Beating the heat by greening the grey: Green Infrastructure in Tokyo

Over half a century ago, the decision was made to hold the 1964 Tokyo Olympics in October instead of the summer months because of heat concerns. Since then, the average temperature of Tokyo has risen by 1.5°C due to climate change and the Urban Heat Island effect (UHI). In recent years heatwaves have wracked Japan, with over 5,000 hospitalisations in 2019 due to heat-related afflictions. Yet the 2020 Tokyo Olympic are to be held from July 24 to August 9, at the height of the Japanese summer.

Daily Mail video showing how heatwaves have driven concern for the Tokyo Olympics.

Tokyo’s Metropolitan Government (TMG) has touted green infrastructure as a potential long-term solution to the city’s heat crisis, integrating nature into urban landscapes. There’s certainly more room for green in Tokyo – only 7.5% of the land is dedicated green space, compared to 40% and 47% in Hong Kong and Singapore. But successfully implementing green infrastructure in such a vast city won’t be an easy task.

Shinjuku Gyoen (新宿御苑), one of Tokyo’s few large green spaces. Source: Japan Guide

Greening the grey

Green infrastructure was put on Tokyo’s agenda with the passing of the Nature Conservation Ordinance in 2001. It required that 20% of floorspace in newly constructed, repaired or extended buildings larger than 1000m² (private facilities) or 250m² (public facilities) be designated for greening, either rooftop or ground-level. The legislation was backed by a prominent advertising campaign and an extension in 2009 to include facilities larger than 5000m². The results are impressive: since 2001, nearly 19,000,000 sq ft of greenery has been added to Tokyo roofs (Shickman and Garg, 2016).

The science behind it is straightforward – research conducted in 2004 determined that simple green roofs on buildings could cut surface temperatures by up to 25°C compared to bare concrete, providing an effective and cheap remedy to UHI. Greening also comes with multifaceted benefits (Jim, 2004); it not only embellishes the otherwise-rugged concrete landscape of urban Tokyo but also can cut carbon emissions, forming a path to sustainable living (Capitanio, 2018). It can also serve as valuable social space for residential communities. The famous Roppongi Hills complex in Tokyo features rooftop rice farms, gardens, pavilions and other green social spaces as part of developer Minori Mori’s vision for a vertical garden city (Harrison, 2013).

Planting rice on a rooftop in Roppongi Hills. Source: Real Estate Japan

As customary of Tokyo, new innovative green infrastructures have been applied to mitigate heat, several to be shown off at the Olympics. Heat-minimising, permeable pavements have been installed across the city along marathon routes, which by reflecting infrared light can reduce pavement temperatures by up to 8°C compared to asphalt. Such innovations were created with sustainability in mind, having been approved for use by the TMG and pavement costs subsidised so they could be used after the Games (Shickman and Garg, 2016). Alongside these measures, the city has also asked residents and businesses to line buildings and roadsides with foliage, while shaded tents are to be filled with greenery to create ‘flower lanes’ that provide heat stress relief and relaxation space.  

Thermal scan of reflective pavements in Tokyo. Source: Shickman and Garg, 2016

Fragmented thinking

Though Tokyo’s work in implementing green infrastructure have been laudable, the city’s governance system could stymie future efforts. In Tokyo, individual municipalities submit Green Master Plans (GMPs) setting out aims and measures for increasing green space. But the exact definition of green infrastructure is difficult to pin down – the concept is contested, irresolute and constantly evolving (Wright, 2011).  With each municipality interpreting and strategizing around green infrastructure differently, the fear is that Tokyo ends up with a fragmented approach to green infrastructure, faulting along ideological differences between municipalities.

Research conducted by Mwirigi (2013) on green infrastructure awareness revealed only 4.4% of municipal workers were well-informed on the topic, while 48.35% had no knowledge at all – potentially hindering successful implementation of green initiatives. Municipalities also prioritised differing aspects of the concept: suburban municipalities were biased towards cycle and walking lanes, while central municipalities preferred green roofs and walls. Similar problems have been observed in Taipei, where conflicts of interest between decision-makers and communities have confounded efforts to promote greenery (Mabon and Shih, 2018). Without improving coordination between municipalities, Tokyo could be going the same way.

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References:

Capitanio, M (2018) ‘More green space in Japanese shopping streets: Assessing the manifold potential of green roofs in Shimokitazawa, Tokyo’, Smart and Sustainable Built Environment, 7, 2, 212-22.

Harrison, B (2013) ‘The Use of Greenery to Combat Urban Warming in Tokyo’, 総合政策研究 (Journal of Policy Studies), 21, 3, 51-66.

Jim, C. Y (2004) ‘Green-space preservation and allocation for sustainable greening of compact cities’, Cities, 21, 4, 311-20.

Mabon, L. and W. Shih (2018) ‘Mapping the socio-political landscape of heat mitigation through urban greenspaces: the case of Taipei Metropolis’, Environment and Urbanisation, 31, 2, 552-74.

Mwirigi, M. M (2013) ‘A study on Green Infrastructure Gauge and affordance enhancement for sustainable urban areas’, research thesis submitted to Chiba University, Japan.

Shickman, K. and S. Garg (2016) ‘The Current State of Urban Heat Island Mitigation Policy’, paper produced for the 2016 Summer ACEEE.

Wright, H (2011) ‘Understanding green infrastructure: the development of a contested concept in England’, Local Environment, 16, 10, 1003-19.