Definitions related to monitoring forest disturbances.

Food and Agriculture Organization of the United Nations (FAO) through the United Nations Framework Convention on Climate Change (2001) [1] describe deforestation as “the direct human-induced conversion of forested land to non-forested land”.
Forest conversion
Any disturbance, natural or anthropogenic, that results in a conversion from forest to another land cover. This includes deforestation and a natural conversion such as permanent waterlogging.
There is no internationally accepted definition of degradation. We define degradation as “any forest disturbance, natural or anthropogenic, which does not result in a land cover change”. The disturbance can cause a change in land use, for example a primary forest turning into a managed forest or partially harvested, but as long as the land cover definition remains forest the event is considered degradation.
We define a forest as any land that contains over 20% canopy cover of trees over 5 meters in height, not being primarily used by urban or agricultural land uses, including natural or non-natural openings, and includes tree plantations.
Forest Disturbance
Any short or long term event that causes destructive damage to a forest. The event can be human caused or natural. The event must have a start and end time, in contrast to trend (such as long term greening or species succession due to climate change).
Secondary Forest:
The FAO (2003) [2] defines secondary forests as “forests regenerating largely through natural processes after significant removal or disturbance of the original forest vegetation by human or natural causes at a single point in time or over an extended period.”
[1]FAO, 2015. Forest Resources Assessment 2015: Terms and Definitions, FAO report.
[2]FAO, 2003. Tropical Secondary Forest Management in Africa:, in: Proceedings on Workshop on Tropical Secondary Forest Management in Africa: Reality and Perspectives. Nairobi, Kenya.