Salties may be pushed out of Queensland

They have been soaking up the sun along parts of the east coast for millions of years.

But salties may one day be a thing of the past in Queensland.

Queensland reptile expert Professor Gordon Grigg estimates that half of the world's 27 species of crocodiles, alligators, caimans and gharial could die out by the end of next century among booming human populations.

Saltwater crocodiles are among the lucky species to have a home where humans are unlikely to populate in remote northern Australia.

But agriculture ruins nesting areas, meaning the species will probably be pushed to smaller parts of the nation as demand for resources grows.

"In a hundred years, I think it's very likely there'll be salties living in parts of the east coast of Australia," Prof Grigg told AAP.

"But in 500 years, I don't think so."

The saltwater crocodile is already extinct through much of heavily populated Southeast Asia.

But there is bad news for those who were hoping global warming might finish off the man-eaters for good.

Prof Grigg says those species that survive human population growth could find new habitats as the world warms.

"There aren't any big aquatic habitats on the planet that are too warm to have crocodiles or alligators in them," he said.

Among the other species likely to survive are alligators in parts of North America and caimans in South America.

Prof Grigg says Australia's freshwater crocodile is also probably secure because of its wide and often remote distribution.