As shown below, I would like to calculate the percentage of each red feature (landscape zones) taken up by a green feature (forest zone). So I need the summed percentage of forest zone for each landscape zone feature. I have a unique ID field each of the landscape zone features. I think I would need to dissolve all the forest zones that fall within each red feature into single features. However, I am unsure how to do this - would it be a spatial join? I believe I could then simply create a new field and divide the forest zone areas by the landscape zone areas to get a percentage of forest zone area for each landscape zone feature. In total I have over 800 landscape zones to do this for.
If I understand what you are trying to do, you don't need to dissolve, you just need to summarize by landscape zone after intersecting the two datasets. If you do this in a geodatabase the area of each polygon is calculated when the intersection is completed.