Climate change resources

Part of a regular series by Claire Thirlwall exploring tools, projects and guidance available to help professional understanding of this issue’s topic.

The Retrofirst campaign, instigated by the Architects’ Journal in 2019, 1 highlighted the wasteful model of demolition, disposal and rebuild. Is there a place for the same approach in landscape architecture?

When a site has designations, such as Listed Park and Garden status or Tree Preservation Orders, we are used to working to conserve existing features, valuing them for their historic or amenity value. Some clients ask that we conserve other features – this can be motivated by the environmental impact of removing items from site or cost of disposal. If the UK construction sector is going to end the 13,827 tonnes of carbon emitted per year 2 , our approach to site redevelopment will need to change.

This change needs to be made throughout the entire design process. Site assessment will need to take a retain-first approach, with removal of items and the resulting carbon impact justified. An item on site has incurred the bulk of the carbon cost, through manufacture, installation and maintenance to date. Incorporating elements from a previous site use will potentially limit the options for site design, but also offers an opportunity for creativity and innovation.

The calculation to retain or replace will need to be over a significant timescale, and consider the implications beyond the site boundary. Retaining a large area of Tarmac for parking may prevent unnecessary carbon costs or material going to landfill for example, but it may impact on flood risk or create a heat island. Understanding the full range of impacts will be essential, yet the tools are not commonly available. The Landscape Institute is looking at how embedded carbon can be assessed, a process that will need the support of clients and suppliers. As legislation changes to enable a zero-emissions economy, there may be costs to the client for not considering carbon costs, but for now the impact of our choices is often borne elsewhere, such as future waste disposal costs or climate impacts.

Our choice of materials must take into account whole life impact, not just the manufacturing stage. We need to consider how an item, whether it is surfacing, street furniture or planting, could be reused in a future scheme. Can it be repaired? Could it be repurposed elsewhere? How complex is it to maintain – will it need carbon intensive processes such as mowing or irrigation? Can it be returned to the supplier when it is no longer needed? The Living Building Challenge, the built environment’s most rigorous performance standard, requires projects to achieve netpositive waste – waste reduction is fully integrated into all phases and the End of Life phase demands adaptable reuse and deconstruction.

Golden Lane Estate where the 1957 landscape has recently been placed on the Historic England register

© Paul Lincoln

Living Building Challenge – Materials

© Declare - International Living Future Institute (living-future.org)

Hemel Water Gardens, Hemel Hempstead Sir Geoffrey Jellicoe 1957

Hemel Water Gardens

© HTA Design

The sympathetic restoration of important landscapes is a useful reference for the retain-first approach. Hemel Water Gardens, a rare example of a New Town post-war landscape, was designed in a period of austerity using inexpensive materials. Over time, the original design principles were lost, but the restoration included the return of the simple colour scheme that tied together the different styles of basic railings, barriers and other elements around the site. Returning the railings to their original “Festival of Britain” white creates striking reflections and a lightness that the intervening dull green lacked. 3

Declare

Declare is a labelling system and database where manufacturers report the details of their product, including embodied carbon, life expectancy and end of life options, such as Take Back programs.

The free to access database allows users to filter results to find products that meet the environmental aims of their project.

Declare label

© International Living Future Institute (living-future.org)

London 2012 Olympic Basketball Arena

© WilkinsonEyre

The London 2012 Olympic Games set and achieved the target of zero wastes to landfill, with over 99% of the “waste” from installing and decommissioning the Games venues reused or recycled. 4 Careful planning at the early stages of design meant that features such as temporary bridges and even venues could be relocated – one example is the seating for the basketball stadium, 70% of which had already been used in another venue and was designed to be re-used post Games. An Olympic Games is an unusual situation to accommodate, with the primary use being just a few months, but like the restoration of historic landscapes it gives us a useful model for creating schemes that can evolve as the use changes.

If our sector is to meet the demands of a zero emissions economy by 2050, we will need to rethink our approach to site redevelopment, and create landscapes that can be adapted as the site use changes, and not pass the problem of site waste to future generations. Materials that are non-recyclable and non-reusable are landfill in waiting – an approach that is uneconomic, unethical and unsustainable.

Claire Thirlwall is a director of Oxfordshire based landscape practice Thirlwall Associates. Her book “From Idea to Site: a project guide to creating better landscapes” for RIBA Books was published in January 2020.