Urbanization affects water quality deterioration

On January 16, 2025. The Directorate General for Economic Affairs. The European Commission’s (EC) Directorate-General for the Environment (DG ENVI) has published information on the results of analyses of studies carried out in 63 countries (a total of 625 studies were carried out) to analyze how urbanization affects water quality and to examine the factors affecting this change and their temporal evolution.

In the analysis, the researchers answered the following questions:

1. What are the research trends and hotspots for the impact of landscape change on surface water quality?
2. What are the general correlations between types of landscape changes and water quality?
3. Who are the facilitators in their correlations? And how do correlations differ among different moderators?

The article tentatively identifies global consistency, but also the lack of it between regions with regard to the relationship between landscape change and surface water quality (keeping in mind the need to maintain water security).

The results of the analysis show that the global expansion of built-up areas has fundamentally worsened water quality around the world. In addition, scientists stress that total nitrogen, total phosphorus and chemical oxygen demand in water are dependent on and sensitive to landscape changes. Indications are that landscape change is a major contributor to water quality deterioration.

General context

The world’s landscape has undergone profound changes in recent decades due to the accelerating development of societies and climate change, which in turn is driving further transformations and disrupting the provision of ecosystem services. Experts point out that landscape change has now overtaken climate change and is a major factor affecting ecological processes in catchments.

With water security at the center of the world’s attention as a necessity to support human life and well-being, improving water quality is crucial to mitigating water scarcity, pursuing sustainable development goals, and supporting food and energy security for the world and its various regions.

Climate change and landscape change resulting from anthropogenic activities have a major impact on surface water quality. Understanding the relationship between these factors is an important prerequisite in the pursuit of equality in water security and sustainability. Nevertheless, as researchers point out, there is still a gap in research answering the question of how landscape change affects surface water quality due to the fact that it is shaped by different environmental factors.

Studies to analyze the impact of landscape changes on water quality

The world’s landscape has changed in recent decades, mainly due to increased agricultural production and urbanization. These changes are affecting nearly three-quarters of the world’s land area, scientists estimate.

The team of scientists cited by the EC analyzed the results of the studies, which included different types of water bodies and used different measures of water quality, such as pH, total phosphorus (TP), total nitrogen (TN), chemical oxygen demand (COD), and heavy metal pollution. In each study, the researchers analyzed the correlation between landscape changes and water quality indicators. They then focused on the role of environmental factors such as water body types, climate zones, seasonality or latitude.

Seven landscape types were analyzed, among which five showed a significant impact on water quality – urban areas, agricultural land, forests, wetlands and grasslands.

Conclusions from the study of the impact of landscape changes on water quality

An analysis of more than 20,000 peer-reviewed publications from 1976-2022 and 625 studies conducted in 63 countries around the world indicates that global urbanization has been identified as a contributor to landscape change and is most responsible for the deterioration of water quality over the past 20 years.

Analysis of changes in urban land and forest cover showed that both were correlated with water quality. Increased urban land area was associated with increased water pollution. Urbanization was also associated with a decrease in the amount of dissolved oxygen in water, which is essential for the survival of fish and other aquatic organisms.

In turn, increased forest cover had the effect of reducing water pollution, including improving dissolved oxygen levels. The researchers suggest that increasing forest cover may help reduce the risk of water pollution.

Seasons also contributed to the impact of urbanization on water quality – the rainy season resulted in more runoff and more pollutants, while the dry season resulted in less dilution and higher concentrations of pollutants.

Overall, the study indicates that the impact of land use change on water quality has been intensifying since the 1990s, with the negative effects of pollution being driven by urbanization and agricultural land use change.

According to the researchers, increasing forest cover can have a regenerative effect, especially at low latitudes, and this can be part of a land-use change management strategy that includes water conservation through nature-based solutions. And knowing how latitude, climate zones and the seasonality of a given landscape can affect water quality is an important factor in supporting the development of action strategies now and in the future.

Information about the publication

According to the EC website, the content and views contained in Science for Environmental Policy are based on independent, peer-reviewed scientific research and do not necessarily reflect the position of the European Commission. In light of the information published on the EC website, it is important to remember that the article described is a summary of only one publication. Other studies may lead to different conclusions.

Science for Environment Policy is a free information service published by the European Commission’s Directorate-General for the Environment (DG ENV). It is designed to help busy policymakers stay abreast of the latest environmental research findings needed to design, implement and regulate effective policies.

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