Regenerative urban greening

Climate change means hotter and wetter cities. What about our green spaces and the impacts of extreme weather on vegetation and landscape? Natasha Jones, director of landscape architecture at Stantec, looks at the future lay of our land. 

Stantec’s Natasha Jones looks at the impact of climate change on our green spaces.

Climate change brings more intense rainfall, warmer, wetter winters and hot summers. 

One moment it’s extremely hot or there’s a risk of drought, and the next torrential downpours. 

In 2050, a 2C increase is predicted to change London’s average temperatures, which could be similar to Barcelona’s in 2019/20 - and the average UK temperature in summer could be 27C. 

In case a response is “at last, a real summer!”, we have to design with the impacts in mind on infrastructure, energy system, environment, nature, health and way of life. 

The Met Office predicted a weather forecast for the year 2050 with hotspots reaching 43C during the day and 24C at night. Think about the resulting heat stress, risk to life warnings, huge peaks in water demand, and urban heat island effects. Urban temperatures in 10 major UK cities will increase significantly. 

Right time, right place, right tree

Extreme weather breaks and uproots trees, changes plant physiology and phenology, increasing tree mortality. 

Spring 2020, the fifth warmest and sunniest spring on record, killed 4,000 saplings on Hackney Marshes in London. The winter storms in 2013-14 caused the greatest loss of mature trees in a generation. 

The Royal Horticultural Society and the Millennium Seed Bank provide annual updates on suitable species that are adapting and withstanding the gradual process of climate change. As the south gets hotter, we’ll have to look at trees and planting trends. 

Palm trees lining the Mall in London? The novelty of these as iconic visual indicators of a once-sought warmer climate would likely be short-lived. Palm trees don’t provide enough shade nor capture carbon and wouldn’t be a sensible approach. The Royal Palm absorbs less than 0.5kg of carbon.

We could have legislation with rules against planting trees in peat areas, or where the soil has organic surface areas less than 50cm thick. 

There could be future limits on our types of woodland focusing on broadleaved species. 

Oak, maple and disease-resistant ash trees would be the climate adaptation choice in southern and eastern UK. Oaks can absorb over 41kg of carbon. By 2050 beech trees would only do well in north and west UK. 

Rising temperatures and reduced frosts in winters could mean a decline in traditional orchards. But we could see more citrus trees planted instead, with home-grown oranges, lemons and even limes in some plots. 

The future is green

To avoid becoming ghost cities, and uninhabitable during summer, cities must manage urban heat island effects. 

Regenerative Urban Greening aims to regenerate and reactivate the worst heat island cities, by replacing hectares of grey infrastructure with green-blue infrastructure and vegetation-clad buildings. 

Grey infrastructure transport routes could be a thing of the past and no longer dominating urban areas, nor dictating the placemaking design process. Instead, Regenerative Urban Greening schemes could be designed around macro-scale connecting urban floodplains and woodlands. Transport routes could be truly green!

British cities could take design cues from the early vertical forest architecture of Singapore, such as PARKROYAL Hotel, and Milan. Vertical greening and green infrastructure are critical for human habitation. 

We could see a boom in tall buildings, placed amongst swathes of urban green floodplains and woodlands to help address rising sea levels, extreme rains, and provide shade and respite from the heat. We could see xeriscaping embedded in planning legislation, an approach to reduce resources and water requirements in urban areas.

Not just a pretty space

From dealing with water run-off and pollution, to green corridors, and increased urban food production, urban parks could be functional and more than just a pretty green space – providing shade, cooling, connection to nature and wildlife, and local produce. 

The landscaped lawn could one day be a distant memory, having been replaced by rain gardens, meadows and species-rich grasslands, even in urban areas, and tree planting. 

Urban tree planting should focus on species that provide shade and function within extensive chains of rain gardens. 

We could have designated Primary Shade Routes—cool and green corridors for people to move using whichever mode they choose in relative comfort during heatwaves and heavy downpours. 

Maturing trees would provide dense canopies for shade and be part of a linear rain garden.

Greener, by law

We’ll need to take note of future climate change and biodiversity crises. 

Would a future UK government finally implement a National Forest Programme? Green Belts could be replaced by Forest and Woodland Belts - substantial areas of undeveloped countryside given over to a nation-wide, macro-scale, 100-year tree planting programme. Would they have greater capacity than original Green Belts and envelope all English major cities and towns? 

Forest and Woodland Belts could help with providing flood mitigation, clean air, green and cool spaces for people and wildlife – particularly in the south of England most affected by searing temperatures and extreme rainfall. 

As we travel further north, it could be rare to see south of Sheffield the ‘millennium-romantic’ landscapes –the formerly managed open landscapes of agricultural countryside, large fields, and lengths of hedgerows. We could see them replaced by substantial areas of phased national tree planting, interspersed with permanent grassland and rough grazing pasture, providing carbon storage.

With more extensive and intensive tree planting programmes, we could see a new timber industry, and a symbiotic relationship between people, woodlands, and forests. The idea of a Garden City is well known now – would this design principle resurge in a new Forest Town format? 

A biodiversity crisis is a climate crisis. We have to take note of the impacts on nature, horticulture, and landscapes. Mitigating them means future generations will be able to survive in public spaces that just a few decades before, were not intolerable to live in. 

Natasha Jones is director of landscape architecture at Stantec.


If you would like to contact Karen McLauchlan about this, or any other story, please email kmclauchlan@infrastructure-intelligence.com.