OMO FOREST RESERVE, Nigeria (AP) — Men in dusty workwear trudge through a thicket, making their way up a hill where sprawling plantations lay tucked in a Nigerian rainforest whose trees have been hacked away to make room for cocoa bound for places like Europe and the United States (US).

Kehinde Kumayon and his assistant clear low bushes that compete for sunlight with their cocoa trees, which have replaced the lush and dense natural foliage. The farmers swing their machetes, careful to avoid the ripening yellow pods containing beans that will help create chocolate, the treat shoppers are snapping up for Christmas.

Over the course of two visits and several days, The Associated Press (AP) repeatedly documented farmers harvesting cocoa beans where that work is banned in conservation areas of Omo Forest Reserve, a protected tropical rainforest 135 kilometres (84 miles) northeast of the coastal city of Lagos in southwestern Nigeria.

Trees here rustle as dwindling herds of critically endangered African forest elephants rumble through. Threatened pangolins, known as armoured anteaters, scramble along branches. White-throated monkeys, once thought to be extinct, leap from one tree to the next. Omo also is believed to have the highest concentration of butterflies in Africa and is one of the continent’s largest and oldest UNESCO Biosphere Reserves.

Cocoa from the conservation zone is purchased by some of the world’s largest cocoa traders, according to company and trade documents and AP interviews with more than 20 farmers, five licensed buying agents and two brokers all operating within the reserve.

They say those traders include Singapore-based food supplier Olam Group and Nigeria’s Starlink Global and Ideal Limited, the latter of which acknowledged using cocoa supplies from the forest. A fewer number of those working in the forest also mentioned Tulip Cocoa Processing Limited, a subsidiary of Dutch cocoa trader and producer Theobroma.

Those companies supply Nigerian cocoa to some of the world’s largest chocolate manufacturers including Mars Inc. and Ferrero, but because the chocolate supply chain is so complex and opaque, it’s not clear if cocoa from deforested parts of Omo Forest Reserve makes it into the sweets that they make, such as Snickers, M&Ms, Butterfinger and Nutella. Mars and Ferrero list farming sources on their websites that are close to or overlap with the forest but do not provide specific locations.

Government officials, rangers and the growers themselves say cocoa plantations are spreading illegally into protected areas of the reserve. Farmers say they move there because their cocoa trees in other parts of the West African country are ageing and not producing as much.

“We know this is a forest reserve, but if you are hungry, you go to where there is food, and this is very fertile land,” Kumayon told the AP, acknowledging that he’s growing cocoa at an illegal plantation at the Eseke farming settlement, separated only by a muddy footpath from critical habitat for what UNESCO estimates is the remaining 100 elephants deep in the conservation zone.

Conservationists also point to the world’s increasing demand for chocolate. The global cocoa and chocolate market is expected to grow from a value of $48 billion in 2022 to nearly $68 billion by 2029, according to analysts at Fortune Business Insights.

The chocolate supply chain has long been fraught with human rights abuses, exploitative labour and environmental damage, leading to lawsuits, US trade complaints and court rulings. In response, the chocolate industry has made wide-ranging pledges and campaigns to ensure they are sourcing cocoa that is traceable, sustainable and free of abuse.

Companies say they have adopted supply chain tracing from primary sources using GPS mapping and satellite technology as well as partnered with outside organisations and third-party auditors that certify farms’ compliance with sustainability standards.

But those working in the forest say checks that some companies rely on are not done, while one certifying agency, Rainforest Alliance, points to a lack of regulations and incomplete data and mapping in Nigeria.