Urban green spaces encourage active and healthy lifestyles, improve mental health, prevent disease, and provide a place for people to socialize. And especially when they feature native greenery, they can improve a city’s resilience. Planting native trees and shrubs in urban spaces can help cities to adapt to the impacts of climate change by bringing down temperatures, buffering storms and floods, and working as excellent air filters.
Biologist Liliana Jaramillo Pazmiño – one of six Young Champions of the Earth in 2017 – is cultivating native trees and shrubs to grow on rooftops in Quito, Ecuador. Her ultimate aim is for these corners of greenery to become part of the city’s infrastructure.
“When you think about urban cities, most of the time you think about concrete. But rooftops are basically wasted space – leftover land,” she says. “It’s time we started converting these spaces into greener spaces for everybody to enjoy.”
“In Quito and in most cities, this means including eco-friendly approaches to urban development and planning. Planting trees in rooftop spaces requires designing buildings with stronger infrastructure to cope with extra weight, for example. If this isn’t tailored into building design, it can be too expensive to do after construction.”
“Even when we do incorporate trees or green areas into urban construction, these often focus on exotic species, which are not native to our land. Reintroducing native species inside the city is important for so many reasons. They help our ecosystem become more diverse, attracting native birds and species to our city spaces.”
“Bringing native trees and shrubs into the city also helps protect them from disappearing, and connects us to nature and our heritage. Part of my project is about creating awareness about which greenery is native, so people can choose local, native species over exotic species and we can feel more connected to our cultural roots, and connect with green spaces outside the city.”
“During the process of urbanization, many of our native species have been disappearing, but we still don’t have a good record of what has been lost. Multiplying and selling them on a wide scale throughout the city is my goal, so that people can easily find them for their rooftops.”
“Bringing native greenery into our urban infrastructure can help us adapt to changing climatic conditions, so that our cities are more resilient to drought, flooding or higher temperatures. We can learn lessons from other cities where this is already being applied.”
21 March is the International Day of Forests. The theme for 2018 is Forests and Sustainable Cities.
The living air purifiers cities need more of
In our all-too-hectic urban lives, a city park is a great place to unwind. Trees and green spaces have mental health and well-being benefits, on top of being great for relaxation and recreation.
Trees also help reduce air pollution. According to the study Tree and forest effects on air quality and human health in the United States, particulate matter, which is particularly damaging to lungs, is retained on tree surfaces, while leaves act as filters, absorbing polluting gases.
But the study also warns that while trees can mitigate the effect of air pollution, deposits of air pollutants on leaves can also affect photosynthesis “and therefore potentially affect pollution removal by trees”. As with everything, balance is key.
The cooling effect of trees
Trees can also significantly cool temperatures in cities. In hot climates, tree cover can reduce energy expenditure on air conditioning, while driving down the consumption of air polluting fossil fuels that power these cooling systems. Experimental investigations and modelling studies in the United States have shown that shade from trees can reduce the air conditioning costs of detached houses by 20–30 per cent.
“Trees could reduce temperatures in cities up to 8°C, lowering use of air conditioning and related emissions by up to 40 per cent,” says Simone Borelli, an Agroforestry and Urban/Periurban Forestry Officer with the Food and Agriculture Organization of the United Nations.
“When part of a wider landscape mosaic, large green patches within and around cities would also reduce emissions through avoided sprawl and excess mobility requirements,” he adds.
Urban tree-planting has to be done right. Species planted should be ones that are most effective at trapping pollution, typically those with large leaves. Officials also need to account for things like wind patterns and tree spacing. If water is scarce, they’ll want to consider drought-tolerant varieties, and avoid trees that increase pollen and allergies.
Action is all the more important given that urbanization is accelerating—the proportion of people living in cities will be 60 per cent in 2030 and 66 per cent in 2050. Nearly 90 per cent of this increase will occur in Africa and Asia. To address the impacts of this rapid growth and the related challenges, a large-scale effort is needed.
Building the Great Green Wall of Cities
Nearly 8,000 km long and 15 km wide, the Great Green Wall is an African-led movement of epic proportions initiated in 2007 to green the entire width of northern Africa, a semi-arid region extending from Senegal to Djibouti. A decade in and roughly 15 per cent under way, the initiative is slowly bringing life back to some of Africa’s degraded landscapes, providing food security, jobs and a reason to stay for the millions who live along its path.
An initiative of this nature in urban areas is being developed by the Food and Agriculture Organization and other partners in preparation for the UN Climate Summit in September 2019. It aims to create up to 500,000 hectares of new urban forests and restore or maintain up to 300,000 ha of existing natural forests in and around 90 cities of the Sahel and Central Asia by 2030. Once established, this “Great Green Wall of Cities” would capture 0.5–5 gigatonnes of carbon dioxide per year and stock carbon for centuries.
On 1 March 2019 the UN General Assembly established the UN Decade on Ecosystem Restoration 2021-2030, which should give further impetus to tree-planting efforts.
