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Skip to 0 minutes and 8 secondsHi. My name is Tijana Blanusa. I'm a Senior Scientist for the Royal Horticultural Society, and research-wise I'm based here at the University of Reading in the School of Agriculture Policy and Development. My research is on urban greening, and specifically about what plants can provide in terms of environmental benefits to our towns and cities. You might be surprised to find out that a large proportion of every UK and Western principal town and city is covered by green infrastructure. And by green infrastructure, I mean urban trees, parks, playgrounds, domestic gardens, green roofs and walls where we have them. Domestic gardens alone in the UK represent between a fifth and a quarter or every city or town.

Skip to 0 minutes and 57 secondsNow, plants in cities provide a number of environmental benefits or, as we scientists call them, ecosystem services. And by that, I mean provision of localised cooling, building insulation, capture of excess rainwater, noise abatement, chopping of particle and gaseous pollutants, biodiversity provision, and many more. However, plants management obviously comes at a cost, both financially and environmentally. Plants require water for their management. Plants also require chemicals and fertilisers, and all those resources have carbon cost, but also a financial cost. Therefore, relative contribution of every plant species to the environmental services provision will differ. This is where we do our research.

Skip to 1 minute and 55 secondsSo for example, here we have grown some plants which could be used on green roofs, and compared a classical green roof species, which is Sedum, over there in that corner, against some more vigorous plants, which have broader leaves and lose more water and potentially cool better. So we have found that these plants with silvery leaves, with hairs, reflect more light and lose more water and therefore provide much better insulation to the surface of the building than a traditional Sedum could. Equally, another hairy plant-- a popular garden plant, lamb's ear, which is very hairy.

Skip to 2 minutes and 40 secondsWe are currently doing some more research looking at how the fact that it has hairs affects its ability to trap more pollutants, more particles, on its surface, and we're actually finding that indeed it is better than species which have really smooth leaves. So this is Stachys byzantina, lamb's ear, a very hairy Mediterranean species. This is common sage, Salvia. And this is one of the Sedum species, which is a frequent choice on green roofs, a succulent, water-conserving plant. So depending on what is the main purpose of your green space, if cooling is really important for you, then considering something which is broad-leafed, lighter-colored, transpires a lot, is probably better than considering a succulent.

Skip to 3 minutes and 26 secondsIf survival is the main issue that is bothering you, then going for something like Sedum has its advantages. I would suggest that on the individual level, we could start by really thinking about providing a diverse range of plants in our domestic gardens, and that sort of diversity could also translate into planning of public green spaces. Between themselves as a group, plants act in different ways. In simple terms, not all plants are the same. So for example, plants with rougher leaves, plants that have hairy structures, are usually better at trapping particle pollutants than plants with smooth leaves.

Skip to 4 minutes and 9 secondsAlso plants that have larger canopies that also inherently lose more water to evapotranspiration will provide better cooling than plants that are more conservative in their water use. Equally, plants differ greatly in terms of their management requirements. So the main message really that I'm trying to convey is that, depending on what we grow in our green spaces and how we manage them, we can reap extremely different environmental benefits.

Urban greening

In this video, Dr Tijana Blanusa looks at how both public and private green spaces in cities can be used effectively to reduce noise and pollution, support biodiversity and create localised cooling.

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This video is from the free online course:

Our Changing Climate: Past, Present and Future

University of Reading