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Tags Current Affairs

Rainforests losing ability to absorb carbon

Date: 07 March 2020 Tags: Climate Change

Issue

The amount of planet-warming carbon dioxide that can be sucked up from the atmosphere and stored by tropical forests is falling as the global climate heats up.

 

Background

The tropics lost 12 million hectares of tree cover in 2018, including 3.6 million hectares of old-growth rainforest, an area the size of Belgium, much due to fires, land-clearing for farms and mining, according to monitoring service Global Forest Watch.

 

Details

  • Rainforests could tip from absorbing carbon to becoming a source of emissions faster than scientists had previously expected - a switch that could happen in the Amazon as early as the mid-2030s.

  • The cause of this is climate change impacts - in terms of heat stress and droughts - on these remaining intact forests.

  • Large swathes of rainforest, including those in Indonesia, Brazil and Democratic Republic of Congo, help regulate rainfall, prevent flooding, protect biodiversity and limit climate change.

  • But the 30-year study showed that the intake of carbon by “intact tropical forests” peaked in the 1990s and had dropped by a third by the 2010s.

  • Intact forests are large areas of continuous forest with no signs of intensive human activity like agriculture or logging. They form part of the world’s roughly 5.5 billion hectares of forest.

  • Trees suck carbon dioxide from the air, the main greenhouse gas heating up the Earth’s climate, and store carbon, which they release when they are cut down and are burned, or rot.

  • Tropical forests are huge reservoirs of carbon, storing 250 billion tonnes in their trees alone - an amount equivalent to 90 years of global fossil-fuel emissions at current levels.

  • Extra carbon dioxide boosts tree growth, but every year this effect is being increasingly countered by the negative impacts of higher temperatures and droughts which slow growth and can kill trees.

Carbon sinks

  • A carbon sink is any natural reservoir that absorbs more carbon than it releases, and thereby lowers the concentration of CO2 from the atmosphere.

  • Globally, the two most important carbon sinks are vegetation and the ocean.

The natural sinks are:

  • Soil is the Earth's greatest carbon store and active carbon sink.

  • Photosynthesis by terrestrial plants with grass and trees serving as carbon sinks during growing seasons.

  • Absorption of carbon dioxide by the oceans via physicochemical and minor biological processes.

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