Which of the following is a characteristic of healthy forest ecosystems?

Healthy forest ecosystems are characterized by multiple layers of vegetation. This vertical diversity is crucial because it creates different habitats for a wide range of species, which fosters biodiversity. Different layers, such as understory shrubs, young trees, mature trees, and the forest canopy, provide various ecological niches that support different types of wildlife and plants. Each layer serves unique roles in the ecosystem, such as photosynthesis, habitat provision, and nutrient cycling.

In addition to promoting biodiversity, these layers help to protect the soil, maintain moisture levels, and improve air quality within the forest. The complexity of a multilayered ecosystem also enhances resilience to disturbances, whether they are natural like storms or human-induced like logging. Such structural diversity is a hallmark of a thriving forest, making it more capable of sustaining ecological processes and responding to environmental changes.

The other options do not reflect the qualities of a healthy forest. Minimal biodiversity, high levels of pollution, and uniform tree height and age all indicate degradation and poor ecological health rather than resilience and diversity.