Areca nut trees in Karnataka, India

Flickr/AloshBennett

[CHENNAI] Researchers have shown that some types of tropical agriculture can sustain biodiversity, contrary to popular belief.  

A study by Indian and US scientists reveals that "traditional" plantations of areca nut palm in a 20-kilometre area of the Western Ghats ecosystem in the district of Uttara Kannada, Karnataka, India, has helped conserve bird species. 

The areca nut palm produces betel nut, a stimulant used by ten per cent of world's population.

Recent research has suggested that certain types of tropical agriculture can support biodiversity, but that the sustainability of this over time was in doubt. 

The researchers looked at the biodiversity of bird species in the 20-kilometre area and found that it was home to 90 per cent of species associated with native forests in the region.  

Ecological historians believe the region has been under cultivation for more than 2,000 years, suggesting that its ability to harbour diversity is sustainable. Some of the groves have been farmed by the same family for over 250 years, says Ranjit Daniels, director of Chennai-based conservation group Care Earth and an author of the study. 

Areca nut plantations such as those in the Western Ghats involve intercropping areca nut with other types of plant, including pepper, cardamom, vanilla, coconut and banana crops. This provides both a complexity that is associated with bird species richness and good revenue for farmers — spices like pepper, vanilla and cardamom are high value crops.

The areca nut palms also intermingle with natural forests, which supply protective leaf litter for the plantations.   

K. Venkataraman, member secretary at India's National Biodiversity Authority, told SciDev.Net that similar studies in Latin American countries have shown that relatively high biodiversity occurs in coffee plantations in the shade of big trees. He adds that further studies of agriculture's effects on biodiversity need to be carried out in India. 

"Certain [bird] species adapt very well to modified ecosystems but, too often, local extinctions do occur," he says.

"The general assumption is that bird biodiversity falls with human activity. This study shows that, even in ecological hotspots like the Western Ghats, people can co-exist with wildlife," Daniels says.  

"We must see how best traditional plantation systems can be integrated into long-term conservation plans," he adds.  

Link to full paper in Proceedings of the National Academy of Science [456kB]