Coffee pulp – no, NOT that granular, gluggy stuff that stays in your coffee pot after a brew – can help restore native forests.
Coffee pulp, a waste product of making coffee, can be used to speed up the recovery of tropical forest areas in areas that previously have been cleared for agricultural production.
Researchers from the University of Hawaii investigated coffee pulp as an agent in forest restoration during a recent study published in the British Ecological Society’s journal, Ecological Solutions and Evidence.
The researchers spread 30 dump truck loads of coffee pulp on a 35 × 40m area of degraded land in Costa Rica and marked out a similar-sized area without coffee pulp as a control.
“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 just two years while the control plot remained dominated by non-native pasture grasses.”
After only two years the coffee pulp treated area had 80 per cent canopy cover compared to 20 per cent in the control area. The canopy in the coffee pulp area was also four times taller than that of the control area.
Coffee pulp is a waste product from the coffee industry. It has, however, been used as animal feed for livestock, pigs, rabbits, and even fish, replacing around 20 per cent of traditional animal feed but the high caffeine content can be a negative factor.
The study found that the addition of the half-metre thick layer of coffee pulp eliminated the invasive pasture grasses which dominated the land.
These grasses are often a barrier to the progression of forest plants and their removal allowed native, pioneer tree species, which arrived as seeds through wind and animal dispersal, to recolonise the area quickly.
The researchers also found that after two years, nutrients including carbon, nitrogen and phosphorous has significantly increased in the coffee pulp treated area compared to the control.
This is a promising finding given former tropical agricultural land is often highly degraded and poor soil quality can delay forest progression for decades.
Dr Cole says: “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.”
Coffee pulp is widely available. Two tons of pulp come from each ton of coffee. It’s also high in nutrients, which means that coffee pulp can be a cost-effective forest restoration strategy.
Such strategies will be important if humanity is to achieve ambitious global objectives to restore large areas of forest, such as those agreed to in the 2015 Paris Accords.
Dr Cole says further research is needed. “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,” she says.
“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.”
A limitation of using coffee pulp or other agricultural by-products is that its use is mostly limited to flat and accessible areas where the material can be delivered, and the risk of the added nutrients being washed into nearby watersheds can be managed.
On further research into the use of coffee pulp, Dr Cole said: “We would like to scale up the study by evaluating this method across a variety of degraded sites in the landscape. Also, this concept could be assessed with other types of agricultural non-market products like orange husks.
“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.”