The fates of humans and other animals are even more intertwined than we thought.
We humans know that when the numbers of other species dips, it's bad. But we can't always pinpoint why. We generally understand that it's sad for the animals that were killed, that disappearing wildlife messes up the planet's ecosystem, and that there's something morally wrong about the way we're dealing with nature.
But now research out of UC Berkeley and UC Santa Barbara is providing evidence that a decline in animals actually means that our social structures are crumbling.
A bunch of scholars, most of them from Berkeley's Department of Environmental Science, Policy, and Management, set out to determine what effect wildlife decline has on society, and to highlight appropriate policy responses. The resulting study, called "Wildlife Decline and Social Conflict" is a policy paper that surveyed experts and existing literature. Science published it in July.
"The harvest of wild animals from land and sea," the paper says, "provides more than $400 billion annually, supports the livelihoods of 15 percent of the global population, and is the main source of animal protein for more than a billion of Earth's poorest inhabitants."
That makes it clearer as to why when fish disappear from the sea and game is gone from the savannah, things tend to go awry for us too.
"I was surprised by the complex and far-reaching ways by which wildlife decline influences society," says Douglas J. McCauley, a UC Santa Barbara ecologist who was one of the paper's 10 co-authors.
One of those ways, the researchers found, is that slavery becomes more common as fauna becomes scarce. When seafood is harder to get, the study says, "a vicious cycle ensues as resource depletion drives harvesters to increase their use of forced labor to stay competitive." Other social effects of declining marine life include human trafficking and heightened poverty.
"It is relatively obvious that collapses of fish stocks can create job loss for fishermen," McCauley says. "But it is much less obvious that fishery crashes can breed regional violence and promote child slavery."
It's the same with land animals. The researchers found that children are forced to become hunters as it becomes difficult for adult poachers to get their goods.
The high demand for animal-sourced luxury items spikes up racketeering and organized-crime rates too -- African terrorist groups including Boko Haram and al-Shabaab are known to poach elephant ivory and rhino horns to fund their attacks.
The scholars note that policies which simply punish criminal acts like poaching are useful but limited because they only get at outcomes, rather than at the factors causing the demand for dead animals.
"If we can raise awareness about how wildlife loss hurts individuals and communities by fostering violence, degrading public health, and promoting human rights abuses," says McCauley, "then we can motivate a more effective response against stopping wildlife decline."
Rosie Spinks contributed reporting.