Its lower cost has made it popular in commercial food production, but after being blamed for deforestation in Asia, palm oil plantations are now getting a similar rap in Africa.

The sheer scale of land required is having an impact in Gabon, Cameroon and the Congo Basin, environmentalists say.

With financing coming from American, European and Asian agri-businesses, palm bunches are cultivated then cut from trees and sent to factories where oil is extracted by hot pressing.

But the production process accelerates deforestation, contributes to climate change and threatens fauna and flora in vulnerable areas, opponents argue.

However the companies say that palm oil is not only less expensive than soya or sunflower oil but requires much less land to produce and provides much-needed jobs.

Gabon -- where forest covers 80 percent of the territory -- is feeling the brunt.

Brainforest and Mighty, two environmental groups, investigated the activities of Olam, an agri-business from Singapore, which said it has planted 58,000 hectares of palm trees in Gabon.

"It is estimated that Olam has deforested 20,000 hectares in its Gabonese concessions of Awala et Mouila since 2012," the groups said in a report released in mid-December. "Investigators on the scene witnessed and filmed bulldozers knocking down huge trees en masse."

Olam said palm trees had been planted on 25,000 hectares of land which had previously been forested, but that this had been "highly logged and degraded secondary forest" and represented just 0.1 percent of Gabon's forests.

In response to the report Olam published advertisements touting the almost 11,000 jobs it has created, the 1,100 hectares of food crops planted and 251 kilometres (150 miles) of roads built.

- A wider impact -
But the impact appears wider. In their report, the environmental groups expressed fears that the Congo Basin, considered the lung of Africa, could go the same way as forests in Sumatra, Indonesia and on Borneo.

"A few decades ago, these places were almost entirely covered with forests, a paradise for orangutans, rhinos, elephants and exotic birds. Today, only 20-30 percent of the forest cover exists."

The report was released in Libreville when an environmental film festival honoured the French documentary "Et Maintenant Nos Terres" (And Now Our Land).

Its directors, Julien Le Net and Benjamin Polle, chronicled how villages in Cameroon and Senegal were being affected by what they called "land grabs" by multinational companies.

In southwest Cameroon 244 farmers have filed a trespassing complaint against a company that intends to plant 20,000 hectares of palm trees.

Hearings in the case against Sustainable Oils Cameroon, formerly a subsidiary of American company Herakles Farms, were postponed after reports of unrest in the area in November.

Greenpeace has asked Cameroon not to renew the company's concession which expired at the end of November, and it cited "six years of illegal foresting, trampling of locals' rights, unfulfilled investments and destruction of forest".

A petition signed by 180,000 people against renewal of the contract was sent last week to Cameroon President Paul Biya, Greenpeace said.

The government has not yet made a decision but Greenpeace said it hoped it would hear the voices of "thousands of Cameroonians".

Meanwhile the plantations of Socapalm, a subsidiary of the Luxembourg company Socfin in which the family firm of French businessman Vincent Bollore owns a large minority stake, were targeted by protests in November.

"No to pollution and massive environmental destruction" read one banner, while another urged the company to open a dialogue with residents.

"More than 5,000 hectares has been used," a resident called Ebeneser Ekango told AFPTV at the time, complaining there wasn't enough land to plant the staple crop cassava. "What do we eat?"

Greenpeace, which has complained that Socfin concessions have included old-growth forests, applauded the company publishing in December a responsible management policy commits to "eliminating deforestation".