dr. michael lee. thank you for joining us. what is sustainability and how do we explain that to people? >> most common definition is the ability to maintain a quality of life today, tomorrow and future generations. that means for everybody and, of course, in a world the way it is going, we have to do it today but added to the population in the coming decades. >> reporter: this is your passion, i can tell. why is it so important? >> let me tell you something about it. it's called the ecological footprint. we can calculate to provide us with energy and resources and compare to how many resources we actually use. americans make up 5% of the population and we use up 25% of the world's resources. so if everybody live like we did we would need six planets to support us. >> reporter: what do we do about it? >> we take a look at all of the things we do and we relate that to maintain it overtime but what are our options. biggest thing we do is consuming energy for transportation in our homes, kinds of food we eat and how they have gotten to us, third thing that very important is amount of goods