Only 20.35% of the catchment of the lake is covered by forest.
Demographic growth and lack of employment are some of the factors that have promoted conversion of forested areas into subsistence agriculture, especially following the coffee price crisis.
The loss of forest cover is particularly critical on steep terrains, which are most susceptible to overland flow and erosion. Soil loss results in siltation farther downslope, as well as in streams and in the lake. It also decreases water recharge of the deep aquifers.