Moderate trek involves some longer walks, and easy to moderate trekking to altitudes between 2000 mts/6500 ft and 3500 mts/11500 ft to 4000 mts/13000 ft for up to 6 - 8 hrs/20 kms a day. Some previous hill-walking experience is desirable. Moderate trek best is described as mild to moderate.
"An ecosystem is a unit of biological organisation interacting with the physical environment such that the flow of energy and mass leads to a characteristic tropic structure and material cycles." -Eugene Odum "the grandfather of ecology"