Exterior Architecture’s Shaun Lyons discusses the effects of the summer sun on our external environment and offers insight into how Landscape Architects can offset those effects through well considered and intelligent design solutions.
As the schools start back up, the nights draw in and the final test match comes to an end it is a good time to reflect on the season just gone. Whist most of us have enjoyed this rare, hot summer, the weather over the last months provides a useful reminder that our climate is a fragile system and over the next few decades it is predicted that we can expect more frequent severe weather events.
The wildfires around Manchester, in Sweden, California and Greece show the devastating effect that the hot, dry weather can have on people and the environment whilst in Japan there have been 138 deaths and over 71,000 hospital omissions on account of the heat. There is no getting around the fact that the Earth’s climate is warming, the rate of temperature increase having doubled over the past 50 years and so it is imperative as designers we take the two main aims of the Paris Agreement; to limit temperature increase and to increase the ability to adapt to the adverse impacts of climate change, into account in all aspects of our work.
The single biggest way to limit temperature increase is to reduce emissions of carbon dioxide and other greenhouse gasses. At every stage in the design process this is something that Landscape Architects should be considering. From designing spaces that promote sustainable travel with pedestrians and cyclists given priority over vehicles to specifying materials that are, where possible, produced and sourced sustainably and locally there are many ways that designers can seek to reduce the environmental impact of the places they create.
The second aim of the Paris Agreement, to increase the ability to adapt to the adverse impacts of climate change is an ambition that Landscape Architects should be spearheading and a challenge that will increasingly shape the profession over the coming decades. Resilience and adaptability to climate change in our public spaces and landscapes can take many forms – providing rest opportunities in the shade, drinking water fountains and of course sustainable drainage systems – there are a myriad of ways that our landscapes can rise to the challenge of climate change. Planting design, however, is one area of landscape where adaptability and resilience are not so much enhancements as necessities.
The summer’s series of heatwaves were broken up by periods of , often torrential, rain. As changes in climate are expected to increase the regularity and severity of both droughts and storms, our planting needs to be able to not only cope with the effects, but positively contribute to the way that these events are managed. We need to be choosing plants that are tough enough to deal with extremes of weather and through providing shade, helping to reduce drainage run-off and continuing to support our wildlife, reduce the impact that climate change has on our cities. The Landscape Institute position statement on the challenges of climate change states:
Landscape architects understand what species to plant, where to plant them and the conditions different species require in order to thrive. This knowledge is invaluable in the face of changing climatic conditions, particularly arising from the impacts on the quality and availability of water and the potential increase in pests and disease.
In truth this is a complex task and real consideration must be given to species selection if we are to futureproof our designs.
Trees are brilliant. They reduce the amount of pollutants in the air, cool our cities through shading and transpiration, help capture storm water and lock up carbon that would otherwise be released into the atmosphere. Our intimate relationship has shaped human history and as we hurtle towards what will be a significant test of our species resolve, trees remain a critical part of any solution. In urban areas the trees that we choose to plant and the places that we choose them can have a massive impact on their ability to thrive and contribute the benefits that they are able to. When planting trees today we need to be conscious that they will (hopefully) still be there in 40, 50 even possibly 100 years time. We need to be aware of the predicted changes in climate over this time and be choosing species that will be successful not only today but throughout the duration of their lifespans. Silver Birch, Betula pedula, is a good example of a widely planted tree that will in the near future be outside of its natural climatic range, certainly in the South of the country. Tree officers, conservationists and landscape architects often push of native species selection, which is valid for many reasons one being that it stands to reason that trees that occur naturally in an area are likely to be suited to the conditions. In the context of a shifting climate this issue becomes trickier. During previous natural shifts in climate, plant species have adjusted to these changes, colonising land that was previously unsuitable. However, the current, human driven, climate shift is happening at a rate much faster than trees are able to keep up with and thus it could be argued that a responsibility lies with us to make corresponding adjustments to the tree species that are location appropriate.
When planting trees in urban areas understanding this and promoting a forward-thinking approach becomes even more critical. Not only are the stresses on trees greater in cities with reflected heat, increased pollution levels and more severe consequences of drought but it is also urban trees that we expect the most from. An understanding of the specific site conditions, how these might change in the future, how can we maximise the potential benefits of the tree are all important factors to consider. One easy step is to, wherever possible, plant trees in the ground as opposed to containers. Containerised trees are more susceptible to drought, can contribute less to storm-water control and are unlikely ever to reach their full potential.
Looking beyond trees, shrub and herbaceous planting also needs to be specified with the themes of resilience and adaptability in mind. Although there may not be the same onus on considering future climate models for these planting types, there are significant climatic pressures on planting and significant benefits to successful schemes. Management of resources and in particular water is a key concern underpinning all truly successful planting. Regular irrigation of planting is a costly and unsustainable solution and this is likely to become truer as water becomes an ever more cherished commodity. On the flip side the importance of ensuring that as much surface water as possible makes its way into areas of soft landscape rather than sewers cannot be underestimated. Landscape Architects need to be considering planting design holistically with input from the design team rather than seeing it as an add-on, a few pretty flowers once the design is fixed.
In these uncertain times it is at least reassuring to observe the resilience and adaptability of nature without the interventions of humans. Examples of woodlands recolonising brownfield land, birds adapting to city life and ferns and mosses creating impromptu green walls sets a benchmark. At ExA we are inspired by these occurrences and practice phenology - the study of seasonal changes in plants and animals from year to year – to track and monitor changes in our environment. We have extended the traditional phenologist’s brief to observe cultural changes – the first time we see a full beer garden, the first children collecting conkers – to give a more rounded picture of the innumerable relationships between climate, nature and humans that occur in our cities every day.