Humanity has global-scale impacts on key ecosystem cycles
SUMMIT COUNTY — A four-day Planet Under Pressure conference in London started with a gloomy look at the state of the Earth, as scientists said that time is running out to minimize the risk of setting in motion irreversible and long-term climate change and other dramatic changes to Earth’s life support system.
In taking stock of the Earth’s vital signs, the scientists pointed to higher levels of carbon dioxide in the atmosphere, phosphorus extraction and fertilizer production causing many large dead zones in coastal areas; rising air and ocean temperatures; melting sea ice, polar ice sheets and Arctic permafrost; rising sea levels and ocean acidification; biodiversity loss; land use changes; and growing consumption of freshwater supplies and energy by a growing global population, of which billions of people still lack even the most basic elements of well-being.
“The last 50 years have without doubt seen one of the most rapid transformations of the human relationship with the natural world,” said speaker Will Steffen, a global change expert from the Australian National University. “Many human activities reached take-off points sometime in the 20th Century and sharply accelerated towards the end of the century. We saw a ‘Great Acceleration,’ Steffen said. “It is the scale and speed of the Great Acceleration that is truly remarkable. This has largely happened within one human lifetime.”
Humanity is altering the carbon cycle, water cycle and nitrogen cycle on a global scale he said, adding that humans produce more reactive nitrogen artificially than all natural processes on land.
Steffen warned of potential tipping points, including the melting of the polar ice sheets and the thawing of perennially frozen northern permafrost soils, where melting could lead to the release of almost unimaginable amounts of carbon dioxide.
“There are signs that some drivers of global change are slowing or changing,” said Professor Diana Liverman, co-Director of the Institute of the Environment at the University of Arizona and visiting Oxford University academic.
“Population growth is slowing and will level off; the intensity of energy and carbon required for a unit of production is declining; agricultural intensification is slowing and forests are starting to expand in some regions.”
“On the other hand, average resource consumption per person, already high in some regions, is growing steeply in emerging economies even as many poor people cannot meet basic human needs.
“In some countries people are consuming far too much, including carbon, water and other resources embodied in trade. We have a long way to go to turn things around.”
“By the end of the 20th Century we have high emissions in China, India, Europe and eastern North America but relatively little across Latin America and Africa. Here lies the core of the debate about responsibilities for climate change in relation to historical and per capita emissions,” she said, referring to a recent study showing the highest income earners are responsible for three times the level of emissions compared with lowest income earners.
“In countries with high income inequality, the richest 10 percent of the population may be responsible for more than 50 percent of the greenhouse gas emissions – and the growing middle classes of many developing or transitional countries are developing consumption habits that add to the burden on the earth system.”
“If you like, our presenters today are akin to doctors saying ‘look, you may not feel too sick at the moment but you’ve got high blood pressure, your cholesterol is going up, and your lifestyle is not conducive to good health,’” said conference co-chair and UNESCO director of the science-policy division, Dr Lidia Brito.
“There is time to turn these trends around and promising, more positive messages will be delivered by colleagues in days to come. We look forward to discussions of our most promising options, the barriers to change and to a prescription for the future.”