The ecosystem of this lake is very fragile.

Acid rain destroys forests and has a serious impact on ecosystems.

The destruction caused by this earthquake was immense.

His actions exerted a great influence on our plans.

Do you understand the seriousness of this problem?

This problem is very serious.

We like to walk in the forest on weekends.

That news greatly influenced his opinion.

His opinion had a big influence on my decision.

He is an expert in ecology.