Early one spring, a group of bird-watchers counted 50 different species of birds in a tract of forest. In the early spring two years later, the
bird-watchers counted 35 species in the same area.
Which statement best summarizes this situation?
O The forest shows a decrease in biodiversity.
O Human beings disrupt the presence of animals in ecosystems.
O It is important to study living things to better understand the earth.
O Birds follow different migratory paths each year.