The socialite is due to give birth this summer (09) and she has been busy creating an eco paradise for their second baby in their Los Angeles home, with Richie demanding every item in the room be as natural as possible.
A source tells the National Enquirer, "She fussed over every imaginable detail, right down to the type of cotton in the sheets and the linens to the type of paint used on the walls.
"She scoured stores and researched on the internet for weeks to find wood products that are made from reclaimed sustainable wood from the Brazilian rain forest.
"Even the toys are an environmentalist's dream. Nicole is a model mum and she's determined to teach her kids to honour the earth."
Rocker Madden and Richie already have a daughter - Harlow, 19 months.