18 September 2023

Urbanization promotes increasing emissions from the soil


As a result of urbanization, soil nitrous oxide emissions increase 153%, according to a new study. At the same time, the ability to absorb methane is reduced

by Matteo Cavallito


Altered soil functions contribute to increased emissions from urban vegetation. This is supported by a study published in the journal Global Change Biology. Increasing urbanization, the research points out, results in the conversion of natural ecosystems to residential areas that incorporate green areas such as parks or lawns.

“Such conversions affect ecosystem functions and impacts biodiversity, ecosystem services such as provision of clean water as well as the function of such ecosystems as climate regulators,” explains Klaus Butterbach-Bahl, a professor at Aarhus University involved in the research, in a statement released by the Danish university. That’s why there is a need to consider sustainable management of urban green space to mitigate its effects on climate.

Urbanization promotes climate change

The investigation, conducted by a group of international scientists including researchers from the Chinese Academy of Sciences and New York University, focused on the relationship between urbanization, soil greenhouse gas emissions and climate. The researchers, in particular, compiled data from several previous research studies to understand the release dynamics of nitrous oxide (N2O) and methane (CH4).

Nitrous oxide, the statement highlights, is a powerful greenhouse gas that contributes to climate change and stratospheric ozone depletion. Methane, meanwhile, has a warming effect.

Nitrogen emissions rise 153 percent

Research shows that urban soils have significantly higher nitrous oxide emissions than rural areas. Key factors are increased deposition of the element that is released in fossil fuel combustion processes and altered soil conditions, such as compaction resulting from urban development.

In addition, conversion of natural lands to urban areas reduces the capacity of soils to absorb methane, leading to higher atmospheric concentrations of this greenhouse gas.

“On average, urbanization increases soil N2O emissions by 153%, to 3.0 kg N per hectare per year, while rates of soil CH4 uptake are reduced by 50%, to 2.0 kg C per hectare per year,” the study states. Moreover, “On a global basis, conversion of land to urban greenspaces has increased soil N2O emission by 0.46 Tg N2O-N per year and decreased soil CH4 uptake by 0.58 Tg CH4-C per year.”

Sustainable solutions

These phenomena, the research continues, “are associated with changes in soil properties (bulk density, pH, total N content, and C/N ratio), increased temperature, and management practices, especially fertilizer use.” These effects, however, “can be mitigated by avoiding soil compaction, reducing fertilization of lawns, and by restoring native ecosystems in urban landscapes.”

“These nature-based interventions can help sequester carbon, reduce emissions, and enhance the resilience of urban environments,” Butterbach-Bahl explains.

By prioritizing sustainable urban planning, the statement says, cities can adopt strategies to reduce greenhouse gas emissions, increase carbon sequestration and improve overall environmental quality. These efforts, the researchers say, will be key to combating climate change and creating livable cities in the future.