Why nature is the tonic for sick cities

More than six million people die prematurely each year in our cities worldwide from air pollution. But there is a scientific solution. Plant more trees, says The Nature Conservancy’s Pascal Mittermaier.

Mittermaier (pictured), the global managing director for cities at The Nature Conservancy, will be in Melbourne next week as part of the Green Cities conference, and will share his thoughts on how “unleashing the power of nature” can help us build resilient, liveable and flourishing cities.

More than 70 per cent of the world’s people will live in cities by 20, and Mittermaier says nature will play a central role in determining the fate of these cities and the people who call them home.

Heatwaves, for example, are an increasing threat to residents of concrete and asphalt-dominated cities. In the United States, heat is already the leading natural disaster killer – responsible for more deaths than all other natural disasters combined – and that figure is expected to accelerate with climate change. Meanwhile, six million people die prematurely each year in our cities because of air pollution and millions more suffer from pollution-related diseases.

We also have a wasteful attitude to water, and Mittermaier says the contaminated rain water that runs from city sewers into rivers and oceans is now the number one cause of water pollution in many parts of the world.

The Nature Conservancy “wants to build on our success in traditional environmental land and water conservation and bring the potential of nature into city planning and management”. Mittermaier says his team is “playing an important role in helping cities tackle some of the issues that will ultimately make or break urban life”.

Trees, for example, cool the air by casting shade and releasing water vapour, and their leaves can filter out fine particulate matter – one of the most dangerous forms of air pollution, generated from burning biomass and fossil fuels. The Nature Conservancy has studied the effects of trees on air quality in 245 of the world’s largest cities and has found that trees and vegetation can filter up to 30 per cent of fine particles.

Mittermaier says planting more trees may seem like a simple solution, but a scientific approach, deployed strategically, is the secret to improving air quality.

The Nature Conservancy’s approach “relies on understanding complex data and spatial planning to target the areas in a city which will benefit the most from trees and vegetation,” Mittermaier says.

“Success depends on mapping neighbourhoods, understanding wind patterns, traffic and density, and looking at what species of trees would best suit each environment. And, of course, understanding the economic benefits as well.”

The Nature Conservancy is working in several cities to examine the beneficial role of trees and vegetation on asthma and cardiovascular health.  One of those projects is a five-year clinical study in Kentucky’s Louisville, a city which boasts some of the worst air pollution rates in the United States. More than 8,000 are being planted and the University of Louisville Medical School is measuring the impacts on residents’ physical and mental health and comparing it to a neighbouring area without additional trees.

“We are looking at nature as a pharmaceutical,” Mittermaier says, adding that other cities, including Sydney, are watching this medical approach with interest.

Hundreds of studies have found trees are good for human health. Just one report from AECOM, published in Australia last year, found urban trees deliver benefits across the health spectrum – respiratory, obesity, mental and heat stress among them – as well as energy efficiency, water quality, infrastructure durability and biodiversity.

The financial benefits are also compelling. AECOM’s research, which zeroed in on three Sydney suburbs, found there was a positive trend between canopy cover and land value. The research revealed that, where there was a 10 per cent difference in net leaf canopy coverage, property prices were on average $,000 higher.

Mittermaier says a similar scientific approach to water management can also reap rewards.

“By mapping and understanding where rain flows, we can create a network of bioswales, rain gardens and other green infrastructure to stop and filter water where it falls, rather than have it flow to antiquated sewers or need to build massive new water treatment systems.”

The City of Philadelphia, for example, aims to “green up” more than 10,000 acres of urban land in the next 15 years, which will help it to manage and better preserve its water resources, Mittermaier says. It would be the first city in the world to manage its storm water run-off using 100 per cent green infrastructure.

Mittermaier notes that “nature alone cannot solve our urban health and sustainability challenges”.

“Many other strategies, such as energy efficiency, clean energy, and new transport modes all need to come together to redefine healthy and resilient cities. Nature is not just an important component to urban planning – nature can also be an important catalyst to redefining ‘what good looks like’.”

For example, one of our greatest challenges is the disconnect that modern city-dwellers feel with the natural world, Mittermaier adds.

“The average high school senior in the US can identify up to 1,000 logos but less than five native species of plants from their own neighbourhood. These kids will spend between six and seven hours on a screen each day, but less than 30 minutes outdoors in nature each week.

“Bringing nature into cities isn’t just about making them more resilient. It’s about connecting urban people with nature.

“The good news is that once this connection is made, people appreciate the value of nature and see how it makes urban life more resilient and liveable. In many cases, this is the inspiration for deeper sustainability across the board.”

Join Pascal Mittermaier in Melbourne next week at Green Cities 2018. A limited number of tickets are still available. But hurry!