Promotion of green curtains in the Kyushu region

Climate change impacts

In Kyūshū and Yamaguchi Prefecture, the average annual temperature has been rising at a rate of 1.73°C per 100 years, which is greater than the overall rate in Japan (1.24°C per 100 years) (Note 1). In addition, manatsubi (days with maximum daily temperatures of 30°C or higher) have increased by 1.6 days per decade, while moshobi (days with maximum daily temperatures of 35°C or higher) have increased by 0.6 days per decade (Note 2). Especially, the annual number of moshobi has been on an upward trend since the late 1990s.

Adaptation activity

Green curtains, which block direct sunlight and lower room temperature by shielding windows with plants, have gained attention as a measure to conserve electricity after the 2011 Great East Japan Earthquake. Green curtains have been installed not only at schools and other public facilities, but also for residential homes. The Ministry of the Environment has been implementing and promoting the Green Curtain Project (Note 3) since 2011, and local authorities are also making similar efforts.
Since FY2010, Kumamoto Prefecture has been promoting the cultivation of goya (bitter gourd) at its facilities as an energy-saving and global warming countermeasure (Fig. 1). The installation and popularization of green curtains in the community is also being actively promoted. In 2017, green curtains were installed in a total of 639 temporary housing units (Fig. 2) in response to the Kumamoto Earthquake. In order to promote the use of green curtains in local communities, model green curtains have been installed by global warming prevention promoters as a promotion of global warming mitigation since FY2018, and green curtains have been installed in five districts in the prefecture (Kumamoto City, Amakusa City, Koshi City, Hikawa-chō, and Kuma-mura) in FY2020. In addition, there is a prefecture-wide Green Curtain Contest to further promote the use of green curtains, with different divisions for private residences and businesses/groups competing for the best green curtains, noting creativity and effectiveness.
Fukuoka City is also promoting the "Green Curtain Project" by distributing morning glory and bitter gourd seeds to elementary, junior high and nursery schools in the city, in addition to hosting talks on "How to Grow Green Curtains", and "Green Curtain Contests" for businesses and the general public.

Outputs / Expected benefits

Green curtains have the effect of blocking sunshine and cooling the surrounding air through moisture evaporated from the plants. In a survey conducted in Kumamoto Prefecture, the temperature of exterior walls was measured by thermography, and a difference of approx. 14℃ was observed between sunlit and green curtain-shaded areas. In terms of indoor temperature, rooms shielded by green curtains were found to be a maximum of 2.2°C cooler than rooms without them (Fig. 3). In a survey conducted by the Ministry of the Environment, many respondents cited emotional satisfaction and lifestyle benefits, such as "growing plants was enjoyable", "the plants have a healing effect" and "I was able to block direct sunlight." In this way, green curtains have attracted increasing attention as an energy-saving and global warming prevention measure that is relatively inexpensive and easily manageable.

Footnote
(Note 1) Statistical period: 1898-2019
(Note 2) Statistical period: 1927-2019
(Note 3) Ministry of the Environment "Green Curtain Project"
https://ondankataisaku.env.go.jp/coolchoice/green/index.html