Air pollution affects growth of trees in São Paulo

A research study conducted by the Institute of Biosciences of the University of São Paulo (IB-USP) found that trees suffer from air pollution, which interferes in the environmental benefits offered by them. As a model, scientists used the tipuana species (Tipuana tipu)—one of the most common trees in São Paulo city, South America’s largest metropolis—and showed that atmosphere pollutants restrain the plant’s development.

Among the benefits brought about by trees are temperature reduction, steam production, a lower storm-water runoff, and pollution removal - Marcelo Camargo

Among the benefits brought about by trees are temperature reduction, steam production, a lower storm-water runoff, and pollution removal. “We’ll need a lot of these environmental services to mitigate the impact of climate change. It’s very important to have trees in the city. The healthier they are, the faster we get these benefits. Trees growing right now are probably suffering from the effects of pollution,” said Professor Marcos Buckeridge, who spearheaded the project.

The research surveyed 41 tipuanas in the Polo Industrial de Capuava, one of the most industrialized areas in São Paulo’s metropolitan region. The area is said to be formed by residential and commercial regions and an industrial center with heavy traffic of trucks and cars.

Study

“We looked at trees where pollution is heavy and compared them with trees where it’s not so strong. Those closest to thoroughfares and exposed to high concentrations of aluminum, barium, zinc—generated by wear and tear of auto parts—showed lower growth throughout the years,” Buckeridge said.

The particulates analyzed—extremely fine particles of solids or liquids in the air, measuring up to ten micrometers, coming from the industrial center—was reported to reduce the growth rate of the trees closest to the area by up to 37 percent. The outcome was compared to the data collected in the Capuava region for over 20 years, put together by the Environmental Company of the State of São Paulo (Cetesb).

The study revealed that heavy metals and particulates influenced the development of the trees by changing the optical properties of the surface of the leaves. “Thus, they increase temperature and reduce the availability of light for photosynthesis. They can also reduce trees’ gas exchange by gathering in leaf stomata—a set of cells in the leaf that allows gas exchange with the environment, as well as plant transpiration.”

Buckeridge pointed out that the research cast light on the impact of pollution in the development of tipuanas, and now, in the new stages of the research, the impact on the city as a whole may be calculated. “Now we’ll have to integrate, do the tree modeling for São Paulo and see, in the case of Tipuana tipu, what the effects are at macro level,” he explained.