The researchers studied bird communities in arecanut plantations found in southwest India to assess whether biodiversity could be sustained in an agriculturally developed system. This area has been identified as a key biodiversity hotspot1. The palm-like arecanut trees produce betel nut, a high value crop. Plantations have been established in the area for many years and traditional farming methods are still used. For example, farmers collect leaf litter from forests floors to use as fertiliser and mulch.
In spite of strong human pressure and continuous farming of the land for over 2000 years, large areas of natural forest remain. The researchers studied these intact forests, where no extraction is permitted, as well as production forests (harvested for non-timber products), arecanut plantations, cashew fields and sparse shrubland.
Of the 114 bird species identified in the area, 96 per cent were seen outside the intact forest. The same community structure of birds was found in both the arecanut plantation and production forests. Overall, the combined production forests and arecanut plantation agricultural system contained 76 per cent of the total bird species across the landscape and 86 per cent of the forest species of birds.
In particular, the richness of bird species was related to the diversity of the vertical structure of the vegetation found in the area. The researchers suggest it is this complexity of vegetation, together with areas of native forests interspersed in the agricultural landscape that provide suitable habitats for the conservation of the bird communities.
The results were compared with those from bird population surveys carried out in the late nineteenth century. Nearly all the birds (90 per cent) recorded by the earlier surveys were also found by the recent survey. In addition, a similar diversity of bird species was found in the plantation areas and in remote and undisturbed forests. This implies that the number of bird species in the area has remained relatively stable over this time.
The researchers suggest that local agricultural practices are responsible for maintaining much of the native biodiversity. It is the value of the arecanut plantations to the local community and the ability to intercrop with other high value crops, such as pepper, banana and vanilla, which ensure the stability of the plantations, preservation of adjacent forests, complex vegetation structure and protection of bird species in the area.
Further agricultural development in South and Southeast Asia could use the combination of arecanut plantations and forest areas to conserve bird communities and other aspects of native biodiversity.