Equatorial forests are known as evergreen forests because the trees in these forests retain their leaves throughout the year. This is due to the consistent warm and humid climate in equatorial regions, which allows for continuous growth and prevents leaf shedding.

Here's a breakdown:

* Equatorial Climate: These regions receive ample rainfall and experience high temperatures year-round, creating a consistently favorable environment for plant life.

* Lack of Distinct Seasons: Unlike temperate regions with distinct seasons, equatorial forests have a near-constant climate with no pronounced dry periods or cold spells. This allows trees to maintain their leaves without needing to shed them for survival.

* Rapid Growth: The abundance of sunlight, water, and nutrients in equatorial forests promotes rapid tree growth. This rapid growth allows for continuous leaf production, ensuring the trees always have leaves.

Therefore, the consistent availability of resources and the lack of harsh environmental conditions allow the trees in equatorial forests to stay green throughout the year, leading to their classification as evergreen forests.