Humans alter Earth's chemistry from beyond grave

The focus of man's impact on nature is often based on live interaction, however, our decomposing corpses also alter the delicate chemical balance in the soil after death, scientists warned on Wednesday.

Whether our bodies are buried or cremated, they leach iron, zinc, sulfur, calcium and phosphorus into ground that may later be used in farms, forests or parks.

While essential as general nutrients, human funerary practices mean the elements are being concentrated in cemeteries instead of being dispersed evenly throughout nature, according to new research.

As a result, in some places the nutrients are overly concentrated for optimal absorption by plants and creatures, while deficient in others.

Furthermore, human bodies also contain more sinister elements, such as mercury from dental fillings.

"Chemical traces of decomposed bodies can frequently be very well distinguished in soil," said Ladislav Smejda of the Czech University of Life Sciences in Prague, who took part in the unusual probe.

"These traces persist for a very long time, often for centuries to millennia," explained Smejda.

"The effects will become more pronounced as more and more dead bodies are laid to rest," Smejda said in Vienna, where he unveiled the research at a meeting of the European Geosciences Union.

"What we do today with our dead will affect the environment for a very, very long time," he said.

"Maybe it is not a huge problem in our current perspective, but with an increasing global population, it might become a pressing problem in the future."

Smejda and a team used X-ray fluorescence spectroscopy to analyze soil chemicals in graves and ash "scattering gardens."

Pushing up daisies

Using animal carcasses, they also measured the theoretical impact of an ancient practice called "excarnation," where the dead are left out in the open for nature to take its course.

In all three cases, the ground contained "significantly" higher concentrations of chemicals compared to its surroundings, Smejda said.

If cemeteries did not exist, human remains, like those of animals, would be distributed randomly and the nutrients they release would be reused "again and again, everywhere," the researcher told AFP.

"[But concentrating them in certain places] is something that can be regarded as not natural. It's human impact, and we are changing natural levels," he said.

Now the question is: "Can we come up with a better idea [of] how to distribute these necessary elements across wider landscapes?" Smejda added.

"Certainly it is potentially possible to invent, develop and put into practice ... new methods of human burial or new treatments that could be more environmentally friendly, more ecological," he added.

He conceded this was a "taboo" topic for many with funerary customs deeply rooted in culture and religion.

"It's a very complex matter, and we are only at the beginning of this discussion, I think," he said.