Populations overheat as major cities fail canopy goals: new research
A new study led by RMIT University in Australia measuring access to nature for eight major global cities found most still have inadequate canopy cover, despite access to an abundance of trees.
RMIT University
image:
Canopy cover at a park.
view moreCredit: Thami Croeser
A new study led by RMIT University in Australia measuring access to nature for eight major global cities found most still have inadequate canopy cover, despite access to an abundance of trees.
Less than 30% of buildings in New York City, Amsterdam, Buenos Aires, Denver, central Sydney and central Melbourne were in neighbourhoods with adequate canopy cover.
New York and Amsterdam both scored almost 0% for canopy cover despite 92% and 50% of buildings having views of at least three trees, respectively.
The research, a collaboration with the Technical University of Munich, studied over 2.5 million buildings across eight cities using an emerging sustainable cities measure, known as the ‘3-30-300' rule.
The rule states every house, school and workplace should have a view of at least three trees, be in a neighbourhood with at least 30% canopy cover, and be within 300 metres of a park.
Only Seattle and Singapore passed the 30% canopy benchmark, with 45% and 75% of buildings in these cities enjoying adequate shade, respectively.
Access to parks was also patchy, with Singapore and Amsterdam scoring high while Buenos Aires and New York City scored poorly.
Lead researcher and RMIT University research fellow, Dr Thami Croeser, said it was concerning that most of the buildings in the study failed the 30% tree canopy test.
With 2023 being the hottest year on record and 25% of the global population experiencing dangerous levels of extreme heat, canopy cover was urgently needed to cool down our cities, he said.
“Previous research has shown depression, anxiety, obesity and heatstroke are more prevalent in urban areas that lack access to shady tree canopy and green open spaces,” said Croeser, from RMIT’s Centre for Urban Research.
“Canopy cover doesn’t just increase cooling, it can also reduce flood risk as well as benefit mental and physical health and support urban biodiversity.
“Studies say we actually need at least 40% canopy cover to substantially lower daytime air temperatures, so the ‘30’ metric is the absolute bare minimum - and most buildings we studied don't even reach that goal.”
Croeser said current ways of designing or retrofitting streets did not support healthy canopy growth as planning prioritised infrastructure such as cabling and pipelines over tree growth.
“We need to stop thinking that allocated spaces for buildings and roads are permanent when they could be reallocated to prioritise green infrastructure,” he said.
“30% canopy cover seems like a high bar if we keep doing things the same way, but it’s totally achievable if we change a bit of our practice.
“Currently, we put trees last, and if it gets in the way of cabling or pipes, we remove the tree or replace it with a sapling.
"Designing trees into streets early, and then figuring out win-win solutions to get in utilities and traffic access, is one of the big changes we need to make a difference.”
Trees currently tend to be planted in conditions that were not easy for them to grow in, Croeser said.
“The soil is compacted, there’s asphalt over them and when it rains, the water runs off into the gutters instead of into the soil.”
“Earlier research shows that if urban trees are planted in better quality soil with enough space for them to grow, where rainwater can run directly into the soil, it will help trees grow bigger faster to address our lack of canopy cover.
"Trees in urban environments are also removed and replaced with saplings, or pruned very heavily, so not many trees get the opportunity to grow into big old canopy trees except in a few lucky areas.”
A new nature access metric with potential
While the ‘3-30-300' rule, devised by Dutch urban forestry expert Professor Cecil Konijnendijk, is still relatively new in Australia, it is gaining momentum internationally, with at least six cities in Europe, the US and Canada implementing the measure in their urban forestry strategies.
Konijnendijk said he devised the benchmark to help set a ‘bare minimum’ for nature in cities.
“Getting more parks and trees into cities is complicated work, and I realised that a simple metric could take the mystery out of it and set a proper benchmark based on evidence,” he said.
“I reviewed decades of science linking nature to human health – and found that views to nature, canopy cover and parks are all really essential if we want to be mentally healthy, physically active and safe from heatwave impacts.”
Professor Wolfgang Weisser, from the Technical University of Munich, said metrics that benchmark the adequacy of green infrastructure at a neighbourhood level in relation to human wellbeing were still rare.
“Some of the metrics we use now are not really sufficient whereas the ‘3-30-300' metric really demands that nature is brought to the areas that people actually live and work in,” Weisser said.
“A municipality with almost treeless streets and a few large, well-forested parks may score well on aggregated metrics of canopy and per-capita greenery but will be exposed as inadequate by the highly local ‘3’ and ‘30’ requirements.”
The researchers collaborated with Dutch firm Cobra Groeninzicht (Green Insights) to visualise the results.
“With the techniques our team has developed, we can calculate the ‘3-30-300’ benchmark for any city in the world,” said Dirk Voets, Senior Advisor Geospatial at Cobra Groeninzicht.
“Acute canopy deficits in global cities exposed by the 3-30-300 benchmark for urban nature”, with Thami Croeser, Roshan Sharma, Wolfgang Weisser and Sarah Bekessy, is published in Nature Communications. (DOI: 10.1038/s41467-024-53402-2))
Canopy cover in a suburban area.
Credit
Thami Croeser
Map of canopy cover in Berlin.
Map of canopy cover in Vancouver.
Map of canopy cover in Washington DC.
