Some of the parameters that made the Earth "remarkably stable" and hospitable have changed over the last century. Reuters

A team of researchers has said in a new study that the human civilization has exceeded four of nine planetary boundaries that are crucial for maintaining a “safe operating space.” The study, conducted by an 18-member research team, was published in the journal Science on Thursday.

The four planetary boundaries that are already beyond the point of no return include climate change, the loss of biosphere integrity, land-system change and altered biogeochemical cycles like the surplus of phosphorus and nitrogen. Surpassing nine of four planetary boundaries means that the human civilization is already 44 percent doomed.

It should be a wake-up call to policymakers that “we’re running up to and beyond the biophysical boundaries that enable human civilization as we know it to exist,” Steve Carpenter, director of the University of Wisconsin-Madison Center for Limnology, said in a statement.

According to Carpenter, Earth had been in a “remarkably stable state” for the last 11,700 years until about 100 years ago -- an era known as the “Holocene epoch”-- when “everything important to civilization” occurred on the planet. But, over the last century, some of the factors that made the Holocene so hospitable have changed.

“It might be possible for human civilization to live outside Holocene conditions, but it’s never been tried before,” Carpenter said. “We know civilization can make it in Holocene conditions, so it seems wise to try to maintain them.”

As part of the study, Carpenter specifically looked at two key elements -- phosphorus and nitrogen. Due to their widespread use as fertilizers for crops, the amount of these chemicals entering the ecosystem has immensely increased.

“We’ve changed nitrogen and phosphorus cycles vastly more than any other element,” Carpenter said. “(The increase) is on the order of 200 to 300 percent. In contrast, carbon has only been increased 10 to 20 percent.”

The phosphorus and nitrogen runoff can cause serious damage to water quality. While increased level of phosphorus is the leading cause of both harmful algal blooms and the oxygen-starved “dead zone” in Lake Erie in North America, nitrogen flowing down the Mississippi River is the main culprit behind the “dead zone” in the Gulf of Mexico, according to the researchers.

“Two core boundaries -- climate change and biosphere integrity -- have been identified, each of which has the potential on its own to drive the Earth System into a new state should they be substantially and persistently transgressed,” the researchers said in the study.