- Globally, tree-planting projects are becoming all the rage, but many are counting on old habits of planting monoculture plantations and calling them forests.
- Still, some researchers say there are ways to make plantation trees aid in actual restoration projects, including innovative projects in the Atlantic Forest of Brazil.
- Reforestation and restoration projects will require monitoring and scrutiny to make sure they are living up to their commitments in regard to both climate and biodiversity.
It’s as if a professional cleaner has been let loose in the rainforest. The whistles of birds and croaks of frogs have been vacuumed up, the messy understory cleared away. Where once chaotic tangles of vines and saplings wrestled over flecks of sunlight beneath a shady canopy, now trees of the same height stand tidy and organized in neatly spaced rows beneath the scorching sun.
This was meant to be a reforestation project. But something has gone very wrong.
Government agencies touted the Prey Lang reforestation project in central Cambodia as the country’s first big venture into climate-focused restoration. Cambodia’s Forestry Administration granted South Korean contractor Think Biotech a 34,000-hectare (84,000-acre) reforestation concession for the ostensible purpose of planting trees and mitigating greenhouse gas emissions.
But what’s happened on the ground doesn’t look much like a win against climate change.
Community members and scientists say Think Biotech has cleared diverse rainforest and replanted it with a monoculture, or single species, of acacia. Customary landowners have been kicked off lands they no longer recognize.
As one community member said at a community meeting in 2015, “It used to be dark, shady, and cool. Now the sun shines through and we feel the heat on our heads.”
The danger that Prey Lang’s climate-reforestation project could be a harbinger of things to come has only intensified as tree-planting commitments skyrocket around the world. It seems planting trees has never been more in vogue. 2019 saw Ethiopia smash the global tree-planting record, reportedly sinking 350 million seedlings into the ground over the course of 12 hours. At least three separate “trillion trees” initiatives are up and running. China is on schedule to plant a green wall the size of Germany in its arid northern region by 2050, in an attempt to claw back the advances of the Gobi Desert.
Even companies are getting in on the action. Pulp and paper conglomerate APP and fossil fuel giant Shell have each received eyerolls and ire for trumpeting the virtues of their own reforestation projects while continuing to chop down forests, and drill up hydrocarbons.
Spurred on by high-level Bonn Challenge commitments to restore an area of degraded lands bigger than India by 2030, tree planting looks ready to be a major part of what the United Nations is coining the “Decade on Ecosystem Restoration.”
Yet at the very heart of this seeming tree-planting frenzy are questions about what restoration even means — and, perhaps most controversially, whether single-species tree plantations should count toward restoration targets.
Seeing the forest for the plantations
You’d be forgiven for thinking that plantations and restoration lie at opposite ends of a spectrum. Plantations are typically a scourge on native ecosystems, concerned with the efficient production of some commodity: oil palm on Borneo, say, or eucalyptus in the Brazilian Cerrado. Often their expansion ravages natural environments, undermining biodiversity and local livelihoods. Restoration, on the other hand, is meant to be a process of ecosystem repair, of reinserting nature’s pumping heart into human-degraded landscapes.
In practice, the story is much more jumbled.
A widely reported assessment in Nature in 2019 revealed that in many countries, the line between plantations and restoration is blurrier than it first appears. Forest researchers combing the fine print on government restoration commitments revealed that nearly half of promised new forests will be monoculture plantations of fast-growing trees like acacia and eucalyptus, rather than the beginnings of recovering ecosystems.
At the time, the study’s two lead authors, Charlotte Wheeler of Edinburgh University and Simon Lewis from the University of Leeds, declared this revelation a 21st-century scandal.
“Curbing climate change via restoring Earth’s ecosystems to their former glory could be a profound positive legacy of the 21st century, but not if governments and their advisers pretend that vast commercial monocultures of trees are forest restoration,” they wrote in a blog post.
Their research concentrates on the disastrous climate consequences of an overly plantation-focused future, showing that long-maturing natural forests eventually store around 40 times more carbon dioxide than plantations that are regularly chopped down. It’s an important reality check as countries and companies scramble to broadcast ever-larger planting targets.
“People have been very interested in the difference between carbon sequestration in naturally regenerating versus plantation forests,” Wheeler told Mongabay.
Yet in many places, plantations are already more than just a climate scandal. In China, researchers have shown that plantations of non-native black locust trees (Robinia pseudoacacia) on the Loess Plateau are sucking up 92% of rainfall during wet years, appropriating the freshwater that keeps rivers flowing. And China’s watery woes aren’t unique. The government of South Africa continues to spend millions of dollars each year on its flagship Working for Water campaign to clear rogue, water-guzzling plantation trees out of critical watershed areas.
