People can cause birds and plants to die.  Dodo birds lived on one island.  They couldn't fly.  The people caught the birds and ate them.  They brought pigs the island that ate the birds' eggs.  By 1680, there were no dodo birds left.

In 1980 the people realized that the calvaria trees were 300 years old.  No more were grwoing.  They didn't know what to do.  Scientists found that the seeds must be eaten.  The seed has to pass through a bird's gut to get it to sprout.  After dodo birds were gone, no other birds were eating the seeds.

The scientists started to feed the seeds to turkeys.  After the turkeys passed the seeds, they were planted in the ground.  And it worked!  Seeds grew.  New trees started.