My impression, and its only that, is that a big step forward for sustainability would be an integrated bicycling policy, that seeks to increase bicycling, even at the expense of other forms of transit.

Very difficult for NYC to do much different than it does, as a 'green' city.  You can recycle a bit more rubbish, maybe get a bit of power from 'green' sources (if someone else, somewhere, builds those sources- -wind farms off Long Island?).  Maybe spend some more money on better air conditioners and Compact Fluorescent Lightbulbs (just giving 2 free ones to every household would probably pay back in peak watts saved).

I'm sure as new buildings are built they can be made more energy and water efficient.  Retrofitting existing buildings is much tougher, but there can be a bit of that.

Fundamentally NYC is still a place where food, energy, water, people flow in every day, to service the needs of its inhabitants.  What flows out is services NYC produces for the rest of the world: media, financial services, architects, legal services, management consulting, corporate HQ services, etc.

But whether someone drives to WalMart or whether food is delivered to his door, it won't be grown in NYC, and it will be distributed (by truck) into NYC.

Sort of random speculating here (looking for an alternative answer).  But at the end of the day it seems what New Yorkers can do is make obvious reductions in their use of gasoline, emission of CO2, in getting around.

The city did just announce [a major cycling initiative http://www.uppergreenside.org/2006/09/12/city-announces-major-biking-initiative] - 200 more miles of bike lanes in 3 years. The next best step is to adopt the legislation allow bikes into all buildings and set up better parking facilities around the city for cyclists. And yes, reducing reliance on the automobile for everyday transportation needs is really the key to reducing the cabon output of the city. Improving energy efficiency around the city is also very important, especially heating and electrical systems. But let me flip your observation about the power and influence that New York has as a consumer of resources from elsewhere. We can make decisions on what we choose to buy from the surrounding areas and the rest of the world to influence decisions made at the site of production. NYC's power as an large market can project a huge influence on our suppliers and create whole new industries and patterns of economics that favor more sustainable agriculture, less packaging, better recycling, more efficient transportation of goods, etc. For instance, NYC spends something like $25 Billion on food every year in grocery stores, restaurants and other places. Changing just a fraction of where that $25 Billion gets spent can influnce what farmers grow and how they grow it to be much more sustainable than it currently is. New York is quickly becoming the new center of the urban environmental movement. It's massive size in population & economics as well as it's influence in the media have the potential to be a major force in influencing sustainable development across the rest of the US.
The city did just announce a major cycling initiative - 200 more miles of bike lanes in 3 years. The next best step is to adopt the legislation allow bikes into all buildings and set up better parking facilities around the city for cyclists.

And yes, reducing reliance on the automobile for everyday transportation needs is really the key to reducing the cabon output of the city. Improving energy efficiency around the city is also very important, especially heating and electrical  systems.

But let me flip your observation about the power and influence that New York has as a consumer of resources from elsewhere. We can make decisions on what we choose to buy from the surrounding areas and the rest of the world to influence decisions made at the site of production. NYC's power as an large market can project a huge influence on our suppliers and create whole new industries and patterns of economics that favor more sustainable agriculture, less packaging, better recycling, more efficient transportation of goods, etc.

For instance, NYC spends something like $25 Billion on food every year in grocery stores, restaurants and other places. Changing just a fraction of where that $25 Billion gets spent can influnce what farmers grow and how they grow it to be much more sustainable than it currently is.

New York is quickly becoming the new center of the urban environmental movement. It's massive size in population & economics as well as it's influence in the media have the  potential to be a major force in influencing sustainable development across the rest of the US.

I agree NYC's big impact can be, as ever, to set the trend.

I think that in American terms, NYC is pretty efficient in how it uses energy.  That is in American terms ie the most energy intensive big country on the planet.

The tragedy is there are newer cities than NYC in America but they haven't been built with well insulated homes, mass transit systems, cycleways etc.  

(in the UK we have repeated the same mistake).

How about more community gardens?  I see plenty of unused lots  in the city (an especially in the boroughs).  These can be converted into green spaces and where possible actually produce an impressive amount of frech food (like raised bed urban farming).  This also cools down buildings and surface temperatures in the city, as well as providing carabon free activities for residents.

Also, I think we can start using trains more to bring cargo in and out of the city...

Yes - all good ideas!

For the Freight rail, Staten Island has recently restored it's freight rail link to New Jersey, but the rest of the four boroughs have the nearest link across the Hudson as Selkrik. One proposal that would change that would be to construct cross harbor freight rail tunnel for freight traffic.

And definitely more community gardens and roof gardens (green roofs).

Interesting quote I noticed in the enviornmental impact study for the cross harbor rail tunnel
"Although freight trains currently operate nationwide on diesel fuel, it is possible that electric freight trains may become more commonly used in the future."
At least they realize the possibility that there can be freight trains not operated by diesel. Especially now that diesel is getting expensive compared to electricity, and rail freight is getting ever more popular, making the case for electrification better and better.