Ecosystem Rainfall Ratio

At a science fair, students are creating models that represent different ecosystems. Mia is working on a model that will include both freshwater and marine ecosystems. She decides to design her model with an area proportional to the ratio of total rainfall in each ecosystem. If the total rainfall for freshwater ecosystems is 800 mm and for marine ecosystems is 400 mm, what should be the area ratio of Mia's model representing the freshwater ecosystem to that representing the marine ecosystem?