“UN Environment promotes the planting of trees as a key way to mitigate climate change and boost land-based biodiversity, 80 per cent of which is in forests,” says Tim Christophersen, head of UN Environment’s Freshwater, Land and Climate Branch, and Chair of the Global Partnership on Forest and Landscape Restoration. “We are working with partners across the planet to boost tree planting for ecosystem restoration. There is scope for planting one trillion more trees, in addition to the 3 trillion that already exist on Earth. But it has to be done right; planting indigenous trees, supported by local communities, is a good way to go.”
Let the stones gather some moss
In those forest ecosystems, trees are not alone in cleaning the air. An ambitious project by Greencity Solutions in Berlin, Germany, seeks to marry high-tech applications with another natural air purifier: moss.
“The ability of certain moss cultures to filter pollutants such as particulate matter and nitrogen oxides from the air makes them ideal natural air purifiers,” says Greencity Solutions.
“But in cities, where air purification is a great challenge, mosses are barely able to survive due to their need for water and shade. This problem can be solved by connecting different mosses with fully automated water and nutrient provision based on unique Internet of things technology,” it explains.
Or by planting more trees that will provide the cover and humidity, that will help moss take hold and grow.
New study expected to chart Melaka’s pathway to urban sustainability
Within the framework of the ‘Sustainable City Development in Malaysia’ project, which seeks to address the country’s urban challenges and which is being implemented by the United Nations Industrial Development Organization (UNIDO), executed by the Malaysian Industry-Government Group for High Technology (MIGHT), and supported by the Global Environment Facility (GEF), the ‘Melaka Sustainability Outlook Diagnostic: Pathway to Urban Sustainability’ was launched today. The report is the result of an assessment performed by the World Bank’s Global Platform for Sustainable Cities (GPSC) in which Melaka actively participates. The study will inform the Melaka State’s Structure Plan and its long-term planning document; it will also offer key recommendations for the State to chart its own pathway to urban sustainability.
The diagnostic consists of an overview report containing a policy brief, an executive summary and a benchmark assessment as well as six supporting reports that cover each of the diagnostic’s dimensions, namely Reinforcing Melaka’s Economic Success; Integrating Environmental Plans; Enhancing Housing and Services; Shaping a Compact, Efficient, and Harmonious Urban Form; Shifting Melaka’s Mobility Modal Split; and Demonstrating Fiscal Sustainability.
One of the report’s recommendations calls for the State and the City of Melaka to obtain a credit rating; accordingly, both entities already agreed to undergo a formal rating assessment with UNIDO’s support. Depending on the assessment’ result, they could tap capital markets to finance future infrastructure projects. Moreover, another recommendation calls for the City of Melaka to complete a climate-smart capital investment plan for which the city indicated its willingness, with UNIDO coordinating local and national inputs to raise funds.
Being one of most urbanized countries in Asia, 75 percent of Malaysians reside in urban areas and over 90 percent of the national economic activities are conducted in cities. Rapid urbanization has created tremendous economic opportunities for the country, but has also put enormous pressure on its urban infrastructure and services.
Make Dhaka Walkable
When it comes to urban mobility, Global South cities suffer significant challenges such as lack of transport equity and poor accessibility for the urban poor. On the March of 25-28, 2019, the Share the Road Programme (a partnership between UN Environment and FIA Foundation) participated in a workshop dubbed ‘make Dhaka walkable’ held in Dhaka, Bangladesh, organized by the Sustainable Transport Equity Partnerships (STEPS) – a global alliance of researchers and practitioners including the Walk21 Foundation, UN Environment and the University of Leeds. The organizations are committed to identifying the essential steps decision makers and multi-disciplinary teams of experts must collectively take to meet the needs of people walking. STEPS aims to promote urban transport systems that can meet the travel needs of low income, city populations in the Global South.
Despite walking making up to 75% of all journeys, the conditions in which people walk in Dhaka are often unsafe and unpleasant. In order to highlight the needs of pedestrians in Dhaka, the meeting brought together engineers, planners, civil rights activists, NGOs, social scientists and many more for a real interdisciplinary perspective of the transferability of global walkability practices.
The opening workshop included representatives from Dhaka Transport Coordination Authority (DTCA), Road Transport and Highways Division, Ministry of Road Transport and Bridges, University of Asia Pacific and others to help push the local walking agenda forward.
One of the gaps identified through the STEPS programme is the severe inadequacies of non-motorized transport in transport policy in the Global South. The Share the Road programme shared knowledge on the experience of non-motorized transport in Nairobi -the small initiatives needed to make big differences, the need to have NMT users included in the planning of road construction projects, and the importance of securing a percentage in transport budgets. The vital and economic aspects of walkability projects cannot be ignored.
Having discussed the ‘eight steps to walkable Dhaka’ facilitated by Walk21, the workshop was brought to a close by Professor Jamilur Choudhury from University of Asia Pacific who gave some personal reflections on the development of transport policy and walking in the city, and stated his commitment to moving the walkability agenda forward locally.
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