Learn Hardcore Spanish (Spain): La sequía y la inundación son dos efectos del cambio climático que vemos cada año. - Drought and flooding are two effects of climate change that we see every year.

la sequía – ends in -ía, and most nouns ending in -ía are feminine (la economía, la energía, la biología).
la inundación – ends in -ción, and virtually all nouns ending in -ción are feminine (la educación, la solución, la contaminación).

So you say:

la sequía (the drought)
la inundación (the flood / flooding)

Could I drop the articles and say Sequía e inundación son dos efectos…?

You can, but it sounds less natural and a bit more like a headline or a very formal/written style.

In normal speech and in most writing, you would keep the articles:

La sequía y la inundación son dos efectos… ✅ natural

Without the articles:

Sequía e inundación son dos efectos… ➜ more like a title, a bullet point, or a very formal summary.

Spanish tends to use definite articles with generic nouns much more than English does.

Why is it del cambio climático and not just de cambio climático?

Del is the contraction of de + el:

de + el cambio climático → del cambio climático

You use el here because you are referring to a specific, known phenomenon: el cambio climático (climate change as the global issue everyone talks about), not just any random climate change.

De cambio climático without the article would usually sound incomplete or wrong in this sentence. You’d normally expect del in this kind of “X is an effect of Y” phrase:

un efecto del estrés (an effect of stress)
las consecuencias de la guerra / del conflicto

Could I say dos de los efectos del cambio climático instead of dos efectos del cambio climático? What’s the difference?

Both are grammatically correct, but they imply slightly different things.

son dos efectos del cambio climático
→ Presents them as effects caused by climate change, without explicitly emphasising that there are more.
son dos de los efectos del cambio climático
→ Clearly implies there are many effects and these are just two of them (a subset of a larger list).

In most explanatory contexts, dos efectos del cambio climático is natural and enough. Use dos de los efectos when you want to stress “these are just two among many.”

Why is vemos used instead of vemos nosotros or a passive like se ven?

Spanish usually omits subject pronouns when the verb ending already shows who the subject is.

vemos already shows we (nosotros) because of the -mos ending.
Saying vemos nosotros is possible, but you only use it for emphasis or contrast:
- Nosotros vemos estos efectos, pero muchos no los quieren ver.

About the passive:

…que vemos cada año = …that we see every year (active, we = subject).
…que se ven cada año = …that are seen every year (impersonal/passive-like).

Both are possible, but the original sentence chooses the active form, which is more direct and natural in many contexts.

Why is the present tense vemos used for something that happens every year? Why not a future tense?

Spanish uses the present simple for habitual actions and regular events, just like English:

Vemos estos efectos cada año.
= We see these effects every year.

You only need future tenses (veremos, vamos a ver) if you want to talk about something specifically in the future, not a general recurring pattern.

So the present vemos is exactly the right tense for “we (regularly) see them every year.”

Could I say cada año vemos… instead of …que vemos cada año? Does the position of cada año matter?

Yes, you can move cada año around. All of these are correct:

…que vemos cada año.
…que cada año vemos. (a bit more formal/literary)
Cada año vemos estos efectos del cambio climático. (new sentence, adverbial at the start)

In Spanish, adverbial expressions of time (hoy, mañana, cada año) are quite flexible in position. Changing the position can slightly shift the emphasis, but all of these are natural.

Why is it cada año and not todos los años? Are they the same?

Cada año and todos los años are very close in meaning and often interchangeable.

cada año = each year
todos los años = all the years / every year

In practice, both usually mean every year:

Vemos estos efectos cada año.
Vemos estos efectos todos los años.

Tiny nuance:

cada año can sound a bit more neutral or systematic (“year after year”).
todos los años can feel a bit more emphatic in some contexts (“all the years, without exception”).

But the difference is small; you can use either here.

Why is it la inundación (singular) when in reality there are many floods every year? Shouldn’t it be plural, las inundaciones?

Here, la inundación is used in a generic sense: it refers to the phenomenon/type of event (flooding) rather than counting individual floods.

Compare:

La inundación es un efecto del cambio climático.
→ Flooding (as a phenomenon) is an effect of climate change.
Las inundaciones son frecuentes en esta región.
→ Individual flood events are frequent in this region.

In the sentence you gave, la sequía y la inundación are being listed as types of effects, so the singular (“the drought” / “drought”, “the flood” / “flooding”) is natural.

Why is ser (son) used instead of estar? Could I say La sequía y la inundación están…?

You use ser here because you’re talking about inherent characteristics / types / classifications, not temporary states or locations.

ser: identity, classification, permanent or defining characteristics
- La sequía y la inundación son efectos del cambio climático.
  → They are (by nature) effects caused by climate change.
estar: temporary states, conditions, locations
- La región está en sequía. → The region is in drought (state).
- La ciudad está inundada. → The city is flooded (condition).

So están dos efectos would be wrong here; you need son dos efectos for “are two effects.”

Why does sequía have an accent on -í-: sequía and not sequia?

The accent mark in sequía breaks what would otherwise be a diphthong and tells you where to put the stress.

Without the accent, sequia would normally be pronounced something like SE-kia (stress on the first syllable, e + i as a glide).

With the accent, sequía is pronounced se-ke-Í-a (four syllables, with stress on -í-).

In Spanish, accent marks often:

show the stressed syllable when it doesn’t follow the usual patterns, or
break diphthongs (día, país, frío, río, sabía).

Sequía follows that pattern: the accent ensures the correct pronunciation se-ke-Í-a and not SÉ-kia.