Eco Business writes that this led to a decline in the population of native species, such as the orangutans and nowadays, the surface taken by palm oil plantations is around 21 million hectares, 30 times larger than the metropolitan area of Jakarta. In the last couple of years, the industry moved to a more sustainable business model, such as zero-deforestation commitments and sustainable farming strategies.

But palm oil farmers don't have to give up on all their crops for the benefit of the ecosystems. Experts at the University of Göttingen in Germany found that, by implementing an island of native tree species within a palm oil plantation, the local ecosystems can be helped to thrive once more, contributing to the development of biodiversity, as well as strengthening the trees' capability to fight pests and disease.

The project, which took place over the course of five years, saw the implementation of 52 tree islands across a palm oil plantation spanning across 140 hectares in Sumatra, Indonesia.

Clara Zemp, lead researcher of the study, said that "it increased biodiversity and ecosystem functioning overall, and it doesn’t decrease oil palm yield at this stage."

The benefits don't stop there, however, as the areas have seen improved water filtration, as well as an improvement in soil fertility, compared to a traditional palm oil farm. Over the first five years, there was no decrease in the yields, while after the first five-seven years there could have been a marginal decline in productivity, but the overall mixed area was just 5% of the total farm.

Edgar Turner, a University of Cambridge zoology professor who co-pioneered the BEFTA program (Biodiversity and Ecosystem Function in Tropical Agriculture), said that "reforestation is one of those areas – so little is known about it – understanding how best to do that in an oil palm context is quite important."

Restoration, he believes, should start from the edge of the rivers, as these areas are the most exposed to the chaotic planting of palm trees and can be the most affected, because palm trees don't provide the ground stability native species do. Additionally, the use of chemicals that farmers might employ to increase yields could infiltrate in the flowing water, leading to environmental damages.

"They’re (rivers) not a huge area and they’re not the most productive, so you can restore them and potentially you can have quite a big impact."

This project tested a variety of approaches and trees, with the initial conclusions, after six years of development, being that no matter which trees have been used, there is a feel of a micro-forest in the middle of the palm olive plantations.

An alternative solution, which can help with invading species of plants, is integrating grazing areas for livestock, a method currently researched by Badrul Azhar, a conservation biology and wildlife ecology professor at the University of Putra Malaysia.

But this strategy is unpopular among farming companies that want to focus just on the palm trees, as the additional livestock will imply spreading the resources into multiple parts of the farm management.

“We need to be thinking more about how we can harness ecosystem services and species found in agricultural systems”, says Faisal Mohd Noor, who leads this WWF-Malaysia project.