I'm Joel Block.

I'm Deborah Byrd, And this is Earth and Sky's 5,000th radio program - on the subject of hope in a human world.

There is now scientific evidence that we humans are linked to nature in a way that's very profound. Scientists now sometimes say that humans and nature are "interconnected. "

There are 6.5 billion people on earth today. Some estimates suggest that world population will increase and finally stabilize at about 9 billion around the middle of this century. Earth has become a "human world."

And what do we mean by "human world?" Just that people are as natural to Earth as wind or trees or grass. Just as Mars is a desert planet, and Saturn is a planet of rings and moons, so earth has become a planet of humans.

To create a sustainable future, we are facing challenges in many areas: global food supply, fresh water, global health, energy, and so on. But as human population and the complexity of human problems have increased, so there's been a major leap forward in our ability to share visions and solve the problems.

At Earth and Sky everyday, we talk to scientists about the challenges. But we also see increasing numbers of scientists working toward solutions, and that's why we are hopeful.

For today, our 5,000th radio broadcast, that's our show. We are Block and Byrd for Earth and Sky.