Question Destroy an object forever when a mission is activated

hi guys, i have a doubt im trying to destroy an object when an other object is activated in the hierachy.
i mean, im blocking the pass with a few trees the when the player activates de second mission i want to destroy that trees to let the player move ahead, but it doesnt work well. When the second mision is activated it destroiees de trees but if i change de scene and the i go back the trees are there again.

i made this:
public class GTFO : MonoBehaviour
{
public GameObject mision2;
public GameObject d1, d2;
// Update is called once per frame
void Update()
{
if (mision2.activeInHierarchy)
{
//Destroy(d1);
//Destroy(d2);
d1.SetActive(false);
d2.SetActive(false);
}
}
}

i was trying different options but it doesnt work. I learing as you can see. Ty for the help.