Why do tropical rainforests usually produce more biomass than cold or dry ecosystems?

Tropical rainforests produce more biomass than cold or dry ecosystems primarily because they exist in climatic conditions that are least limiting to plant growth.1

The rate of primary productivity—the conversion of solar energy into organic compounds—depends heavily on environmental factors such as temperature, water availability, and light. In tropical rainforests, these conditions support year-round growth, whereas cold ecosystems like the taiga are often limited by low soil temperatures, and dry ecosystems like deserts lack the water necessary for high rates of photosynthesis.213

While tropical rainforests exhibit high rates of gross primary productivity, they also experience significant energy loss through plant respiration and consumption by herbivores. Ultimately, the combination of favorable climate and continuous growing seasons allows these forests to maintain a larger total mass of living organisms compared to environments where growth is restricted by extreme temperatures or water scarcity.12