The chances of limiting climate change appear to be growing slimmer by the day — and this may have big implications for Australia's wildlife.

Recently a number of crocodiles have been trapped in the Mary River, just 105 kilometres north of Noosa and 250km south of their usual range.

Irukandji jellyfish too, appear to be expanding south, with 10 suspected stings near Fraser Island and a child stung at Mooloolaba last year.

Numerous tropical fish have been recorded up to 1,000 kilometres south of their traditional range, such as the Great Barrier Reef's lemon-peel angelfish which turned up on Lord Howe Island in 2009, and habitat-modifying sea urchins have landed in Tasmania.

According to Climate Action Tracker (CAT), the world is not reducing emissions sufficiently to limit warming to below 2 degrees.

So how will warming of 2 degrees affect the distribution of Australian animals?

Will we have crocodiles sunning themselves on the beaches at Noosa and Irukandji in Byron Bay? And what happens when rare species clinging to mountain tops run out of room to climb?

Crocodiles in Noosa?

Crocodiles like this one have been showing up regularly in the Mary River, 100 kms north of Noosa. ( ABC Wide Bay: Brad Marsellos )

The average annual monthly maximum temperature difference between Gladstone and Noosa is 1.8 degrees Celsius, according to Bureau of Meteorology records.

Although a 2-degree average temperature increase does not mean all regions will warm uniformly, if we take it as a rough guide it does mean Noosa's climate would be inside the present range of crocodiles.

Crocodiles have been known to travel hundreds of kilometres in order to find new territory, according to Darwin zoologist Adam Britton.

"If two points are connected by water then they can get there. And the only thing that really stops them if there's water involved is temperature."

Although they are fairly generalist in nature, there are a few environmental factors that crocodiles prefer when seeking new habitat.

'That'll be good fun if that was the Gold Coast.' ( ABC News: Xavier La Canna )

"They tend to prefer tidal river systems — everything from the mangrove habitats you find in the estuaries, up into the less-saline habitat you see further upstream."

Certainly estuarine habitats exist all the way down the Queensland coast and into New South Wales.

But there is uncertainty about whether the recent instances of crocodiles in southern waters is climate related or due to increasing numbers.

Crocodile populations have dramatically recovered from the brink of extinction since the 1970s, and the need for new territory may push some individuals to move outside their natural range.

A Queensland Department of Environment and Science (DES) spokesperson said they currently "don't have evidence" to suggest crocodiles are expanding south.

"To establish a better scientific understanding of Queensland's wild population of estuarine crocodiles, the Queensland Government commenced a three-year crocodile survey and monitoring program in April 2017," they said by email.

"We will be considering size, habitat, distribution and abundance of estuarine crocodiles in Queensland waterways."

But Professor Stephen Williams from James Cook University (JCU) agreed that as the climate warmed, southward migration was inevitable.

"They're a big reptile, they're reliant on warmer water and sunbaking to keep warm and their southern extent certainly will be affected by the temperature. I'm guessing that'll continue and move further south," he said.

"I was at the beach just up at the Daintree the other day and we saw a three-metre croc swim past just out past the surf line … it's like yeah that'll be good fun if that was at the Gold Coast."

Irukandji

A child was stung by an Irukandji jellyfish at Mooloolaba. ( ABC News: Matt Bamford )

Although "Irukandji syndrome" was known from the 1940s in North Queensland, its cause was unknown until toxinologist Jack Barnes allowed himself, his nine-year-old son, and a volunteer lifesaver to be stung by a jellyfish the size of a fingernail.

All were hospitalised but recovered, and Barnes documented the sting symptoms of what came to be known as the Irukandji jellyfish.

Several species of Irukandji are common in Australia's tropical waters but numerous stings have recently occurred around Fraser Island, and one as far south as Mooloolaba on the Sunshine Coast last year.

Despite there being limited knowledge of Irukandji biology, toxinologist associate professor Jamie Seymour from JCU who has studied them extensively, said they were already responding to warming conditions.

"If you go back 50 years ago, you find that the [stinger] season was around two months long. Now the season is about six to seven months long," he said.

"We looked at how far south the stings were 50 years ago and they were around about the Whitsundays. And we looked at where we're getting stings now, which is the southern end of Fraser Island."

Jack Barnes stung himself and his nine-year-old son with an Irukandji. ( Supplied: Lisa-Ann Gershwin )

Although some have argued Irukandji live in the reef and so are limited in how far south they can travel, Dr Seymour does not think that is the case.

Juveniles inhabit water that is less saline than open ocean, but that may be shallow inshore waters or even around estuarine systems.

"I think the major reason people think you [only] find them around reefs is because that's where people swim," he said.

"By and large, the East Australia Current is going to push them further south until it gets too cold and they can't survive, so their southern distribution is temperature limited — we're fairly certain about that."

CEO of the Queensland Tourism Industry Council Daniel Gschwind said the tourism industry was supportive of scientific research in this field and would adjust their advice to tourists accordingly.

"If something changes in our environment then we have to make sure people are aware of this," he said.

But he also cautioned it was important to keep things in perspective.

"Do you know what is the greatest risk to tourists that come to Australia? Car travel followed by beach safety," he said.

Dr Seymour also said the threat posed by Irukandji was sometimes overblown.

"The numbers are fuzzy but we reckon we get something like 400 or 500 stings per year in Queensland, and out of the entire history that we know of we've only had two deaths [worldwide]."

Nowhere to go but up

White lemuroid possums are one of many species that may run out of mountains to climb. ( www.wettropics.gov.au )

While marine animals are able to migrate north and south in search of cooler waters, a lot of Australia's mountain-dwelling animals do not have the same option.

As temperatures rise, species like the white lemuroid ringtail possum in the wet tropics of North Queensland are being pushed to higher, colder altitudes.

The problem is, with Australia's relatively low mountain ranges, there is only so high they can go, according to Professor Stephen Williams.

"Fifteen years ago, I was happily going along studying ecology and rainforest biodiversity, and then I did some work on climate change as a side project and realised that almost everything I worked on could go extinct this century," he said.

"The mountains here aren't very big, they only go up to 1,500 metres. Most of them are actually only 1,000 to 1,200 metres, so they just slowly contract up the mountain until there's nowhere for them to go."

The wet tropics are home to numerous endemic species. ( ABC News: Eric Tlozek )

An increase of 2 degrees or more could send more than 50 per cent of mountain-dwelling species in the wet tropics extinct.

And there are signs animals are already on the move, according to Professor Williams.

"Things like ringtail possums, we used to see them at 600 metres, now we haven't seen them at 600 metres for seven or eight years, and we can only find them now above 700 metres," he said.

"And that pattern is relatively consistent across all of the species that we've got enough data to do anything with, statistically."

The 2-degree warming limit in the Paris Agreement that countries signed up to in 2015 wasn't plucked from thin air.

The IPCC report states many ecosystems are subject to, "very high risks with additional warming of 2 degrees Celsius, particularly Arctic sea-ice and coral-reef systems".

Beyond 2 degrees, there is likely to be "extensive" biodiversity loss, restricted crop yields, and significant sea-level rise.

For Australia's mountain-dwelling animals, Professor Williams said the 2-degree target was critical.

"Our models predict that we don't really get any extinction until about one-and-a-half degrees, and that makes sense because anything that is here now has already survived one-and-a-half degrees in the past," he said.