“I speak for the trees, for the trees have no tongues.” The Lorax is the story of an entrepreneur named the Once-ler who follows the lure of profit until his enterprise destroys the environment. The Lorax speaks on behalf of the plants and animals that can’t defend themselves, but his cries are mostly in vain. The now regretful Once-ler, the narrator of the story, speaks to you, the reader, and asks that you repair the damages his corporate greed inflicted upon the earth.

Brian Roach, a Tufts professor and Senior Research Associate at the Tufts Global Development and Environment Institute, assigns The Lorax as required reading for the first day of class. He said that in addition to making economics more approachable and connecting economics and the environment, it endorses the idea that nature deserves rights. In America, even corporations have many more rights than trees. We have environmental movements that aim to speak for the trees, but even some of the most environmentally conscious Americans live unsustainably. If everyone lived like an American, we would need about four Earths to sustain the world’s population. We have one Earth, not four, but our drive to maximize our own utility pushes us to consume more.

The Lorax presents an analogy for how economic goals lead humans to violate nature’s rights. The Once-ler wasn’t evil, he was just self-centered. He chased economic incentives without concern for the ways in which he was destroying the environment. It is easy to complete the analogy by replacing Once-ler with BP, Exxonmobil, or any other company that profits at a tremendous expense to our natural resources. But if a gallon of gasoline has an environmental cost, shouldn’t we make the polluters pay? After all, they are freeloading off of the resources we all rely on, like clean air and a stable environment.

“Economics as we apply it to environmental issues is about getting prices right,” Roach said. When prices properly account for environmental damages, only then can the free market optimize society’s well-being. Then, economics can help protect nature’s rights, rather than motivating us to violate them. Roach and other environmental economists speak for the trees by arguing in favor of a new tax model where producers are taxed for polluting the environment. “We can show through economics that even though consumers face higher prices and producers face lower profits, overall, society benefits,” Roach said.

Our neighbors in Cambridge are showing us another way that economic incentives can reduce pollution. Their BYOB ordinance—“Bring Your Own Bag”—bans stores from giving their customers plastic bags and requires that they charge a minimum of 10 cents for all other bags, in order to “protect the marine environment, advance solid waste reduction, reduce greenhouse gas emissions and protect waterways,” according to the Cambridge Department of Public Works website.

Michael Orr, Cambridge’s Waste Reduction Program Manager, says that despite some pushback from customers and corporations, the public has been overwhelmingly supportive of the ordinance. “This will be as easy of a behavioral change as taking a reusable water bottle with you when you go to the gym,” Orr said. Plenty of companies and citizens donated reusable bags that were given to citizens, especially low-income and elderly populations. Cambridge is providing a clear example that economic incentives can motivate people to make small changes that can have big impacts.

Towards the end of the book, the Once-ler asks for your help: “Unless someone like you cares a whole awful lot, nothing is going to get better. It’s not.”

To slow down global climate change and take better care of Earth, we need to continue the Lorax’s work of speaking for the trees by advocating for economic solutions. We have no time to lose—if the earth’s temperature rises two degrees centigrade, which looks very likely at this rate, we will face a global emergency.

We need to speak for the trees with good economic policies, and in order to do this we must first elect candidates who want to solve the problem. One-third of Congress still denies that humans must work to slow down climate change, as do presidential candidates Trump, Cruz, and Kasich. Meanwhile, at least 97 percent of actively publishing climate scientists agree that we humans are warming the globe.

As citizens, we can contribute to big improvements with our votes and our dollars. At the polling place, we can vote for representatives who will prioritize the environment and take climate change seriously. As consumers, we can limit our consumption of products that pollute the earth. We can also incorporate new technologies that reduce our footprint, such as home solar panels and electric cars.

So, says the Once-ler, “Plant a new Truffula. Treat it with care. Give it clean water. And feed it fresh air. Grow a forest. Protect it from axes that hack. Then the Lorax and all of his friends may come back.”