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News Article

Importance of agroforestry systems in carbon sequestration


Agroforestry can store more carbon than conventional farming

Agricultural systems, such as agroforestry, that combine trees with livestock and crops on the same area of land, are particularly popular in developing countries.  This is mainly because it enables small shareholder farmers, who have limited land available, to make the most of their resources.  For example, they can plant grain and vegetable crops around trees that produce fruit, nuts and wood and the trees in turn produce shade for livestock that provide meat and milk. A new study, by researchers at Penn State University, has found that, in addition to these economic benefits, agroforestry could also have a role in mitigating climate change.  This is because it sequesters more atmospheric carbon in plants and soil than conventional farming.

During their research, the team analysed data from 53 published studies that monitored changes in soil organic carbon after land had been converted from forest to cropland and pasture/grassland to agroforestry. They found that while forests sequester around 25 percent more carbon than any other land use, on average, agroforestry stored notably more carbon than agriculture. 

According to study author Professor Michael Jacobson, the shift from agriculture to agroforestry significantly increased soil organic carbon by 34 percent on average.  The conversion from pasture/grassland to agroforestry produced soil organic carbon increases of approximately 10 percent, on average.

“We showed that agroforestry systems play an effective role in global carbon sequestration, involved in carbon capture and the long-term storage of atmospheric carbon dioxide.  This process is critical to mitigating or deferring global warming,” said Prof. Jacobson.

Lead researcher Andrea De Stefano noted however, that carbon was not stored equally among the different soil levels.  He explained that the study provided a foundation to support growing agroforestry systems, as a tool to reduce carbon dioxide concentrations in the atmosphere as well as mitigate climate change.

“The conversion from forest to agroforestry led to losses in soil organic carbon stocks in the top layers, while no significant differences were detected when deeper layers were included,” said De Stefano.  “On the other hand, the conversion from agriculture to agroforestry increased soil organic carbon stocks at all levels, in most cases. Significant increases were also observed in the transition from pasture/grassland to agroforestry in the top layers, especially with the inclusion of perennial plants in the systems, such as in silvopasture and agrosilvopastoral systems.”

While forests can store vast quantities of carbon compared to agricultural systems, in terms of carbon sequestration agroforestry was considered to lie somewhere in between.  However, this study was the first to record these differences. 

In some countries in the tropics, such as Kenya, Brazil and Indonesia, government programs are paying farmers to grow trees on their land, as a way of mitigating climate change.  This approach is widely encouraged because farming systems are much more integrated in the tropics where economic benefits are desperately needed.

“In the United States, you can see agroforestry much more from an environmental point of view and the economic benefits, while important, are secondary,” said Jacobson. “But in the tropics, you must have the economic benefits to make it work or farmers won't do it. Most only have an acre or two of land and they need all these products for their families to survive, so the trees are vital.”

In the US, sustainable agriculture and agroforestry are closely connected and much of the landscape in the country is comprised of a mosaic of both these uses.

"Unfortunately, there is a tendency to treat agriculture and forestry separately when addressing natural-resource concerns, but agroforestry offers a set of conservation and production technologies that can help to integrate forestry and agriculture efforts beyond carbon cycles, such as water quality and biological diversity."

The paper is published in the journal Agroforestry Systems.

Further information on this topic is available on the Forest Science database.  For example, using the searchstring agroforestry AND sustainability AND "carbon sequestration" yields 127 records.  A selection of these is provided in the further reading section below.

Article details

  • Author(s)
  • Stephanie Cole
  • Date
  • 22 February 2018
  • Source
  • Penn State University
  • Subject(s)
  • Agroforestry