Wise viewers, welcome to Planet Earth: Our Loving Home for the first in our two-part series on green roofs or rooftops covered with vegetation to reduce the Urban Heat Island effect, promote energy savings, improve air quality, grow fresh produce, minimize storm water runoff and lessen climate change.

There are two main types of green roofs – intensive and extensive. The former requires a large flat surface area, features many kinds of plants including trees and shrubs, has greater than 10 centimeters of soil substrate and is high-maintenance. The latter has less than 10 centimeters of soil substrate, is generally made up of herbs, grasses, mosses and other types of groundcover and is low-maintenance.

Today we will focus on the greening of building rooftops in metropolitan areas. In large cities, skyscrapers, concrete buildings, infrastructure and pavement trap heat from the Sun, as well as waste heat from cars, air conditioning units, factories and other sources, creating “Urban Heat Islands” or UHIs. This effect can raise the temperature in a city two to 10 degrees Celsius higher than if it was a vegetation-filled rural area.

The United Nations Intergovernmental Panel on Climate Change states in its Third Assessment Report, “It is well-known that compared to non-urban areas urban heat islands raise [both] night-time temperatures [and] daytime temperatures.”

UHIs cause energy imbalances, degrade living conditions and can also affect local weather by altering wind patterns, producing clouds, fog and humidity and changing the frequency and intensity of precipitation. The extra heat generated by UHIs can induce thunderstorm activity. The resulting rapid, heavy rainfall heated by hot pavements and rooftops flows into streams, rivers, ponds, lakes, and seas producing stress in aquatic ecosystems.

In recent years, global warming has intensified and those living in large metros have been especially affected by rising temperatures exacerbated by the UHI phenomenon. In 2003 a devastating heat wave in Europe killed 35,000 people, many of whom were living in urban areas.

Many structures standing today are energy inefficient. For example, a 2007 analysis of China’s largest buildings, comprising 46 billion square meters of floor space found only four percent could be classified as energy efficient. Green roofs serve as extra layers of insulation, reducing the amount of heating needed in winter and air conditioning in summer, thus decreasing power consumption.

On a hot summer day, the rooftop of the City Hall building in Chicago, USA, a model intensive green roof, will be the same as that of the surrounding air temperature, say 32 degrees Celsius. By contrast, the rooftop of a neighboring building without any greenery may reach almost 71 degrees Celsius.

For many years Western European nations, particularly Germany, have been promoting the installation of green roofs to mitigate UHIs, improve local ecosystems and enhance the quality of city life. The green roof trend is now taking off in large Asian metros as well. For example in Japan, the government at the national and local levels has enacted laws to encourage urban roof greening.

We recently visited Tokyo and interviewed Mr. Taro Hitokoto, chief official of the Green Spaces Environment Office, a part of Japan’s Ministry of Land, Infrastructure, Transport and Tourism. Mr. Hitokoto will now discuss one of the Ministry’s demonstration rooftop garden projects.

This roof garden with an area of 500 square meters was installed on the building by the Ministry of Land, Infrastructure and Transport in 2002, seeking to verify rooftop gardening technology, measure the garden’s effects and provide information (on rooftop gardening) to the public.

Does it involve experimenting with weights of soil or which plants are suitable for rooftop greening?

Yes, when installing we seek weight-saving materials for greening and verify which of the various soils, pavements and containers are suitable. Also, we use environmentally-friendly materials such as scrap tires and paper for the pavement material.

Ten years ago when rooftop greening was not yet widespread in Japan, you started rooftop greening on the Ministry of Land, Infrastructure and Transport building. Could you tell us about the results of this project?

Yes. Actually, we have data showing that the inter-building temperature fell when the rooftop was greened.

How is it structured under this turf?

First of all, there’s a layer of light soil about 15 centimeters deep. Beneath this layer is a permeable filter, through which water can pass but plant roots cannot pass easily. Beneath it is a five centimeter-wide path for water to flow. At the bottom is a layer to protect the building from intrusion by both water and plant roots.

How many degrees did the surface temperature of the roof go down through the impact of rooftop gardening?

This graph shows the surface temperature during a day in summer, and here it is when the tiles become the hottest. Here is the surface temperature of the lawn. The temperature fell about 20 degrees Celsius.

I wonder how many beings have increased their presence due to this rooftop garden.

