Reducing CO2 emissions could impair water quality, new study finds

Before implementing strategies that limit climate change, we need to consider the potential impact they may have on water quality due to nutrient inputs, according to a study that was recently published in the scientific journal Nature Communications. According to the authors, efforts to reduce CO2 emissions could pose the risk of impairing water quality.

Nutrients originating from human activities such as agriculture and wastewater treatment plants get washed into waterways with stormwater runoff, posing the risk of nutrient overloading in waterways. Nutrient overloading can lead to eutrophication of freshwater systems, resulting in toxic algal blooms and hypoxic dead zones that are devoid of life-supporting oxygen.

Study authors, Anna Michalak and Eva Sinha from the Carnegie Institution for Science, have been assessing the impact of nitrogen runoff over several years, including looking at the negative impacts that projected changes in future rainfall patterns as a result of climate change could have on water quality.

In their latest study, they analyze the impact that land-use, agriculture, development and climate change mitigation could have on water quality across the US. They also took into account how changing rainfall patterns resulting from climate change would further contribute to an increased risk to water quality.

According to the study, climate change mitigation strategies that heavily promote the use biofuels could result in an increase in nitrogen runoff entering waterways across the country, which could in turn lead to a reduction in water quality. By the same token, extensive expansion of local food production in the future would not only pose a risk to water quality, but would also result in an increase in GHG emissions.

However, according to the study, with adequate planning it is also possible to have a scenario with win-win solutions; with the most promising scenarios including sustainable growth and environmental conservation.

"It is entirely possible to fight climate change in ways that don't have unintended consequences for water quality," says Anna Michalak. "We need an approach that takes multiple benefits into account in the planning process."

According to the study's findings, in the US, the impact of nitrogen loading resulting from land use and projected changes in precipitation would be greatest in the Northeast, while on a global scale, waterways across Asia would be most at risk of reduced water quality resulting from eutrophication due to the projected increase in precipitation together with an increase in fertilizer application.

"Our findings show that it is crucial to consider the potential for water quality impairments when making societal choices about how land is used and developed, as well as about how we work to fight climate change," said Sinha. "Access to clean water is essential for human survival, food and energy production, and a healthy ecosystem. Preserving our ability to access clean water must be a top priority."

Journal Reference

E. Sinha, AM Michalak, KV Calvin & PJ Lawrence. Societal decisions about climate mitigation will have dramatic impacts on eutrophication in the 21st century. Nature Communications. Volume 10, Article number: 939 (2019)