indicates that for every 1 km² increase in wetland area, the mean LST decreases by 1.34°C.  Ultimately, the severe wetland reduction of 4.5 km² between 1985 and 2025 contributed to an approximate 6°C increase in local land surface temperature. Given the continuous depletion of wetlands and the persistent threat to the environment, it's essential to identify and implement strong strategies to manage the remaining wetland.