Like little Johnny Appleseeds - if Johnny Appleseed had wings and pooped out seeds instead of planting apple nurseries across the frontier - birds and bats introduce a surprising number of trees into new forests, a study in the journal PLOS One shows. When a team of Mexican and American biologists examined the vegetation in a restored tropical forest in southern Mexico, they found that bats and birds were responsible for 94 percent of the plant species not reintroduced by conservationists.
By regurgitating, defecating or burying seeds, the authors point out, birds, bats and other fruit-eating animals help most tropical trees reproduce. (Some plants also grow sticky or spiky seeds that latch onto birds' feet and feathers, and there's evidence that the color of certain fruits evolved to attract birds.)
For over six years, the conservation researchers monitored plots of land, previously used as cattle pasture, in a rainforest in southern Mexico. Over time, the number of "recruited" plants - sprouting from bird- or bat-borne seedlings - shot up, contributing at least 19 new species in the restored rainforest.