Coconut oil production could be more damaging for the environment than previously thought, worsening already-high extinction rates in tropical forests. According to a new study, coconut oil may actually be worse than palm oil, whose production is widely regarded as extremely harmful to the environment.

Researchers from the University of Exeter found that coconuts affect 20 threatened species per million liters of oil produced, while palm oil only affects 3.8 species per million liters. Globally, coconut farms occupy 12.3 million hectares (30.4 million acres) of land, about two-thirds the area of oil palm plantations.

A growing number of consumers have put the spotlight on the environmental impact of vegetable oils, with palm oil being particularly damaging due to the amount of land needed to be cleared to make way for the crop. But consumers are less aware of the impact of farming coconuts, the study argued.

“The outcome of our study came as a surprise,” said lead author Erik Meijaard, of Borneo Futures in Brunei Darussalam. “Many consumers in the West think of coconut products as both healthy and their production relatively harmless for the environment. As it turns out, we need to think again about the impacts of coconut.”

Coconut is mainly grown by smallholder farmers on tropical islands in Indonesia and the Philippines, which have rich biodiversity and unique species, the study showed. On a global scale, coconut farms take much less space than other oil crops but affect more than 60 species in IUCN’s Red List.

Scientists believe coconut crops have driven many island species to extinction, including the Marianne white-eye in the Seychelles (Zosterops semiflavus) and the Ontong Java flying fox (Pteropus howensis) in the Solomon Islands, which hasn’t been seen for the last 42 years and is considered extinct.

While the study focuses on coconut, it highlights that other oil crops, such as olive, soy, and rapeseed, can also have serious environmental issues attached to them. For example, it references a piece in Nature that says high-powered machines used to harvest olives kill 2.6 million birds each year in Spanish Andalucía.

“The production of olive oil, however, rarely raises concerns among consumers and environmentalists,” the researchers wrote. “There are various perceptions at play — the olive oil industry benefits from the belief that it represents a sustainable practice with an extensive heritage and mythology, claims of health benefits and being locally based.”

The findings show how hard it can be for consumers to make environmentally conscientious spending choices. Many turn to dairy-free substitutes, such as coconut milk, with a greener environmental image. But without real guidance on the environmental impact of crops, it’s quite difficult to make an informed decision.

The palm oil industry is dealing with its environmental impacts with the help of initiatives, such as the Roundtable on Sustainable Palm Oil. But there aren’t any similar initiatives for coconut oil production. The study focused on the biodiversity impact of vegetable oils and did not address the impact on greenhouse gases, which could be quite different for each source.

Coconut is a popular product on a global scale, mostly used for oil but also for copra, milk, and water. Its production affects a high number of species but the authors emphasize that the objective of the study is not to add coconut to the growing list of products that consumers should avoid.

“Consumers need to realize that all our agricultural commodities, and not just tropical crops, have negative environmental impacts,” said in a statement co-author Professor Douglas Sheil of the Norwegian University of Life Sciences. “We need to provide consumers with sound information to guide their choices.”

The study was published in the journal Current Biology.