Up to now, 180 kinds of insects have been identified. The Imperial Palace is nearby and various insects fly in and live here since we’ve made a green space a little way from the Palace.

In Japan, local governments offer subsidies to popularize wall greening, or covering exterior walls of buildings with plants, and rooftop greening. We’ll next speak with Mr. Munetaka Takahashi about the operation of this subsidy system in Tokyo’s Minato Ward, as well as the current status of the program. Mr. Takahashi is the chief of the Greenery Promotion Subsection of the Environmental Section, a part of Minato’s Environment and Recycling Support Department.

Would you explain the subsidy system for rooftop and wall greening?

Minato Ward has been subsidizing those who install green rooftops since 2008; ¥25,000 (US$300) per square meter is the upper limit. The total subsidy amount is up to ¥5 million (US$60,000) and rooftop greening up to 200 square meters per building is subsidized. The actual result last year was 15 projects, which means an area of about 980 square meters of new green rooftop space was created.

Does the subsidy encompass all buildings including private residences and office buildings?

Those that have lot areas of less than 250 square meters are eligible. When a building of over 250 square meters is newly constructed, rooftop greening is required. Thus, we limit subsidies to buildings over five years old with lot areas of over 250 square meters. Our concept is to enable as many people to install green rooftops as possible.

I understand that in Minato Ward, the upper limit of the subsidy for rooftop greening was raised from ¥300,000 (US$3,500) to ¥5 million (US$60,000) in May 2008. What was the reason for this move?

Yes. Roads and buildings exceed 70% of the ward’s total area. As a way to increase green areas in this ward in the future, the rooftop space of a building becomes very important. In Minato Ward there is a lot of rooftop space on both private houses and office buildings.

We want to increase rooftop greening as much as possible, and in the case of private housing, it doesn’t cost much. However, promoting the greening of big buildings requires a lot of money. So, we think that large areas should also be eligible for subsidies. In Minato Ward, we are seeking a green ratio of 25% or covering 25% of the ward’s total area with plants. We are also about to promote rooftop gardening as part of a focused policy.

How effective was it to raise the upper limit of the subsidy? Has it contributed to increasing the area and the number of rooftop gardens?

After the upper limit was raised, we could secure five times the greened area of before.

How are you going to promote rooftop gardening in the future in order to reduce global warming?

We would like people to install green rooftops as much as possible, because it also becomes a measure to counter global warming. Also, we would like to continue with creating pleasant surroundings for living things and humans.

I think it’s really wonderful for the government of Japan to implement such a subsidy system for this highly necessary and effective approach to counteracting global warming. I sincerely hope other urban areas will be covered by green areas in the future. Thank you very much.

Thank you very much.

Finally we visit Meguro Ward Office’s green roof, which is very elegant. Our guide is Mr. Yojiro Shigeno of the Parks and Greenery Section of Meguro’s Urban Planning and Development Department.

What was the concept behind this roof garden, which is beautifully designed like a Japanese garden?

Yes, it’s a garden designed with a modern Japanese-style theme. It was designed by Dr. Kondo of the Tokyo University of Agriculture.

I saw a little while ago that the trees are watered by an automatic sprinkling system.

Yes, this automatic sprinkling system depends partly on wind power and solar-electric power generation.

Will you talk about future plans for rooftop gardening at the Meguro Ward Office?

Yes, the Meguro Ward is planning to build a rooftop park at the Ohashi junction in 2012. We will build a rooftop park on artificial ground about a hectare in size, where people will be able to enter. One building has already been built, but we’ll construct another one in the future to be connected by a bridge so that people can come and go freely.

The rooftop garden will slope and lead to the new nine-story building, and the park will slowly descend from the building’s ninth story towards the other building’s fifth story. Moreover, further ahead the park will be connected with Route 246 by a bridge, so that people can go down to a part which is as high as a two- or three-story building. This will be completed in 2012.

Thank you very much for speaking with us today.

Thank you for coming here.

We would like to sincerely thank Taro Hitokoto, Munetaka Takahashi, and Yojiro Shigeno for providing us with the opportunity to explore some of the cool and inviting green rooftops in Japan. May many more buildings in this great nation and elsewhere in the world soon feature their own gardens in the sky.

Friendly viewers, thank you for your company today on our program and please join us next Wednesday on Planet Earth: Our Loving Home for the conclusion of our series on green roofs. Enlightening Entertainment is up next, after Noteworthy News. May your days be filled with joy and love.

