Excessive heat, droughts and floods – how can ‘blue-green infrastructure’ help?

Picture of a flat roof in london, with a skylight, that has moss growing on top
A green infrastructure project in London (c) Daniel Johns

Kathryn Brown, Grantham Research Fellow and Head of Adaptation at the UK Committee on Climate Change, blogs on why we need to prepare for climate change impacts, and how bringing the natural world into our urban landscape can help us to do just this.

The last few months have been fairly unprecedented in terms of weather across the UK. While some people have enjoyed basking in beautiful sunshine, the heat and lack of rain have had a host of negative impacts.

Some parts of South East England endured 49 consecutive days without a single drop of rain – local councils asked residents to help to water young trees that were dying in the heat; hosepipe bans were planned in the North West; the Environment Agency has moved fish out of drying rivers; and wildfires have affected the sensitive peatland habitats on Saddleworth Moor and Winter Hill. It’s still too early to assess the full scale of the damage.

Extreme temperatures are projected to increase in frequency and severity as the global climate continues to change. The impacts of extreme heat, as experienced this summer, are a wake-up call to alert us about what is to come; and remind us how important it is to plan in advance for the future effects of climate change. Our hope is to minimise the risk of these events turning into national emergencies.

Bringing the natural world into an urban landscape

A washing up bowl pond, with lots of foliage
A pond made from a washing up bowl (c) Indra Thillainathan

Ponds, lakes, trees, hedges, grass, green roofs and green walls – so-called ‘blue-green infrastructure’ – are absolutely critical in helping us to deal with extremely hot (as well as wet!) weather.

Living plants, for example, bring multiple benefits. They don’t simply provide shade from the sun, they help reduce the ambient air temperature through evaporative cooling; they help to mitigate floods by attenuating surface water runoff; they can improve air and water quality by absorbing pollutants through their leaves and roots; they provide a home and food for wildlife; and they absorb carbon dioxide, locking it in storage and out of the atmosphere.

There are hundreds of peer-reviewed papers that highlight the benefits of blue-green infrastructure. For example, one recent study found that buildings with trees positioned next to them had an indoor temperature 4ºC lower in summer and 6ºC higher in winter, compared to buildings without trees. Furthermore, the tree-shaded buildings used 26% less energy. Another study found that adding a green roof to existing buildings reduced the surface temperature of the roof by around 20ºC.

However, despite the resounding case for implementing good quality blue-green infrastructure to improve the overall quality of life in cities, the proportion of urban areas with green spaces in England declined significantly from 63% in 2001 to 56% in 2011, and has since remained static.

Three things standing in the way of blue-green solutions

I have been looking for evidence on the benefits of and barriers to blue-green infrastructure as part of a research fellowship at the Grantham Institute this year. I have interviewed people working for government departments, local authorities, property developers, water companies, consultancies and the charity sector – and the same three barriers keep coming up:

  1. There are minimal standards. There is a lack of statutory requirements for blue-green infrastructure in new or existing developments.
  2. Quantity at the expense of quality for new housing. There is overriding pressure from government for as many new homes to be built as cheaply as possible. As a result, attempts to incorporate blue-green infrastructure, seen as an ‘optional extra’, is met with resistance.
  3. Lack of understanding about the benefits of blue-green infrastructure. Blue-green infrastructure is often seen purely as an unnecessary expense by local authorities, developers and the government, and the benefits are not being quantified or recorded.

These three issues mean that whilst blue-green infrastructure may be included in the early plans for a construction project, they often fall victim to being ‘value engineered out’ and rarely see the light of day. The problems with ‘standards’ and ‘quantity over quality’, can only really be solved at the central government level by changing planning policy. However, we can better understand and account for the full benefits of blue-green infrastructure with the help of academics.

My colleague Dr Ana Mijic, Senior Lecturer in Systems Water Management at Imperial’s Department of Civil and Environmental Engineering, wants to help people make the case for more blue-green infrastructure (BGI). She is testing a new approach to the evaluation of blue-green infrastructure, which takes into account its multiple functions, and who benefits from it. The method also maps the potential cost savings across the system that result from the implementation of BGI, such as reduction in energy costs due to surface water management and building cooling.

Together, we’re also looking into the reasons why financing for green infrastructure, like sustainable drainage systems (SuDS), only covers single benefits like flood risk reduction, when there’s an opportunity to have greater effect with innovative finance schemes that fund projects with multiple benefits. Ultimately, we want to show that blue-green infrastructure is a sustainable option for climate change adaptation, that enhances the overall quality of life in cities. We’ll be publishing the results of our work in the autumn.

Create your own blue-green haven

A frog, in a pond made from a washing up bowl
Even the tiniest of ponds can be a haven for wildlife like this frog (c) Indra Thillainathan

In the meantime, there are things you can do to take care of, and make the most of, existing blue-green infrastructure while we ride out the remaining summer weather.

Be sure to water your plants and put out drinking water for wildlife. Find shaded, tree-lined routes to walk in during the day, as they will be much cooler. Put new plants in the ground, create your own green roof, or send a climbing plant up the walls of your home. Build a pond if you have any space – even tiny ponds the size of a washing-up bowl can attract wildlife like frogs.

Maximising your own little patch of blue-green infrastructure will not only benefit you, but can also contribute to addressing climate change and minimising its impacts, albeit on a very local level.

Read more from Imperial academics about the heatwave, and the impact of climate change on extreme weather

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