sciencetech-blog

comments

Climate change and high rates of extinctions of animals and plants are pushing the Earth into a 'danger zone' for humanity, a scientific report card about mankind's impact on nature has concluded. 

An international team of 18 experts, expanding on a 2009 report about 'planetary boundaries' for safe human use, also sounded the alarm about clearance of forests and pollution from nitrogen and phosphorus in fertilisers.

The research charts the 'Great Acceleration' in human activity from the start of the industrial revolution in 1750 to 2010, and the subsequent changes in the Earth System - greenhouse gas levels, ocean acidification, deforestation and biodiversity deterioration. 

The research charts the 'Great Acceleration' in human activity from the start of the industrial revolution in 1750 to 2010, and the subsequent changes in the Earth System - greenhouse gas levels, ocean acidification, deforestation and biodiversity deterioration.

'It is difficult to overestimate the scale and speed of change. In a single lifetime humanity has become a planetary-scale geological force,' says lead author Professor Will Steffen, who led the joint project between the International Geosphere-Biosphere Programme (IGBP) and the Stockholm Resilience Centre. 

'I don't think we've broken the planet but we are creating a much more difficult world,' Sarah Cornell, one of the authors, told Reuters.

'Four boundaries are assessed to have been crossed, placing humanity in a danger zone,' a statement said of the study in the journal Science, pointing to climate change, species loss, land-use change and fertiliser pollution.

Of a total of nine boundaries assessed, freshwater use, ocean acidification and ozone depletion were judged to be within safe limits. 

Others, including levels of airborne pollution, were yet to be properly assessed.

The report defined climate change and loss of species as two core areas of concern. 

Each 'has the potential on its own to drive the Earth System into a new state should they be substantially and persistently transgressed,' the authors wrote.

Rising concentrations of carbon dioxide, the main greenhouse gas, are about 397 parts per million in the atmosphere, above 350 ppm that the study set as the boundary for safe use.

'When we first aggregated these datasets, we expected to see major changes but what surprised us was the timing. 

Researchers also sounded the alarm about clearance of forests and pollution from nitrogen and phosphorus in fertilisers

'Almost all graphs show the same pattern. 

'The most dramatic shifts have occurred since 1950. 

'We can say that around 1950 was the start of the Great Acceleration,' said Professor Steffen, a researcher at the Australian National University and the Stockholm Resilience Centre.

'After 1950 you can see that major Earth System changes became directly linked to changes largely related to the global economic system. 

'This is a new phenomenon and indicates that humanity has a new responsibility at a global level for the planet,' he added.

Almost 200 governments will meet in Paris in late 2015 to try to agree a deal to limit global warming to avert floods, droughts, heatwaves and rising sea levels blamed on rising emissions of greenhouse gases.

The study said that rates of extinctions of animals and plants, caused by factors ranging from pollution to deforestation, were 10 to 100 times higher than safe levels.

'Transgressing a boundary increases the risk that human activities could inadvertently drive the Earth System into a much less hospitable state,' said lead author Will Steffen, of the Stockholm Resilience Centre and the Australian National University, Canberra.

The report expanded definitions of the planetary boundaries set in 2009, making it hard to compare trends.