Climate leader Greta Thunberg offered advice to young people wanting to take action to help solve the climate crisis and met for the first time with natural historian Sir David Attenborough as she took over editor's duties on Monday's episode of the BBC's "Today" radio program.

The 16-year-old activist—who's helped lead millions of people in worldwide climate strikes—guest-edited the show, using the hour-long program to discuss her entry into climate activism and the challenges of fighting against a system that prioritizes fossil fuel companies' profits over the health of the planet.

Thunberg spoke with Attenborough, the longtime BBC broadcaster whose documentaries about the environment and ecosystems Thunberg credited with inspiring her to speak out about protecting the planet.

The young climate activist, Attenborough said, has in just 15 months "achieved what many of us who have been working on it for 20-odd years have failed to achieve."

"You have aroused the world," he said of her work leading climate strikes. "We don't want to spend our time marching through the streets, but we have to, and you've shown very great bravery in doing that."

Thunberg also offered advice to people of all ages who may not know how to fight the climate crisis in a meaningful way, considering that grassroots movements are up against powerful oil, gas, and coal corporations which have received government subsidies for centuries as they have pumped tens of billions of tons of climate-warming carbon into the atmosphere.

As millions of young people did as they prepared to march in the Global Climate Strike in September, people Thunberg's age must help convince the adults in their lives to fight alongside them.

"Speak to your parents," she said. "Put pressure on your parents and the other adults around you."

Some advice from @GretaThunberg on how young people can help fight climate change - even though they may feel they don't have control over very much... https://t.co/SrJJVT8kNt | #r4today pic.twitter.com/lPmXxgLjtt — BBC Radio 4 Today (@BBCr4today) December 30, 2019

However, Thunberg said in an interview with the BBC's Mishal Hussein that climate-denying leaders like U.S. President Donald Trump, who pulled the U.S. out of the 2015 Paris climate agreement aimed at limiting global warming to 1.5 degrees Celsius, may not be worth trying to sway.

When asked what she might have said to Trump if she'd spoken to him when both were at the U.N. in September, she replied, "Honestly, I don't think I would have said anything because obviously he's not listening to scientists and experts, so why would he listen to me?"

"So I probably wouldn't have said anything, I wouldn't have wasted my time," Thunberg added.

In addition to Attenborough's work, Thunberg said, she was driven to take climate action after spending several years coping with depression.

"I think it was a medicine in a way to become active," she told the BBC. "I felt like I'm doing everything I can...so there's no reason to be sad and feeling depressed."

Above all, Thunberg said, convincing politicians to make the policy changes necessary to protect the Earth for future generations—instead of remaining beholden to fossil fuel corporations—will take an engaged global citizenry.

"Read up. Inform yourself about the actual science and situation," she said. "Be an active democratic citizen. Of course to vote, but also to be active, because democracy is not only on election day, it's happening all the time."

What advice does #r4Today guest editor @GretaThunberg have for people hoping to make a difference? "Read up. Inform yourself about the actual science and situation... Be an active democratic citizen... Democracy is not only on election day, it’s happening all the time" pic.twitter.com/kpMyi7MWt7 — BBC Radio 4 Today (@BBCr4today) December 30, 2019

Listen to the whole episode here.