Map of canopy cover in Melbourne
Map of canopy cover in Sydney
Credit
Cobra Groeninzicht
Journal
Nature Communications
Method of Research
Imaging analysis
Article Title
Acute canopy deficits in global cities exposed by the 3-30-300 benchmark for urban nature
Article Publication Date
19-Nov-2024
Mixed forests reduce the risk of forest damage in a warmer climate
Umea University
image:
Micael Jonsson, Associate Professor at Umeå University
view moreCredit: Ulrika Bergfors
Forests with few tree species pose considerably higher risk of being damaged and especially vulnerable is the introduced lodgepole pine. This is shown in a new study by researchers from Umeå University and the Swedish University of Agricultural Science in Uppsala. The results can be useful for preventing forest damages and financial losses related to the forest industry.
Fungi, insects, fires and cervids, such as moose, are examples of natural factors behind tree damages in Swedish forests. Sometimes, the damages become so extensive that they impact the function of forest ecosystems, not least the ability of forests to provide wood and other tree products.
“In a warmer climate with more extreme weather and new pest organisms, and with a more intense forestry, forest damages are expected to become more common and more severe. It is therefore important to understand causes of forest damages and whether it can be prevented,” says researcher Micael Jonsson at Umeå University, who led the study.
The Swedish national forest inventory has collected extensive data from Swedish forests. Since 2003, data on forest damages have also been collected.
In the current study, the research group has analyzed 15 years of these data from all over Sweden, to investigate which damages are most common and which factors determine the risk of a tree becoming damaged. The study is more extensive both in time and geographically than previous studies.
The results show that wind and snow are the most common causes of tree damage, followed by forestry and then fungi. Damages from cervids – mostly moose – are on fifth place. 94 percent of all trees showed some kind of damage. Coniferous trees and young stands showed the highest risk of damage, and in warmer parts of Sweden, stands with few tree species showed a considerably higher risk of being damaged compared to stands with a higher number of tree species.
“Our results show that there is a potential to reduce the risk of forest damages via a changed forest management. Especially, a higher proportion of broadleaf trees in the otherwise so coniferous-dominated production forest would result in fewer damages. We can for example see that the lodgepole pine, introduced by the forestry industry, has the highest risk of damage. Its introduction therefore counteracts a profitable forestry,” says Micael Jonsson.
The results also indicate that a higher number of tree species in a stand act as an insurance against extensive forest damages in a warmer climate.
“We must adapt Swedish forests and forest management methods to a future warmer climate. Including more tree species in production forests seems to be an adaptation that could work!” says co-author Jan Bengtsson at the Swedish University of Agricultural Science.
However, the study also shows that the data material has some weaknesses. For example, it has not been possible to establish the cause behind a large proportion of the damages.
“The national forest inventory collects important data for our understanding of the forest, but when it comes to the damage inventory, the data quality needs to improve to be fully usable in forestry practices,” says Jon Moen, co-author at Umeå University.
Mixed forest in Sweden.
Credit
Jan Bengtsson
Journal
Ecosphere
Method of Research
Data/statistical analysis
Subject of Research
Not applicable
Article Title
Tree damage risk across gradients in tree species richness and stand age: implications for adaptive forest management
Article Publication Date
19-Nov-2024
What are the belowground responses to long-term soil warming among different types of trees?
Wiley
Through a 20-year experiment, investigators have shown how different trees adjust their strategies for acquiring nutrients through their roots as soil warms with climate change.
The research, which is published in Global Change Biology, included trees that associate with different fungi that help roots absorb nutrients. Measurements showed that when exposed to warmer soils, oak trees associated with ectomycorrhizal fungi reduce interactions with soil microbes while increasing fine root exploration, whereas maple trees that associate with arbuscular mycorrhizal largely maintain their belowground patterns.
The findings suggest that the root systems of arbuscular mycorrhizal trees may not need to adjust their belowground foraging strategies as much as ectomycorrhizal trees to remain competitive as global temperatures rise.
“The structure of future forests under global warming will probably be influenced by the ability of tree roots and their fungal partners to compete belowground in warmer soils,” said corresponding author Nikhil R. Chari, a PhD student at Harvard University.
URL upon publication: https://onlinelibrary.wiley.com/doi/10.1111/gcb.17550
Additional Information
NOTE: The information contained in this release is protected by copyright. Please include journal attribution in all coverage. For more information or to obtain a PDF of any study, please contact: Sara Henning-Stout, newsroom@wiley.com.
About the Journal
Global Change Biology is an environmental change journal dedicated to shaping the future and solving the world's most challenging problems by tackling sustainability, climate change and environmental protection, food and water safety and provision, as well as global health.
About Wiley
Wiley is one of the world’s largest publishers and a trusted leader in research and learning. Our industry-leading content, services, platforms, and knowledge networks are tailored to meet the evolving needs of our customers and partners, including researchers, students, instructors, professionals, institutions, and corporations. We empower knowledge-seekers to transform today’s biggest obstacles into tomorrow’s brightest opportunities. For more than two centuries, Wiley has been delivering on its timeless mission to unlock human potential. Visit us at Wiley.com. Follow us on Facebook, X, LinkedIn and Instagram.
Journal
Global Change Biology
Article Title
Long-term soil warming drives different belowground responses in arbuscular mycorrhizal and ectomycorrhizal trees
Article Publication Date
20-Nov-2024
No comments:
Post a Comment