Meanwhile, some scientists warn that in Chad, large plantation efforts could imperil the reintroduction program of the scimitar-horned oryx (Oryx dammah). And in northern Mozambique, satellite surveys show that more than two-thirds of timber plantations between 2001 and 2017 were established on croplands, potentially exacerbating poverty, malnourishment and rural unemployment by displacing food production.
So why, after millennia of homogenizing Earth’s ecosystems, do so many countries plan to homogenize the means of repairing them? Why focus on monoculture solutions in restoration commitments?
Wheeler says it comes down to two things: speed and ease.
“Short-rotation monocultures have faster rates of carbon sequestration than naturally regenerating forest, so in the short-term they are very appealing,” she says.
Plantations are also much easier and more profitable in our current economic system to plant than natural forests, since the latter require people to gather native seeds and seedlings from existing forests and nurture them in nurseries.
This speed and ease has helped make tree plantations a mainstay of tropical landscapes. But beyond the undeniable damage they have wrought on certain ecosystems, tree plantations have another side as well, one rarely addressed in conservation circles. Beyond the glaringly bad and the ugly, tree plantations can have a good side too, it seems.
The good and the bad
When Emperor Menelik II first started constructing Ethiopia’s capital city, Addis Ababa, around 1884, he faced an immediate challenge. The surrounding native forests were mostly gone. How was he going to build his new metropolis and provide fuelwood for his people given the lack of timber? Menelik’s answer came in the form of arguably one of Australia’s most world-changing exports: eucalypts. Over the course of his reign, and under the advice of French railway engineer Casimir Mondon-Vidailhet, Menelik oversaw the introduction of 15 species of eucalypts into Ethiopia.
Today, in the towns and home gardens of southwestern Ethiopia, Menelik’s legacy lives on. The weight of under-construction schools, houses and hospitals are held up by needle-straight poles of eucalyptus scaffolding. At the foot of every rural home garden, overtopping the thatched-roof gurage huts and patchwork fields of enset, sorghum and fava bean, hardy woodlots of eucalypts dominate the skyline.
These small woodlots are a far cry from the mechanized, horizon-hugging expanses of industrial plantations familiar in the likes of Brazil and Indonesia. Yet in many parts of the world, this is what timber plantations look like: small, locally owned, and a readily available source of fuelwood and construction material for some of the world’s poorest people. In Tanzania, more than half of woodlots are smaller than 1 hectare (2.5 acres) in size. But combined, they occupy an area larger than all government and corporation plantations put together. In India, many states’ forestry departments actively promote social forestry as a means of improving livelihoods and alleviating logging pressures on nearby natural forests.
The main purpose of such plantations is the production of fuelwood and timber, and it’s a job they excel at. Unmanaged timber plantations in southern Ghana, abandoned for more than 40 years, create as much as five times the timber revenue as nearby, similarly aged recovering native forests. But certain plantations, especially those nearer natural ecosystems, provide somewhat surprising additional benefits. It turns out that some tree plantations can harbor biodiversity to boot.
Just how much wildlife depends on a number of factors, says Matt Betts, a professor of forest ecology at Oregon State University. Plantations with mixed species and those that retain “legacies” of former habitats, such as remaining trees or downed wood, tend to be of much higher habitat quality than young, monoculture plantations. The number of years between bouts of chainsawing, known as the rotation length, is also important.
“Many plantations are harvested to maximize economic return or yield — which is often substantially younger than the return interval of natural disturbance,” Betts says.
Older plantations can support large numbers of birds and can even act as corridors through which certain forest-dwelling animals can move. Plant life, too, can benefit from certain plantation management practices, challenging the orthodoxy that plantations are depauperate by design.
“Many conservationists see timber plantations as ‘green deserts,’ devoid of natural regeneration in the understory,” Pedro Brancalion, a professor at the University of São Paulo, told Mongabay. “That’s really the case of short-rotation, intensively managed plantations, but may not be the case of long-rotation plantations, which can have a rich diversity of native plants in the understory.”
Across the tropics, scientists have repeatedly shown that less-intensively managed (or abandoned) and structurally diverse plantations function as unanticipated seedling nurseries, harboring a notable number of growing saplings beneath their canopies.
Brancalion is on a mission to use this nursery potential to give eucalypts a reputational revamp. He agrees with other conservationists that plantations can never replace the conservation value of natural ecosystems. But through a large-scale reforestation experiment in Brazil’s Atlantic Forest, Brancalion and his team say they hope to redefine eucalypts from conservation’s bad boy to restoration’s newfound ally.
The experiment he leads grapples with a common restoration hurdle. Massive reforestation commitments are all well and good, but how are they to be funded? One option, Brancalion says, is interplanting fast-growing, marketable eucalypts within regenerating, more-natural forest.
