Productivity of tropical rainforests is the highest. The tropical rainforests coveringan area of $3,00,000 \mathrm{~km}^2$ contain more than $50 \%$ of the total flora and fauna of the world. They are found in the equatorial regions rainfall exceeds $140 \mathrm{~cm}$. The warm humid climate supports broad leaved evergreen plants. Productivity is very high and the vegetation show stratification into two or more well defined layers.