At a time when forests are disappearing in the race for development, a rare study conducted in the third-largest national park in the country at Namdapha in Arunachal, has shown that hornbills help in propagation of forests. The bird with its unique ability of seed dispersal is very important for retaining biodiversity and maintaining forest.
The study was conducted by Nature Conservation Foundation based in Mysore. Apart from Namdapha Tiger Reserve, the study also covered Miao reserve forest too in Arunachal Pradesh.
Both the forests are known for the presence of hornbills. The study points to a situation of contrast between the two forests. While Namdapha is a protected area, Miao is a disturbed area. Hunting down hornbills is thus easier in Miao. This was found to have a direct impact on the spread of forests as the bird is known for its seed dispersal abilities.
The study indicated steep decline in both fruiting plants and hornbills, and very low rates of seed dispersal in the disturbed Miao reserve forest, as compared to the Namdapha Tiger Reserve.
As per the study, there were 22 times more hornbills in Namdapha, as compared to the disturbed Miao reserve forest. This resulted in two times greater abundance of fruit trees and seven fold higher seed dispersal.
Hornbills are the largest fruit eating birds in the Asian forests, and play a very important role in seed dispersal. According to Rohit Naniwadekar, the lead author of the study, their unique habit lies in the fact that they can swallow the whole fruit intact. The seeds pass through their digestive system and come out through their droppings intact.
This helps in dispersing undamaged viable seeds at different locations. Since hornbills can fly far and wide, there is a chance, that the seeds get carried long distances from the parent tree. Their role in maintaining the forest ecosystem is so immense that they are regarded as the “farmers of the forest”.
While the effect of hornbill hunting on forest cover may not be visible over a short time period, the study showed that the number of hornbills was directly linked to the arrival of seeds in the forest. The loss of hornbills is therefore expected to greatly impact the forest cover in the long run, said the study.
Hornbills are facing extinction in many places and the loss of hornbills would have cascading negative effects on the seed dispersal of plants dependent on them in future, thereby affecting forest cover, the study cautioned.