"There is a risk when you are vocal about these things and don't practise as you preach, then you will be criticised and what you are saying won't be taken seriously."
Along with shunning air travel, the young activist also revealed that she plans to avoid purchasing new clothes in a bid to reduce her environmental footprint.
"I don't need new clothes," she said.
"I know people who have clothes, so I would ask them if I could borrow them or if they have something they don't need any more.
"The worst-case scenario, I guess I'll buy second-hand."
Aside from celebs and fast fashion, the young teen was asked her thoughts on having children at a time when the planet is so clearly under pressure.
Thunberg was quick to say she did not consider it selfish to have children, adding it was "not the people who are the problem, it is our behaviour".
The 18-year-old – who was named Time magazine's 2019 Person of the Year – touched briefly on being the face of a global movement, particularly on how it has impacted her family.
"When it impacts the people around you then it becomes something else," she said, addressing the death threats and ridicule she's copped during her three years in the public eye.
