In São Paulo, Brazil, the largest and most populous city in Latin America, trees fall every day, but most trees occur during the rainy season, mainly due to the effects of temperature, strong winds and heavy rains. When trees fall during the dry season, the main direct cause is not the weather, but the lack of control and the proper conditions for the survival of street vegetation.
These are important discoveries of research published by a group of Brazilian researchers in the journal. Tree — structure and function As part of its “Urban Trees” collection.
Scientists analyzed daily windthrow data and identified about 7,000 outbreaks over a three-year period. São Paulo lost 1% of its roadside trees during this period, with an average of 6.2 drops per day. The worst day was December 29, 2014, with 337 fallen trees reported in 24 hours. Due to the large number of trees that fell in the storm, Ibirapuera Park, the city’s largest green space, had to be closed.
Trees are considered important for maintaining or improving the quality of the urban environment. They play an important role in carbon storage and uptake and help mitigate the negative effects of global warming and pollution. They also help reduce floods by increasing the more permeable soil area and reducing the rate and amount of stormwater runoff by blocking some of the rain.
“Of the 652,000 roadside trees in São Paulo, 7,034 fell between 2013 and 2016. According to our analysis, tree falls are caused by precipitation, gusts and temperatures during the rainy season. Directly affects the fall of trees, but it affects both precipitation and gusts. Although the trees fell in two-thirds of the rainy season, they were not associated with such a climate in the dry season and stewardship. The problem with the badness of the was confirmed. And the condition “, the article can be summarized in conclusion.
The data used in this study is from the Emergency Management Center in the city of São Paulo. The exact location of the fall of each tree was not available. Researchers estimated the immediate effects of a few days after the storm and the effects of rain and wind, and focused on the correlation between daily weather and tree fall.
“The more rainfall, the more water the tree holds and the more it weighs. In addition, the more water on the ground reduces the friction between the soil and the roots, making it easier to tip over. However, when the soil is flooded, the soil increases. The weight offsets the loss of friction and the trees may not fall during heavy rains. When the soil dries, the weight decreases without increasing friction. , Can fall, “said Giuliano Locosselli, a researcher at the IB-USP Faculty of Botanical Sciences. The first author of the article told Agência FAPESP.
Co-authors included Marcos Silveira Buckeridge, a professor at the Institute of Biological Sciences (IB-USP) at the University of São Paulo, and Priscilla Cerqueira, an agricultural engineer and head of the Urban Trees Division of the São Paulo City Environment Bureau. ..
According to Locosselli, the results show that climate effects are concentrated in rainy season.. “During the dry season, trees fell without any apparent climate-related causes, demonstrating the lack of care and structural problems that had been occurring for some time,” he said.
For example, trees are often accidentally pruned, their structure and balance weakened, sidewalks strangler figs, hinder tree growth, and there is not enough space for trees to grow.
“Unmanaged trees can collapse without obvious climate-related causes. Photosynthesis, root support, growth, and pathogen resistance that take advantage of urban climate to reproduce and develop. Obstacles can cause aging vegetation to fall. It’s not uncommon to find poorly-conditioned trees that can fall for no apparent reason. “
For Serqueira, demonstrating the effects of rain and wind delays as the cause of tree collapse is one of the most important aspects of research. “Front-line local government workers see what’s happening every day and know that tree collapses are reported all year round, but used the dry season as a baseline,” she said. Said. “The effects of late weather are important. Now we are taken shortly after storm rains and winds to minimize the risk of trees falling and to be prepared to act if they happen. You need to think about what you should do. “
Researchers did not analyze the direct impact of age and pollution on tree health, but Loco Seri said the fact that many São Paulo trees were planted in the 1950s and 1960s was a vulnerability. He said it contributed to the possibility of falling.
Regarding air pollution, according to an article published in 2019 and co-authored by Locosselli, air pollutants hinder the growth of one of the city’s most common tree species, the Tipuana tipu. It has been shown to impair ecosystem services. Provided (see agencia.FAPESP.br/30552 for details).
Studies show that some of the actions needed to protect the roadside trees in São Paulo include management and planning that take into account the biology of the species, resilience to extreme weather, and the characteristics of the local infrastructure.
The authors also recommend implementing tree monitoring programs using tree health indicators and educational campaigns to gain public support for science-based government decisions.
The city of São Paulo is legally responsible for the management of roadside trees (City Law 10,365 / 87). This includes planting, protecting tree health, pruning, and replacing trees as needed. The actual work is outsourced to a contractor. Power companies can arrange canopies to give way to fictitious power lines.
According to Cerqueira, a 20-year city-city tree plan was implemented in September 2020 to provide urban resilience to climate change, provide shade and aesthetic benefits, and plan and manage to increase “national satisfaction”. It became the purpose.
“Some aspects of tree management and tree planting highlighted in the study are consistent with the problems diagnosed by the city’s plans detailing the programs and actions to address each problem,” she said. ..
The plan will be reviewed in 2025. The first five years will set priorities such as developing a fall risk analysis protocol and creating an emergency management project that includes auditing contracts signed with contractors and utilities. Reduces the amount of pruning and tree damage.
“The public is more aware of the importance of trees. The number of popular participants is increasing. There are even more phones when trees fall, especially after a storm. We have technology for the general public. We plan to improve the material, “said Serqueira.
São Paulo has more than 12 million inhabitants, covers an area of ??1,521 square kilometers and has a subtropical climate. Approximately 75% of the streets are home to a variety of native trees, including trees from the Atlantic Forest and exotic species, but most are in the more central areas of the city. Planting trees in the suburbs is one of the purposes of municipal planning.
Locosselli said he has embarked on a new study with Cerqueira and other colleagues, analyzing georeference data available since 2012 for 30,000 trees in the city. “Where are we looking wood It is arranged to understand how the fall of trees is affected by the surroundings and the environment. The survey includes 19 variables such as pollution, sidewalk width and slope, climate, and building height. It should be pretty much done by the end of the year. ”
For more information:
Giuliano Maselli Locosselli et al, tree climate driver collapses on the streets of Sao Paulo, Brazil, wood (2021). DOI: 10.1007 / s00468-021-02145-4
Quote: Studies suggest that the fall of trees in the dry season of São Paulo is due to poor management (2021, August 12) https://phys.org/news/2021-08-tree- Obtained August 12, 2021 from falls-season-paulo-city.html
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Studies suggest that logging in the dry season in São Paulo is due to poor management.
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