Sir David Attenborough has riled up British MPs, urging them to make radical changes to tackle climate change.
Speaking to a UK parliamentary committee, he said the government needed to make tough, unpopular decisions like hiking up the price of airline tickets.
"No one thought that human beings could change the climate," he said. "And now we know we are, and what is worse is that we are changing the climate in a way that is irreversible.
"Certainly, well not in our lifetime, but in our country's life time if we carry on the way we are."
Sir David said inaction could impact immigration with parts of Africa becoming "even less inhabitable" than they are now.
Food and the way humans live would also be affected.