Why are kelp forests considered underwater rainforests?

The answer

Kelp forests are among the most productive and biodiverse ecosystems on Earth, rivaling tropical rainforests in the complexity of life they support. Giant kelp (Macrocystis pyrifera) can grow up to 2 feet (60 cm) per day, reaching lengths of 175 feet (53 meters), creating dense underwater canopies that shelter over 800 species of marine animals and plants. Like terrestrial forests, kelp forests have distinct vertical layers: the canopy, mid-water stipes, and holdfast communities on the seafloor, each supporting different species. Kelp forests absorb massive amounts of CO2 through photosynthesis and export large quantities of organic carbon to deep ocean food webs. Sea otters play a keystone role in maintaining kelp forests by controlling sea urchin populations that would otherwise overgraze and destroy the kelp.