Climate and natural vegetation

Location answers use vague "above/below the equator" instead of compass direction and latitude (e.g. "about 15-30° north and south of the equator"). Name the continent, the latitude band, and north or south. And the driest deserts (Atacama, Namib) sit on the WESTERN side of continents, from cold offshore currents -- often the omitted point.

Why deserts are so dry is among the worst-answered questions. Give a named mechanism, not "it's hot so it doesn't rain": air that lost moisture at the equator DESCENDS near 30°, holding moisture rather than releasing it (high pressure); a COLD OCEAN CURRENT cools onshore air on west coasts; OFFSHORE winds keep the interior dry; a RAIN SHADOW sits behind mountains.

A sharp substitution error: even when "equatorial" is emboldened, candidates write about the hot desert. The climates are opposites: equatorial = high, constant rainfall (over 2,000 mm, no dry season), tiny annual range; hot desert = very low rainfall (under 250 mm), large diurnal range. An answer about the wrong climate scores nothing.

Candidates swap the terms for plant water loss. TRANSPIRATION is water loss THROUGH a plant -- vapour from the leaves. EVAPORATION is water becoming vapour from an open surface (soil, a lake). A xerophyte's small, waxy, spine-like leaves cut water loss by reducing TRANSPIRATION; "reduces evaporation" for the leaf adaptation is the wrong process.

Two different processes. DEFORESTATION is clearing trees so the land can be used otherwise (ranching, soya, logging) -- a rainforest process. DESERTIFICATION is productive dry-margin land degrading into desert, from BOTH climatic change (drought) AND human overuse (overgrazing, overcultivation, fuelwood) -- the Sahel. It is not simply "cutting trees".

The lush forest misleads candidates into calling the soil fertile. In fact most nutrients are in the living vegetation (biomass), not the soil: heat and rain decompose leaf litter fast and trees reabsorb it quickly, leaving thin, poor soil. That is why deforestation degrades it so fast -- with no canopy or litter, heavy rain leaches nutrient away and erodes the topsoil.

A testable wrong belief: that a hot desert's large diurnal range is caused only by intense daytime sun. That is only HALF: at night the near-cloudless sky traps no outgoing heat, so the day's heat escapes rapidly and temperatures fall sharply, sometimes near freezing. A full answer needs BOTH intense daytime heating AND rapid night-time heat loss.