Lewis Hamilton has defended his use of social media to raise awareness about global environmental issues.
The five-time world champion has been accused of hypocrisy because of his role in Formula 1 and the high number of flights he takes every year.
"It's not easy as we're travelling the world and our carbon footprint is higher than the average homeowner who lives in one city," said Hamilton.
"That doesn't mean you should be afraid to speak out for positive change."
Hamilton used his Instagram feed last week to say he felt "like giving up on everything", that the world was "messed up" and to ask people to follow his example in taking up a plant-based diet to help the environment.
But his former rival Fernando Alonso told Spanish radio: "I would never release a message like Lewis. You can't send out a message one day and the next day do the opposite.
"We all know the lifestyle that Lewis has, and that Formula 1 drivers take 200 planes a year. You can't then say: 'Don't eat meat.'"
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But Hamilton rejected the criticisms and said everyone could do more to protect the environment.
"It is something over time I have become more and more aware of," he said. "It is not a quick fix. It takes time to understand the implications. I would feel I wasn't doing anything positive if I didn't mention it.
"It's important to be able to be open and not hold things in. I'm always very open and transparent with my feelings, whether people like it or not."
Speaking on the eve of the Mexican Grand Prix weekend, where he has the possibility to clinch his sixth world title, Hamilton gave a long list of efforts he was making in his own life to protect the planet.
These included trying to make sure he is carbon-neutral by the end of the year, forbidding his office or anyone in his household from buying plastics, selling his private plane, travelling less, using an electric car and encouraging Mercedes - both the F1 team and the car company - to make relevant changes.
He also emphasised that the turbo hybrid engines introduced into F1 in 2014 use a third less fuel than previously.
He was backed by Ferrari driver Sebastian Vettel and other drivers in the official news conference in Mexico City on Thursday.
Vettel said: "It is very difficult for us to have acceptance from the outside because we don't have the smallest [carbon] footprint. The races are around the world and we do have to travel.
"But I feel F1 should do more. It is a worldwide operating platform and we should send a more positive message.
"Everyone can do something, contribute a little bit and if the whole world acted like that it would make a huge difference. It is inevitable change is coming and hopefully sooner rather than later."
Red Bull's Alexander Albon added: "What Lewis said was really good. Just because we are in F1 doesn't mean we can't care about the environment."
Hamilton doubts he will clinch title in Mexico
Hamilton played down his chances of sealing the championship in Mexico this weekend.
To do so, he needs to score 14 points more than team-mate Valtteri Bottas, the only driver who has the mathematical possibility to overhaul Hamilton's points score.
"I don't think in the season I have finished 14 points ahead of Valtteri at any point," he said. "It may have been one race, Valtteri has been strong all year and I expect him to be strong this race as well."
The only time Hamilton has done so was in the Hungarian Grand Prix in early August, when he won and Bottas finished eighth after damaging his car in a collision with Ferrari's Charles Leclerc on the first lap.
Hamilton expects Ferrari to be strong favourites in Mexico because the track rewards straight-line speed, where the Italian cars have a significant advantage over Mercedes.
"We go into the weekend knowing Ferrari are massively quick on the straights and they are a powerful part of this circuit," he said.
"I don't know when we'll be getting another pole but it is not all about qualifying. It's about getting the car ready for the race, this track bodes well for the Ferrari and Red Bulls but maybe we will have a better chance than in the past."
Bottas, who won the last race in Japan, is 64 points behind Hamilton and after this race there will be a maximum of 78 available.
The Finn said: "I'm not superstitious in any way really but crazy things can always happen, I believe. I've seen many different crazy things. You never know.
"It's getting for sure tougher in each race. But there's no point saying it's over because it isn't. It is when it actually happens.
"Obviously, it's a bit of a long-shot, if I'm being realistic, but we'll just focus on individual races and this weekend, like in Japan, really try to do the best I can and try to win the race."
How Hamilton can win the title in Mexico
- Win plus fastest lap with Bottas lower than third
- Win with Bottas lower than fourth
- Second plus fastest lap with Bottas lower than seventh
- Second with Bottas lower than seventh
- Second with Bottas lower than eighth if Bottas sets fastest lap
- Third and fastest lap with Bottas lower than eighth
- Third with Bottas lower than ninth