Gallery: More Than Charismatic: The Ecology of Big Animals
01big-fish-and-coral-reefs
Of all mankind's impacts on nature, perhaps none is more pervasive than the systematic elimination of large animals. Of those that lived 20,000 years ago, many are gone: There are no more saber-toothed tigers or dire wolves or woolly mammoths. Many others, like rhinoceros and South China tigers, are so few in number that from an ecological perspective they're already extinct. Other big animals have retreated into fragments of their former ranges. Despite the ubiquity of these changes, however, the ecological consequences are hard to perceive. Most people grew up in places where so-called apex predators and megaherbivores were already gone. Absence is a tricky thing to quantify. Ecologists have also been challenged to study processes that can involve subtle interactions over large regions, and take decades if not centuries to become apparent. In recent years, however, the science has matured. Researchers have a better understanding of just how important large animals are to their environments. They affect what lives and grows, how nutrients cycle and even how disease spreads. Take them away — or reintroduce them — and you change the very nature of nature. This research is described in a review published July 14 in *Science*. On the following pages, Wired.com looks at comparisons of environments without and with large animals. Above: Big Fish and Coral Reefs ------------------------------- At left, the coral reef ecosystem around Kirimati Island in the South Pacific, where fishing pressures have eliminated large fish. At right, a reef ecosystem around nearby Jarvis Island, which is unfished. *Image: Science*
02tipping-points-and-bass
Tipping Points and Bass ----------------------- Some of the most thorough research on large animal loss has involved bass in experimentally-altered northern lakes. At Long Lake in Michigan, researchers artificially divided the lake and removed all largemouth bass from the area at left. Over time, that part of the lake became oxygen-depleted and nutrient-choked, dominated by algae and small invertebrates. Similar effects can be seen in creeks and streams, like those pictured above and located in Oklahoma. Underlying these changes are the dynamics of what ecologists call "alternative stable states": A given region can support one type of ecosystem or another, and the transition between them is rapid and radical. Large animals can keep ecosystems in equilibrium. Losing them results in tipping points where one state gives way to another. *Image: Science*
03sea-otters-and-sea-urchins
Sea Otters and Sea Urchins -------------------------- At left is an Aleutian island seafloor in 2009, after sea otter populations collapsed. At right is a photograph from 1971, when the otters were still healthy. In their absence, sea urchin populations exploded, crowding out everything else and becoming so densely packed that diseases spread like fire. According to study co-author James Estes, a University of Santa Cruz marine ecologist, the otter-less seafloors are now dominated by boom-and-bust cycles of sea urchin growth. *Image: Science*
04big-cats-and-forests
Big Cats and Forests -------------------- At left is a forest on the Venezuelan island of Lago Guri, where jaguars, cougars and eagles no longer live. At right is a mainland forest where predators are still present. Without predators to control herbivores, seedlings are quickly eaten and don't have a chance to grow. When old trees die, they may not be replaced. In centuries to come, forest may turn to grassland. *Image: Science*
05wolves-in-the-west
Wolves in the West ------------------ At left is a field in Yellowstone National Park in 1997 before the reintroduction of wolves. At right is the same field four years later, after wolves came back. Freed from overgrazing by elk, willows have a chance to grow. They reduce streambank erosion and provide water-cooling shade, so trout populations are healthier. There's probably no animal more controversial in the United States than wolves, which have become a wilderness icon. Estes hopes this research will people see the animals as more than a symbol. "The reason for caring about big predators until this point has been mostly aesthetic," he said. "But they matter so much more than that." *Image: Science*
06wildebeest-and-fire
Wildebeest and Fire ------------------- After a parasite outbreak nearly wiped out wildebeest in Tanzania, small trees and shrubs grew rapidly. Fires could thus spread quickly from branch to branch, creating a hazard for people living nearby. "When you lose one role in an ecosystem, it could have a whole cascading series of effects that are not so obvious," said ecologist David Wardle of the Swedish University of Agricultural Sciences, a co-author of the new paper. *Image: Science*
07whales-and-the-future
Whales and the Future --------------------- In the absence of big animals, nature will continue. There's no question about that. But if the question is what sort of nature people would like to have, then protecting these creatures takes on new meaning. "The world's not going to end if we don't restore apex consumers. But the world we live in, and many things we take for granted as natural, are not natural," said Estes. "There are a lot of things that might be different, and some might be better, if large animals were still running around." One area of particular interest for Estes is the ecological role of cetaceans. Research suggests that, prior to industrial hunting, whales — specifically, whale poop — actually played a central role in cycling nutrients from ocean depths to shallow waters, helping make those regions more bountiful. *Image: [Richard Giddins](http://www.flickr.com/photos/strangeones/308910342/)/Flickr*
