Summary and Conclusion

The results obtained through our investigation and analysis are summarized as follows.

• The results of multiple regression analysis, using the mean daily maximum temperatures in August as dependent variables and the size of woodland area and amount of anthropogenic heat emissions as explanatory variables, showed that an increase in trees contributes to a reduction in temperature in urban areas, and that an increase in the amount of anthropogenic heat emissions causes a rise in temperature.

• The cooling potential of 22,500 m2 of trees in Minato-ku is equivalent to moderating and offsetting the total anthropogenic heat released per day from approximately 70 commercial buildings of a typical type and size for Minato-ku, each having a floor area of approximately 3,000 m2. In other words, wooded areas in the densely and increasingly overpopulated commercial heart of the city have the effect of moderating and offsetting the rise in temperature caused by anthropogenic heat emissions from air conditioning systems, which inevitably arise in downtown Tokyo. That is, green spaces in urban areas have an air conditioning function provided by nature.

• The value of green space consisting of trees and other vegetation has generally been assessed in terms of how much CO2 the trees absorb. This study demon­strates that green space can be evaluated from a new perspective, the cooling potential of green space, particularly in urban areas, in offsetting the waste heat from air conditioners (anthropogenic heat emissions) that spreads throughout the neighborhood, and contributing to a reduction in the amount of CO2 in the atmosphere released by power stations and related facilities. Comparing the effects per 22,500 m2 of trees in Minato-ku, we found that trees have the potential to reduce 236 times as much CO2 as the amount of CO2 they absorb.