By Arti Mulchand

Eco-cities

Songdo international business centre, near Incheon, South Korea

The US$30 billion (S$41 billion) Songdo international business centre has quickly become a model for sustainable development, thanks to steps taken to reduce the city's carbon footprint right from the conceptualisation stage.

The city, which is being developed on 600ha of reclaimed land along Incheon's waterfront, includes features like underground cisterns which trap storm water run-off for irrigation systems and non-potable uses for commercial buildings.

It also has hectares of green space, fuel-cell buses, water taxis and extensive bike ways.

It opens officially in August next year but when fully completed in 2015, the business centre will be home to 65,000 people, and 300,000 will work there.

Songdo was named one of the winners of the first Sustainable Cities Award, sponsored by the Financial Times and the Urban Land Institute, earlier this year - the only Asian winner.

Dongtan, China

Located on Chongming island, about an hour from Shanghai, Dongtan's goal is to stay as close to carbon neutral as possible - with city vehicles that produce no carbon or particulate emissions, and highly efficient water and energy systems.

All its energy will come from renewable sources, including biofuels, wind farms and solar panels.

Most of its waste will be reused as biofuel for additional energy production, and organic waste will be composted.

Even human sewage will be composted and processed for energy and composting.

Dongtan expects to use 64 per cent less energy than a comparable conventional city of its size.

Construction is expected to begin some time this year. Up to 10,000 people will live in the city on completion of the first phase, which is planned for 2010.

Curitiba, Brazil

Mayor Jaime Learner and his government are credited for Curitiba's transformation into a model of sustainability, by drawing on a combination of sound transport policies, recycling and low-tech solutions.

Two-thirds of the city of 1.6 million people used public transport by the 1990s, thanks to a sophisticated and efficient bus system which acts almost like a railway, and integration between different forms of transport.

It means the city has 25 per cent less congestion and noticeably cleaner air than cities of similar size.

Recycling in Curitiba is also so advanced, two-thirds of the city's daily waste is processed.

The city is also home to 21million sq m of parks, woods, gardens and squares.

The parks' lakes are used to hold back floods, and function as water-flow regulators during the rainy season.

Freiburg, Germany

The humble bicycle has gone some way to help establish Freiburg as Germany's ecological capital since the 1970s.

One-third of all journeys are by bike.

By 1986, sustainability received a further push from the city's vision to be reliant on an ecologically oriented energy supply.

Ten years later, Freiburg passed the Climate Protection Concept, a resolution to cut emissions to 25 per cent below 1992 levels by 2010 - by targeting energy use in buildings, homes and businesses, as well as transport.

In a decade, the city's emissions came down by more than 10 per cent per head.

Public transport use has also doubled, with a third of the city's residents choosing not to own a car.

Today, its solar, energy efficiency and transport programmes are among the best in the world.

Transport

Mexico City

Oneof the primary sources of Mexico City's carbon emissions - and a major contributor to its air pollution - is the transport sector.

The sector accounted for more than a third of its 2000 estimate of 51 million tonnes of carbon dioxide emitted.

Thus, many of the city's sustainability solutions zoom in on that sector.

One municipal government-sponsored programme is that of replacing 10,000 of Mexico City's taxis that are at least eight years old with more fuel-efficient models.

So far, 3,090 taxis have been replaced. More than 40,000 other taxis have also gone greener - thanks to taxi drivers who got loans on their own and changed their cabs.

Energy use

San Francisco, United States

San Francisco is home to the largest city-owned solar power system in the United States.

Located at San Francisco's Convention Center, it covers 60,000 sq ft, equivalent to the size of a football field, and generates 826,000 kwh annually.

This is equivalent to powering 184 homes in San Francisco for a year, or the power saved by removing 7,000 cars from the road, or not driving 141 million km.

Over the lifetime of the project, it will reduce emissions of carbon dioxide by 35,000 tonnes.

Water management

Singapore's Marina Barrage

Touted as the poster child of Singapore's quest for environmentally sustainable development, the $226 million Marina Barrage provides far more than waterfront beauty.

Not only does the island's 15th reservoir increase its water supply, but the tidal barrier will also help alleviate flooding in the city's low-lying areas during high tide.

When officially opened next year, it will be Singapore's first reservoir in the city, and will offer recreational activities.

It is one of the crown jewels in the national water agency PUB's water management plans.

Biodiversity

Chek Jawa, Pulau Ubin, Singapore

Given Singapore's small land area and need for economic growth, a pragmatic approach has been adopted in trying to balance development and biodiversity management.

The country's model focuses on protecting nature reserves and areas rich in biodiversity, such as Chew Jawa Wetlands on Pulau Ubin. Chek Jawa Wetlands made news in 2001, when there was a strong petition against the Government carrying out reclamation work in the area.

Nature lovers spoke up for the area's unique ecosystem.

About 20,000 people visit Chek Jawa annually.

This article was first published in The Straits Times on 21 June 2008.