About this video

• Video Title: National Geographic - Strange Days on Planet Earth - Part 3 of 4 - Predator
• Channel: maan100283
• Speakers: Not specified
• Duration: 53:34

Overview

This video explores the crucial role of large predators in maintaining healthy ecosystems, both on land and in the sea. It highlights how the removal of predators can lead to cascading negative effects, such as unbalanced animal populations, vegetation destruction, and the collapse of entire food webs. The documentary presents case studies from Venezuela, Yellowstone National Park, and the Caribbean to illustrate these ecological disruptions and the ongoing efforts to reintroduce or protect predators to restore ecological balance.

Key takeaways

• The domino effect of predator loss: When large predators are removed from an ecosystem, it triggers a chain reaction. For instance, without predators to control herbivore populations, vegetation can be overconsumed, leading to habitat degradation and the decline of other species.
• Ecological experiments in isolation: The creation of islands in Lake Guri, Venezuela, due to a hydroelectric project, inadvertently created isolated ecosystems. Scientists observed how the absence of predators on these islands led to overpopulation and destructive behavior in species like howler monkeys and leaf-cutter ants.
• Restoration in Yellowstone: The reintroduction of wolves to Yellowstone National Park after their near-extinction has had profound positive impacts. It helped control elk populations, allowing vegetation like willows to recover, which in turn supported the return of beavers and the restoration of riverbank stability.
• Oceans in peril: The video reveals that the removal of large predatory fish through overfishing in the Caribbean has led to coral reef degradation. Without these predators to control herbivore populations and a subsequent decline in herbivores (like the spiny urchin), algae overgrowth suffocates the coral.
• Marine reserves offer hope: Efforts like marine reserves in St. Lucia, similar to national parks on land, show promise in allowing fish populations, including predators, to recover, benefiting both the ecosystem and local fisheries.

Yes, the video mentions pollution in the context of marine ecosystems. Specifically, when discussing the collapse of coral reefs in Discovery Bay, Jamaica, Daniel Pauly notes that while pollution is often a suspect, he is focusing on another factor: fishing. Later, in the context of St. Lucia's reefs, it's mentioned that the reserves are meant to address issues like overfishing and the impact of human activity, which can include pollution.

The video explains that when wolves hunt and kill elk in Yellowstone, it has several crucial impacts:

• Controls Elk Population: It helps regulate the elk population, preventing overgrazing.
• Reshapes the Landscape: By reducing the elk population and influencing their behavior (making them move more and graze less in certain areas), wolves allow vegetation, particularly willows, to grow back.
• Supports Other Species: The increased growth of willows provides food and habitat for other animals. For instance, it allows beaver colonies to re-establish, as beavers rely on willows for food and dam-building.
• Benefits the River: The recovering vegetation helps stabilize riverbanks, reducing erosion and improving the health of the river ecosystem.
• Creates Scavenger Opportunities: Wolf kills provide a food source for a variety of scavengers, including ravens, magpies, coyotes, eagles, and even bears, creating a hub of activity and supporting a wider range of wildlife.

False.

The video indicates that while the reintroduction of wolves had significant positive ecological impacts, it was not without controversy. Ranchers living near the park expressed concerns about wolves preying on their livestock, making their jobs harder and creating conflict. The decision to remove a specific wolf that had been raiding sheep was met with mixed reactions, highlighting that not everyone was entirely glad about the situation, even as the ecosystem benefited.