So, while the native, slow-growing species start to steadily reform a complex rainforest below, the intercropped eucalyptus trees are already shooting skyward. Subsequently harvesting and selling these speedy timber trees can then help to repay the initial planting costs and fund ongoing maintenance of the biodiverse understory.
In their study, Brancalion and his team found that by harvesting rapidly growing eucalypts, restoration managers could offset 45-75% of the costs of planting and maintaining native trees within five years, all without negatively affecting understory regeneration.
Counterintuitive as it might seem, Brancalion says this cost-recouping intercropping system holds significant potential elsewhere in the tropics, with a couple of companies already busy putting it into practice on Brazil’s Atlantic coast.
How much tree plantation is too much?
From water-guzzling, habitat-destroying green deserts to potential allies of restoration, livelihood providers, and alleviators of forest degradation, the story of tree plantations is a multifaceted one. But the question remains: How much tree plantation is too much when it comes to large-scale reforestation commitments?
Wheeler says some level of tree plantations should be included in restoration targets, especially where these plantations provide timber resources that reduce logging pressure in natural forests.
But she also says restoration operations need to move away from growing softwood species of eucalyptus and acacia destined for pulp and paper mills. The carbon in such short-lived products breaks down quickly, returning back to the atmosphere and aggravating climate change. Instead, to have lasting climate benefits, they must concentrate on growing hardwoods, like teak and mahogany, which produce the same sorts of long-lasting, carbon-locking timber typically overexploited in natural forests.
For others, restoration shouldn’t focus on wood production at all.
“I haven’t done a thorough analysis on this, but my hypothesis is that plantations focused on wood production should not count toward national restoration targets — unless restoration is the explicit goal of the plantation (and efforts have been made to diversify plantations),” says Betts, an expert in forest ecology.
Such diversification can involve switching from monoculture to multispecies plantations, reducing forest management of the understory, or making sure that all plantation trees come from genetically diverse enough parent stock that they are resilient to the curveballs of drought and climate change.
Brancalion says industrial plantations simply don’t count.
“Industrial timber plantations are great for producing timber, and that’s all,” he says. “They are important as an economic activity and play an important role in modern economies, but cannot be accounted as ecosystem restoration.”
He adds they can’t be relied on to maximize biodiversity, contribute to carbon recovery, or boost local livelihoods or watershed services.
Matt Fagan, a professor at the University of Maryland, says the exact proportion of national lands that countries choose to allocate toward plantations or natural forest is not the most important part of their restoration commitment, and is up to the countries themselves to decide. But what ultimately matters is making sure monoculture plantations don’t replace natural ecosystems. He cites the case of Costa Rica, where governments have subsidized the expansion of monoculture tree plantations, but these have largely replaced pasture, rather than forest.
In fact, according to Fagan, the best place for expanding monoculture plantations in the tropics is into abandoned, grass-dominated pastures.
“[Doing so] would not displace human uses of the land, it would not lower biodiversity, and it is likely to quickly grow and sequester carbon,” he says.
As for the worst place to grow a tree plantation, there are several options.
“First, you replace an old-growth rainforest or dry forest with a plantation,” Fagan says. “Second, you expand plantations into the lands of nearby smallholder farmers, either taking their lands or paying them to move. They likely struggle financially, and move on to clear other habitat for agriculture.”
Last, he says, is to grow plantations over old-growth natural grasslands, introducing trees into an environment where they choke out local grassland-adapted biodiversity and are vulnerable to plantation fires.
Regardless of the nuance around plantations, all scientists are united behind one point: restoration that involves clearing of natural habitats, as has happened in Prey Lang and elsewhere, isn’t worthy of the name.
A sign of things to come?
As we enter the U.N.’s Decade on Ecosystem Restoration, there are lessons to learn from the past few decades of tree expansion: Where has it happened? With what consequences? And how much of this expansion has been tree plantations versus natural regrowth?
The answers to these questions are vital for a society embarking on historic reforestation efforts. Yet for a very long while, straightforward answers have remained elusive. The reason boils down to a technicality. Until very recently, distinguishing natural forest regrowth from tree plantations at large spatial scales has been a complicated endeavor, something of a holy grail for satellite scientists.
“Although monoculture plantations are often distinct to our eyes as a block if we see them from a plane, from a color standpoint they often overlap with natural forests, and thus confuse computer algorithms working with blurry pixels,” Fagan says. In other words, computers have a hard time distinguishing natural forests from plantations.
Add to that the fact that cloud cover often conceals satellite views of tropical landscapes, and it starts to become clear why answers have long remained evasive.
But Fagan and his team say they recently cracked it. They used the enormous processing power of Google Earth Engine, as well as cloud-penetrating radar technologies and more than 600,000 known plantation and natural forest locations, to teach machine-learning algorithms the difference between a plantation and a natural forest. Now, for the first time, we can start to unpick past patterns of tree plantation expansion in the tropics.
