Scientists studied a 40-hectare old-growth forest to understand why there are different types of plants and animals in different areas. They used different models to see how species are distributed in the forest. They found that some species are more common in certain areas, while others are spread out more evenly. At small scales, where things are closer together, the type of habitat a species prefers is important. But at larger scales, where things are more spread out, all species have an equal chance of being there. This shows that both habitat preferences and random chance play a role in how many different species are found in a forest.