The tree line could be cut back. Remove the nearest cover, create a clear killing field. [That's what Saïx would do to try to ease this.] It would be a simple matter to re-plant, once the crisis is resolved. [And the lumber could always be put towards defenses or buildings.

... hmmmm. And what they learned about just now...] With climbing clearly being a skill they lack, as well... [They could dig out a ditch, effectively a moat, but without the water. And that's just one way they could take advantage of that.]