Since leeches rely on moist environments, their healthiness reflects the quality of the forests they live in. The rainforest has many layers that divide it from top to bottom. The canopy is the highest layer and in old, healthy forests, it is full of leaves. A dense canopy will prevent sunlight from reaching the forest floor, which keeps the understory, one of the lower levels of the rainforest, cool and moist since little or no sunlight ever reaches it. This cool, moist environment is perfect for leeches because it prevents the animals from drying out.
Old, healthy forests are those with very tall trees and a full canopy. This makes them cool and moist, allowing for the survival of many leeches. Forests that have been logged or are recovering have smaller trees and canopies which are less dense. This allows more heat and sunlight to reach the understory, drying it out.
While leeches can be found in recovering forests, there are many more leeches in old healthy forests. Like many other animals, leeches rely on healthy forests to survive.
