Which of the following ecosystem is most productive in terms of net primary productivity?.

Tropical rain forests

The correct answer is Option (3) - Tropical rain forests

Primary production is defined as the amount of biomass or organic matter produced per unit area over a time period by plants during photosynthesis. It is expressed in terms of weight (gm^–2) or energy (kcal m^–2). The rate of biomass production is called productivity. It is expressed in terms of gm^–2yr^–1 or (kcal m^–2)yr^–1 to compare the productivity of different ecosystems. It can be divided into gross primary productivity (GPP) and net primary productivity (NPP).

Gross primary productivity of an ecosystem is the rate of production of organic matter during photosynthesis. A considerable amount of GPP is utilised by plants in respiration. Gross primary productivity minus respiration losses (R), is the net primary productivity (NPP).

GPP – R = NPP

Net primary productivity is the available biomass for the consumption to heterotrophs (herbiviores and decomposers).

Among different ecosystems, the tropical rain forest has the highest NPP due to the following reasons:

High Temperature and Moisture: Tropical rain forests are located near the equator and experience warm temperatures and abundant rainfall throughout the year, which are ideal for photosynthesis and plant growth.

Rich Biodiversity and Vegetation Density: These forests have a dense canopy of vegetation with multiple layers (e.g., emergent trees, canopy, understory), allowing maximum utilization of sunlight.

Year-Round Productivity: Unlike temperate forests, tropical rain forests do not have dormant seasons (e.g., winter), which allows continuous growth and productivity.