As Nature’s primary scavengers, vultures have always been credited with performing a useful service to society and now scientists have put a value to it, highlighting that the birds’ declining population could be costlier than thought.
A recent study by the International Union for Conservation of Nature (IUCN) estimates that 600 vultures consume the same amount of animal waste as a medium utility plant required to dispose it. The India office of IUCN has arrived at a value based on the scavenging services: A vulture is worth Rs 6.96 lakh in urban India and Rs 5.85 lakh in rural areas.
Vultures’ ability to feed on dead animals makes them crucial for the environment and society as they help contain contamination from rotten carcasses, lowering the risk of diseases in humans and livestock.
However, in the past two decades, the vulture population in the country has declined drastically. Today less than 1% vultures are left of their population in the early 1980s. “Vulture numbers declined from about 40 million in the 1980s to less than 0.1 million now. This is the steepest decline in the population of any species,” said Vibhu Prakash, principal scientist at the Bombay Natural History Society.
The decline is primarily blamed on the extensive use of non-steroidal anti-inflammatory drug diclofenac to treat livestock. The drug residue present in the carcass is consumed by vultures indirectly. Though the drug to treat livestock is banned in the country, there have been reports of its illegal use.
The absence of vultures has led to a crisis of carcass disposal across the country.
“Earlier people would remove the skin of the animals for their use and throw away the rest of the carcass. Vultures helped them quickly decay. But, in the absence of the birds, stinking carcasses started piling up, spreading diseases and leading to an increase in the population of secondary scavengers such as dogs,” Prakash said.
This forced the governments to put in place carcass rendering plants at several places. IUCN India scientists studied the cost of carcass disposal through these plants to estimate the economic value of the service provided by the birds.
The cost of processing four-five carcasses per day at a rendering plant is estimated to be about Rs 15 lakh, taking into account the establishment and maintenance cost of these plants and the transportation and processing work.
“A medium utility plant processes 164,400 kg of meat in a year, whereas the amount consumed by 600 vultures in a year is between 115,200 kg and 172,800 kg,” the study said. A medium plant is valued at Rs 6.7 crore in rural areas and Rs 7.9 crore in urban. This gives a vulture a value of Rs 5.85 lakh in villages and Rs 6.96 lakh in cities.
Declining vulture population has other indirect costs, too. “Anecdotal evidence shows the population of secondary scavengers such as dogs, jackals and rodents has been increasing. This might be leading to increased expenditure on diseases such as rabies, leptospirosis in humans and canine distemper in tigers. Besides, the increase in feral dogs’ population and the change in their feeding habits might also have an impact on the prey base for tigers in future,” said NM Ishwar of IUCN who led the study.
The scientists are making a case for breeding vultures and releasing them in the wild. “A vulture safety zone for breeding 600 birds and releasing them in the wild would cost 75% of the cost of a medium carcass rendering plant. All the other natural ecosystem services will be in place. Thus it makes more sense, at least in rural areas, to invest in vulture breeding,” Ishwar said.