حماية الغابة مهمة.

Because this is a nominal sentence in the present tense. In Arabic, the verb to be is usually not stated in the present.

So:

حماية الغابة مهمة
literally follows the pattern:

Protecting the forest — important

but the natural English meaning is:

Protecting the forest is important.

If you wanted past or future, Arabic would use a verb such as كان.

حماية is not a verb here. It is a noun, specifically a verbal noun (called a maṣdar).

It comes from the verb حمى / يحمي = to protect.

So حماية can mean:

• protection
• protecting

That is why the sentence can be understood as either:

• The protection of the forest is important
• Protecting the forest is important

Arabic usually does not use a separate word for of in this kind of phrase. Instead, it uses the iḍāfa construction, often called the construct phrase.

So:

• حماية الغابة = protection of the forest

In this structure:

• حماية is the first noun (muḍāf)
• الغابة is the second noun (muḍāf ilayh)

So Arabic expresses of the forest simply by putting الغابة after حماية.

Not grammatically, no.

In English, you might think of the forest as the thing being protected, so it feels like an object. But in Arabic syntax, حماية is a noun, not a verb, so الغابة is not a direct object here.

Instead, الغابة is the second part of an iḍāfa phrase:

• حماية الغابة = the protection of the forest

So the relationship is noun + noun, not verb + object.

Because it agrees with حماية, which is a feminine noun.

Arabic adjectives usually agree with the noun they describe in:

• gender
• number
• definiteness

Here, the subject is حماية الغابة, and its head noun is حماية. Since حماية is feminine, the predicate adjective is feminine too:

• masculine: مهم
• feminine: مهمة

So مهمة is used because حماية is feminine.

Because in an iḍāfa construction, the first noun usually does not take ال.

So Arabic says:

• حماية الغابة

not:

• الحماية الغابة

The definiteness of the whole phrase comes from the second noun. Since الغابة has ال, the whole phrase حماية الغابة is definite.

So this phrase is literally:

• the protection of the forest

even though حماية itself does not have ال.

Because it is the predicate adjective, and in a sentence like this it is normally indefinite.

So:

• حماية الغابة مهمة = Protecting the forest is important

The adjective مهمة is describing the subject, but it does not need ال here.

If you added ال and said المهمة, it would usually not mean the same thing. It could be understood more like:

• the mission
• or the important one

depending on context.

So مهمة without ال is the normal form here.

With full case endings, it would be:

حِمايةُ الغابةِ مُهِمَّةٌ

Here is the grammar behind the endings:

• حِمايةُ = nominative, because it is the subject
• الغابةِ = genitive, because it is the second noun in an iḍāfa
• مُهِمَّةٌ = nominative, because it is the predicate

In normal everyday writing, these short vowels are usually omitted, so you normally just see:

حماية الغابة مهمة

A careful fully vocalized pronunciation is approximately:

ḥimāyatu l-ghābati muhimmatun

In more ordinary pause-based reading, learners often hear something closer to:

ḥimāyat al-ghāba muhimma

A useful thing to notice is the ة:

• In حماية, because it is in an iḍāfa, it is connected as -at
• In مهمة, at the end of the sentence in pause, it is usually heard as -a / -ah

So the sentence does not sound like each word is pronounced only as it would be in isolation.

Yes, but the given order is the most neutral and straightforward.

The basic sentence is:

حماية الغابة مهمة

You may also see something like:

مهمةٌ حمايةُ الغابةِ

This can be used for emphasis or a more formal/literary style, but it is less neutral for a beginner.

So for normal use, حماية الغابة مهمة is the best pattern to learn first.