APRIL 2016|| 9Increasing levels of methane in the atmosphere
since 2007 are most likely due to agricultural
practices, and not fossil fuel production as
previously thought, according to research
published in Science(tinyurl.com/zmu4wcn).
Methane levels in the atmosphere are esti-
mated to have risen by about 150% since
1750, but levels plateaued between 1999 and
- Since then methane levels have been
rising again.
Scientists at New Zealand’s National
Institute of Water and Atmospheric
Research irst noticed these trends in the
data collected at monitoring stations in
Wellington and Antarctica. With only
Southern Hemisphere data to go on, the
scientists collaborated with American and
German researchers who were taking similar
measurements in a number of locations across
the world.
“We found we could distinguish three
different types of methane emissions,” said Dr
Hinrich Schaefer. “One is the burning of organic
material, such as forest ires. Another is fossil fuel
production – the same processes that form natural
oil and gas – and the third is formed by microbes
which come from a variety of sources such as
wetlands, rice paddies and livestock.”
Around the time the plateau in methane emis-
sions occurred, economic collapse in the Soviet
Union reduced oil production dramatically, and
this could be detected in the atmosphere.
However, analysis of the atmosphere since 2006
rules out fossil fuel production as the source of
the current rise in methane levels.
“That was a real surprise, because at that time
the US started fracking and we also know that
the economy in Asia picked up again, and coal
mining increased. However, that is not
relected in the atmosphere,” Schaefer said.
“Our data indicate that the source of the
increase was methane produced by bacteria,
of which the most likely sources are natural,
such as wetlands or agricultural, for example
from rice paddies or livestock.”
Previously published studies had deter-
mined that the methane originated from
an area that includes South-East Asia,
China and India, which are dominated by
rice production and agriculture. “From
that analysis we think the most likely source
is agriculture,” Schaefer said.
“The good news is that if the source was
wetlands, we couldn’t do anything about it. But
there is ongoing research that is looking at reducing
methane production in agricultural practices.”
However, global warming could change this.
Wetlands produce more methane if there is more
rain and if it’s warmer. Thawing permafrost
produces methane, and methane is also found in
ice-like structures in ocean sediments. “You could
have a situation where humans are causing global
warming, which causes natural methane sources
to emit more methane, contributing to further
warming,” Schaefer said. “We don’t see that, not
yet. Our indings at least give us an angle to tackle
the problem.”
Schaefer also warned: “If fossil fuel production
picks up again that may change the situation
dramatically”.Agriculture, Not Fuel, Is Behind Rising Methane
As antibiotic resistance has reduced the effectiveness of treatments
for a bacterium associated with stomach cancer, researchers from
the Murdoch Childrens Research Institute have found a way to
switch on the production of a protein that prevents infection.
The bacterium Helicobacter pyloritriggers inflammation of the
stomach lining, causing peptic ulcers and stomach cancer. Current
preventative therapy for stomach cancer is based on antibiotic
eradication of H. pylori. However, an increased global prevalence of
antibiotic-resistant H. pyloristrains has reduced their effectiveness,
leading to efforts to find new ways to combat stomach cancer.
Dr Treve Menheniott and Prof Andy Giraud found that
Gastrokine-2 (GKN2), a protein normally present at high levels in
the healthy human stomach, is switched off in people with stomach
cancer, and suggest that it might function to protect against H.
pyloriinfection.
The team found that GKN2-deficient mice that were infectedwith H. pylori developed more severe stomach inflammation and
experienced accelerated pre-cancerous disease and tumours than
mice with normal GKN2 levels. When normal levels of GKN2 were
restored, tumour growth was significantly inhibited.
Menheniott says that the findings identify GKN2 as a critical
suppressor of inflammation-driven stomach cancer. “GKN2 may have
novel therapeutic value in 15% of infected individuals for whom
antibiotic treatment fails or in people with irreversible pre-cancerous
stomach lesions,” he says.
Giraud said that the research could help protect those at risk of
stomach cancer by inhibiting tumour growth. “While the survival
rate for people with stomach cancer is only around 27%, these
findings are really exciting for us because stomach cancer can be
treated much more efficiently if diagnosed early,” he said.
The research has been published in the Journal of Clinical
Investigation(tinyurl.com/z9veyaq).Blocked Bacteria Protects Against Stomach Cancer
iStockphoto/Eric Isselée