Houston, we have a problem.
The oil and gas rich city, which is also the fourth largest in the U.S., now wants to live clean, and not green, but clean.
As part of our week-long series The City,
CNN talks to Houston's mayor to see how residents are looking at energy in a whole new light.
I'm Annise Parker. I am mayor of Houston, Texas, United States of America.
We're the fourth largest city in the United States.
We have to provide essential city services to millions of people every day.
We are on the banks of Buffalo Bayou.
Buffalo Bayou was where Houston was founded.
We were where the railroads met the sea and the ships came up this bayou, you see a little bit farther here, and off-loaded.
This is restoring the banks. It's opening up green space, putting some meanders back in the river that were originally straightened.
It'll clear the water up, be better for the fish and the turtles that live in here, but it will also be great for flood control.
Just because some mistake was made in the past doesn't mean you have to live with it forever. You can go back and fix it.
Just because we have built a city on the profits of oil and gas doesn't mean that we don't respect the environment, care about the environment.
We've cut our greenhouse gas emissions by 26 percent and we are going to continue to lead by example.
We're standing in front of Houston B-Cycle.
It is a bike share, or bike rental program for the city of Houston.
It's just over a year old and it is [has] just exploded in popularity.
We went from three stations to now 22 stations and 200 bikes.
We want to expand the bike share through the more dense areas of inner-city Houston.
We have 2,400 signalized intersections across the city of Houston, and it burns a lot of energy.
We originally decided to invest in LED lights, because we would save energy.
But what we found out -- LED lights last longer and they have to be changed out less frequently.
So the return on investment is almost immediate.
In my view, a sustainable city is a city that can project into the future that the air quality stays high and the water quality stays high,
that there are [there's] a range of housing options for people to live in the city.
A sustainable city is a city that works today, but is building and investing for tomorrow.