the poaching of rhinos in namibia has declined since the early 2000 it was observed rewrite in report speech

The scientist said (that) the poaching rhinos in Namibia had declined since the early 2000 it was observed.

Explanation:

We use the reported speech to report what another person said. To make a sentence in reported speech we use verbs like say, tell, ask, etc.

In some cases, we need to change the tense, like in our example, where we put the Present Perfect to Past Perfect Tense, while the rest of the sentence remains the same.