Drop in overall wildlife populations is causing brutal battles, organized crime and child labor worldwide, according to a new study by the University of California Berkeley.

The researchers said that food scarcity and employment problems from global wildlife declines are directly proportional to the birth of human trafficking, political instability and other crimes. They are urging biologists to collaborate with economists, political scientists, criminologists, public health officials and international development specialists to combat the global challenge.

"This paper is about recognizing wildlife decline as a source of social conflict rather than a symptom," said lead author Justin Brashares, associate professor of ecology and conservation at Department of Environmental Science, Policy and Management in a statement. "Billions of people rely directly and indirectly on wild sources of meat for income and sustenance, and this resource is declining."

"It's not surprising that the loss of this critical piece of human livelihood has huge social consequences. Yet, both conservation and political science have generally overlooked these fundamental connections."

The researchers said that since animal-based food products are in demand, deprived families sell their children to fishing boats as cheap labour. They are forced to work 18 to 20 hours a day at sea for years to capture scarce wild animals and fish.

Since wildlife population is declining, these businesses do not fare well sometimes and therefore owners refrain from paying laborers on a timely basis. Due to fewer animal populations, farmers need to produce more crops to meet the food demand, thereby increasing the burden on farming.

"Impoverished families are relying upon these resources for their livelihood, so we can't apply economic models that prescribe increases in prices or reduced demand as supplies become scarce," said Brashares.

The finding is published in the journal Science.