Nature-based Solutions in our cities
Introduction
When I first arrived in Utrecht, I was stunned by how beautiful the city was. There were cute paved streets everywhere with intricate brick houses, tightly in a row, instead of the grass and concrete of my hometown.
However, that first summer, in an attic apartment on campus, I began to see a serious downside. Why were the houses so hot inside, when the temperature outside wasn’t even reaching 30 degrees? And why wouldn’t the house ever cool down properly?
What I was feeling was just a tiny taste of the true problem that our urban areas now face, and a problem which is projected to get much worse in the coming years. Dutch housing was built with a cooler climate in mind, but with climate change causing hotter summers, it’s increasingly difficult to keep our homes cool.
The urban heat island effect - the reason that urban areas are often hotter than the countryside - increases the stress on people’s health. This is a large contributor to why heatwaves are so deadly, (see this link and references therein). Multiple factors such as lack of sleep, and difficulty keeping well hydrated leads to the death of thousands every year.
The physics of the problem
So why are cities so hot?
A good deal of the answer lies in our building materials, and how these respond to the heat radiated from the sun. The warmth of the sun is absorbed by the objects it touches, to various degrees. When the sun goes down at night, the warmth that has been absorbed then radiates back into our surroundings.
Have you ever gone for an evening walk after a warm day, and felt the heat radiating off a brick wall? Compare this to how it feels to walk past a wooden fence. The building materials concrete, brick, and tile have an enormous capacity to absorb heat during the day, which influences how this heat is then re-radiated at night.
While this is an advantage on a cold day (any sunlight captured helps keep your brick house warm and reduces your energy bills), during the summer this effect is opposite to what we want. The more concrete an area has, the more intense the heat island effect. With our densely built cities, there is also reduced windflow available to remove this heat. (Reference: “Weather in the City“)
We could solve this problem by preventing the heat from being absorbed in the first place, but how can we do that without rebuilding an entire city?
Nature-based solutions
In a nutshell, Nature-based solutions are inspired by nature, cost-effective, and provide various environmental, social and economic benefits. They make our cities more resilient, and bring more nature into urban areas. (Full definition and EU background here)
In cities, the goal of Nature-based solutions is to make areas cooler and less prone to floods. Interventions such as green roofs or walls help reduce summer heat, while replacing paving with gardens, grass, or swales helps water absorb back into the ground, minimising flooding and relieving some of the pressure on the city sewerage systems
While these principles can be used when designing new parts of the city, the situation is more complex when we need to refurbish an already existing part. This complexity, and the balance between building new buildings and keeping the ones we already have, leads to some important questions.
What are the biggest problems in our cities, and what are the most effective ways of tackling these?
What interventions can we carry out in order to have the biggest impact, and how do we prove this?
And which practical steps should we take to improve the health of our most vulnerable residents?
These are the questions that I’m focused on solving, through implementing green interventions and collaborating with researchers.
Graphic showing global heating 1850-2024 , source here
Nature-based solutions for private homes and streets.
Do you have interest in using Nature-based solutions in your own garden, or perhaps with neighbors on your street? There is growing evidence that the combined contributions from even small gardens can have a cumulative effect on neighbourhood air temperature measurements and the heat experienced by residents. A green facade, for example, can lower the indoor temperature by up to 3 degrees, while reducing the temperature of the wall itself by up to 30 degrees (“Weather in the City“ and references therein).
Do you have problems with excessive heat in your home? Are you curious what measures are suitable for your house, terrace, and/or garden? Then, this blog is for you! I’ll be sharing advice, summaries of research results, and how-to’s. If you’d like personal advice, please reach out!
