Think global, act local. The slogan has been around for decades. But as the impacts of rapid urbanization increase around the world, it has perhaps never been more relevant.
In 1950, less than one out of three people lived in a city or town. Today nearly half 3 billion live in urban areas. By 2030 almost two out of three will live in cities and 90 per cent of this urban population growth will be in developing countries. In 1950, only New York City had more than 10 million inhabitants: by 2015 there will be 23 of these megacities, 19 of them in the developing world. Yet the most rapid urbanization will not be in these, but in urban centres with currently fewer than 500,000 people.
The reasons for this rapid urbanization are economic, social, and cultural. In the past, urbanization in the developed world was mostly based on economic growth, where jobs were available, and resulted in urban productivity. The new urbanization in developing countries, however, is not always tied to the availability of jobs. Many people come to the city for social interests or the hope of a job, only to find themselves trapped in slums, with few prospects. More than a billion people are in this situation, mainly in Asia, Africa and Latin America and they could grow to more than two billion in just the next 15 years. For the environment the important issue however, is not why, but how this urbanization is taking place and its consequences for the planet and its ecosystems.
Natural ecosystems are at the core of our survival, whether we live in a city or rural area. They provide air to breathe and food and water to eat and drink. They regulate our environment by cleansing our air (e.g. by trees) and filtering our water (e.g. though wetlands). Finally, they enrich our lives with green space and wilderness areas where we can recreate and be at peace. Without each of these of services our entire wellbeing would be at risk.
Urban areas import huge amounts of goods such as fuels, foods and water from ecosystems beyond their borders, like rural farms, forests, and water catchments. Cities then export their, they enrich our lives with green space and wilderness areas where we can recreate and be at peace. Without each of thes services our entire wellbeing would be at risk.
Urban areas import huge amounts of goods such as fuels, foods and water from ecosystems beyond their borders, like rural farms, forests, and water catchments. Cities then export their wastes such as garbage, wastewater, air pollution back out of the city. Both processes have an impact on the delivery of ecosystem services.
Urbanization has led to damaged ecosystems well beyond city borders up to national and global levels
Urbanization has led to damaged ecosystems well beyond city borders up to national and global levels. Forest and wetland ecosystems, supporting vast biodiversity, are threatened by the unsustainable import of goods, such as from felling forests, and from the construction of unplanned housing in critical periurban and rural ecosystems. žExportsÓ of wastes increasingly pollute downstream rivers and coastal waters as cities swell beyond their capacity adequately to treat, and dispose of, wastes. Air pollution also knows no boundaries: about 80 per cent of greenhouse gases leading to climate change now come from cities.
This climate change may not be immediately on the minds of local governments under pressure of urbanization. Nevertheless, the resulting increase in the frequency and intensity of storms has significant human and financial costs, particularly in coastal cities subject to hurricanes. Climate change also leads to unpredictable and extreme temperatures which can translate to higher urban energy costs for production, heating and cooling, thus creating a vicious cycle of more greenhouse gas emissions.
Sustainable solutions exist. Even more importantly, there are solutions that simultaneously address both local and global environmental problems. Take, for example, improvements to transport and energy generation, the largest contributors both to urban air pollution and to worldwide climate change. Cleaner transport fuels and vehicles, cleaner cooking fuels like natural gas, renewable energy sources, and greater energy efficiency, would significantly reduce air pollution and mitigate global warming. Cleaner air would improve public health, and thus bring greater productivity and economic gain for individuals and the community.
Water resources also present such localglobal links and solutions. Cutting rural forests to žimportÓ wood fuel into cities and žexportingÓ inappropriately treated wastes and wastewaters both degrade important ecosystems and water resources. Once degraded, watersheds lose their ability to supply, store and cleanse the citys water resources. But cities that have invested in protecting water resources outside their borders have saved money on treatment costs.
World Environment Day and its focus on Green Cities Plan for the Planet embodies the localglobal link and presents an opportunity to share, debate, and learn about such solutions. Best practices in public transport, energy, urban green space, water resource management, and other issues, must be shared and expanded. Cities from all countries must join together for both the local and common good. Lessons are there to be shared, North to South, South to South and South to North. In 2000, the worlds leaders united and agreed the Millenium Development Goals (MDGs). The seventh goal environmental sustainability ≠ runs as a thread woven into all of them. Rapid urbanization threatens quickly to unravel this MDG fabric unless we recognize that ecosystems provide vital services for urban dwellers and integrate this into development planning.