Just 20 countries are home to 94 per cent of the world's remaining wilderness, excluding the high seas and Antarctica, according to our global wilderness map, published in Nature.

A century ago, wilderness extended over most of the planet. Today, only 23 per cent of land — excluding Antarctica — and 13 per cent of the ocean are free from the harmful impacts of human activities.

More than 70 per cent of remaining wilderness is in just five countries: Australia, Russia, Canada, the United States (Alaska), and Brazil.

We argue that wilderness can still be saved. But success will depend on the steps these "mega-wilderness nations" take.

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Wilderness areas are vast tracts of untamed and unmodified land and sea.

From the lowland rainforests of Papua New Guinea, to the high taiga forests of Russia's Arctic, to inland Australia's vast deserts, to the great mixing zones of the Pacific, Antarctic and Indian Oceans — these areas are the last strongholds for endangered species, and perform vital functions such as storing carbon, and buffering us against climate-change effects.

In many wilderness areas, indigenous peoples, often the most politically and economically marginalised of all, depend on them for their livelihoods and cultures.

Yet despite being important and threatened, wilderness areas and their values are overlooked in international environmental policy. In the main, wilderness is not formally defined, mapped or protected, so there is nothing to hold nations, industry, society and community to account for it.

Beyond boundaries

Almost two-thirds of marine wilderness is in the high seas, beyond nations' immediate control.

Effectively, it's a marine wild west, where fishing fleets have a free-for-all. There are some laws to manage high-seas fishing, but no legally binding agreement governing high-seas conservation, although the UN is negotiating such a treaty. Ensuring marine wilderness is off-limits to exploitation will be crucial.

And we cannot forget Antarctica, arguably Earth's greatest remaining wilderness and one of the last places where vast regions have never experienced a human footfall.

While Antarctica's isolation and extreme climate have helped protect it from the degradation experienced elsewhere, climate change, human activity, pollution, and invasive species threaten its wildlife and wilderness. Parties to the Antarctic Treaty must act to help reduce human impacts, and we must curb global carbon emissions before it is too late to save Antarctica.

Our maps show how little wilderness is left, and how much has been lost. Between 1993 and 2009, 3.3 million sq km of terrestrial wilderness — an area larger than India — was lost to human settlement, farming, mining and other pressures.

In the ocean, the only regions free of industrial fishing, pollution and shipping are confined to the poles or remote Pacific island nations.

Saving wilderness

Almost every nation has signed international environmental agreements that aim to end the biodiversity crisis, halt dangerous climate change, and achieve global sustainable development goals. The remaining wilderness can only be secured if its importance is recognised within these agreements.

At a summit in Egypt this month, the 196 signatory nations to the Convention on Biological Diversity will work alongside scientists on developing a strategic plan for conservation beyond 2020. This is a chance for all nations to recognise the issue, and to mandate a global target for wilderness conservation.

A global target of retaining 100 per cent of all remaining wilderness is achievable. It would mean stopping mining, logging, and fishing from spreading.

Committing to it would make it easier for governments and non-governmental organisations to leverage funding and mobilise action in nations that are still developing economically.

Similarly, the role of wilderness in guarding against climate change — such as by storing huge amounts of carbon — could also be formally documented in the UN Framework Convention on Climate Change. This would encourage nations to make wilderness protection central to climate strategies.

Mechanisms such as REDD+, which allows developing nations to claim compensation for conserving tropical forests, could be extended to other carbon-rich wilderness areas such as intact seagrasses, and even to wildernesses in rich countries that do not receive climate aid, such as the Canadian tundra.

Nations can, via legislation and rewarding good behaviour, prevent road and shipping-lane expansion, and enforce limits on big developments and industrial fishing in their wilderness. They can also establish protected areas to slow industrial activity's spread into wilderness.

The planet faces not just a species extinction crisis, but a wilderness extinction crisis. If lost, wild places are gone forever. This may be our last chance to save the last of the wild.

• James Allan is a postdoctoral research fellow, James Watson is a professor, Jasmine Lee is a PhD candidate, and Kendall Jones is a PhD candidate, all at the University of Queensland.

- The Conversation