About one-fifth, or 20 percent, of the Amazon rainforest has disappeared in the past 50 years.

Forest has been lost due to farming, building cities, and logging. The loss of forest harms the millions of different plants and animals that live in the Amazon River region. It also affects humans around the world.

Some of the world's best scientists are trying to save the rainforest. National Geographic explorer Dr. Thomas Lovejoy is one of those scientists. We talked to him about the Amazon and why it matters.

NG: You have worked in the Amazon for more than 50 years. How have you seen the region change?

TL: In the 1960s, there was only one highway in the entire Amazon region. That's an area as large as the continental United States, with one highway and 3 million people. Today, there are between 30 million and 40 million people and countless roads. About 20 percent of the forest has disappeared, too.

There has been progress, though. Today, there are many more national parks in the Amazon. More than 50 percent of the Amazon is protected in some way. The real challenge is how to plan and manage the Amazon.

When we talk about protection of the Amazon, it's hard for many people because they don't feel connected to the region. How can we change that?

It's true that we are far away. But our daily lives are very connected to the Amazon.

For example, a snake called the bushmaster lives in the Amazon. This snake kills its prey with a poison that causes the prey's heart to stop. Scientists studied this snake to develop medicine for our hearts. Today, millions of people use these medicines to treat high blood pressure. They now have longer and more productive lives. People have a nasty snake far away in the Amazon to thank for it.

Climate change affects everyone on the planet. It is happening in part because of the extra carbon dioxide in the atmosphere. Tropical forests trap a lot of carbon dioxide. The Amazon holds about half of the world's rainforests. Losing the Amazon would release that carbon dioxide and increase climate change.

The Amazon basically makes half of its own rainfall. Some of the rain from the Amazon travels south, which is really important for agriculture in Brazil and Argentina. Brazil is currently in a drought that might be the worst in its history. It is happening partly because the region is getting less rainfall from the Amazon.

What is your vision for the future of the Amazon?

There has been a lot of damage done and forest lost, but nothing is gone until it's gone.

We hope for the Amazon to return to be about 90 percent of what it was originally. We want it to be managed together by the nine Amazon nations: Brazil, Peru, Colombia, Venezuela, Ecuador, Bolivia, Guyana, Suriname, as well as French Guiana. We want to see the people in charge of transportation, energy, agriculture, and the other businesses in the region plan together. We think Amazon cities can have higher quality of life, too. That would keep people in cities, so there is less reason to cut down trees.