Half Earth: an idea whose time has come

As far-fetched as it may sound, the idea of giving half of Earth back to nature is gaining momentum.

Dandelion against emerald green background

What if humans gave half of planet Earth back to nature?

In this future, half of the world's land would be permanently protected. That would not only save animal and plant species threatened with extinction, it would also help us reach climate change goals.

To the casual observer, such a world-changing ambition looks far-fetched. Yet to its advocates - such as biodiversity organisations Half Earth Project or Nature Needs Half coalition - the idea is rapidly gaining acceptance among policymakers and business leaders

The concept isn't new. Canadian conservationist Harvey Locke and American biologist E.O. Wilson first proposed the Half Earth idea in the early part of the last decade. 

Initially, their views didn’t gain traction. Yet the tide of opinion has recently been turning in their favour.

So much so that the United Nations' landmark biodiversity summit in 2021 will draw heavily on the Half Earth concept. The organisation hopes to include clearer biodiversity goals within its new Convention on Biodiversity.

Under discussion are objectives that would commit the world to increase the proportion of lands conserved for nature to 30 per cent by 2030 and to 50 per cent by 2050. The summit is being billed as the most important on the environment in more than a decade.

Neglected for much of the 2000s, protecting biodiversity has in recent years become a top priority for international organisations and governments. It now commands the same importance as CO2 emissions in the climate change debate.

The significance of this shift in emphasis is difficult to overstate. Human activities such as resource extraction and intensive agriculture threaten to trigger a "biological holocaust", if left unchecked, says Wilson.

Yet the science behind species loss is complicated. No one knows for sure how many species the world is home to, which makes extinction rates rough estimates at best.

The UN estimates that up to one million animal and plant species are at imminent risk of extinction. Other models, such as Stockholm Resilience Centre’s Planetary Boundaries, estimate that human activities are responsible for increasing the extinction rate to a level that is 100 times faster than the natural one.1

Yet species loss is only one side of the biodiversity story. Animals, insects and plants cannot exist without the habitats and ecosystems that they are adapted to live in.

And that is why the Half Earth concept becomes an especially effective as a policy tool.

Its greatest appeal is its simplicity. Half Earth is an intuitive concept that is easily understood by the general public. Contrast that with the existing and soon-to-lapse biodiversity agreement, which contains 20 largely unmet targets that included protecting 17 per cent of land and sea area.

“Half Earth is a bold vision. But it's also simple: between you and me, what's the fair way to share a resource?” says Dr Erle Ellis, Professor of Geography and Environmental Systems at University of Maryland, Baltimore County, and a leading researcher of Half Earth.

“It represents a big picture that enables people to think about what kind of biosphere they want to leave to future generations. And to be clear, we're actually talking about the whole Earth, not just half.”

Since long before the industrial revolution, humans have been converting forests, grasslands and wetlands to feed and house their growing numbers.

This land system change – and related habitat loss – is identified as the biggest cause of biodiversity loss. Worryingly, about half of Earth’s land surface is already in use. Increasing demands for land from human populations, which are projected to reach 10 billion by 2050, will only make it more difficult to protect natural habitats.

Beach, sky and birds

Which half, where and how?

If successful, Half Earth would equate to the most extensive conservation project in history, incorporating a land area greater than 70 million square kilometres – fifty times larger than the world's biggest existing conservation network, which is in Europe.2

A group of environmental scientists have proposed an “ecoregion”-based approach to achieve Half Earth's goal. Spanning Alaskan and Yukon forested areas, Angolan mopane woodlands and Himalayan alpine shrubs and meadows, ecoregions are a network of protected and diverse habitats, which are home to threatened and globally important species and ecosystems.

Currently, 13 per cent of 864 ecoregions meet the Half Earth target, while 37 per cent fall short but have potential to meet the goal.3

For all the benefits that come with biodiversity protection, there are concerns that Half Earth and other approaches to wildlife conservation could threaten indigenous and other rural populations.

Critics claim that at its extreme, a “Fortress Conservation” approach could lead to land seizures and evictions.

This is why scientists say it is essential that local communities and indigenous people – stewards of more than a third of all remaining intact wild areas – are given autonomy in managing their lands sustainably in a more inclusive system.

“Not all conservation benefits the people who live and work in conservation areas. Fortress Conservation – which focuses largely on keeping people out – is an unjust strategy and deserves to be attacked... With Half Earth you have to put this issue right at the top,” Dr Ellis says.

But with the right strategies, the potential for conservation to help vulnerable people is also unprecedented.

He cites one example in Namibia, where the government allowed local communities to create conservancies – areas with defined borders and governance and management structures outside of parks – to protect wildlife. Now regarded as a success for both nature and people, these conservancies cover more than 20 per cent of the country and generate more than USD10 million a year in cash income and benefits for local people.4

The path to Half Earth

Some scientists believe Half Earth could work in tandem with the Paris Climate Accord to reduce global warming. Nations are falling behind the Paris goal as temperatures are projected to rise 2.8C by the end of the century, close to twice the sustainable limit.5

By protecting habitats and the carbon they hold, Half Earth could be part of the solution.

“Burning fossil fuels has become like printing money – a huge force in societies – making it so hard to keep carbon out of our skies and safe in the ground. Though clean energy is increasing, it is so slow to turn a big ship like this. With land, we have a different trajectory,” Dr Ellis says.

The UN estimates that almost 15 per cent of the earth's land surface is currently protected – this means the world is almost a third of the way to achieving the 50 per cent goal.6

For Half Earth to have a chance of success, agricultural practices need to change radically.

Here too, there are reasons for optimism. Advances in agricultural technology are helping improve the efficiency of food production and stabilise the global area of land used for growing food, Dr Ellis says.

Data backs up his view. The average cereal yield has more than doubled in the past half century, outpacing the rate of the population growth. Today, the world can produce almost three times as much cereal from a given area of land as it did in 1961. 

This means the global amount of cereals produced per person has increased. As a result, the world has spared 1.26 billion hectares of global land from agricultural production – roughly equal to the area of Mexico and Europe combined.7

half earth

Dr Ellis says that economic incentives and scientific research should reinforce this positive trend. Businesses can also help in advancing the Half Earth proposal.

“Every land manager, everyone in the supply chain, has to make decisions. Businesses and institutions can work together to encourage larger-scale conservation practices,” he says.

“We should be doing better business with the biosphere.”

[1] Planetary Boundaries framework analyses the nine critical environmental dimensions of climate change; biodiversity loss; land-system change; biochemical flows; chemical pollution; freshwater use; ocean acidification; ozone depletion and atmospheric aerosol loading. Rockström et al. 2009
[2] Ellis, E. and Mehrabi, Z. Current Opinion in Environmental Sustainability, vol 38, 22-30 (2019)
[3] Dinerstein, E. et al. Bioscience. 2017 Jun 1; 67(6): 534–545.
[4] WWF
[5] Climate Action Tracker
[6] World Database on Protected Planet
[7] Our World in Data