What is a summary of importance of this article?

Wolves, as you have undoubtedly heard, are once again thriving in Yellowstone. The 66 trapped in Canada and released in Yellowstone and the Idaho wilderness in 1995-96 have generated more than 1,700 wolves. To the delight of scientists and tourists — and the dismay of many ranchers — more than 200 wolf packs exist in the area today. Courts and government agencies are still sorting out how the wolves should be managed. But one thing is abundantly clear: The reintroduction has succeeded in ways that extend far beyond the health of the wolves themselves. It has reshaped an entire ecosystem.

When we exterminated wolves from Yellowstone in the early 1900s, we de-watered the land. That's right; no wolves eventually meant fewer streams, creeks, marshes and springs across western landscapes like Yellowstone where wolves had once thrived.

The chain of effects went roughly like this: No wolves meant that many more elk crowded onto inviting river and stream banks. A growing population of fat elk, in no danger of being turned into prey, gnawed down willow and aspen seedlings before they could mature. As the willows declined, so did beavers, which used the trees for food and building material. When beavers build dams and make ponds, they create wetland habitats for countless bugs, amphibians, fish, birds and plants, as well as slowing the flow of water and distributing it over broad areas. The consequences of their decline rippled across the land.

Meanwhile, as the land dried up, Yellowstone's overgrazed riverbanks eroded. Spawning beds for fish silted over. Amphibians lost precious shade. Yellowstone's web of life was fraying.

The decision to put wolves back in Yellowstone was a bold experiment backed by the best conservation science available to restore a cherished American ecosystem that was coming apart at the seams.

The unexpected relationship between absent wolves and absent water is just one example of how large predators such as grizzlies, wolves and mountain lions regulate their ecosystems from the top down. The results are especially relevant in an era of historic droughts and global warming, both of which are stressing already arid Western lands.

At the time wolves were reintroduced, Yellowstone had just one beaver colony. Today, 12 colonies are busy storing water, evening out seasonal water flows, recharging springs and creating habitat. Willow stands are robust again, and the songbirds that nest in them are recovering. Ravens, eagles, wolverines and bears, which scavenge wolf kills for meat, have benefited. Wolves have pushed out the coyotes that feed on pronghorn antelope, so pronghorn numbers are also up. Riverbanks are lush and shady again. With less competition from elk for grass, the bison in the park are doing better too.

That is not to say there were no losers. Elk numbers have been diminished — but that, after all, was one purpose of reintroducing wolves. The elk population of Yellowstone is still larger than at its low point in the late 1960s, but there are fewer elk today than in recent decades. Still, the decline has alarmed elk hunters — and the local businesses that rely on their trade.

Worse yet, from the hunting point of view, elk behavior has changed dramatically. Instead of camping out on stream banks and overeating, they roam far more and in smaller numbers, browsing in brushy areas with more protective cover. Surviving elk are healthier but leaner, warier, far more dispersed and significantly harder to hunt. This further dismays those who had become accustomed to easy hunting and bigger animals.

As wolf reintroduction has taken hold and wolves have migrated out of Yellowstone as far as Oregon to the west and Colorado to the east, ranchers have also grown nervous.

Until now, where wolves and cows mix, cows have ruled. What wildlife advocate George Wuerthner calls the "bovine curtain" limits full wolf restoration to within Yellowstone's boundaries. Outside the park, wolf packs continually form but are often slaughtered, usually at the insistence of ranchers who can legally shoot wolves that attack cattle. Wolf predation accounts for only about 1% of livestock deaths across the Northern Rockies, but those deaths generate disproportionate resentment and fear.

In the arid West, a cow may require 250 acres of forage to live. In the states where wolves are spreading, cows wander wide and don't sleep safely in barns at night as they do in the East. Wolves need room to roam too, so overlap and predation are inevitable. If wolves are ever to effectively play their ecological role again across the West, significant changes in animal husbandry — like adding range riders and guard dogs — would be required and, undoubtedly, less grazing overall.

But as Yellowstone's experience demonstrates, there would likely be unexpected benefits as well.

It's far clearer now that nature is more efficient than we'd realized at creating healthy, viable ecosystems. Matter and energy are never wasted in food webs where synergy is the rule. Think of wolf reintroduction, then, as a kind of hinge point between the two paradigms. After centuries of not leaving the natural world's order to chance, micromanaging wherever we could, we are now taking a chance on nature.

Hard days are ahead as the weather, once benign and predictable, becomes hotter, drier and ever more chaotic. Western landscapes are already stressed — whole forests are dying and deserts are becoming dustbowls. To maintain their vitality in the face of such dire challenges, those lands will need all the relief we can give them. We now understand far better the many ways in which nature's living communities are astonishingly connected and reciprocal. If we could only find the courage to trust their self-organizing powers to heal the wounds we have inflicted, we might become as resilient as those Yellowstone wolves.