Invasive plants can accelerate the greenhouse effect by releasing carbon stored in the soil into the atmosphere, says a study.
Since soil stores more carbon than both the atmosphere and terrestrial vegetation combined, the repercussions for how we manage agricultural land and ecosystems to facilitate the storage of carbon could be dramatic.
"Our findings highlight the capacity of invasive plants to effect climate change by destabilising the carbon pool in soil and shows that invasive plants can have profound influence on our understanding to manage land in a way that mitigates carbon emissions," said Indian-origin plant ecologist Nishanth Tharayil from the Clemson University in the US.
The researchers examined the impact of encroachment of Japanese knotweed and kudzu, two of North America's most widespread invasive plants, on the soil carbon storage in native ecosystems.
They found that kudzu invasion released carbon that was stored in native soils, while the carbon amassed in soils invaded by knotweed is more prone to oxidation and is subsequently lost to the atmosphere.
Kudzu invasion results in the release of 4.8 tonnes of carbon annually, the same amount of carbon emitted annually by consuming 540 million gallons of gasoline or burning 5.1 billion pounds of coal, Tharayil estimated.
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The findings provide particular insight into agricultural land-management strategies and suggest it is the chemistry of plant biomass added to soil rather than the total amount of biomass that has the greatest influence on the ability of soil to harbour stable carbon.
"Our study indicates that incorporating legumes such as beans, peas, soybeans, peanuts and lentils that have a higher proportion of nitrogen in its biomass can accelerate the storage of carbon in soils," Tharayil added.
The study appeared in the journal New Phytologist.