top of page
Search

Ecosystem Restoration

Author: Bryan Lin 

Editors: Elizabeth Li & Eason Gao

Artist: Alicia Chen


The absence of key species can completely transform an ecosystem, turning thriving habitats into degraded versions of themselves. Conservationists have focused on protecting existing wildlife to maintain healthy environments, but one of the most interesting forms of environmental restoration involves reintroducing missing species. When a species disappears from an ecosystem, it leaves a gap in the food web's functionality that can have devastating effects throughout the entire habitat. The damage resulting from the disappearance can persist for decades, with simplified food webs and reduced biodiversity causing once-vibrant ecosystems to become dull. However, scientists are discovering that reintroducing species can fill these gaps and lead to ecosystem recoveries.

ree

One such example is the reintroduction of gray wolves in Yellowstone National Park. Gray wolves were once nearly driven to extinction in the area around the 1900s because of hunting and poisoning. These destructive efforts were primarily carried out by farmers in the area, who feared that the wolves would wander onto their properties and harm their livestock. During the period when the wolves were missing, the Yellowstone elk population experienced an extreme population boom, reaching approximately 19,000 animals by the early 1990s. The massive elk herds caused devastating overgrazing throughout the park, preventing aspen and willow trees from growing beyond the seedling stage — the youngest stage — for nearly 80 years. The lack of tall trees and shrubs also meant that songbirds lost their nesting habitats, while beavers disappeared from many areas across Yellowstone due to the absence of the trees they relied on for food and dam construction. When 31 wolves were reintroduced from Canada in 1995 and 1996, a remarkable transformation occurred. The elk population, which had been rampant, decreased from 19,000 in 1993-1994 (the last census data before wolf reintroduction) to 5,000 in 2015-2016. The wolves had brought the elk population back to sustainable levels in such a small amount of time, protecting Yellowstone’s ecosystem from further long-term damage.

ree

Another interesting restoration story occurred along the West Coast, more specifically along California’s coast. From the 1740s to the early 1900s, Sea otters along California’s coast were hunted for their incredibly dense fur. By the early 1900s, only about 50 sea otters remained, clinging to survival. This represented a significant decline from the original population of approximately 150,000 to 300,000. Their absence from most of California’s coast led to an exponential growth in sea urchin populations, since sea otters were their main predator. The sea urchins devoured entire kelp forests, leaving them bare down to the rock, creating underwater deserts that supported minimal marine life. Fish populations plummeted in the absence of kelp forests, and many marine food webs were severely affected. But miraculously, in the 1930s, a small colony of sea otters was discovered off the Big Sur coast after more than a century of fur hunting. This time, the Marine Mammal Protection Act prevented hunting, and the small population began to recover slowly. As the otters expanded their range along the central California coastline, a dramatic transformation occurred. Kelp forests in Central California increased by 56 percent, a statistic attributed to the rise of otter populations. Today, with approximately 3,000 sea otters along the California coast, sea urchin populations have been slowly declining and kelp forests are returning to California’s waters once again.

ree

The success stories of the reintroduction of the Grey Wolf population and the resurgence of the Sea Otter population demonstrate the significant impact a single species can have on the overall balance of an ecosystem.

Citations:

Errick, J. (n.d.). 9 wildlife success stories. National Parks Conservation Association. Retrieved

5 successful wildlife restoration efforts throughout history. (2023, November). EcoWatch. Retrieved

Loveless, K. (2019, April 4). Fewer elk counted this year on Yellowstone's famous northern range—

But what does it mean? Mountain Journal. Retrieved August 27, 2025, from

New study shows sea otters helped prevent widespread California kelp forest declines over the past

century. (2024, January 18). Phys.org. Retrieved August 27, 2025, from

Stokstad, E. (2020, February 25). 25 years after returning to Yellowstone, wolves have helped

stabilize the ecosystem. National Geographic. Retrieved August 27, 2025, from

10 successful habitat restoration projects that revived ecosystems. (2025, March). What is Green

Living? Retrieved August 27, 2025, 

U.S. Department of the Interior. (n.d.). Restoration success stories and outreach. Retrieved August 27,

U.S. Geological Survey. (2024, September 23). California sea otter surveys and research. Western

Ecological Research Center. Retrieved August 27, 2025, from

Vynne, C., & Gosling, J. (2022, February). Research shows reintroduction of 20 species could restore

large mammal populations to a quarter of land on Earth. UN Environment Programme World

Conservation Monitoring Centre. Retrieved August 27, 2025, from https://www.unep-

wcmc.org/en/news/research-shows-reintroduction-of-20-species-could-restore-large-mammal-

populations-to-a-quarter-of-land-on-earth

World Wildlife Fund. (n.d.). Eight species making a comeback. Retrieved August 27, 2025, from

Comments

bottom of page