LEWIS Hamilton described a visit Tuesday to parts of Australia ravaged by months-long bushfires as heartbreaking, saying it was "one of those days that really put things into perspective".

The six-time Formula One world champion, who starts his title defence at the season-opening Australian Grand Prix in Melbourne this weekend, is a passionate supporter of environmental and animal welfare issues.

At the height of the bushfires, which have now been extinguished, he donated US$500,000 to "support the animals, wildlife volunteers and rural fire services" affected by the crisis.

After arriving from London, he headed straight from Sydney airport to the New South Wales countryside to see the devastation wrought by the fires, which experts warned may have killed up to one billion creatures.

"When you read about it or when you watch it on TV it looks horrifying but when you see the real devastation up close, and how vast the land is, it's even more heartbreaking," he said in a video posted on his social media channels.

"Knowing over, I think, 1.5 billion animals perished during that time as well, it was really important for me to try and support some of the people out there who are trying to look after them and rescue the animals.

"I wanted to come out here and see it. It's been a really amazing experience."

He added to his 14.6 million Instagram followers that "it was one of those days that really put things into perspective" after being shown recovering koalas, baby kangaroos and wombats.

The fires, which killed more than 30 people and destroyed thousands of homes, began in September and were only put out in February.

Scientists say they were fuelled by drought and unfavourable weather conditions that were exacerbated by climate change.