Why people waste of nature resources? how can i tell them to stop it?

i am live in homestay with some international students in oz, the landlady is so kindness.she gives more freedom to us, like you can cook,watching tv whole night drink beer or have party in home, she doesn’t care as well as we are not disturb other students. maybe is more freedom,maybe is they are spoil by landlady,that is why my friends start waste of food,water,and energy, expecially water.
so how can i tell them to stop wasting of nature resources?