Earth has exceeded four of the nine limits for hospitable life, scientist claims

'For the first time ever, we might shift the planet from friend to foe.'

(Getty)

Humanity has raced past four of the boundaries keeping it hospitable to life, and we're inching close to the remaining five, an Earth resilience strategist has found.

In a paper published in Science in January 2015, Johan Rockström argues that we've already screwed up with regards to climate change, extinction of species, addition of phosphorus and nitrogen to the world's ecosystems and deforestation.

We are well within the boundaries for ocean acidification and freshwater use meanwhile, but cutting it fine with regards to emission of poisonous aerosols and stratospheric ozone depletion.

"The planet has been our best friend by buffering our actions and showing its resilience," Rockström said. "But for the first time ever, we might shift the planet from friend to foe."

This table by Ted shows where we're at according to his scale:

Rockström came up with the boundaries in 2007, and since then the concentration of greenhouse gases in the atmosphere has risen to around 400 parts per million (the 'safe' boundary being 350 parts per million), risking high temperatures and sea levels, droughts and floods and other catastrophic climate problems.

The research echoes a recent debate over whether the Earth has moved from the Holocene epoch to a new one scientists are calling the Anthropocene, named after the substantial effect mankind has had on the Earth's crust.

It's not all doom and gloom though.

"Ours is a positive, not a doomsday, message," Rockström insisted.

He is confident that we can step back within some of the boundaries, for example through slashing carbon emissions and boosting agricultural yields in Africa to soothe deforestation and biodiversity loss.

"For the first time, we have a framework for growth, for eradicating poverty and hunger, and for improving health," he said.