Their results paint a worrisome picture. Between 2000 and 2012, tree cover expansion was dominated not by biodiverse natural forest regrowth, but by those neat rows of monoculture plantations. In total, these plantations made up roughly two-thirds of observed tree expansion, a massive 92% of which happened in “biodiversity hotspots.”
Drylands, too, have been hit hard.
“Dense tree plantations in arid lands are likely to either grow slowly (if at all), burn up in a fire, or suck up all the groundwater,” Fagan says. “And yet, a fifth of all the plantations we observed were planted in arid biomes.”
But the most dire finding, Fagan says, is what’s happened in protected areas. One in 11 protected areas have experienced the nibbling pressures of tree plantations, their protected status unable to keep expanding monocultures at bay.
These results are a warning sign for large-scale reforestation promises. Or, as Fagan puts it, “Let’s hope past is not prologue.”
Meanwhile, any plantation expansion that does take place under the banner of reforestation may have to contend with other challenges, old and new. Colonial histories are often tightly coupled with questionable decisions around plantation establishment. For example, Trisha Gopalakrishna at Oxford University points out that many of India’s biodiverse savannas are incorrectly classified as “wastelands” due to colonial misclassification of India’s vegetation.
“This is a major problem as much of India’s open ecosystems [grasslands and savannas] are being targeted for afforestation activities to meet India’s goals and targets as part [of] the Paris Agreement,” she says.
Then there is the ongoing onslaught of climate change itself, which Gopalakrishna describes as “a big threat to not just ecosystem restoration but all associated ecosystem functioning and processes.”
Evidence suggests that plantations are more vulnerable to fires, droughts and diseases than naturally regenerating forests, throwing yet another potential spanner in the works.
So whether you think tree plantations should count toward reforestation or not, one thing’s for certain: As tree-planting projects proliferate, we sure need to keep an eye on them.
Citations:
Bey, A., & Meyfroidt, P. (2021). The expansion of large-scale tree plantations: Detection, pathways, and development trade-offs. Research Square. doi:10.21203/rs.3.rs-73265/v1
Brancalion, P. H. S., Amazonas, N. T., Chazdon, R. L., Melis, J., Rodrigues, R. R., Silva, C. C., … Holl, K.D. (2019). Exotic eucalypts: From demonized trees to allies of tropical forest restoration? Journal of Applied Ecology, 57(1), 55-66. doi:10.1111/1365-2664.13513
Brown, H. C. A., Berninger, F. A., Larjavaara, M., & Appiah, M. (2020). Above-ground carbon stocks and timber value of old timber plantations, secondary and primary forests in southern Ghana. Forest Ecology and Management, 472, 118236. doi:10.1016/j.foreco.2020.118236
Fagan, M., Kim, D., Settle, W., Ferry, L., Drew, J., Carlson, H., … Ordway, E. (2021). The expansion of tree plantations across tropical biomes. Research Square. doi:10.21203/rs.3.rs-604751/v1
Kimambo, N. E., L’Roe, J., Naughton-Treves, L., & Radeloff, V. C. (2020). The role of smallholder woodlots in global restoration pledges — Lessons from Tanzania. Forest Policy and Economics, 115, 102144. doi:10.1016/j.forpol.2020.102144
Lewis, S. L., Wheeler, C. E., Mitchard, E. T. A., & Koch, A. (2019). Restoring natural forests is the best way to remove atmospheric carbon. Nature, 568(7750), 25-28. doi:10.1038/d41586-019-01026-8
Naia, M., Tarroso, P., Sow, A. S., Liz, A. V., Gonçalves, D. V., Martínez-Freiría, F., … Brito, J.C. (2021). Potential negative effects of the Green Wall on Sahel’s biodiversity. Conservation Biology. doi:10.1111/cobi.13755
Scheidel, A., & Work, C. (2018). Forest plantations and climate change discourses: New powers of ‘green’ grabbing in Cambodia. Land Use Policy, 77, 9-18. doi:10.1016/j.landusepol.2018.04.057
Schwärzel, K., Zhang, L., Montanarella, L., Wang, Y., & Sun, G. (2019). How afforestation affects the water cycle in drylands: A process-based comparative analysis. Global Change Biology, 26(2), 944-959. doi:10.1111/gcb.14875
Styring, A. R., Ragai, R., Unggang, J., Stuebing, R., Hosner, P. A., & Sheldon, F. H. (2011). Bird community assembly in Bornean industrial tree plantations: Effects of forest age and structure. Forest Ecology and Management, 261(3), 531-544. doi:10.1016/j.foreco.2010.11.003
Banner image: A landscape containing native forest in the process of natural regeneration in the understory of a eucalyptus plantation. Image courtesy of Paulo Guilherme Molin/Federal University of São Carlos.
Credits
