Landscape metrics approach for analyzing the relationship between urbanization patterns and water quality in Laguna Lake tributaries, Philippines.

Abstract

Landscape spatial pattern analysis is a viable approach for examining the arrangement of landscape features and their relationships to ecological processes, especially when large datasets are unavailable. This study quantified landscape metrics and explored their potential relationships with water quality parameters at river monitoring stations in Laguna Lake, Philippines, from 2017 to 2023 using correlational analysis. Using FRAGSTATS 4.2 and the Environmental Systems Research Institute (ESRI) Sentinel-2 annual land cover, landscape metrics were derived within a 500 m buffer around the river monitoring stations and correlated with selected water quality parameters. Significant positive correlations were observed between specific built-up landscape metrics (percentage of landscape, most extensive patch index, and effective mesh size) and pollutants (fecal coliforms, ammonia, and phosphates), suggesting that larger, more connected built-up areas are associated with higher pollutant concentrations. This pattern may reflect the presence of extensive impervious surfaces, which are commonly linked to greater runoff and wastewater discharges. In contrast, the same metrics applied to cropland areas showed significant negative correlations with fecal coliform, ammonia, and phosphate, and a significant positive correlation with nitrate. Hence, this indicates that better-connected cropland is associated with lower pollutant levels, possibly reflecting vegetation that intercepts or filters runoff before it reaches rivers. The study demonstrates the use of landscape spatial pattern analysis as a potential indicator of water-quality degradation in rivers and lakes. It identifies innovations to improve the health of the riverine ecosystem.