Coffee pulp, a waste product of coffee production, can be used to help speed up tropical forest recovery on post-agricultural land, according to a new study, the findings of which have been published in the British Ecological Society journal, Ecological Solutions and Evidence.

Researchers from ETH-Zurich and the University of Hawaii spread 30 dump truck loads worth of coffee pulp on a 35×40m area of degraded land in Costa Rica as part of the study, as per a news release published in EurekAlert. They marked an area with the same size without coffee pulp as a control to compare the two.

The study was conducted on a coffee farm in Coto Brus county in southern Costa Rica, which is now being restored to the forest for conservation. The region had undergone rapid deforestation in the 1950s. Forest cover in the region had reduced to 25 per cent by 2014.

“The results were dramatic,” said Dr Rebecca Cole, lead author of the study.

“The area treated with a thick layer of coffee pulp turned into a small forest in only two years while the control plot remained dominated by non-native pasture grasses,” explained Cole.

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The area treated with coffee pulp had an 80 per cent canopy cover within two years, compared to 20 per cent in the area without the pulp. Furthermore, the canopy in the area where the coffee pulp was spread was four times taller than that of the control area.

Coffee pulp can help eliminate the invasive pasture grasses dominating the land that can often be often a barrier to forest succession. Removing such pasture allows native, pioneer tree species that arrived as seeds through wind and animal dispersal, to recolonise the area.

The research also found a comparatively higher amount of nutrients, including carbon, nitrogen and phosphorous, on the coffee pulp treated area after two years.

Dr Cole said: “This case study suggests that agricultural by-products can be used to speed up forest recovery on degraded tropical lands. In situations where processing these by-products incurs a cost to agricultural industries, using them for restoration to meet global reforestation objectives can represent a ‘win-win’ scenario.”

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The coffee pulp can be a cost-effective way to treat forests as it is a widely available waste product. However, further research is required to test this.

“This study was done at only one large site so more testing is needed to see if this strategy works across a broader range of conditions. The measurements we share are only from the first two years. Longer-term monitoring would show how the coffee pulp affected soil and vegetation over time. Additional testing can also assess whether there are any undesirable effects from the coffee pulp application,” said Dr Cole.

Dr Cole added: “We would like to scale up the study by testing this method across a variety of degraded sites in the landscape. Also, this concept could be tested with other types of agricultural non-market products like orange husks.”

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