The ecosystem of this lake is very fragile.

His actions exerted a great influence on our plans.

The problem of overfishing is having a serious impact on marine ecosystems.

Due to overfishing, there is a possibility that the marine ecosystem could be destroyed.

His opinion had a big influence on my decision.

That news greatly influenced his opinion.

This problem is very serious.

Do you understand the seriousness of this problem?

We learned about the protection of the main sea.

He is an expert in ecology.