About half of the people in the world live in cities. This share has more than doubled over the last 40 years, and is projected to reach 55% by 2050.[i] Urbanisation has helped to drive growth, tackle poverty and boost quality of life and well-being.
Yet urban activities are harming our environment through consumption of land and materials. In particular, urban sprawl is resulting in a loss of biodiversity, which is now considered to be among the top global risks to society, together with climate change. According to a recent report of the World Economic Forum, 44% of GDP in cities around the world – USD 31 trillion – is at risk of disruption from biodiversity and nature loss. How can our cities reset their relationship with nature?
Making room for nature
Perhaps cities’ most powerful tool is spatial planning. A recent OECD study illustrates that land-use planning, zoning and urban design can be used to protect, or even expand, biodiversity. For example, the city of Glasgow in the United Kingdom is making more room for nature by creating new local nature reserves. Through these reserves, the city have brought 500 hectares of woodlands into active management and replanted 2 kilometres of hedgerows. The city has also created over 55 new ponds and planted 14 000 locally grown wildflowers since 2001, mobilising 12 000 days of volunteer conservation work to support its effort to enhance biodiversity.
Across the Channel, planners in the city of Paris are making the best of rainy days through the Paris Rain Plan (Paris Pluie), which encourages nature-based solutions including green roofs to increase water absorption and rainwater use.
Such measures help avoid the overflow of saturated drainage systems from heavy rains and cloud bursts, alleviate heatwaves, whilst benefiting biodiversity. Urban planning can also tap into opportunities to enhance biodiversity in urban centres, urban fringes and brownfield land. The value of brownfield land in particular is often underestimated: many of these areas have a higher biodiversity than managed urban green spaces. In particular, brownfield sites have low nutrient soils which inhibit fast-growing plants from dominating, and can support a rich variety of invertebrates, plants, birds, bats, reptiles and amphibians. In recognition of this, the UK government has added some brownfields to its list of priority sites to protect the natural environment.
Meanwhile, in the West Side of Manhattan, New York City, the “High Line”, a historic, elevated freight railway was transformed into a 2.3-kilometre-long greenway, featuring 110 000 plants and trees of more than 500 species. Nearly half of the plants are native species, and many were produced by local growers, better adapted to grow successfully in the dry urban climate. The plants are also a source of food and shelter for wildlife species, including native pollinators in New York, which is home to more than 400 species of wild bees. The area now attracts almost 8 million visitors annually and hosts a diverse line-up of free public events, community and teen engagement programmes, performances, and art shows, making it one of the most popular attractions in the city.
Greening the budget
Cities are beginning to embed biodiversity priorities into budget-setting. For example, the city of Mulhouse, France, has established the programme “Nature in the City and Biodiversity” in 2021 to identify investment expenditures related to biodiversity. The Department of Mayenne, France, was the first in France to apply green budgeting in December 2020, and found that 5.5% of its budget is environmentally harmful, mostly related to road investments.
Green budgeting provides a prompt for cities to turn to biodiversity-enhancing Nature-based Solutions (NbS). A recent report from the World Economic Forum found that NbS are, on average, 50% more cost-effective than “grey” alternatives and deliver 28% more added value. They also have the potential to create 21 million jobs by 2030.
Raising ambitions
Cities are setting ambitious targets and tracking progress. For example, the Paris Biodiversity Plan sets aims to create of 20 biodiverse public spaces by 2020 and convert 50% of land surface to permeable vegetated surface by 2030. Cities like Edinburgh, Paris and Singapore are using the Singapore Index on Cities’ Biodiversity to monitor their progress over time. Berlin, Malmö, Seattle and other cities have using the Green Space Factor to measure tree diversity, and the availability of bird boxes, bat boxes and biotope of insects. The Urban Biodiversity Hub (UBHub) provides tools to visualise progress. These targets and tools are also helping to raise awareness and mobilise volunteers.
Going wild
As cities weigh up their investment plans pandemic, they have a one-in-a-lifetime opportunity to reset their relationship with nature. NbS received just 0.3% of overall spending on urban infrastructure in 2021, a figure that can be expanded rapidly to create jobs, natural habitats and resilient infrastructure. It’s time to go wild.
Read more on the OECD work on Cities and Environment.
- [i] The figures are based on a new harmonised global definition of cities developed jointly by the OECD and European Commission. Cities are defined as high density places of at least 50,000 inhabitants. For more information, please refer to OECD/European Commission (2020), Cities in the World: A New Perspective on Urbanisation, OECD Urban Studies, OECD Publishing, Paris, https://doi.org/10.1787/d0efcbda-en.
Tadashi Matsumoto leads OECD’s work on sustainable urban development and manages the global relations at the Cities, Urban Policies and Sustainable Development Division. He provides strategic leadership and oversees the research and analysis on topics related to the zero-carbon transition in cities, a territorial approach to SDGs, urban green growth, energy efficiency in buildings, urban resilience and national urban policies.