Productivity

Story hook

In the 1960s, two American ecologists — Howard and Eugene Odum — set up a tedious experiment in the salt marshes of Sapelo Island, Georgia. They clipped Spartina alterniflora (cordgrass) every two weeks, dried it, weighed it, and over years built the first reliable map of how much organic matter a salt-marsh ecosystem produces per square metre per year. The answer was astonishing: ~3,300 grams of dry biomass per m² per year, making salt marshes among the most productive ecosystems on Earth — more productive per area than tropical rainforests, more than agricultural fields, more than any open ocean.

Yet salt marshes occupy less than 0.3 % of Earth's land area. We have drained or paved most of them. India has lost an estimated 50 % of its coastal wetlands since 1970. The Odums' work seeded what we now call "blue carbon" — the recognition that mangroves, salt marshes, and seagrasses sequester carbon 40 times faster per hectare than tropical forests.

This file extends the ecosystem story to the rate at which life produces biomass (productivity), the geometric way we visualise it (ecological pyramids), the transition zones where two ecosystems meet (ecotones), and the unique role each species plays (the niche). Together these concepts let us quantify why some ecosystems are powerhouses and others are not.

Why this matters for UPSC

Productivity is a Prelims-heavy topic — examiners love asking about which ecosystem is most productive, comparison of GPP/NPP, why aquatic biomass pyramids invert, ecotone characteristics. Mains questions tie productivity to food security (agricultural ecosystems), climate (carbon sequestration), and conservation (which ecosystems to prioritise). 1-2 Prelims questions appear most years; Mains coverage is moderate.