This property is brand new to me, and I am brand new to owning land. How can I help this hill?
The long term goal is to run livestock here - goats on the top of the hill, horses at the bottom. The bottom is level but gets swampy, so I planned to create a bioswale at the base of the hill and grade the horse area to drain toward it.
Before I do that - I feel like I need to stabilize this hillside, especially in the back of the property (last two pictures). Obviously it has been eroding for a while, and I'm worried about losing the trees with exposed roots. How would you go about this?
I think what you are planning will make things worse.
In my opinion any erosion of the bank is very slow, and it will not cause any problems with the trees.
But having goats and horses around may compact the soil and cause hard panning of the soil, increase water runoff and thus potentially erosion of the slope.
I would consider at the very least, fence the slope off from any animals.
How much land do you have?
We had a hill like that. We had a guy come in - he put heavy landscaping fabric down and then placed large rocks/boulders to form a wall. Because it was our house in front of the wall, and the hill was gradually going to hit the back of the house, I felt it necessary.
I only have 3 acres, and the horses and goats have no where else to be. The slope itself will be fenced off, as well as 10' back from the edge at the top where the trees are to reduce compaction at the edge. But I do need to have animals living on the top level of the property, so there will be traffic above, from that fence to the top of the property.