It's difficult to give a single example of a major disturbance that an ecosystem recovered completely from without more context. "Completely" is a very high bar, and ecosystems are constantly changing. Even seemingly "recovered" ecosystems might still show long-term effects of past disturbances.

Here's why it's difficult to find perfect examples:

* Definition of "completely recovered": How do we define "completely recovered"? Does it mean returning to the exact same state as before the disturbance? Or reaching a new stable state that is still functional?

* Time scales: Ecosystem recovery can take decades, centuries, or even millennia. Many disturbances that seem to have been "recovered" from might still be influencing the ecosystem in ways we don't fully understand.

* The nature of disturbance: Different disturbances have different impacts. Some, like wildfires, can actually be beneficial to certain ecosystems. Others, like deforestation or pollution, can cause lasting damage.

Here are some examples of ecosystems that have shown resilience and remarkable recovery from major disturbances, but it's important to note that "completely recovered" is a complex and debatable concept:

* Forests after wildfires: Some forest ecosystems are adapted to periodic wildfires. After a fire, the soil is enriched with nutrients, and new growth is stimulated. However, the composition of the forest might change over time.

* Coral reefs after bleaching events: While bleaching events can be devastating, some coral reefs have shown remarkable resilience and can recover, albeit with changes in species composition.

* Volcanic eruptions: Volcanic eruptions can be incredibly destructive, but the lava flows can create new land and habitats over time. Ecosystems can eventually colonize these new areas.

It's important to remember that:

* Every ecosystem is different, and its capacity for recovery depends on many factors, including the type and severity of the disturbance, the ecosystem's resilience, and the surrounding environment.

* Even if an ecosystem appears to have recovered, it may still be vulnerable to future disturbances.

* Studying these examples can help us understand the mechanisms of ecosystem resilience and inform our efforts to protect and manage ecosystems in the face of ongoing disturbances.

To give you a more specific example, I'd need to know more about the type of disturbance and the ecosystem you are interested in.