03/01/2026
There is some buckthorn in RL area, it is extremely invasive.
WHAT ARE WE LOOKING AT?
This is the problem with buckthorn. Notice a couple of things here that are why I equate this to cancer for habitat.
Berries
If I remember right there are four seeds in each buckthorn berry. So that one tree with berries has thousands of new plants.
Seed Viability
According to the University of Minnesota, 95% of the seeds that hit the ground will germinate the very next season. That's a blessing and a curse. The blessing is if you can attack it for a few years it is similar to thistle and other biennial w**d control. A couple seasons of control will make a pretty big dent in the seed supply. 
Two Genders
With buckthorn there is a male tree and a female tree--a berry tree and a tree that is just a tree. Don't worry too much about keeping them separate. It's not really important that you know which is which. Just get after the berry trees first. Stop the cancer first. You can work on complete eradication later. 
Complete Canopy
There is literally nothing growing under this buckthorn thicket's canopy. Not even grass could grow because of the complete shade. It was down to the dirt with a light covering of buckthorn leaves. For this reason, it is not very possible to control buckthorn with fire. There's never enough fuel to carry a flame. 
Wildlife Use
Every single native berry is gone by fall because they are preferred by the birds and bears. Buckthorn is last on the deer preference list for the leaves as well. It doesn't get eaten much unless it's all that's left. It takes over because of its lack of preference as wildlife browse as well as its prolific seed production.
Control
Your two choices for control are rip it out or kill it with herbicide. That's pretty much all we have right now as far as the effective removal of buckthorn and other invasive brush. Goats and mowing just prolong the problem. You have to get the roots.  I will post the link to the chemical I use and my invasive species control playlist in the comments.