Human population growth has led to a reduction
 in the populations of predators throughout
 natural ecosystems across the United States.
 Scientists consider the loss of these predators to
 have a
 (1) positive effect, because an increase in their
 prey helps to maintain stability in the
 ecosystem
 (2) positive effect, because predators usually
 eliminate the species they prey on
 (3) negative effect, since predators have always
 made up a large portion of our food supply
 (4) negative effect, because predators have an
 important role in maintaining stable
 ecosystems