Early one spring, a group of bird-watchers counted 30 different species of birds in a tract of forest. in the early spring two years later, the bird-watchers counted 15 species in the same area. which statement best summarizes this situation?
birds follow different migratory paths each year.
the forest shows a decrease in biodiversity.
human beings disrupt the presence of animals in ecosystems.
it is important to study living things to better understand the earth