Step 1: Understand the negation.
The negation of a conditional statement \( P \Rightarrow Q \) is \( P \Rightarrow \neg Q \).
Step 2: Conclusion.
Thus, the negation of the proposition is \( \text{If we control population growth, we do not prosper.} \).
Final Answer:
\[
\boxed{\text{If we control population growth, we do not prosper.}}
\]