Distinguished guests, ladies and gentlemen
For thousands of years, cities have been magnets for people, commerce and ideas.
Our great cities, and the different architectural styles in which they are built, demonstrate the ingenuity, diversity and success of our species.
You only need to walk outside and look at the New York skyline to understand the scale of human achievement.
But cities also embody some of the worst qualities of humanity, including our hubris.
They are testament to the price we have paid, and the price we have made the planet pay, for our success.
They are the major drivers of climate change, biodiversity loss and pollution.
The reasons for this are clear.
- According to the 2019 IPBES report, urban areas have more than doubled since 1992 – at the expense of nature and the ecosystem services it provides.
- Over half of the world’s population now lives in urban areas, making cities responsible for over 70 percent of greenhouse gas emissions and resource use.
- Only 12 percent of our cities meet World Health Organization standards for air quality.
We all know that urbanization and population growth is only going to increase the scale of these problems.
We are expanding urban areas at the rate of a city the size of Paris every week1.
By 2050, there will be around 2.5 billion more people living in cities.
It is clear that we need to rethink how we design our cities, build infrastructure and live urban lifestyles to deliver on the Sustainable Development Goals and the Paris Agreement.
So I come to you today with four messages.
One, the source of the problem can find its own solutions
But just as cities cause problems, their concentration of people and ideas means they can solve them.
The International Resource Panel says that well-designed cities could cut up to 54 percent of greenhouse gas emissions, and save on land, water and metals.
Today, we could talk about any number of solutions for making cities more sustainable.
- Integrating urban systems across sectors to achieve higher resource savings.
- Urban design that promotes cycling, walking and clean public transport.
- Bringing nature into cities, from urban parks to biodiversity corridors.
But the focus of this event is the buildings and construction sector, which brings me to my second message.
The urban expansion still to come provides a window for innovation.
The impact of the buildings and construction sector is already massive.
The sector accounts for almost 40 percent of energy- and process-related CO2 emissions, and 36 percent of global final energy demand. It is responsible for 25 percent of global water use. Construction material use grew 34 times between 1900 and 2005, yet 10-15 per cent of building materials are wasted, and 54 percent of demolition waste is landfilled.
Again, growth will mean more negative impacts.
Floorspace globally is expected to double by 2050 to 2060.
This could use up over 40 percent of the remaining carbon budget to avoid reaching the 2℃ temperature target of the Paris Agreement.
But it is this very growth that gives us an opportunity to do things differently.
As close to 70 percent of 2050 urban infrastructure is yet to be built, we can make new buildings zero-emission and resilient.
Many of the approaches to achieve this are relatively well-known.
Energy efficiency measures and nature-based solutions, such as green walls and roofs to provide cooling, are part of the mix.
But there is on aspect of the sector that very few people are talking about, and that is the raw materials we use.
My third message, therefore, is that we need to change our building blocks.
We are fixated on concrete, cement and steel.
We do not consider the embodied carbon and other environmental effects linked to these building materials – such as sand and water use.
Water is the largest resource extracted and traded by volume. Sand and gravel resources are the second-largest.2
We extract 40 to 50 billion tonnes of sand and gravel per year, with negative effects on rivers and coastal areas.
And we are not even talking about steel in this mix.
The solution is to switch to natural bio-based materials.
These materials require little energy during production.
They absorb carbon dioxide when growing, which means we can use them to construct zero-carbon buildings, where the materials absorb more CO2 than is consumed during construction.
We can also make agricultural waste, like bamboo, coconut, rice, soy and corn, valuable construction commodities, thereby making our economies more circular.
Natural bio-based materials have 20 percent better insulation properties than conventional materials like fiberglass.
Because it can be locally sourced, the insulation material achieves a 50 percent reduction in embodied energy.
It is astonishing that the sector hasn’t looked harder at these construction materials before.
My fourth and final message is that we need to shout to the rooftops about the potential of new kinds of architecture.
To begin taking full advantage of new construction techniques such as bio-based materials, we need to let people know about them.
In the UN Environment Programme’s Partnership with the Yale Center for Ecosystems in Architecture and other partners, we are doing exactly that.
We have created and displayed a 3D-printed modular structure, made from biodegradable bamboo, that shows how solar energy, water systems and plant walls can make homes self-sufficient and zero carbon.
This kind of architecture, centred around human and planetary well-being, has multiple benefits. It eradicates or minimizes environmental impacts and saves on utility bills through energy and water efficiency. And it improves the lives of people who live and work in green buildings.
There is so much potential in this space.
Only a few countries have explicitly highlighted the buildings and construction sector in their Nationally Determined Contributions.
Even fewer have set concrete targets and measures.
We need to let everyone know about the massive opportunity they are overlooking.
We need to make the solutions we are discussing today viable and marketable so that they can be picked up at scale.
We need to keep dreaming, innovating and finding new ways to ensure our built environment works with nature and not against it.
If we do this, we can bring real and positive change for our planet, and improve the lives of the billions of people who call cities home.
UN Environment Programme