Scientists are aware and account for that. One way they do that is by focusing not on megafauna but on creatures that exist in immense numbers in a biosphere l

Scientists are aware and account for that. One way they do that is by focusing not on megafauna but on creatures that exist in immense numbers in a biosphere like insects or even smaller creatures. They also look at pollen and other biological matter that gets spread evenly. They can also look at the effects life has on the structure and chemistry of earth. For instance, they know when oxygenation happened because there are chemicals in older rocks that can not form in the presence of oxygen, while there are chemicals in younger rocks that can only form in the presence of oxygen. A big evidence that the end-Permian effected land as much as the ocean is the behavior of rivers. When plants are present, rivers tend to meander because plant roots hold onto the river banks. When plants are not present, the river is able to take the shortest path to the ocean. Rivers banks laid down at the end of the Permian meander, river banks laid down at the start of the Triassic do not.