High-resolution satellite images have revealed the "rapid deforestation" of Papua New Guinea's biodiversity rich rainforests over the past 30 years.
An international team of researchers estimates that the current rate of loss could result in more than half of the nation's tree cover being lost by 2021.
They added that the main threats came from commercial logging and burning.
Existing conservation measures were failing to protect the world's third largest rainforest, the team concluded.
Scientists from the University of Papua New Guinea (PNG) and the Australian National University spent five years analysing satellite images that showed deforestation and habitat destruction between 1972 and 2002.
They estimated that in 2001 the nation's accessible forests were being cleared or degraded at an annual rate of 362,000 hectares (3,620 sq km).
The images also showed that trees in protected areas were being felled at the same rate as unprotected regions, the team added.
Although it only accounts for less than 0.5% of the Earth's land cover, the heavily forested island nation is home to an estimated 6-7% of the planet's species.
"It is still one of the most forested nations on the planet," said lead author Phil Shearman.
"However, the report details how the forests are being lost at a far higher rate than previously thought."
Fears for the future
The researchers mapped forest cover and degradation in 2002, using high-resolution images from Landsat ETM+, SPOT4 and SPOT5 satellites.
Logging operators did not attempt to minimise their impact, the study says
They then compared this with a baseline detailed map from 1972 to show the extent of forest loss over a 30-year period.
The team found that the main drivers were commercial logging, subsistence agriculture and burning.
"Contrary to the popular opinion that little is happening, rates of change are high and accelerating," explained Julian Ash, one of the report's co-authors.
"Commercial logging operations are extracting more than 2.6% of the accessible resources yearly and causing the release of about 22 million tonnes of carbon."
The nation's forestry minister, Belden Namah, said the report would be uncomfortable reading but added that he welcomed such a detailed assessment of the state of the tropical forests.
"Over the past decades we have imagined that our forests are limitless," he wrote in the report's foreword.
"Perhaps the rapid modernisation that has occurred in PNG has made us reticent to accept the notions of scarcity; perhaps we have been too focused on local developments to see the bigger picture.
"If this report is the bitter pill that we need to swallow to ensure that we maintain our forests into the foreseeable future, so be it."
Papua New Guinea's government realises that protecting its forests could prove to be financially beneficial.
It backs the concept of Reducing Emissions from Deforestation and Degradation (REDD), which was considered at last year's global climate summit in Bali.
Under the scheme, developing nations with large forested areas could be paid by industrialised countries not to cut down trees.
The rich nations could then offset some of their own emissions against the carbon dioxide absorbed and stored by the trees that they paid to be protected from being felled.
But Mr Shearman said that the current rate of forest loss would make it hard for officials to convince people that they were serious about protecting the forests.
"If they are allowing multinational timber companies to take everything that's accessible, all that will be left will be the lands that are physically inaccessible to exploitation and would never have been logged anyway."
Mr Namah said the report's findings provided an important insight into the impact of logging and agriculture was having on the landscape, and would complement the government's forestry policy.
"There is a need for rapid action to replace tree loss," he told reporters. "For every tree that is cut down, we should be able to plant three trees."
However, Dr Ash warned: "It takes centuries, not decades, for rainforests to recover from such changes.
"This report is a wake-up call to address the future of their forests; these issues have global impacts and should also galvanise the international community."