A new analysis of 625 studies from 63 countries shows that the global expansion of built-up areas has fundamentally degraded water quality across the globe and suggests increases in forest cover can help reduce water pollution risks.

Photo credit: Adam Sondel

In recent decades the world’s landscapes have experienced profound changes, mainly due to increases in agricultural production and urbanisation – which have affected nearly three-quarters of global land. Alongside these changes there have been losses in natural landscapes such as forests and wetlands.

Landscape change is a major contributor to the deterioration of water quality. There has been plenty of research in this area at a regional level, but little has been done globally to understand the impact of the different changes in landscape and the role of environmental factors such as climate, seasons and type of water body.

This study examined over 20 000 peer-reviewed publications dating from 1976 to 2022 and identified 625 studies that used statistical and machine-learning methods from 63 countries. These studies covered different types of water bodies and used a variety of water-quality measures such as acidity, total phosphorus and total nitrogen which are indicators of eutrophication, chemical oxygen demand (COD, which measures organic pollution) and heavy metal pollution.