If you have a flat roof, you plant up there. You don’t plant everywhere but you can use some plastic box or something or ceramic box and fill it with earth, fill your compost and just keep planting, planting - very fun. You go out and see the whole roof is green and edible - beautiful. It’s really beautiful.

Peaceful viewers, welcome to Planet Earth: Our Loving Home for the conclusion of our two-part series on green roofs or rooftops covered with vegetation to reduce the Urban Heat Island effect, promote energy savings, improve air quality, grow fresh produce, minimize storm water runoff and lessen climate change.

Last week in part one we saw how the Japanese government is promoting green roofs to keep heating and cooling costs down in buildings and make metropolitan areas less warm, as skyscrapers, concrete buildings, infrastructure and pavement trap heat from the Sun, as well as waste heat from cars, air conditioning units, factories and other sources, creating “Urban Heat Islands” or UHIs. This effect can raise the temperature in a city two to 10 degrees Celsius higher than if it was a vegetation-filled rural area.

Today we will shift to Formosa (Taiwan) to see how growing crops on rooftops can not only bring the previously mentioned benefits but also provide local communities with highly nutritious food, mitigate climate change and help us treat our Earth in a gentler manner. Let us now visit the National Taiwan Normal University’s Graduate Institute of Environmental Education’s rooftop agriculture demonstration project that serves as a model example of sustainable living in an urban setting.

Will you please introduce us to the special features of the roof-top farm at the National Taiwan Normal University?

Sure, I will show you around.

Thank you very much.

This is our vegetable garden. We offer the garden for “adoption,” mainly to our students. Apart from the students, in recent years local residents and colleagues from other departments on our campus have also felt that it’s meaningful to have a piece of land in a metropolis for planting vegetables. So, we’ve opened the vegetable garden to all our students and colleagues residing on the campus as well as the residents of our local community to adopt for planting.

Regarding the design of an eco-roof, if it’s a new building we can take everything into consideration. There shouldn’t be any problem. But for old buildings, load bearing is very important. These factors were given special consideration to make sure that it could bear the weight of the soil. This is a very important matter.

When building an eco-farm on a rooftop, load bearing and water-proofing are two very important issues. We planned it to be a self-sustaining environment. So, after you have consumed the vegetables that you grew, we hope you will collect the remaining leaves to be used as compost.

Is it similar to kitchen-waste compost?

Yes, it’s similar. The finished compost can be used as fertilizer for growing plants here in the future.

According to the United States Department of Agriculture, approximately 15% of the food the world produces comes from cities. As large metros have millions of people, by greatly increasing this percentage, the environment would benefit in many ways including reducing the greenhouse gas emissions generated from transporting produce to these municipalities. Another advantage of locally grown crops is lower fruit and vegetable prices as transport costs are minimal.

Humans should maintain a harmonious relationship with nature. We should realize that, excessive exploitation of nature will cause repercussions from her that can severely threaten the existence and development of humanity. In light of the problem of natural disasters, which are becoming more frequent, I think we should think carefully about how to live in harmony with nature and refrain from overexploitation of our natural resources.

From the viewpoint of sustainable living, it’s apparent that our concept emphasizes sustainable recycling of natural resources. Without obstructing the process of sustainable recycling, I think nature will go on forever. As a result, humans can also live on forever! This is our way of thinking. Yes!

Nearly a billion people worldwide are malnourished. Sadly, food that could be directly consumed by humans is instead being diverted to livestock. Approximately 43% of the world’s cereal production and 85% of all the soy produced globally goes to the animal agriculture industry.

The ecological damage caused by animal-based foods is so severe that a 2010 United Nations Environment Programme study concluded: “A substantial reduction of impacts would only be possible with a substantial worldwide diet change, away from animal products.”

This is the most efficient way that we humans can use solar energy. Through photosynthesis in plants, we transform solar energy into energy in the food that we consume, and again transform it into energy that the human body can use for physical activities. So this is how to use energy in the most economical way. The most direct way is making use of plants through the photosynthesis of vegetables and fruits with sunlight.

So, from the standpoint of energy use, I believe that eating more plant-based food is absolutely the most correct choice. The cause of the recent global warming is due to the high concentration of greenhouse gases in the atmosphere. So if we can reduce the consumption of meat, I think it will be very helpful in reducing the emission of greenhouse gases. Of course, from the angle of efficient use of energy, eating more plant-based foods is the correct way and to be encouraged.

