Steven Blake, an ecologist with WCS, followed several herds of forest elephants across several different wildlife refuges—in Congo, Cameroon, Gabon, and elsewhere—observing their behavior and collecting dung samples along the way for more than a decade. Here’s what he learned: These elephants gobble up hundreds of pieces of fruit from a single tree. Then, as they walk on, they deposit the seeds of that fruit throughout the forest, with a generous helping of fertilizer. They can cross an entire national park in the space of 3 days, defecating roughly 50 times along the way. Each pile of dung contains thousands of individual seeds from more than a dozen different plant species. It may be gross, but it’s no trivial matter.

“Tropical forests are so diverse that a seed that lands near its parent plant has a suite of predators and pathogens waiting to nab it,” Blake says. “So if you’re a seed and you land under your parent, the probability of you surviving is almost zero.” Without the elephants to disperse them, Blake says that plants with large fruits and seeds would eventually disappear.

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“The balance would be tipped in favor of those species that are dispersed by wind or other abiotic agents.”

Of course, the impact elephants (or a lack of elephants) have on their ecosystem goes even further than that. In fact, the forest elephant is a keystone species (see Chapter 10): Not only does it disperse seeds and mobilize large amounts of nutrients with its feces, it also orders the physical structure of the forest—trampling vegetation, felling trees, and opening up the forest canopy in ways that facilitate plant growth and keep the ecosystem healthy. Savanna elephants also play a role as a keystone species. Without their grazing and trampling of young woody vegetation, the savanna grasslands that so many antelope and other species (and the predators who feed on them) depend on would quickly convert to shrublands. “Once they’re gone,” Blake says, “overall biodiversity will likely plummet.”

Numbers of forest elephants are sharply declining (Blake and colleagues estimate that 65% of all forest elephants were killed between 2002 and 2013), making them more endangered than the savanna elephants that inhabit more open areas in Africa. But why exactly are elephants so imperiled in the first place? They have long been coveted for their ivory; why is poaching suddenly getting worse?

As it turns out, elephant feces provide researchers like Blake with some clues to that question as well. By diligently and systematically mapping the location of elephant dung across vast swaths of land, scientists have been able to detail the effects of newly created access points to various segments of forest. The elephants themselves proved elusive and difficult to count, but their dung provided a proxy census. The results of that census were a bit surprising.

“It’s not the logging or mining that’s doing the most damage,” says Kate Evans, an animal behaviorist at the University of Bristol in the United Kingdom, and founder of the nonprofit Elephants for Africa. “It’s the construction of roads.” An endless network of new roads has cut its way into previously remote tracts of forest—slicing the landscape up into a patchwork of segregated fragments as they go. These roads have made elephant herds that were once protected by the dense maze of greenery easily accessible to poachers.

The elephants themselves are responding to the incursion. As Evans and others have documented, they travel 14 times faster than normal when crossing a road that is unprotected from poachers. Ultimately, as more and more roads crop up, their world shrinks. “If you put a 20-mile ring of death around your house, the chances are you won’t want to go more than 15 miles from home,” Blake explains. “And if that ring closes in, you’re going to feel besieged. You won’t be able to go to the places you need to, you won’t be able to see your friends, you will become imprisoned, and most likely the food will start to run out. It’s just like that with forest elephants.”