Learn Hardcore Spanish (Latin America): La tormenta causa daño en el bosque.

Spanish generally requires a definite article before singular, countable nouns, even when speaking about things in general. So instead of dropping the article as in English (“storm”), you say la tormenta. Here it can refer to a specific storm or the idea of a storm in general.

What does the verb causar mean, and can I use hacer daño instead?

Causar means “to cause.” You can also express the same idea with hacer daño (“to do harm”), e.g. La tormenta hace daño en el bosque.

Causar daño is a bit more formal
Hacer daño is more colloquial

Why is the noun daño used here instead of the verb dañar?

Using daño (damage) turns the action into a noun phrase: causar daño. If you prefer a verb form, you can say La tormenta daña el bosque (“The storm damages the forest”). Both are correct; it’s just a stylistic choice between a noun phrase and a verb phrase.

Why is the preposition en used before el bosque? Could I use a or skip the article?

En el bosque = “in the forest,” emphasizing where the damage happens.
If you want “cause damage to the forest” as a direct object, use a + el = al: La tormenta causa daño al bosque.
You cannot omit the article; bosque is a masculine noun, so it needs el (or los in plural).

Why is daño singular here? Can it be plural?

Daño is often an uncountable (mass) noun when talking about harm in general, so it stays singular. If you want to emphasize multiple discrete damages or legal claims, you can use the plural daños, e.g. La tormenta causa muchos daños al bosque.

What is the squiggly line on the ñ in daño? Is it an accent?

The squiggle (tilde) on ñ is not an accent mark—it’s part of the letter itself. In Spanish, ñ is a separate letter pronounced [ɲ], like the “ny” in “canyon.”

Is bosque masculine or feminine, and what is its plural?

Bosque is masculine, so you say el bosque in singular and los bosques in plural.

How would I say this sentence in the plural to talk about storms and forests generally?

Make both nouns plural and adjust the verb:
Las tormentas causan daño (or daños) en los bosques.
You can keep daño singular for the general idea of damage or use daños for multiple instances.

How do you pronounce tormenta, causar, daño, and bosque?

Here are approximate pronunciations using stressed capitals:

tormenta: tor-MEN-ta
causar: kaw-SAR
daño: DAH-nyo
bosque: BOS-keh