In Disney's live-action remake of "The Jungle Book," young human Mowgli is still palling around with bears and panthers. In reality, however, the world has changed since Rudyard Kipling's tales first hit shelves more than a century ago.
Speaking figuratively, biodiversity's bag of Skittles has not only gotten smaller, it now has fewer flavors.
Just how different are things? One expert puts it this way: If Mowgli were around today, he would most likely be raised by cows, goats and chickens instead of wolves and panthers and orangutans. If he were really unfortunate, his compatriots could be even worse.
"Maybe even rats and cockroaches, if things go badly," said Charles Barber, former forest chief at the U.S. Department of State's Bureau of Oceans and International Environmental and Scientific Affairs, in an interview with CNBC.
The problem, according to some scientific experts, is that humans have changed the world so dramatically that it has also altered the diversity of life on Earth. "Most of these changes represent a loss of biodiversity," analysts wrote in the Millennium Ecosystem Assessment in 2005, a report that chronicled the effects of human activity on nature produced by the United Nations and the World Resources Institute, where Barber now works.
Among the Millennium Assessment's findings were that humans have "changed ecosystems more rapidly and extensively than in any comparable period in human history," due to food, fresh water and fuel needs. The spillover from those changes has contributed to big gains in humanity's development, but "have been achieved at growing costs in the form of the degradation of many ecosystem services," researchers wrote at the time.
This means that "plants and animals are now sharing the planet with a whole lot of people," Barber said, adding that "we're dealing with a fantastically different world."
One measure of biodiversity loss is just how fast certain species are now disappearing. Organizations like the Center for Biological Diversity state that an "extinction crisis" is underway that is wiping out plants and animals at a breathtaking pace.
The last few hundred years have borne witness to mass extinctions that occur much quicker than the so-called natural "background rate" of one to five species per year. The CBD estimates that "literally dozens" of species are dying every day, which could see 30-50 percent of endangered populations being wiped out by midcentury.
Today, scientists say nearly a quarter of all mammals and coniferous trees are threatened with extinction. Saving them is a costly endeavor that would require around $5 billion per year and perhaps as much as $76 billion annually to be spent on conservation efforts, a team of British researchers estimated a few years ago.
Animal populations are also taking a hit. A recent report by the World Wildlife Fund found that between 1970 (the year Earth Day was born) and 2010, the number of mammals, birds, reptiles and fish fell by more than 50 percent. It further found that biodiversity loss not only disproportionately occurs in developing countries, but also correlates with the growing use of resources by higher-income countries.
"We're gradually destroying our planet's ability to support our way of life," said WWF CEO Carter Roberts, at the time the report was published.
Supporting that way of life has promoted the perpetuation of certain crops and domestic animals, which makes the most economic sense for a swelling human population. That said, experts point to a troubling side-effect: It has driven down genetic diversity around the world.
In addition to habitat changes, scientists believe other drivers impacting biodiversity include climate change, species that prey on other forms of life, over-exploitation and pollution. Each has a different degree of impact on regions that range from tropical forests and deserts to coastal and inland waters.
Experts find that the loss of all this "natural capital" has already begun to have an adverse effect on local and global economies.
The World Bank states that "the loss of biodiversity has negative effects on livelihoods, water supply, food security and resilience to extreme events." Governments, for example, are already spending millions of dollars to control invasive species on land and in the waters. Meanwhile, for those along coastlines, flood insurance rates are on the rise.
For nearly the past 70 years, the World Bank has provided loans to more than 12,500 projects in 173 countries aimed at ecosystem rebuilding in diverse places like China, Iceland and India. This year, it has committed more than $30 billion in lending, or 33 percent more than it did a decade ago.
"One of the first things you see when an ecosystem collapses is that the apex animals collapse," said WRI's Barber. "They're not exactly the canary in the coal mine."
The good news is that experts believe there is still time to taper and even reverse some of these changes. The bad news is that some of them see that the policies and practices required for that to happen are "substantial and not currently underway."
The end result means that come next century, a fictional Mowgli could face a very real set of problems — namely deforestation and the loss of animal life — that require substantial international political action.