Permaculture is about harmony between humans and nature and seeks to design biologically diverse, ecologically balanced habitats and food production systems. Professor Chiu of Tzu Chi University in Formosa (Taiwan) teaches courses on this subject and is a big proponent of growing produce on rooftops to improve food security and address climate change.

If we go with nature today while we manage a rooftop or a piece of land, then we’re going with the laws of nature. As long as we have a correct method, we don’t need to expend too much effort because this is the direction nature has always intended to go to, while we humans just follow along. Therefore, to face the future water crisis, the impact of environmental changes, and food crises, we have to go along with the way nature manages land.

We can also add some elements that we humans need. For example, we can change plants into edible ones. This way, we’re not just going along with nature; we’re also taking care of ourselves. That’s why we’re carrying out plans for green rooftops.

Of course, this is an excellent plan because green roofs can help reduce urban warming, save energy for a building, and more importantly, help us face future impacts. To transform a rooftop into a vegetable garden is something very important. That’s why we have to start to build food security and build a food forest, an eco-friendly vegetable garden in our own homes.

We have to expand this movement because right now we’re facing global climate change, and our global food supply system is very, very fragile. If each individual can do it, it will help us pass through the future crisis.

One smart idea that has been proposed is to use what is called “gray water” or used water from sinks, bathtubs and water fountains in a building to water crops growing on the rooftop. Gray water can augment the water supply from a rainwater collection system installed on the roof. This approach, along with others, can help further minimize the environmental footprint of a structure.

We also have to recycle the waste produced in our buildings or in our living surroundings and reuse it in our garden. That’s why it’s very important to have various kinds of compost systems. We should have a variety of compost systems, and each should be connected with the others. It will be a lot of fun for us to build such systems because we use the least resources produce the smallest amount of waste and achieve the greatest amount of recycled products.

As we’re designing the recycling system, every element is important, and each element is closely related to the others, and all the local resources are completely utilized, be it local Sun energy, water, wind energy or nutrients, because the usage of them is cyclical.

So, if we can build a society in which every little rooftop has its own recycling system, and every community has its own recycling system, then the small recycling systems will combine into a large recycling system. Only this kind of design can help us humans use our limited planetary resources and pass through the global crisis we’ll be facing.

Rooftop agriculture can help city dwellers transition to the Earth-loving organic vegan diet, the quickest way to cool our planet, as the abundant produce grown can readily feed many people in the vicinity. In what other ways can this style of agriculture help mitigate climate change? Let’s hear Professor Chiu’s perspective.

Green roofs can help reduce global warming in several ways. First, they can help reduce heat because the soil can help absorb heat through evaporation Green roofs can also reduce the solar heat radiation gains over the rooftops. As a result, we can reduce the energy we use for air conditioning. Second, green roofs themselves are a greenery indicator, because the plants on the roof can absorb CO2.

Therefore we can quantify the greenery indicator of the nine indicators of a green building calculating how much CO2 it can reduce. Also, of course, you can enjoy the vegetables you plant. You don’t have to buy imported food anymore. Normally, to produce one unit of imported food, we might need to spend 22 units of energy, but if we eat the vegetables we grow on our own, and if we grow them organically, we won’t need chemical fertilizers or fossil fuels to produce them.

So this kind of lifestyle can greatly help to reduce global warming. So, I think at this point in time, we must focus on self-sufficiency in our food supply. We don’t have much flexibility anymore. To attain self-sufficiency in our food supply, we can start from one rooftop and expand it to the entire community, and then we can expand it to an entire region, and then we can expand it to the entire island of Formosa (Taiwan). We have to develop from the bottom up.

According to the United Nations, over half of humanity now lives in cities. It is up to government leaders and ourselves to use the resources that we have such as rooftops, balconies and even unused spaces in urban areas to plant delicious organic fruits and vegetables and splendid trees, shrubs and flowers.

By greening our surrounding environment, not only do we make our world more beautiful, we lessen climate change and celebrate the magnificence of our planet. Finally, we thank Professors Chang and Chiu for sharing their expert insights into rooftop agriculture and wish them the very best in their future research in the field.

Esteemed viewers, we thank you for joining us for today’s program. Coming up next is Enlightening Entertainment, after Noteworthy News. May we all join hands and work together for a brilliant future.