March 29 (UPI) -- Coffee pulp, a byproduct of the coffee production process, can aid the recovery of degraded forests in the tropics, according to a news study published in the journal Ecological Solutions and Evidence.
For the study, researchers marked off two large test sites across plots of degraded forest in Costa Rica. On one site, researchers dumped a few dozen loads of coffee pulp, enough to build up a layer measuring nearly 20 inches. The other site went without treatment.
"The results were dramatic," lead study author Rebecca Cole, environmental scientist at the University of Hawaii at Manoa, said in a news release.
"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," Cole said.
After two years, the coffee-treated site had increased its canopy by 80 percent, compared to just 20 percent on the control site. The treated site also grew a canopy four times taller than the control site.
The thick layer of coffee pulp worked to snuff out native grasses and allowed native tree species -- from seeds dispersed by wind and animals -- to gain a foothold across the test site.
The coffee waste also helped rejuvenate the soil in the treated test site. After two years, scientists measured heightened levels of carbon, nitrogen and phosphorous.
"This case study suggests that agricultural by-products can be used to speed up forest recovery on degraded tropical lands," Cole said. "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."
The test sites used by Cole and her colleagues were located in a region of Costa Rica that was deforested and converted into coffee farms several decades ago. The forest canopy in Coto Brus county in southern Costa Rica is 25 percent of what it was in 1950.
In addition to measuring the height and size of each site's canopy, researchers also recorded the thickness of tree stems and charted species diversity. The coffee-treated plot featured colonization by five different tree species, while the control plot was colonized by only a single species.
"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," Cole said.
"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," Cole said.
Researchers suggest their coffee treatment wouldn't be feasible everywhere.
The method requires easy access to the coffee waste material, as well as a relatively flat piece of land for application.
"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," Cole said.
"We hope our study is a jumping off point for other researchers and industries to take a look at how they might make their production more efficient by creating links to the global restoration movement," Cole said.