Biodiverse plantations increase cocoa yields

Flickr/Bill Zimmerman

Growing cocoa with other crops on the same plot boosts the productivity of cocoa farms, compared with growing cocoa alone, a study has found.

The researchers, from the University of Queensland, Australia, say their study is one of the first to quantitatively examine the effects of crop diversity on the efficiency of cocoa farms.

They surveyed more than 300 farmers from three of the six cocoa-growing regions in Ghana — the world's second-largest cocoa producer — and estimated their cocoa output.

"We were able to show statistically that [on average] cocoa farms that have other crops yield more cocoa per hectare than plots with only cocoa," said John Asafu-Adjaye, co-author of the study.

The practice of converting forests into cocoa farms has led many to advocate growing cocoa with other trees — a form of agroforestry — to conserve biodiversity.

But cocoa agroforestry can also benefit farmers by increasing their income, said co-author Adeline Ofori-Bah.

"On average, a ten per cent increase in the production of other crops is associated with a 1.6 per cent decrease in the marginal cost of producing cocoa," the researchers wrote in the journal Ecological Economics last month (15 June).

Ofori-Bah said: "To the extent that multiple cropping is good for biodiversity conservation and income generation for farmers, cocoa farmers should grow tree crops on their farms".

The study did not look at which species are best to plant alongside cocoa.

Victor Afari-Sefa, a consultant for the Sustainable Tree Crops Program — managed by the International Institute of Tropical Agriculture, in Nigeria — said that not all tree species are likely to be equally beneficial to cocoa farmers.

Farmers may be better off planting timber species, which also have an economic value, according to Afari-Sefa.

Yet convincing cocoa farmers to plant timber is a challenge, he said, citing an old law that made Ghana's government the owner of all timber trees as one of the obstacles.

"Timber contractors would just go to the farms and cut down timber trees without giving the farmers any compensation," he said.

Another obstacle is that timber takes a long time, around 20 years, to come to harvest. And yet, when it does, the overall benefit is worth the wait, said Afari-Sefa. "The timber trees can serve as farmers' pensions," he said.

Link to article abstract in Ecological Economics