In Kazakhstan, workers have planted tens of thousands of trees along a river delta.
Their aim is to rebuild a special riverside forest habitat that once covered the area.
This habitat is exactly the kind of place that tigers need to survive.
The Caspian tiger used to roam Central Asia, but it went extinct there long ago.
Now conservationists want the closely related Amur tiger to take its place.
Bringing back a top predator like this is very difficult and rarely tried.
Many people say it is one of the boldest tiger reintroduction plans ever attempted.