Rubber, Oil Palm Tree Plantations Do More Harm Than Good To Ecosystems, Suggests Study

The study has found that some trees planted in the tropics may be doing more harm than good. The researchers found that 92 per cent of new tree plantations were in biodiversity hotspots.

Trees store carbon, filter the air, provide habitat to organisms, and supply a wide array of benefits to animals and people. It is important to plant the right trees, in the right places, in consultation with others, in order to support goals like addressing climate change and improving lives. A new study, led by Matthew Fagan, an assistant professor at University of Maryland Baltimore County, has found that some trees planted in the tropics may be doing more harm than good. The study was recently published in the journal Nature Sustainability. It examines the increase in tree cover across the global tropics between 2000 and 2012. 

The researchers who conducted the study found that tree cover gains during that period were equally attributable to natural forest regrowth and the creation of tree plantations, including rubber, Eucalyptus and oil palm. 

92 % Of Tree Plantations Found In Biodiversity Hotspots

According to Fagan, tree plantations are not always harmful to the environment, and even much-aligned oil palm can be farmed sustainably. The researchers found that 92 per cent of new tree plantations were in biodiversity hotspots, threatening a range of plant and animal species. Trees are unlikely to thrive in arid biomes, and likely to damage existing ecosystems. In these regions, 14 per cent of plantations are found. According to the study, tree plantations had encroached into nine per cent of accessible protected areas in the humid tropics, such as national parks. 

In a statement released by University of Maryland Baltimore County, Fagan said ecologists have been sounding the alarm on plantations damaging ecosystems for over a decade, but no one has had a hard number about how much this is actually happening. 

Dozens of nations have committed to restoring large areas of forest in recent years. Tree plantations make up 45 per cent of commitments to the Bonn Challenge, which is an international initiative to restore degraded and deforested landscapes, the statement said. Fagan is concerned about the unintended consequences plantations may have.

Countries Have Committed To A Tree-Planting Effort

Several countries including China have undertaken a massive tree-planting effort. For instance, China has undertaken these efforts at the edge of the Gobi desert. Many African countries have committed to planting trees at the transition between the Sahara desert and Sahel grassland. The goal of these efforts is to prevent desert expansion. However, the plantings can cause harm. 

What Harm Do Plantations Cause To Ecosystems?

Plantations can disturb the soil, as a result of which carbon is released. Also, trees use a lot of water. Because of this, they end up "killing off the grassland that was there, and then they often die of drought," Fagan said. Tree planting is a 'lose-lose' when these factors are taken into consideration, the statement.

Soy farmers in Brazil moved out of the Amazon and into the Cerrado, one of the world's largest savannas. They started managing pine and eucalyptus tree farms. Fagan explained that the Cerrado supports a wealth of biodiversity, and the carbon it stores underground rivals rainforest carbon sequestration, which is the process of capturing and storing atmospheric carbon dioxide. 

Tree crops in the Cerrado may be a part of the efforts made to fulfil Brazil's reforestation commitment. However, these crops could actually be a step backward in mitigating climate change and biodiversity loss.

Fagan said that in the US, there is a huge area of relatively wet woods, and people tend to idolise planting trees as sort of the ultimate environmental act. He added that there is a lot of value in grasslands and savannas that we do not necessarily see, and when one ants trees, they essentially destroy that ecosystem.

Fagan expressed his desire to see governments around the world reassess their restoration plans, or at least be more transparent when their plans involve tree planting, especially in areas that may not be appropriate for planting trees.

Parks Are Compromised Due To Plantations Around Them

The new paper revealed the extent to which tree plantations are invading protected areas. Fagan had to overhaul the algorithm his team used to differentiate between data representing natural forest regrowth and tree plantations. 

The algorithm initially used park boundaries as an indicator for natural forest regrowth areas, but that was not working. Fagan spot-checked 20 parks to determine what was wrong, and observed that three parks had multiple plantations around them.

After six weeks, Fagan manually checked for plantations in every park in the tropics. He redrew the park's boundaries when he found plantations. If the park was too compromised, he removed it from the data completely. The new algorithm, which now used new maps, could differentiate between natural forest regrowth and tree plantations with more than 90 per cent accuracy.

Fagan said it was very disturbing to see there were just so many parks that were compromised. 

Using the new maps, the team could find many more regrowth areas and plantations than expected from government estimates. Several undergraduates from the University of Maryland Baltimore County took part in the study, with each student manually checking at least 1,000 patches. Some students even checked 3,000 patches each.

Fagan said that in the end, the tropics are a much more modified place than they were expecting. He said there are a whole host of reasons behind these encroachments, but they are definitely happening all over the world. The plantations are causing a steady erosion of these parks. 

Why Planting Has To Be Done Right

The study team had a simple question before starting the research: 'How many planted trees are there in the world?' Fagan said it seemed like a strange thing to know. The researchers asked whether the trees were being planted where they should not be, and whether plantations were expanding into parks. Though the team found the results to be concerning, they also have reason for hope.

It is true that trees can do a lot of good, and planting more of them can be a significant factor in addressing the impacts of climate change, but it has to be done right. Fagan said the paper shows it is possible to monitor natural forest versus plantation at a global scale.

Fagan hopes the results will inspire everyone to be more conscious of where these products, from paper to food to shampoo to tires, come from, the statement said. He also hopes the results will inspire everyone to demand that companies producing those products in tree plantations adopt more sustainable practices. 

Fagan noted that despite the love for trees in the US, forests are not the only ecosystems that can help mitigate the effects of climate change and biodiversity loss. He explained that savannas and prairies also have an important role to play. 

Fagan concluded that we need to be cognizant that not all tree planting is beneficial for the ecosystem involved, and that the right tree in the right place is the right answer.