There are now believed to be only two viable populations of Sumatran tigers in the wild after a year-long survey found the tigers' habitat is still being cleared for industries like palm oil.

Key points: Only two populations big enough to survive long term

Only two populations big enough to survive long term Tiger density increased in protected areas but decreased overall

Tiger density increased in protected areas but decreased overall Road building, oil palm plantations key culprits in tiger decline

Scientists estimate that the number of critically endangered tigers remaining is down to 618 as of 2012, a reduction of more than 16 per cent on estimates since 2000.

But critically, they say in a paper published in Nature Communications today, land clearing has fragmented many of those tigers into small, isolated groups that will not be able to survive long term.

With only two of the groups containing more than 30 breeding females, the risk of extinction of the Sumatran tiger (Panthera tigris sumatrae) is greater than ever, said the study's lead author Matthew Luskin.

"There are two forests that are still large enough to independently sustain tigers over the long and medium terms," said Dr Luskin, who conducted the research as part of his PhD at the University of California, Berkeley.

"It's important to get those deforestation rates down and get those parks secured because [they are] the last strongholds."

The researchers studied the tigers across a range of lowland, montane and logged habitat using hundreds of remote cameras triggered by movement.

Individual tigers were able to be identified by their unique stripe pattern which enabled the researchers to avoid duplication.

Corruption, palm oil trade paves way for wildlife poachers

Kerinci Seblat National Park was estimated to have 42 breeding females in 2012. ( Supplied: Matthew Scott Luskin )

Although habitat fragmentation caused by roads is one threat to tigers, the access the roads provide can spark a further cascade of pressures, according to Mason Campbell, a tropical ecologist at James Cook University.

"Indonesia is investing heavily in putting in big [roads] through the major islands," Dr Campbell said.

"These roads go in there and usually straight behind them, the first people in are the poachers — they clean out the tigers and elephants and anything else that may be of value.

"In behind them is often the selective loggers and the illegal loggers who go in and steal some of the high-value timber."

According to Dr Campbell, the conservation status of forests can be downgraded after they have been logged, giving industry a foothold to begin development.

"It's bigger, larger, richer companies coming in, and they're often — I'm trying to put this politely — intricately linked with the local government officials who've approved those roads," he said.

"Once it's a production area it's a bit of a free-for-all for palm oil companies."

Hope in untouched areas

Although the researchers found an overall decline in Sumatran tiger numbers, they were encouraged to find that tiger population density had increased in areas that remained untouched.

"The results are a mixed bag for tigers," Dr Luskin said.

"Because the density of tigers increased through time in protected areas, but the total forested area had decreased at an alarming rate."

The World Wildlife Fund (WWF) publishes a yearly updated scorecard that rates companies' use of palm oil.

Whilst some retailers like Coles and Woolworths scored highly in 2017, a number of big brand names refused to share their data.