22 June 2006

Africa: Fertiliser Bumps Up Rainforest Emissions of CO2

Beijing — Fertiliser use in tropical rainforest soils is increasing the amount of greenhouse gas carbon dioxide released into the atmosphere, say researchers.

The study published this week (June 19) in Proceedings of the National Academy of Sciences shows how soil microbes increased their emissions of carbon dioxide by about 20 per cent over a year when phosphorus or nitrogen were added to areas of forest in Costa Rica.

"This is the first time anyone has taken a close look at how changes in key nutrients may alter soil carbon dioxide emissions in tropical forests," says lead researcher Cory Cleveland of the University of Colorado, United States. He says that what happens in the tropics affects the rest of the planet.

Both phosphorus and nitrogen are key nutrients for living organisms. But Cleveland says that human activities, namely burning fossil fuels and using fertilisers in agriculture, has increased their prevalence in the environment.

He says his study shows that even small changes in nutrients could have a profound impact on the release of carbon dioxide from tropical rainforest soils.

Tropical rainforests play an important role in regulating atmospheric carbon dioxide levels, accounting for at least one third of the biosphere-atmosphere carbon dioxide exchange.

Martyn Caldwell, a program director at the US National Science Foundation which funded the research, says the team's finding is "a new dimension in understanding these important ecosystems".

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