OnMarch 21, 1995, biologists hired by the U.S. National Park Service released 14 grey wolves into Yellowstone National Park. It was an attempt at addressing a problem that had steadily deteriorated the park’s ecosystem since the 1920s: the overpopulation of elks. The scientists predicted that by reintroducing an apex predator they could trigger a trophic cascade — a domino effect that causes the recovery of individual species in an ecosystem, one by one, based on each species’ rank in the food web.
In the months and years following the release, the biologists observed with suspense how their rewilding effort was affecting the park’s flora and fauna. What they discovered was astounding. In line with their predictions, the wolves started to prey on elk, reducing the local elk population. This allowed aspen and willow trees to recover, providing food and construction material for beavers. When those beavers multiplied and started to build dams, they created new habitat for fish. Plant life along river banks began to thrive, reducing soil erosion. The hunting patterns of wolves also meant that carrion became available throughout the year, a blessing for ravens and bears. In short, the experiment was a resounding success and became the most celebrated ecological intervention in history.
Restoring an ecosystem of the size and complexity of a national park could be enormously time consuming and costly. Instead, it was accomplished with a simple measure: the reintroduction of an animal sitting on top of the food chain. There are other examples of relatively simple actions that have generated outsize impacts:
- 30 years ago, the United Nations adopted the Montreal Protocol, a document of only 49 pages that saved the Earth’s ozone layer and avoided an estimated 250 million cases of skin cancer.
- In 2016, the two largest retailers in Switzerland started charging five cents for grocery bags made of plastic, causing the use of these bags — previously thought to be indispensable — to drop by a staggering 80%.
- When Mark Carney, governor of the Bank of England, gave his famous Tragedy of the Horizon speech in 2015, he sent shock waves through the financial industry and fundamentally changed how corporate executives thought about climate change.
Why could these small actions trigger such wide-ranging effects? Because they had leverage in driving systems change.
Leverage is powerful. Pull on the right lever and you will change the course of history. Yet leverage is also elusive — difficult to find and engage, particularly for such complex problems as global warming. In Search of Leverage is a new Medium publication that will explore a seemingly trivial but surprisingly difficult question: In our effort to curb climate change, what should we focus on?