We use “the” to refer to shared concepts like “the environment” and “the countryside” and “the government.”
For instance, when we say the environment, we’re usually referring to the whole natural world around us. This makes it a shared, singular concept that everyone is familiar with. Sort of like the sky or the Earth. So we can say:
“Everyone should work hard to protect the environment from being harmed.”
The countryside works the same way. It refers to the rural parts of a region or country, in contrast to towns and cities. We tend to think of it as a single general area that everyone is familiar with. So we can say:
“I would prefer to live in the countryside.”
Likewise, even though a government is made up of many people and institutions, we treat it as a single governing body that everyone is familiar with. So we can say”
“The government ought to prioritize public transportation.”
You can also check out this related grammar post about physical environments.