Greener cities following the model of nature

Replacing concrete and asphalt with trees, ponds, and green roofs is an example of how cities are adapting to deal with heavy rains and climate change. But time is running out. According to the researchers, for nature-based solutions to have a global impact, we need to act quickly.

On a late summer day in August 2014, 100 mm of rain fell over a 24-hour period in the Sovelund district of Malmö. The lower floors were flooded and rainwater gushed from the sewers. Those who own their own pump consider themselves lucky. Within hours, there were no more pumps left in Malmö’s shops.

says Joanna Alkan Olsson of the Center for Environment and Climate Sciences, Lund University in Sweden.

In the year 2023, the world faces several simultaneous and partly contradictory crises: the climate is warming, and species and ecosystems are threatened. At the same time, humans need access to nature and its resources for recreation and health. What if we could use nature’s own solutions in order to bridge a few problems and solve many of the challenges we face, all at the same time? This is exactly what researchers at Lund University are working on, on a global scale, at the level of landscapes and urban environments.

“Simply put, nature-based solutions involve using nature’s own methods to solve social problems. These properly designed solutions can benefit biodiversity, mitigate climate change and enhance human well-being,” says Joanna Alkan Olsson.

Concrete causes floods

Events in 2014 made it clear that Sovellund’s water and sewage systems were not dimensioned to handle large amounts of rainfall. The hard surfaces that have historically been characteristic of urban environments, namely areas covered in concrete, paved roads, and sidewalks, have contributed to the problem.

“Concrete and asphalt absorb heat while preventing water from penetrating the soil, creating floods. Meanwhile, our sewage systems were built long ago when populations were less dense, there were fewer hard surfaces and extreme weather events were more Rarity,” says Joanna Alkan Olson.

“But how do we build cities where future rainfall won’t cause problems? In another district of Malmö, Ostenburg, just a stone’s throw from Sovelund, they have deployed a whole host of nature-based solutions. These include not digging pipes to lead the water away, Instead they choose to make use of it – this precious water is used in above ground ‘blue and green’ solutions.Puddles, rain pans and bowl-shaped lawn beds appear everywhere. There are many trees, green walls and even a vegetable garden on the roof of a multi-storey car park , and some of the roofs are covered with turf instead of the traditional roof tiles or sheet metal.

“These are all good examples of how nature-based solutions can be used in a city. Rainwater is directed into a stream that waters trees and supports plant life. The opposite approach is to direct water from roofs through gutters and downpipes to the ground under wells where underground pipes lead it away from the city The aim is to conserve water locally in the urban environment, thus enabling conditions for trees and plants to grow and enjoy,” says Joanna Alkan Olsson.

at the top of the political agenda

Nature-based solutions to climate change and biodiversity loss in 2022 are particularly highlighted during the United Nations Climate Conference (COP27) and the United Nations Conference on Biodiversity (COP15). According to the Swedish Environmental Protection Agency’s report “Nature-Based Solutions – A Tool for Adaptation to Climate and Other Societal Challenges”, studies show that nature-based solutions have the potential to account for the 30% cost-effective reduction in emissions required by 2030 in order to sustain The average global temperature rise is under 2 degrees.

“We are not just talking about nature-based solutions in cities, but land stewardship in a broader sense. Nature-based solutions cover urban, agricultural and forest environments” says Henrik Smith, Professor at the Center for Environmental and Climate Sciences (CEC) and Coordinator of the Future-Based Solutions Profile to Nature at Lund University.

Protecting and restoring mangrove swamps is an example of a nature-based solution that reduces the amount of greenhouse gases in the atmosphere and contributes to increasing biodiversity. Wetland rehabilitation is a widely discussed and researched topic, not least in Sweden. Many areas of dry wetlands release large amounts of carbon dioxide that was previously stored in plant material collected in the wetlands.

“Nature-based solutions are our most important tool”

In the agreement reached among the world’s nations at COP15, nature-based solutions are described as a way to restore, conserve and encourage the contribution that nature makes to humanity, and as a way to reduce the effects of climate change.

“The world is facing a double crisis – a changing climate and an accelerating loss of biodiversity. These two crises are closely linked and influence each other. We cannot solve the climate crisis without dealing with biodiversity loss and we cannot stop it without addressing the climate crisis. Nature-based solutions are one. One of the most important tools we have to deal with this two-sector challenge,” says Henrik Smith.

What do you hope the research will contribute to the field of nature-based solutions?

“Our climate issue is very acute, and these kinds of interdisciplinary solutions are exactly what we need if we are going to succeed. What sets our research apart is that we work at the nexus, at the cross-section between ecological processes, climatic processes and social processes. In the field of research in nature-based solutions We try to solve many problems at once, rather than the climate problem alone – as was the case previously. It is a great advantage that Lund University has chosen this as a profile area because it means we can work in the long term and across the boundaries of the subject. This is crucial If we want to find a solution,” says Henrik Smith.

What happens if we don’t take nature-based solutions on board now?

“Biodiversity loss is irreversible, and the costs will increase dramatically, both for people and the environment, if we don’t reach these environmental targets quickly. We can mitigate these crises at a much lower cost now than if we wait. If we wait too long, Maybe it’s too late.”