Wanderlust World Wanderlust World Intuition suggests rainforests—Earth's "lungs"—should have higher oxygen. Reality is more nuanced: oxygen production is higher in rainforests, but atmospheric concentration is globally uniform (~20.95%) due to rapid mixing. The question likely confuses production with local concentration, or compares microenvironments.
Atmospheric circulation mixes gases thoroughly on ~1-year timescales. O2 concentration varies <0.1% globally. Measuring "rainforest air" vs. "desert air" at surface level shows no meaningful difference—both ~20.95% O2. The biosphere's net oxygen flux is balanced by weathering, combustion, and respiration globally.
Rainforests: Gross primary production (GPP) ~2,200 gC/m²/yr — highest on Earth. But ecosystem respiration (plants + microbes + animals) nearly equals GPP in mature forests. Net ecosystem production ~0. Oxygen produced = oxygen consumed locally.
Deserts: GPP ~100-300 gC/m²/yr. Low respiration (sparse biomass). But minimal oxygen production too. Net flux near zero.
Oceans (phytoplankton): Produce ~50-80% of Earth's oxygen — but also consume most via respiration. Net contribution to atmospheric O2 accumulation is small on human timescales.
At centimeter scale, gradients exist:
These are biologically relevant but atmospherically negligible.
Rainforests are carbon reservoirs (200-400 tC/ha), not oxygen tanks. Deforestation releases stored carbon as CO2 — the climate threat. The "lungs" metaphor misleads: lungs exchange gases; rainforests store carbon. Protecting them stabilizes climate, not atmospheric O2.
Deserts have lower biological oxygen cycling — less production, less consumption. But atmospheric O2 is identical. The difference is in turnover rate, not concentration.
Bottom line: Breathe easy in both. The air's oxygen content is a planetary property, not a local one. What differs is the living machinery processing it — furious in rainforests, frugal in deserts.