Researchers from the University of Hawai’i and ETH-Zurich have been comparing the recovery of two post-agricultural plots of land in Costa Rica, one covered with a half metre-thick layer of coffee pulp and the other a control plot without any coffee pulp. They found that over two years from 2018, the recovery was much more advanced on the test plot with the coffee pulp.
“The results were dramatic,” says Dr Rebecca Cole, lead author of the study from the University of Hawai’i. “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.”
A number of variables were measured on both plots: soil nutrients such as carbon, nitrogen and phosphorus, ground cover, understory vegetation, tree establishment and canopy cover.
In the plot with the coffee pulp, there was 80% canopy cover compared to 20% in the control plot, and substantially higher levels of soil nutrients. The latter is important in forest restoration, as former farmland in tropical areas is usually degraded and has poor soil quality, which can delay recover. In addition, the canopy was four times higher than in the control plot.
The coffee pulp had eliminated the invasive pasture grasses, which are a barrier to nature forest succession.
As the study only looked at two comparative plots across two years, further research is needed to assess future use of coffee pulp on former farmland.
One limitation will be where coffee pulp, or other agricultural products, can actually be used, since relatively flat and accessible areas will only be suitable for the delivery of the materials. In addition, the added nutrients need to be prevented from washing away into nearby watersheds.
“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,” adds Dr Cole. “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.”
“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.”
Main image: Coffee pulp delivery. © Rebecca Cole