articles - earth or the earth?

Did we use the article "the" correctly in these sentences?

1 - The most serious problem for the earth is the contamination of water.

In actuality, Jose, the earth, as in the planet, is completely neutral on such issues. I'd recommend a change to 'the environment'.

2- I think the life in the earth is threatened because of the contamination of the water.

2A- I think life on Earth is threatened because of the contamination of the water supply.