By Tundi Agardy, MEAM Contributing Editor,

The gray, concretized urban landscape couldn't be farther from protection of nature and oceans in most people's minds. Yet coastal cities may hold the key to a sustainable future, and will be crucial to ensuring that EBM unfolds effectively and efficiently around the world.

We speak of "greening cities", which conjures up the image of taking something inherently ugly and bad and giving it a makeover so it better suits our new environmentally conscious sensibilities. But that is not why gray is the key to green in a blue world. What I propose is that there are characteristics of cities that should make them focal areas for EBM – perhaps the most important combatants in the fight to preserve marine and coastal ecosystems.

My mind was first opened on this issue when I had the good fortune of working on the Millennium Ecosystem Assessment ( alongside some brilliant big-picture thinkers from around the world. As lead on the coastal portion of the assessment, I spent much time with other thematic lead authors, including Gordon McGranahan, who oversaw the urban systems assessment. Putting urban systems on equal footing with natural ecosystems was already a renegade move that got a lot of conservationists and ecologists scratching their heads, but we all quickly learned why this made sense. Cities are indeed ecosystems, and the effects that urban consumption and growth have on ecosystem services go well beyond their boundaries. But these effects are both positive and negative – and there are clear ways that we can use cities as a force for positive change.

Why do cities occur where they do? In large part, it is the ecosystem services that attract people to these places and support population growth there. The worldwide population is unevenly distributed: about two thirds live in the coastal fringe, which itself represents only 5% of inhabitable land mass. The pull factors that explain this human settlement include safe harbors and navigation routes both inland and offshore, access to water and food resources, and waste disposal, among others. These factors are behind demographic trends that have a large majority and fastest-growing segment of the human population living near major estuaries.

Cities are key to getting our ocean management right not only because of the numbers. By their nature, cities can prevent widespread habitat alteration by concentrating coastal development in discrete areas, preventing sprawl. Smart growth minimizes exurban and suburban habitat conversion creep – and this is some of what is behind the greening of cities.

Positive impacts of coastal cities

But coastal cities can do more than just reduce negative impacts – they also increase the potential for positive impacts. By concentrating people in small areas, the opportunity to do everything necessary to use coastal resources sustainably and minimize our impacts on ecosystems is more readily achievable. Waste management is easier; education and outreach can more readily reach the masses; people have more opportunity to support local businesses and buy from local markets; and there can be enhanced participation in governance. Cities also create opportunities for progressive leadership – like Honolulu with its watershed approaches that mimic traditional practices, or San Francisco and its growth management to maximize resilience in the face of coastal hazards, or Copenhagen where kayak-commuting is an objective in the city's forward planning! Even smaller Milford, Connecticut, in the US has had a string of mayors who have been a shining light in climate change adaptation debate and action.

Coastal cities have a unique ability to focus awareness and management on the full suite of areas and activities needed to make EBM a reality. Take UNEP's Hilltops-to-Oceans (H20) initiative, coordinated by the Global Programme of Action's Takehiro Nakamura. Coastal cities, especially those located in estuarine areas, can not only lead coastal management but influence watershed management as well. They even have the (economic and political) power to influence what happens offshore in marine management. The social scale of cities is conducive to achieving true integration – these are coherent social units that are not so big as to become too complex to govern and not too physically large to effectively manage. And as concentrations of wealth and power, coastal cities can also influence what happens in a wider region, and have a voice even on the world stage.